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DEC-12-SRZB-D

August 1971

321 pages

Original

12MB

Document:	PDP-12 System Reference Manual 3rd Printing
Order Number:	DEC-12-SRZB-D
Revision:	0
Pages:	321
Original Filename:	http://bitsavers.org/pdf/dec/pdp12/DEC-12-SRZB-D_PDP-12_System_Reference_Manual_Aug71.pdf

OCR Text

Digital Equipment Corporation
Maynard, Massachusetts

~nmnomn

PDP-12

SYSTEM
REFERENCE MANUAL

DEC-12-SRZB-D

PDP-12
SYSTEM REFERENCE MANUAL

DIGITAL

EQUIPMENT

CORPORATION • MAYNARD, MASSACHUSETTS

1st Printing (Preliminary) June 1970
2nd Printing (Revised) July 1970
3rd Printing (Revised) August 1971

The material in this manual is for reference
only. Instruction times, operating speeds,
and the like are provided solely as reference
information, and are subject to change at
any time without prior notice. The drawings, specifications, and descriptions herein
are the property of Digital Equipment
Corporation, and shall not be reproduced or
copied in whole or in part as the basis for
the manufacture or sale of items without
written permission.

The following are trademarks of Digital Equipment
Corporation, Maynard, Massachusetts:
DEC
FLIP CHIP
DIGITAL

PDP
FOCAL
COMPUTER LAB

CONTENTS

Chapter

Page

CHAPTER 1 GENERAL DESCRIPTION
1.1
1.1.1
1.1.2
1.1.3
1.1.4
1.1.5
1.2

Description
System
Central Processor
Memory
Operating Modes
Input/Output Facilities and Display
Symbols and Abbreviations

1-1
1-1
1-3
1-4
1-4
1-5
1-6

CHAPTER 2 CONTROLS AND INDICATORS
2.1
2.2
2.3
2.4
2.5

PDP-12 Console Controls and Indicators
Data Terminal
CRT Display, Type VRl 2
LINCtape Transport, Type TU5 5
Teletype, Model 33 ASR

2-1
2-1
2-1
2-1
2-1

CHAPTER 3 LINC MODE PROGRAMMING
3.1
3.1.1
3.1.2
3.1.3
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.3
3.3.I
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10

Organization of Memory
General
Program Counter
Instruction and Data Field Registers
Memory Addressing Methods
General
Direct Addressing
Indirect Addressing: {3-Class
Addressing: a-Class
LINC Mode Instructions
Instruction Formats
Instruction Descriptions
Full-Word Instructions
Full-Word Logic
Full-Word Comparison
Half-Word Operations
a-Class Operations
Program Control
Shift and Rotate Operations
Skips

3-1
3-1
3-2
3-2
3-3
3-3
3-3
3-3
3:-6
3-6
3-6
3-7
3-7
3-11
3-12
3-13
3-14
3-15
3-16
3-19

iii

CONTENTS (cont)
Page

Chapter
3.3.11
3.3.12
3.3.13
3.3.14
3.3.15
3.3.16
3.3.17
3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.5
3.5.l
3.5.2
3.6
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.7
3.6.8
3.6.9
3.6.10
~.6.11

3.6.12
3.6.13
3.6.14

Miscellaneous
Console Switches
Mode Control
Input/Output Bus
Memory Address Control
Special Functions
Instruction Trap
CRT Display, Type VR12
Point Displays
Character Displays
Half-Size Characters
Character Set
Data Terminal
Analog Inputs
Relays
LINCtape Type TC 12
Organization of Data
Programming
Tape Motion
LINCtape Instructions
Extended Operations
Extended Address Format
Extended Units
Tape Interrupt Enable
No Pause Condition
Hold Unit Motion
MARK Condition
Maintenance Mode
Tape Trap
Tape Word Skip

3-21
3-22
3-22
3-23
3-24
3-29
3-30
3-31
3-32
3-32
3-33
3-33
3-35
3-35
3-36
3-37
3-37
3-41
3-42
3-43
3-45
3-46
3-47
3-47
3-48
3-48
3-48
3-49
3-49
3-49

CHAPTER4 8 MODE PROGRAMMING
4.1
4.1.1
4.1.2
4.1.3
4.2
4.2.1
4.2.2
4.2.3
4.3
4.3.1
4.3.2
4.4
4.4.1
4.4.2
4.5
4.5.1
4.5.2
4.5.3
4.6

Organization of Memory
Organization
Page 0
Extended Memory
Memory Addressing Methods
Direct Addressing
Indirect Addressing
Au to indexing
8 Mode Instructions
Memory Reference Instructions
Operate Class Instructions
Program Interrupt
Operation
Using the Program Interrupt
Extended Arithmetic Element Type KE 12
Operation
EAE Instructions
EAE Programming
Extended Memory

4-1
4-1
4-1
4-2
4-2
4-2
4-3
4-4
4-5
4-5
4-6
4-12
4-12
4-13
4-13
4-13
4-13
4-16
4-19

CONTENTS (cont)
Chapter

4.6.1
4.6.2
4.6.3

Page

Registers
Instructions
Programming

4-19
4-20
4-21

CHAPTER 5 INPUT/OUTPUT BUS DESCRIPTION
5.1
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.1.6
5.1.7
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.2.6
5.2.7
5.2.8
5.2.9
5.3
5.3.1
5.3.2
5.3.3
5.3.4
5.3.5
5.4
5.4. l
5.4.2
5.4.3
5.4.4
5.4.5

Programmed Data Transfers and 1/0 Control
Timing and IOP Generator
Device Selector (DS)
Input/Output Skip (IOS)
Accumulator
Input Data Transfers
Output Data Transfers
Program Interrupt
Multi-Level Automatic Priority Interrupt
Interrupts
Push
Restore-"POP" (REST-IOT 6771)
Vectoring
Maintenance Logic
Programming
Programming Restrictions
Instruction List
DM12
Data Break Transfers
Single-Cycle Data Breaks
Input Data Transfers
Output Data Transfers
Memory Increment
Three-Cycle Data Breaks
Interface Design and Construction
PDP-12 Interface Modules
M Series Flip Chip Modules
Construction of Interfaces
IOT Allocations
Interface Connections

5-4
5-6
5-7

5-8
5-9
5-10
5-11

5-11

5-15
5-15

5-15
5-16

5-16
5-17

5-18
5-19

5-19
5-20

5-21
5-22
5-22

5-23
5-27
5-29
5-30

5-30
5-34
5-39
5-43
5-44

CHAPTER 6 PERIPHERAL DEVICES

6.1
6.1.1
6.1.2
6.1.3
6.1.4
6.1.5

6.2
6.2.1
6.2.2
6.3
6.3.l
6.3.2

Introduction
Teletype
Model 33 ASR
Model 33 KSR
Model 35 KSR
Model 37 KSR
Teletype Controls
Real Time Clocks
Real Time Interface, Type KWl 2-A
KW12-B and KW12-C Fixed Interval Clocks
Disk Storage
Random Access Disk File, Types DF/DS32 and DF/DS32-D
Disk Memory System Type RF /RS08

6-1

6-3
6-3

6-3
6-4
6-4
6-4
6-18
6-18

6-25
6-27
6-27

6-30

CONTENTS (cont)
Page

Chapter
6.3.3
6.3.4
6.4
6.4.1
6.4.2
6.4.3
6.5
6.5.1
6.5.2
6.6
6.6.1
6.6.2
6.7
6.7.1
6.8
6.8.1
6.8.2
6.8.3
6.9
6.9.1
6.10
6.10.1
6.11
6.11.1
6.12
6.12.1

RK8 Disk Cartridge Memory System
Disk Software
Magnetic Tape
Automatic Magnetic Tape Control, Type TC58
Magnetic Tape Transports
LINCtape Option TCl 2-F
Line Printers
Line Printers and Control, Type LP 12
Line Printers and Control, Type LP08
Card Readers
Card Reader and Control, Type CRl 2
Optional Mark Card Reader Type CM 12
Incremental Plotters
Incremental Plotter and Control, Type XYl 2
Paper Tape
High-Speed Paper-Tape Punch and Reader, Type PC 12
High-Speed Paper-Tape Punch, Type PPl 2
High-Speed Paper-Tape Reader, Type PR 12
Data Buffers
Data Buffer Type DB 12-P, N
Power Fail/Restart
Power Failure Option, Type KP 12
Analog-To-Digital
General Purpose Multiplexed Analog-to-Digital Converter System, Type AFO 1-A
Digital-To-Analog
Digital-to-Analog Converter, Type AAOl-A

6-38
6-44
6-45
6-45
6-54
6-57
6-59
6-59
6-60
6-63
6-63
6-66
6-68
6-68
6-71
6-71
6-71
6-72
6-73
6-73
6-74
6-74
6-76
6-76
6-82
6-82

CHAPTER 7 PROGRAM LIBRARY

7.1
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5
7.1.6
7.1.7
7.1.8
7.1.9
7.1.10
7.1.11
7.1.12
7.1.13
7.1.14
7.1.15
7.1.16
7.1.17
7.1.18
7.1.19
7.1.20
7.2
7.2.1

PDP-12 Programs
LAP 6 - DIAL Display Interactive Assembly Language (DEC-12-SE2D-D)
Peripheral Interchange Program (PIP)
QUANDA (DEC-12-FISA-D)
DATAM (DEC-L8-FDAA-D)
GRAPHA (DEC-L8-UGAA-D)
FRQANA (DEC-L8-FANA-D)
MAGSPY (DEC-12-UZSA-D)
COMPAR (DEC-L8-EUCA-D)
SEARCH (DEC-L8-EUSA-D)
CONVERT (DEC-12-ESYB-D)
MARK 12 (DEC-12-YITB-D)
L8SIM (DEC-12-Sll B-D)
FRED (DEC-12-FZFA-D)
PRTC 12-F (DEC-YIY A-D)
SIGAVG/SINPRE (DEC-12-UZ I A-D/DEC-12-UW4A-D)
CATACAL (DEC-12-UWlA-D)
NMRSIM (Nuclear Magnetic Resonance Simulation) (DEC-12-UWSA-D)
ADTAPE/ ADCON (DEC-12-UW2A-D)
TISA (DEC-l 2-UW3A-D)
FOCAL12
PDP-8 Programs
System Programs

7-1
7-1
7-3
7-3
7-3
7-3
7-3
7-3
7-3
7-3
7-3
7-4
7-4
7-4
7-4
7-4
7-4
7-4

7-5
7-5
7-5
7-5
7-5

CONTENTS (Cont)
Chapter
7.2.2
7.2.3
7.3

7.4

Page
Elementary Function Routines
Utility Program
DECUS Program
Diagnostic Programs

7-7
7-9

7-10
7-27

APPENDIX A LINC MODE INSTRUCTIONS
APPENDIX B 8 MODE INSTRUCTIONS
APPENDIX C I/0 BUS INSTRUCTIONS
APPENDIX D 8 MODE PERFORATED-TAPE LOADER
APPENDIX E TAPE MAINTENANCE INSTRUCTIONS
E.l
E.2
E.2.1
E.2.2
E.2.3
E.2.4

General
Tape Maintenance Instructions
IOT 6141
IOT 6152
IOT 6154
IOT 6154 Detailed Transfer Information

E-1
E-1
E-1
E-2
E-2
E-3

APPENDIX F TABLE OF CODES

F. l
F.2
F.3

F.4
F.5
F.6

Model 33/35 ASR/KSR Teletype Code
Model 33 ASR/KSR Teletype Code in Binary Form
LT-37 Transmit and Receive Code Table
Card Reader Codes
LP08 Line Printer Code
LP 12 Automatic Line Printer Code

F-1
F-2
F-3
F-5

F-6
F-7

APPENDIX G CABLE CONNECTIONS TO PDP-12 FRONT PANEL
APPENDIXH MATHDATA

INDEX

vii

TABLES

Title

Table No.

Page

4-1

Central Processor Register Indicators
Central Processor Major State Indicators
Central Processor Miscellaneous Indicators
Tape Processor Major State Indicators
Tape Processor Miscellaneous Indicators
Function of Computer Consoel Keys
Toggle Switch Registers
Individual Console Toggle Switches
Analog Knobs and Power Switch Panel
Relay and Analog Input Panel
VR 12 Display Scope Controls
TU55 Tape Transport Controls and Indicators
Teletype Model 33 ASR Controls
ASR-33 Character Set Display Pattern
Summary of Addressing Methods in 8 Mode

2-3
2-3
2-3
2-4
2-4
2-5
2-7
2-7
2-9
2-9
2-11
2-12
2-14
3-34
4-4

5-1

Stack Register

5-16

5-2

M Series Module Summary
Cable Connections to the PDP-12 1/0 Bus
PT08 Specifications
PT08 Device Codes
DC02-E Specifications
DF32 Instructions Compared with RF/RS08 Instructions
Input Signal Scaling
System Conversion Characteristics
LINC Mode Instructions
8 Mode Memory Reference Instructions
8 Mode Group 1 Operate Microinstructions
8 Mode Group 2 Operate Microinstructions
8 Mode Extended Arithmetic Element Microinstructions
IOT Instructions
AC Bit Functions
AC Bit Functions
IOT 6154 Effect of Tape Maintenance Instructions
Tape Maintenance Instruction Register Equals 10 8
Tape Maintenance Instruction Register Equals 11 8
Tape Maintenance Instruction Register Equals 12 8
Tape Maintenance Instruction Register Equals 13 8
Tape Maintenance Instruction Register Equals 148
Tape Maintenance Instruction Register Equals 15 8
Model 33/35 ASR/KSR Teletype Code (ASCII) in Octal Form
Model 33 ASR/KSR Teletype Code (ASCII) in Binary Form

5-35
545

2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
2-12
2-13
3-1

5-3

6-1
6-2
6-3
6-4
6-5
6-6
A-1
B-1
B-2
B-3
B-4
C-1
E-1
E-2
E-3
E-4
E-5
E-6
E-7
E-8
E-9
F-1
F-2
viii

6-10
6-11
6-14
6-35
6-77
6-79
A-1
B-1
B-3
B-3
B-4
C-1
E-1
E-2
E-2
E-3
E-4
E-4
E-4
E-5
E-5
F-1
F-2

TABLES (cont)
Table No.
F-3
F-4
F-5
F-6
G-1

Title
LT-37 Transmit and Receive Code Table
Card Reader Codes
LP08 Line Printer Code
LP12 Automatic Line Printer Code
Cable Connections for PDP-12 Front Panel

Page
F-3
F-5
F-6
F-7
G-2

ILLUSTRATIONS

Figure No.
Frontispiece
1-1
2-1
2-2
2-3
2-4
2-5
2-6
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
3-13
3-14
3-15
3-16
3-17
3-18
3-19
4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-10
5-1
5-2
5-3

Title
PDP-12 Program Data Processor
PDP-12 Functional Block Diagram
PDP-12 Operator Console
Analog Knobs and Power Switch Panel
Relay and Analog Input Panel
Type VRl 2 CRT Display
TU55 Tape Transport Control Panel
Teletype Model 33 ASR
Assignment of LINC Address within Memory
Direct Address Instruction Format
{J-Class Instruction Format
{J-Class Format
a-Class and Non-Memory Reference Format
Rotate Left
Rotate Right
Scale Right
QAC Transfer Path
Data Path: IB, IF, DF, and AC
Data Path, RMF Instruction
Special Functions
CRT Grid
Display Pattern for DSC
Relay Terminals and Corresponding AC Bits
Standard LINCtape Format
LINCtape Processor Information Paths
LINCtape Instruction Format
Extended Operations Buffer Bit Assignments
Organization of Memory, 8 Mode
Memory Reference Instruction Format
Group I Operate Class Instruction Format
Rotation Scheme for RAR, RTR, RAL, RTL
Group II Operate Class Instruction Format
EAE Instruction Format
Shift Path for NMI, SHL
Shift Path for ASR
Shift Pa th for LSR
Data Path to SF and AC
Logic Symbols
IOT Instruction Decoding
Programmed Data Transfer Interface Block Diagram

Page

1-2
2-2
2-8
2-10
2-10
2-11
2-13
3-1
3-3
3-4
3-6
3-6
3-17
3-17
3-18
3-22
3-27
3-28
3-29
3-31
3-33
3-36
3-38
3-40
3-41
3-45
4-2
4-3
4-7
4-8
4-10
4-13
4-15
4-16
4-16
4-20
5-3
5-4
5-5

ILLUSTRATIONS (cont)
Figure No.

Title

Page

5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12

Programmed Data Tt:.ansfer Timing
Generation of IOT Command Pulses by Device Selectors
Typical Device Selector
Use of IOS to Test the Status of an External Device
Accumulator Input or Output
Loading Data into the Accumulator from an External Device
Loading a Six-Bit Word into an External Device from the AC
Program Interrupt Request Signal Origin
Multiple Inputs to IOS and PI Facilities

5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-12
5-13

5-13
5-1.4
5-15

Illustration of Push and POP Operations

5-13
5-17
5-20

5-16
5-17
5-18
5-19
5-20
5-21
5-22
5-23
5-24
5-25
5-26
5-27
5-28
5-29
5-30

6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
6-9
6-10

Vector Flow Diagram
DM12 Cable D~agram

Data Break Transfer Interface
Single-Cycle Data Break Input Transfer Timing
Device Interface Logic for Single-Cycle Data Break Input Transfer
Single-Cycle Data Break Output Transfer Timing
Device Interface Logic for Single-Cycle Data Break Output Transfer
Memory Increment Data Break Timing
Three-Cycle Data Break Timing
Typical M111 /M906 Positive Input Circuit
Typical M516 Positive Bus Receiver Input Circuit
Typical M623/M906 Positive Output Circuit
M660 Terminated Bus Driver Output Circuit
M103 Device Selector Logic Circuit
M 101 Bus Data Interface Logic Circuit
1/0 Bus Configuration
1/0 Cable Connections
Relationship Between Paper Tape and Accumulator
Punched Paper Tape Format for the Number 4
PT08 Equipment Configurations
PT08 Program Response Time
KW 12-A Real Time Interface
KW 12-A Organization
Simplified Input Synchronizer Logic Diagram
KW 12-A Timing Diagram
Automatic Restart Program Events
Typical Power Failure Program Service Routine

5-21
5-23
5-24
5-25
5-26
5-27
5-29
5-31
5-31
5-32
5-32
5~33

5-34
540
5-41

6-3
6-4
6-11
6-13
6-18
6-19
6-20
6-21
6-75
6-75

- 1

00
00

2 •.

PDP· 12 Progr~mmed flata Processor

CHAPTER t
GENERAL DESCRIPTION

1.1 DESCRIPTION

1.1.1 . System
The PDP-12 (Programmed Data Processor-12) is a versatile digital computer which includes within its single central
processor two distinct operating modes, each with its own complete instruction set. This versatility of the PDP-12
makes it, on the one hand, a laboratory-oriented machine with several built-in facilities for input/output, auxiliary
storage, and control and sensing of external equipment; and on the other hand, a general-purpose computer with a
flexible input/output capability to which numerous peripheral devices may be easily attached. The central
processor logic is fully parallel, using a basic word length of 12 bits. The processor cycle time is 1.6 microseconds
±20%; most instructions require from 1 to 3 cycles for execution.
Like its predecessor, the LINC-8, the PDP-12 operates in one mode as a LINC (Laboratory Instrument Computer)
and in the other mode as a PDP-8 computer - specifically, a PDP-8/I. Unlike the LINC-8, however, the PDP-12 has
one central processor, and both operating modes have equal status. (In the LINC-8, the LINC mode was
subordinate to the PDP-8 mode.) The computer may be stopped and started in either mode, and programs may
switch from one to the other at will. Computations in one mode are immediately available to programs operating in
the other mode because only one set of processing registers is involved.
The PDP-12 is offered in three configurations, A, B, and C, in order of decreasing capability. The two smaller
systems, B and C, are expandable into the A configuration. The system discussed in this handbook is the PDP-12A.
The capacity of basic core memory storage in the PDP-12 is 4096 ( 4K) 12-bit words which can be expanded to
32,768 (32K) 12-bit words.
Figure 1-1 shows a system block diagram with many of the options and peripherals available, such as:
LINCtape -

Two TU55 tape transports or one TU56 dual drive transport controlled by a
buffered subprocessor

CRT Display -

6" x 9" screen, two intensification channels

Analog Inputs -

Eight external inputs, eight variable potentiometers

Relay Buffer -

Six relays for control of external equipment
1-1

CARO
READER

r---- - -- ----------- ---,

REMOTE VR12 (UP TO
r- -1200' BCl2-A EXTENSION
:
CABLE)

r-:-----;-----I

BASIC PDP-12

EXPANDER CABINETS H961C

I
I

POSITIVE DATA BREAK FACILITY

~L-~J

T~~ T~~~

CR12
DBI 2

I DC02-E
I LP12
I

UP TO 2
.TRANSPORTS
PDP-12A
EXISTING
OPTIONS

I
I
I

IERAL EXPANDER

VR12
DISPLAY

VC12

js~2;ER;;,,

' POSITIVE 1/0 BUS

I p~i'~-iER

TTY*
STATION#3
TTY*
STATION#2

~
STATION#!

TTY*
STATION#O

LINE
PRINTER

AD12

m%~2P6~N.fsTAPEI

DWOB-A

ADDITIONAL
TU56

' I~MTt~~u~~F
I

TC12

110 8 DATA

BREAK CONV.

TC12)
NEGATIVE l/O BUS

11 I ""' I

TC12-F

I I
I I T

KP12

DP12

XY12

ADDITIONAL
OPTIONS
IN SYSTEM
CABINET

I
:

I
I

I' ''~""

~~~~E~Hl:N
ONE NEG.BUS

MM81-A
00

II
II

AF01-A
A-D

DMOl
MEMORY
MULTIPLEXER**
'----~-----'

RFOB
DISK CONTROL

DF32
DISK
CONTROL
DS32
DISK

I
TC 58
MAG. TAPE
CONTROL

KWl2-A-----1,B,C

RSOB
DISK
UPTO
4 DISK
OPTIONS

I
rL

UP TO 7
DEVICES
2 DISKS
PER CABINET
MAXIMUM

DS32
DISK

KT 12

L.___- -_____._ - -

AF04-A
O-A
CONVERTER

UP TO 32K

KE12

1 - - - 1

{

DEVICE CONN.
TO DATA BREAK
FACILITY

- - - - - - ...J

VP 12 A 12" INCR
PLOTTER HOUSTON
COMPLOT
VP12 Bl2" INCR.
PLOTTER HOUSTON
COM PLOT
VP12 C 30 INCR.
PLOTTER HOUSTON
COM PLOT

DS32

DISK

L___________ ----------------~
TU20
TU10
MAGNETIC
WITH
TAPE UNIT
TC5B
1------t•CONTROL
MOUN TE
TU30
INSIDE

UP TO 8 MAGNETIC
TAPE TRANSPORTS

Figure 1-1. PDP-12 Functional Block Diagram

NOTE *
TTY OPTIONS AVAILABLE
KSR33, ASR33
KSR 35, ASR35
NOTE**
DM04 POSITIVE BUS MEMORY
MULTIPLEXER ALSO AVAILABLE
(DOES NOT REQUIRE DWOB-A)

The PDP-12 is also equipped with a positive-logic, PDP-8/1-type, input/output (1/0) bus which can be used for
interfacing all 8-family peripherals and options, as well as the standard Teletype® Model 33 ASR.

1.1. 2 Central Processor
The central processor contains all the logic and registers required to carry out the functions of both operating
modes of the PDP-12. The central processor can best be described in terms of its active registers:

Accumulator(AC) 12 Bits

This register contains data being operated upon. Its
contents may be shifted or rotated right or left; incremented, cleared, or complemented; stored in memory or
added to the contents of a memory register; and logically
or arithmetically compared with the contents of any
memory register. The AC holds the sum after an addition,
and part of the product after a multiplication. The AC is
also involved in the transfer of data to and from various
other registers outside the central processor.

Link ( L) 1 Bit

The Link is an extension of the AC. When a carry occurs
out of AC 00 during a 2's complement addition, the Link is
complemented. It may be set or cleared independently of
the AC under 8 mode control, and may or may not be
included in shifting and rotating operations performed on
the contents of the AC.

Program Counter (PC) 12 Bits

This register contains the address of the next instruction to
be executed within the memory field selected by the
Instruction Field Register (see below J. In 8 mode, the PC
acts as a 12-bit counter; in LINC mode, it acts as a I 0-bit
counter.

Instruction Register (JR) 12 Bits

This register contains the complete binary code of the
instruction being executed.

Memory Address Register (MA) 12 Bits

This register contains the address for memory references.
Whenever a core memory location is being accessed, either
for reading or for writing, the MA contains the address of
that location.

Memory Buffer (MB) 12 Bits

All information passing between memory and other
registers in the PDP-12 must go through the Memory
Buffer Register, whether the transfer involves the central
processor, an external 1/0 device, or another memory
register.

Mode Status Register 1 Bit

This register indicates the current operating mode (LINC
or 8) of the central processor.

®Teletype is the registered trademark of the Teletype Corporation.
1-3

Instruction Field Register (IF) 5 Bits

This register selects the memory field containing the
executable program. In the LINC mode, it is used to
designate one of up to thirty-two 1024-word segments. In
the 8 mode, the three high-order bits of the IF are used to
designate one of up to eight 4096-word fields.

Data Field Register(DF) 5 Bits

This register selects the memory field containing data to be
indirectly accessed by the memory reference instructions
of a program. The fields are specified in each mode in the
same way that the IF specifies the Instruction Field.

1.1.3 Memory
The principal unit of core memory is a module of 4096 (4K) 12-bit words. Additional modules of 4K words may
be added, up to a total of eight, or 32,768 words. Within each module, the logical organization of memory depends
on the operating mode. In the LINC mode, each module is divided into four 1024-word segments. At any given
time, only two of these segments are active: the Instruction Field, which contains the executable program and the
directly accessed data; and the Data Field, which contains only indirectly accessed data. Absolute addresses may be
assigned and changed at will using the IF and DF described above.
In the 8 mode, the memory field (a 4K module) is divided into 32 pages of 128 words each. Within a single page,
data may be accessed directly; between pages, indirect addressing must be used. If more than 4K of memory is
provided, the IF and DF registers specify the active fields.

1.1.4 Operating Modes
The two operating modes, LINC and 8, are independent of each other, though they can be combined and
intermixed within a program. The user can run programs from the already-existing libraries for the 8 family of
computers, including the LINC-8. By using the 1/0 Handler (LINC-8 Simulator Trap Processor) program provided
with the PDP-12 basic software, most programs written for the LINC-8 can be run without modification. (Some
LINC-8 programs may require slight changes.) A complete software system designed for the PDP-12 allows the
programmer to assemble coding for either or both modes in a single program.
LINC Mode - In this mode, the instruction set of the classic LINC computer is implemented. In addition, several
new provisions are available:
Extended Tape Addressing - This allows the programmer to transfer information between LINCtape and any
section of core, removing the restriction of data transfer to only specific segments of a given memory field. Other
features include:
a. Tape Interrupt, which connects the tape processor status to the Program Interrupt.
b. No-pause, which permits the central processor to resume operation after initiating a tape transfer without
waiting for completion.
c. Hold-motion, which allows a unit to remain in motion after it has been deselected.
I/O Bus Access - In LINC mode the user has immediate access to those devices activated by LINC instructions:
analog inputs, Display, Relays, Sense Lines, and LINCtape. Devices connected to the I/O bus may be directly
accessed from LINC mode programming by means of a special two-word instruction, in which the second word
enables the bus and initiates the PDP-8 IOT timing chain. This second word is interpreted as a standard PDP-8 IOT
instruction, but the program continues to operate in LINC mode.
1-4

Special Functions - The LINC programmer may, by setting certain flip-flops,
a. Change the size of characters displayed on the CRT;
b. Enable the program trap, which intercepts certain LINC instruction codes;
c. Disable interrupts from the ASR-33;
d. Speed the sampling of analog inputs;
e. Clear the PDP-12 1/0 status by generating an 1/0 PRESET pulse.
8 Mode - In this mode, the user has available the entire PDP-8/1 instruction set.
Interaction Between Modes - The user may switch from one mode to the other at will. In the LINC mode,
execution of the instruction PDP causes the processor to change immediately to 8 mode operation, and all
subsequent instructions are interpreted as PDP-8/I instructions. To switch from 8 mode to LINC mode, the IOT
instruction LINC is used.

1.1. 5 Input/Output Facilities and Display

There are two main paths for the transmission of data from the central processor or memory to peripheral devices.
One path, which is controlled by LINC mode programming, leads to the CRT display, LINCtape, A-D converter,
and relays. The other path, which is the 1/0 bus, leads to the ASR-33 and to a large number of optional devices,
such as plotters, high-speed paper tape, magnetic tape, A-D, and card readers, disk storage, and line printers.
Display - The Cathode Ray Tube has a 58.5-square-inch (6.5 x 9 inches) screen, on which individual points and
whole characters may be displayed. The unit has two selectable channels, controlled by programming and by a
switch on the display. Characters are plotted on a 4-point x 6-point matrix; a full character can be displayed with
two instructions. Provision is made for displaying two sizes of characters.
Data Terminal - A Data Terminal provides a flexible means of receiving analog inputs and controlling the
operation of external equipment not internally interfaced to the PDP-12.
Analog Inputs - Sixteen analog inputs feed a 10-bit A-D converter. A single LINC mode instruction
samples any one of the 16 channels. Eight of the inputs are taken from phone jacks mounted on the Data
Terminal Panel and fed through preamplifiers to the converter. The remaining eight are taken from
continuously variable 10-turn potentiometers which are also mounted on the panel. A second set of 16
channels, with preamplifiers, may be added to the basic facility.
Relay Buffer - Six relays, mounted on the data terminal panel, can be switched individually or in
combination, by means of a LINC mode instruction. The relays may be used to start and stop operations
in external equipment. The states of the relays can be read into the AC.
Auxiliary Scope Connector - A connector mounted on the Data Terminal Panel is wired to accept an
auxiliary CRT for displaying information. All display information (X, Y and Z) available to the internal
display is also available at the remote connector.
Sense Lines - These 12 digital sense lines may be individually tested with a LINC mode instruction.
LJNCtape - Two TU55 transports (or one TU56 dual drive transport) are controlled by a fully-buffered tape
processor; once initiated by the LINC program, tape operations are carried out independently of the central
processor. Tapes normally are written and read in standard LINCtape format, though nonstandard formats may be
used. A special hardware option, TC 12-F, permits the use of tapes with a different format, such as PDP-8 DECtape.
In addition to the basic LINCtape commands, the PDP-12 also includes an Extended Operations facility, which
1-5

allows, among other features, the transmission of data between tape and any program-defined area of memory, and
the addition of TU55 transports to a total of eight (or four dual drive TU56s).
Input/Output (1/0) Bus - This connecting facility provides the control and data transmission path between the
central processor and any peripheral device attached to the bus. Some devices, such as paper tape readers and
punches, line printers, and incremental plotters, transfer data via the accumulator (AC). Others, including magnetic
tape and disk, use the three-cycle or single-cycle Data Break for direct memory access. The 1/0 bus uses positive
logic and accepts peripherals used with the 8 family of computers. The processor is prewired to accept the
following 1/0 bus options:
Extended Arithmetic Element (EAE), Type KE 12
Programmable Real-time Clocks, Type KW 12-A, B, or C
Incremental Plotter and Control, Type XY 12
TTY /Data phone®, Type DP 12-A, B
With the inclusion of the BAI 2 Peripheral Expander and the DW08A 1/0 and Bus Converter, many other devices
can be added to the PDP-12 1/0 bus. The Peripheral Expander allows the addition of high-speed paper tape reader
and punch, card reader, line printers, and optional communication interfaces. The Bus Converter provides for the
addition of disk and IBM-compatible magnetic tape storage and A/D converters and associated multiplexers
designed for the negative-logic PDP-8 1/0 Bus.
Keyboard/Printer (Model 33 ASR) - An important means of direct communication between the user and the
operating program is the Model 33 ASR Keyboard/Printer, standard on all configurations of the PDP-12. It is

connected to the I/O bus, and can be accessed for input or output by programs in either operating mode. The
Model 33 ASR is equipped with paper tape reader and punch; the reader and keyboard use the same input path and
instructions, while the printer and punch use the same output path and instructions. The maximum transfer rate in
either direction is 10 characters per second.
The Model 33 ASR operates in full-duplex mode, that is data may be transmitted in both directions
simultaneously.

1.2 SYMBOLS AND ABBREVIATIONS

The following symbols and abbreviations are used throughout this handbook:
AC, MB, PC, MQ, MA, L, IF, DF, IR

Central Processor registers: Accumulator, Memory Buffer,
Program Counter, Multiplier Quotient, Memory Address,
Link, Instruction Field, Data Field, Instruction Register.

General representation of any register.

C (R)

The contents of register R.
The content of bit j of register R.
The contents of bits j through n, inclusive, of register R.

® Dataphone is a registered trademark of A.T.&T.
1-6

The contents of the left half of register R.
The contents of the right half of register R.
C (R)

The one's complement of the contents of register R.

The effective address of an operand.

The Indirect address bit of an instruction. In the LINC
mode, I represents bit 7; in the 8 mode, bit 3.

C (R)-+C (S)

The contents of register R replace those of register S.

N-+C (R)

The quantity N replaces the contents of register R.

Inclusive OR
Exclusive OR

AND

1-7

CHAPTER 2
CONTROLS AND INDICATORS

This chapter describes the function of the controls and indicators of the PDP-12 computer console, Data Terminal,
Type VR12 CRT Display, Type TU55 LINCtape Transport, and Teletype Model 33 ASR.
2.1 PDP-12 CONSOLE CONTROLS AND INDICATORS
Tables 2-1 through 2-8 describe the controls and indicators located on the console of the PDP-12. Figure 2-1
provides a front view of the console.
2.2 DATA TERMINAL
The Data Terminal is the area behind the door on the left front of the PDP-12. Normally, up to four separate
panels are placed here. A storage rack to hold LINC tapes may be placed in any of the unused spaces of the Data
Terminal area. The four standard panels are:
I. Power Switch Panel
2. Relay and Analog Input Panel
3. Analog Extension Panel

4. Clock Input Panel
The first two are described in Tables 2-9 and 2-10 and illustrated in Figures 2-2 and 2-3; the last two are described
with the associated options (AG 12 and KWl 2-A).
2.3 CRT DISPLAY, TYPE VR12

Table 2-11 lists the controls and indicators ·of the Type VRl 2 CRT Display. Figure 2-4 shows a front view of ~he
CRT Display.
2.4 LINC TAPE TRANSPORT, TYPE TU55

Table 2-12 lists the functions of controls and indicators of the Type TU55 LINCtape transport. Figure 2-5 provides
a front view of the transport.
2.5 TELETYPE, MODEL 33 ASR
Table 2-13 lists the functions of controls of the Teletype, Model 33 ASR. Figure 2-6 provides a front view of the
teletype.

2-1

rJl

....
0

~
....
Q)

0..

-~
N

i:l.

2-2

Table 2-1. Central Processor Register Indicators
Indicator

Bits

Table 2-2. Central Processor Major State Indicators
Indicator

State

INST FIELD

Instruction Fetch

DATA FIELD

Deferred Address

RELAYS

Instruction Execution

INSTRUCTION REGISTER

Instruction Execution 2

PROGRAM COUNTER

INT

Program Interrupt

MEMORY ADDRESS

Word Count

MULTIPLIER QUOTIENT

Current Address

ACCUMULATOR

Break

LINK

Tape Break

MEMORY BUFFER

Table 2-3. Central Processor Miscellaneous Indicators

Indicators

Interpretation When Lit

SKIP

Skip Flip-Flop is set

FLO

Overflow Flip-Flop is set

8MODE

Processor is in the PDP-8 Mode

LINC MODE

Processor is in the LINC Mode

RUN

Processor is running

AUTO

Auto Restart Flip-Flop is set

TRAP

Trap flip-flop is set

INT PAUSE

An internal pause is occurring

ION

Program Interrupt facility enabled

I/O PAUSE

An 1/0 Pause is occurring

2-3

Table 2-4. Tape Processor Major State Indicators
Indicator

State

Idle

Block

Check Word

Turn Around

Table 2-5. Tape Processor Miscellaneous Indicators

Indicator

Interpretation

Function

In Progress

Indicates that a tape operation is In Progress.

Extended Address Mode

Indicates that the processor is in the Extended
Address mode.

No Pause Mode

Indicates that the processor is in the No Pause
mode.

Mark Flip-Flop

Indicates that the Mark Flip-Flop is set.

TAPE INST

3-bit Tape Instruction Register

These three lights indicate the contents of the 3-bit
Tape Instruction register.

2-4

Table 2-6. Function of Computer Console Keys

Key

Function

1/0 PRESET

This switch causes the processor to halt when it is in Internal Pause state
during a tape instruction, and sets processor mode to the state of the console
MODE switch. The Inst Field register is set to 2 and the Data Field register is
set to 3. 1/0 PRESET pulse and the 1/0 BUS INITIALIZE pulse clear all 1/0
device flags and operations. The AC and Link are cleared.

This switch causes the processor to perform one instruction. In the LINC
mode, the processor performs the instruction defined by the Left Switches
(and the Right Switches, if it is a double word instruction). In the 8 mode,
the processor performs the instruction defined by the Left Switches.

START 20

This switch causes the processor to start at location 20 of the currently
selected Instruction Field.

START 400

This switch causes the processor to start at location 400 of the currently
selected Instruction Field.

START LS

This switch causes the processor to start at the 15-bit address specified by
the Left Switches and the Instruction Field Switches.

CONT

This switch causes the processor to resume operation.

EXAM

The contents of the Left Switches are transferred into the Memory Address
register. The contents of the absolute core address designated by the Left
Switches are displayed in the Memory Buffer register.

STEP EXAM

This switch increments the contents of the Memory Address register and
displays the contents of this new address in the Memory Buffer register. This
incrementing extends over 10 bits in LINC mode and 12 bits in 8 mode.

FILL

The contents of the Left Switches are transferred into the Memory Address
register. The contents of the Right Switches are deposited into the memory
location whose absolute address is designated by the Left Switches and the
Instruction Field switches.

FILL STEP

Depressing this switch causes the contents of the Right Switches to be
deposited into the memory location whose address is in the Memory Address
register. Releasing this switch increments the contents of the Memory
Address register. This incrementing extends over 10 bits in the LINC mode
or 12 bits in the 8 mode. The Memory Buffer register then displays the
contents of the location specified by the new contents of the Memory
Address register.

MODE

This switch determines the mode (LINC or 8) to which the processor will be
set when the 1/0 PRESET switch is activated. The MODE switch is effective
only when the computer is not running.

2-5

Table 2-6. Function of Computer Console Keys (cont)

Key

Function

AUTO

This switch sets the AUTO RESTART flip-flop if it is held down at the same
time one of the following keys is actuated: STEP EXAM, FILL STEP, DO,
or CONT.
The AUTO RESTART flip-flop causes the central processor to start
automatically at the end of a variable time delay (determined by the console
controls) after the central processor stops for any of the following reasons:
a. SING STEP switch activated
b. FETCH STOP address match
c. EXEC STOP address match
d. The end of a STEP EXAM operation
e. The end of a FILL STEP operation
f. The end of a DO switch operation

The Auto Restart Flip-Flop is cleared by any of the following conditions:
a. STOP switch pressed while processor is running
b. DO, FILL STEP, or STEP EXAM switch activated and the AUTO
switch not pressed
c. A processor HLT instruction executed (either mode)
d. I/O PRESET pulse is generated
To start a program in AUTO RESTART mode:
a. Start the program with the SING STEP switch up.
With the AUTO key depressed, depress CONT.

2-6

Table 2-7. Toggle Switch Registers

Bits

Function

LEFT SWITCHES

These switches form a 12-bit word which can be
read into the accumulator with the LINC mode
instruction LSW (517). This word also specifies the
address to be examined when the EXAM switch is
used, the address in to which data will be placed
when the FILL switch is used, the stopping address
for EXEC STOP and FETCH STOP functions, and
the instruction to be performed when the DO
switch is used.

RIGHT SWITCHES

The contents of these switches form a 12-bit word
which can be read into the accumulator with the
LINC mode instruction RSW (516) or the 8 mode
instruction OSR (7 404 ). This word also provides
data to be stored in memory when the FILL or
FILL STEP switches are used. When the DO switch
is used, the Right Switches contain the second
word of two-word instructions.

INST FIELD

These are a high-order extension of the Left
Switches. They provide addressing information for
systems equipped with 8K or more of memory for
the EXAM, FILL, START LS, EXEC STOP, and
FETCH STOP functions.

SENSE SWITCHES

These switches are individually interrogated by
LINC mode skip instructions, thereby enabling
console control of program branching.

Table 2-8. Individual Console Toggle Switches

Switch

Function

STOP

This switch causes the processor to stop at the end of an instruction. For the
purposes of the STOP switch, Traps, Interrupt, Tape Break, and single-cycle
Data Break are considered to be single-cycle instructions. During a
three-cycle Data Break, the processor is stopped after the Break cycle.

SING STEP

This switch causes the RUN flip-flop to be cleared, thereby disabling the
timing circuits at the end of one cycle of operation. Thereafter, repeated
operation of the CONT switch steps the program one cycle at a time so that
the operator can observe the contents of registers in each major state.

FETCH STOP

This switch causes the processor to stop when the address designated by the
Left Switches matches the current address in the Memory Address register
during the Fetch cycle. For systems with more than 4K of memory, the Inst
Field switches designate the three most significant bits of the address.

2-7

Table 2-8. Individual Console Toggle Switches (cont)

Switch

Function

EXEC STOP

This switch causes the processor to stop when the address designated by the
Left Switches matches the current address in the Memory Address register
during any computer cycle except a Fetch cycle. For systems having more
than 4K of memory, the Inst Field switches designate the three most
significant bits of the address.

Figure 2-2. Analog Knobs and Power Switch Panel

2-8

Table 2-9. Analog Knobs and Power Switch Panel

Panel Controls

Function

OFF /ON/LOCK

This 3-position, key-locking switch is used to turn the PDP-12 on as well as
inhibit console intervention during an operating program. When fully
counterclockwise, the PDP-12 is off. When turned to the center position, the
PDP-12 is turned on and the console activated. When the switch is fully
clockwise, the PDP-12 is on, but console control functions are totally
inhibited while the PDP-12 RUN light is on. Only the Left Switches, Right
Switches, and Sense Switches remain operative.

SPEAKER VOLUME

The volume of the speaker is controlled by this knob. (The speaker, which is
driven by AC bit 0, is added to the system when the AD 12 is included in the
system configuration.)

AUTO RESTART DELAY

These two knobs control the delay period of Auto Restart after a processor
stop due to an EXEC STOP, FETCH STOP, or SING STEP operation. (See
AUTO switch description in Table 2-6.)

COARSE and FINE

ANALOG CHANNELS 0-7
(knobs)

The COARSE delay selects overlapping ranges from 2.4 µs to .38 sec. The
FINE control gives variation within a range of 20: 1 of the selected COARSE
delay.
These 10-turn potentiometers are connected to analog input channels 0-7 of
the AD 12 Analog-tcrDigital Converter. These knobs therefore provide eight
continually-variable parameters within the range of ±512 1 0 for program
usage.

Table 2-10. Relay and Analog Input Panel
Terminals

Function

ANALOG CHANNELS 10-1 7
(Input Jacks)

These are 3-conductor phone jacks providing± 1 Volt input connections for
AD 12 Analog-to-Digital converter channels 10 8 -17 8 .

RELAY REGISTER
Contacts

One set of form C contacts for each of the six system relays is available at
the binding posts.

EXTENSION SCOPE

A 24-pin connector for an extension scope provides for remote operations,
multiple displays, or photographing of display output. See Appendix G for
pin connections and drive characteristics.

2-9

Figure 2-3. Relay and Analog Input Panel

Figure 2-4. Type VR 12 CRT Display

2-10

Table 2-11. VR 12 Display Scope Controls

Control

Function

CHANNEL

Selects one or both channels for scope display.

BRIGHTNESS

Controls level of brightness.

X GAIN

Controls horizontal size of display.

X POS

Controls horizontal position of display.

Y GAIN

Controls vertical size of display.

Y POS

Controls vertical position of display.

Figure 2-5. TU55 Tape Transport Control Panel

2-11

Table 2-12. TU55 Tape Transport Controls and Indicators

Control or Indicator

Function

Forward Tape-motion Switch
(designated in Figure 2-5 by arrow
pointing to the left)

Provides forward tape motion (i.e., from right to
left) only if REMOTE/OFF /LOCAL switch is set
to LOCAL.

WRITE ENABLED/WRITE LOCK switch
WRITE ENABLED

Permits TCl 2 control system to write information
on the TU55.

WRITE LOCK

Prevents writing. If TC 12 control system is
commanded to write on tape while the WRITE
LOCK is set, the control signals a TAPE NOT OK.

WRITE ENABLED

Lights when WRITE ENABLE/WRITE LOCK
switch is in the WRITE ENABLE position.

Unit Selector

When this selector is dialed to one of the numerals
and the REMOTE/OFF /LOCAL switch is set to
REMOTE, the central processor may gain access to
the unit.

0
I
2
3
4
5
6
7
OFF LINE

When the selector is dialed to OFF LINE, the
transport cannot be selected by the tape control.
NOTE
Some earlier units were equipped with a unit
selector position 8, which is the same as unit
0.

REMOTE/OFF /LOCAL Switch

2-12

REMOTE

Permits tape processor to control the transport.

OFF

Removes power from reel motors and releases the
brakes. This permits the operator to change the
tape.

Table 2-12. TUSS Tape Transport Controls and Indicators (cont)

Control or Indicator

Function

LOCAL

Permits the forward and reverse tape-motion
switches to provide tape motion in direction of the
arrows. The transport cannot be selected.

REMOTE Indicator

Lights only when transport is selected by the tape
processor.

Reverse Tape-motion Switch
(designated in Figure 2-5 by arrow
pointing to the right)

Provides for motion in the reverse direction (i.e.,
from left to right), but only when REMOTE/OFF I
LOCAL switch is on LOCAL. If both reverse and
forward tape-motion switches are pressed simultaneously, reverse motion takes place.

Figure 2-6. Teletype Model 33 ASR

2-13

Table 2-13. Teletype Model 33 ASR Controls

Control

Function

Punch Controls
REL Pushbutton

Disengages the tape in the punch to allow removal
or loading.

B SP Pushbutton

Backspaces the tape in the punch one space,
allowing manual correction or rubout of the
character just punched.

ON and OFF Pushbuttons

ON engages the punch for operation under local or
program control. OFF removes the punch from
control.

Reader Control

2-14

ST ART /STOP /FREE

In the FREE (lowest) position, the tape feed wheel
is disengaged, and tape can be loaded or unloaded.
In the STOP (center) position, the wheel is engaged
but the reader cannot be operated. In the START
(highest) position, the reader can be operated
under local or program control.

LINE/OFF /LOCAL Switch

In the LINE position, the Teletype is energized and
connected as an 1/0 device to the computer. In the
OFF position, the Teletype is not energized. In the
LOCAL position, the Teletype is energized for
off-line operation, and signal connections to the
processor are disconnected. Both LINE and
LOCAL use of the Teletype require that the
computer OFF/ON/LOCK switch is ON.

CHAPTER 3
LINC MODE PROGRAMMING

3.1 ORGANIZATION OF MEMORY
3 .1.1 General

The LINC mode instruction set deals with two 1024 10 -word Memory Fields. The INSTRUCTION FIELD is the
1024 1 0 -word section of memory from which programs are executed, and in which data may be directly or
indirectly accessed. The DAT A FIELD is a second 1024 1 0 -word section of memory to which the LINC instruction
set allows only indirect reference for data manipulation and storage. The physical locations of the Data Field and
Instruction Field within the maximum 32,768 10 -word memory are specified by the contents of the 5-bit Data
Field Register and the 5-bit Instruction Field Register. These are set and modified under program control or from
the console; they need not be adjacent, or in any particular order, and can even be identical. With respect to a
LINC program, addresses within a Field remain constant, regardless of the actual location of the Field. Addresses
within the Instruction Field are 0000 through 1777 8 ; addresses within the Data Field are 2000 8 through 3777 8 .
Thus, no matter where they are assigned, the two fields may be considered logically contiguous.
The PDP-8 instruction set (described in Chapter 4) divides memory into 4096 1 0 -word Fields, which are specified
by the most significant 3 bits of the Instruction Field and Data Field Registers. Therefore, the term Field
designates a l 024 10 -word segment of memory in LINC mode, and a 4096 1 0 -word segment of memory in 8 mode.
In Figure 3-1, the division of the first 4096 1 0 words of memory is shown, assuming LINC mode, INST FIELD =
01, DATA FIELD= 03.

ABSOLUTE ADDRESS (OCTAL)
FIELD
LINC ADDRESS (OCTAL)

0000-1777

2000-3777

4000-5777

6000-7777

INST

DATA

0000-1777

2000-3777

, 2-0176

Figure 3-1. Assignment of LINC Addresses within Memory

3-1

3.1. 2 Program Counter

The Program Counter acts as a 10-bit counter in the LINC mode, so that executable programs can be stored only in
the Instruction Field. If the contents of PC 2 - 11 are incremented beyond 1777, they return to 0000; the two
high-order bits of the PC are unaffected. Thus, incrementing C(PC) = 3777 yields C(PC) = 2000. Likewise, 5777 is
incremented to 4000, and 7777 to 6000. This 10-bit indexing is very common in LINC mode operations.
3.1.3 Instruction and Data Field Registers

These two 5-bit registers select the 1K segments to be used by the LINC program. The three high-order bits of each
register are the three bits of the corresponding 8 mode Memory Field register. The contents of the IF and DF may
be set, changed, or examined at any time by the use of LINC instructions.
3.1.3. l Instruction Field Reserved Locations - This field contains the executable program. The following registers
are set aside in this field for special uses:

Field Address

Use

0000

Holds return address after execution of JMP.

0001

Holds horizontal coordinate during execution of
DSC.

0001-0017

As [3-registers, used by indirect-reference
instructions to hold the effective address of an
operand.

0000-0017

As a-registers, used by SET, XSK, and DIS.

0020

Program start location when Start 20 key is
pressed.

0400

Program start location when Start 400 key is
pressed.

When the instruction field is assigned to the lowest segment of memory (that is, when C(IF) = 00), the following
registers are also reserved:
Field Address

Use

0000
0001

PDP-8 Interrupt locations (Paragraph 4.4)

0040

Holds return address after a program interrupt
during LINC mode operation.

0041

Location to which control is transferred after a
program interrupt during LINC mode operation.

0140

Holds return address after an instruction trap.

0141

Location to which control is transferred after an
instruction trap.

3.1.3.1 Data Field Reserved Locations - There are no specially-reserved registers in this field. Its contents cannot
be accessed directly; data.can be stored or retrieved only by indirect addressing.

3-2

3.2 MEMORY ADDRESSING METHODS

3. 2.1 General
Almost every program, at some time during its execution, will need an item of data stored in memory. Such an
operand can be obtained only by specifying the address of the register in which it is stored or to be stored. An
instruction which requires a reference to memory can designate the desired location in two ways. It may include
the address of the operand as part of the instruction itself and directly address the location of the operand. Or, the
instruction may specify the address, not of the operand, but of a register containing the address of the operand,
thus indirectly addressing the data storage register.
The need for indirect addressing is readily apparent; with eleven bits required to specify a Data Field address, not
much is left of a 12-bit word to use for instruction codes. It is necessary to reduce the number of address bits
available within a memory reference instruction, and to use a limited set of directly addressable locations as
pointers containing the effective address of the desired data. The LINC instruction set provides for both types of
addressing.

3.2.2 Direct Addressing
In LINC programming, direct access to memory registers is limited to the Instruction Field. A full address in this
field requires ten bits (0000-1777), leaving only two bits for instruction codes. The three instructions, ADD, STC,
and JMP, are described in detail in Paragraph 3.3. The format of a direct-address instruction is shown in Figure 3-2.
Bits 0 and 1 are used for the operation code, bits 2-11 for the address.

OPERATION
CODE
ADDRESS
_ _J...___~~~~~~~~~~-A-~~~~~~~~~~
~--y
'\
4

Figure 3-2. Direct Address Instruction Format
3.2.3 Indirect Addressing: {3-Class
For access to registers in the Data Field, an indirect address is required. The instruction specifies one of a small set
of special registers which are used to hold the effective addresses of desired data. The format of these /3-class
instructions is shown in Figure 3-3. Bits 3-6 are available for operation codes; bits 8-11, together with bit 7,
determine which of four addressing schemes is to be used.

3-3

OPERATION
CODE
~~~--A-~~~-,

. "-y-)

Figure 3-3. {3-Class Instruction Format
3.2.3.1 .(3-Registers - In a .(3-class instruction, the contents of bits 8-11, when not zero, designate one of fifteen
registers at locations 0001-0017 of the Instruction Field. The contents of the specified .(3-register are used to
determine the effective address of the operand. When the contents of bits 8-11 are zero, the effective address is
found in the register which immediately follows the referencing instruction.
Bit 7, the I-Bit, determines the manner in which the register designated by bits 8-11 is to be used in locating the
operand. There are four addressing schemes, described in the following table.
Bit 7 (I)

Bits 8-11 (.(3)

The contents of bits 1-11 of the
immediately following the instruction.

The address of the register immediately following
the instruction. The operand itself is in this
register.

01-17

The contents of bits 1-11 of the designated
{3-register.

01-17

The contents, incremented by 1, of bits 1-11 of the
designated 13-register. Ten-bit indexing is used (see
text).

Effective Address
register

In the first scheme, the register which follows the referencing instruction contains the effective address. In the
second scheme, the operand itself is in that register. When either of these two schemes is used (that is, when the
contents of bits 8-11 are zero), the program counter automatically skips over the register immediately following the
instruction, and the next instruction is fetched from the second register following.
The following examples illustrate the use of all four addressing schemes.
The instruction STA (Store Accumulator) causes the contents of the AC to be stored in memory. The operation
code for STA is 1040. The register R is the one which immediately follows that containing the STA instruction.
(1) STA 0

3-4

Octal code: 1040
I=O, {3=00
Destination of C(AC):

C(R)=2345
Location 2345 (Location 345 in the Data Field)

Octal code: 1060
I=l, ,B=OO
Destination of C(AC):

(2) STA I 0

(3) STA 12

(4) STA I 12

Location R

Octal code: 1025
I=O, ,6=12
Destination of C(AC):

C(OOl 2)=3456

Octal code: 107 2
I=l, ,B=l 2
Destination of C(AC):

C(OOl 2)=3456

Location 3456 (Location 1456 in the Data Field)

Location 3457 (Location 1457 in the Data Field)
(The contents of ,B-register 0012 are incremented
by 1, and the result, 3457, is used as the effective
address.)

In the next example, the use of these addressing schemes in a program sequence is demonstrated. The instruction
ADA (Add to Accumulator) adds the operand to the contents of the AC, leaving the result in the AC. The program
sequence .~tarting at location l 000 adds the numbers N 1 , N2 , N3 , and N4 , leaving the sum in the AC.

ADDRESS

OCTAL

CONTENTS

REMARKS

0007

1500

/REPLACED BY 1501 AFTER INDEXING

*1000
1000

1100

ADA

/INDIRECT THROUGH 1001, ADD Nl to C(AC)

1001

1477

1477
ADA

/ADDRESS OF Nl

1002

1120

1003

3211

1004

1107

ADA 7

/INDIRECT THROUGH 7 TO 1500, ADDS N3

1005

1127

ADA I 7

/INDIRECT THROUGH 7, INDEXED, ADDS N4

1477

1234

NI,

1234

1500

1235

N3,

1235

1501

4321

N4,

4321

N2,

/DIRECT TO 1003; ADDS N2 TO C(AC)

3211

*1477

3.2.3.2 ,B-Register Indexing - When the ,B-indexing scheme is used (I= 1, ,B =I= 00), effective addresses may specify
registers in either memory field, but the ,B-register cannot be incremented from one field to the other. Indexing is
only over ten bits, as it is in the PC; the two high-order bits are unaffected. Thus, the contents of the ,B-register will
be incremented from 1777 to 0000, from 3 777 to 2000, from 5777 to 4000, and from 7777 to 6000. To change
access from one field to the other, it is necessary to change the contents of bit 1 of the ,B-register.

3-5

Bit 0 of the J3-register has no effect in most indirect references, but it does have a special use in half-word
operations, in multipiication, and in character display.
3.2.4 Addressing: a-Class
Three LINC mode instructions - SET, XSK, and DIS - have specialized memory reference schemes. Although each
of them accesses memory in a unique way, all make use of one of the registers in locations 0000 through 0017.
These are called a-registers, to differentiate between these instructions and those of the ,8-class.
SET and XSK are described in Section 3.3. DIS is described in Section 3.4.

3.3 LINC MODE INSTRUCTIONS
(Complete list is provided in Appendix A.)
3.3.1 Instruction Formats
There are three basic LINC mode instruction formats.

3.3.1.1 Direct Address (See Figure 3-2) - This class consists of the three instructions ADD, STC, and JMP.

3.3.1.2 Indirect Address, (3-class (See Figure 3-4) - This class consists of 15 (3-class instructions, with operation
codes between 1000 and 1740.

OPERATION
0

CODE
_ _ _ ___,A
_ _ _ __

r--- ~

(

\
4

Figure 3-4. (3-Class Format

3.3.1.3 a-class and Others (See Figure 3-5) - There are 16 basic instructions in this group, and they have operation
codes between 0000 and 0777. Each of these instructions has up to 32 variants, depending on the contents of bits
7-11.

ALL ZEROS

r_ _ _ _A_ _ _ _\

~
3

y
OPERATION
CODE

9
l

OPERATION
CODE, Q - REGISTER
OR FUNCTION DESIGNATORS

Figure 3-5. a-Class and Non-Memory Reference Format

3-6

3.3.2 Instruction Descriptions
The descriptions are organized according to function and class, as follows:
Full-word Data Transfers
Full-word Arithmetic
Full-word Logic
Full-word Comparison
Half-word Operations
a-class Operations
Program Control
Shift and Rotate
Skips
Miscellaneous
Console Switches
Mode Control Switch
1/0 Bus Enable
Memory Address Control
Program Interrupt
Special Functions

STC, LDA, STA
ADD,ADA,ADM,LAM,MUL
BCL, BSE, BCO
SAE, SRO
LDH, STH, SHD
SET,XSK
JMP
ROL, ROR, SCR
APO, AZE, LZE, QLZ, FLO, SNS,
SXL,KST,SKP,STD,TWC
HLT,CLR,COM,NOP,QAC
LSW, RSW
PDP
IOB
LIF, LDF, IOB/IOTs
IOB/IOTs, DJR
ESF, SFA

Instructions related to the Display, Data Terminal, and LINCtape are described in Sections 3.4, 3.5, and 3.6.
In general, the description of each instruction is presented in the following manner:

Mnemonic
Form
Octal code
Execution time
Operation

Operation Performed

The second line shows the general form of the instruction when used in a program. The octal code is that of the
instruction itself, plus the octal value of any other elements which may be present, such as the I-bit or '3-register
bits. (The I-bit, for example, being represented by bit 7, has an octal value of 20 when it is present.)

3.3.3 Full-Word Instructions

3.3.3. l Full-Word Data Transfers Accumulator and Memory.

STC

These three instructions move complete 12-bit words between the

Store and Clear (Direct Address)

Form:
Octal code:
Execution time:
Operation:

STC Y
4000+ y
3.2 µs
Store the contents of the AC in register Y, then clear the AC. This is a direct address
instruction; Y must be in the Instruction Field.

3-7

LDA

Load Accumulator ((3-Class)

Form:
Octal code:
Execution time:
Operation:
STA

LDA I (3
1000 + 20I + (3
4.8 µs; 3. 2µs. when I = 1 and {3 = 00
Place the contents of register Y, where Y is the address specified by I and C({3), in the AC. The
previous contents of the AC are lost; the contents of Y are unchanged.

Store Accumulator ((3-Class)

Form:
Octal code:
Execution time:
Operation:

STA I {3
1040 + 201 + (3
4.8 µs; 3. 2 µs. when I = 1 and {3 = 00
Store the contents of the AC in memory register Y, where Y is the address specified by I and
C({3). The previous contents of Y are lost; the contents of the AC are not changed.

3.3.3.2 Full-Word Arithmetic - The instructions ADD, ADA, and ADM use one's complement arithmetic. If, as a
result of an addition, a 1 is carried out of bit 0 of the sum, 1 is added to the sum. This end-around carry is the
defining property of a one's complement addition. If there is no carry, the sum is left as is.
Example 1:

Example 2:

2435
+1704
4341

no carry; sum is left as is.

2435
+5704 (-2073)

c1 ~4!

end-around carry; 1 added to sum.

0342
In either case, the Link is not affected.
The instruction LAM uses two's complement arithmetic. If a carry from bit 0 of the sum occurs, the Link is set to
1; the sum is left unaffected.

3.3.3.2.1 Overflow - In any LINC mode addition, a number is considered to be positive if its high-order bit (bit 0)
is 0, and negative if this sign bit is 1. Whenever two addends of like sign produce a sum of opposite sign, overflow is
said to occur. When this happens, the FLOW flip-flop is set to 1. If no overflow occurs, the FLOW flip-flop is set to
0. Overflow cannot, by definition, occur when the addends have unlike signs. Note that overflow and carry are not
the same thing.

3.3.3.2. 2 Instructions
ADD

Add to Accumulator (Direct Address)

Form:
Octal code:
Execution time:
Operation:

3-8

ADD Y
2000 + y
3.2 µs
The contents of register Y are added to the contents of the AC, using one's complement
addition; the sum is left in the AC. The previous C(AC) are lost; the Link and C(Y) are not
changed.

ADA

Add to Accumulator ({3-Class)

Form:
Octal code:
Execution time:
Operation:

ADA I {3
1100 + 201 + {3
4.8 µs; 3.2 µs. when I= 1 and {3 = 00
The contents of register Y, as specified by I and C(/3), are added to the contents of the AC,
using one's complement addition; the sum is left in the AC. The previous C(AC) are lost; the
Link and C(Y) are not changed.

ADM Add to Memory ({3-Class)

Form:
Octal code:
Execution time:
Operation:

ADM I {3
1140 + 201 + {3
4.8 µs; 3. 2 µ.s. when I = 1 and (3 = 00
The contents of register Y, as specified by I and C((3), are added to the contents of the AC,
using one's complement addition; the sum is left in both the AC and Y. The previous contents
of both registers are lost; the Link is not changed.

LAM Link Add to Memory ({3-Class)

Form:
Octal code:
Execution time:

LAM I {3
1200 + 201 + {3
4.8 µs; 3.2 µ.s. when I = 1 and (3 = 00
NOTE

This description presents the logical sequence of events; in practice, the operations
are carried out simultaneously.
Operation:

The contents of the Link are added to the contents of the AC, using two's complement
addition; the sum is left in the AC. If there is a carry out of bit 0, the Link is set to 1; if not,
the Link is cleared. Next, the contents of register Y, as specified by I and C((3), are added to
the new contents of the AC, again using two's complement addition; the sum is left in both the
AC and Y. If there is a carry from bit 0 this time, the Link is set to I; if not, the Link is
unchanged.

C(AC) = 3743

Example:
(1)

(2)

Results:

C(AC)
+C(L)

C(AC)

C(Y) = 6517

3743
1
3744

no carry; Link is cleared.

3744
+6517
1 2463

carry; Link is set to 1.

C(AC)
C(Y)
C(L)

C(L) = 1

2463
2463

3-9

MUL

Multiply ({3-Class)

Form:
Octal code:
Execution time:
Operation:

MUL I f3
1240 + 20I + f3
9.6 µs; 8 µs. when I= 1 and f3 = 00
The contents of the AC (multiplicand) are multiplied by the contents of register Y
(multiplier). The product is left in the AC and the MQ. The sign of the product appears in the
Link and AC 0 .

The multiplier and multiplicand are treated as 12-bit one's-complement numbers. If bit 0 of an operand is set to 1,
the operand is negative. The sign of the product is always correct; that is, operands of like sign give a positive
product, and operands of unlike sign give a negative product. Overflow cannot occur; the FLOW flip-flop is not
affected by multiplication.

Either integer or fractional operands may be specified, as follows: if bit 0 of the designated {3-register contains a 0,
the operands are treated as integers; the binary points of both multiplier and multiplicand are considered to be to
the right of bit 11. If C(f3 0 ) = 1, the operands are taken as fractions; the binary points are considered to be between
bit 0 (sign) and bit 1. Note that when I = 1 and f3 = 00, there is no effective address. In this case, integer
multiplication is performed.
When integer multiplication is performed, the low-order 11 bits of the product appear in AC 1 _11 and the absolute
value of the low order 11 bits of the product appears in MQ 0 _ 1 0 . The sign appears in AC 0 and the Link. The
high-order bits of the product are lost.
When fractional multiplication is performed, the high-order 11 bits of the product appear in AC 1 -i 1 and the
absolute value of the low-order bits appears in bits MQ 0 - 1 0 . The sign appears in AC 0 and the Link. The contents of
the MQ can be accessed by using the QAC instruction (see Paragraph 3.3.11 ).
Examples:
(1)

(all octal form)
Integers
(a.)

(b.)

(c.)

3-10

0432
x0006
00003234

C(AC)

C(Y)
product

2764
x0153
00476374
2764
x7624
77301403

(= -153)
(= -00476374)

C(AC)=3234

C(MQ)=6470

C(AC)=2374

C(MQ)==4770

C(AC)=5403

(= -3154)

C(MQ)=4770

(2)

Fractions
(a.)

(b.)

(c.)

0432
x0006
00003234

C(AC)
C(Y)
product

C(AC)=OOOO

C(MQ)=6470

2764
x0153
00476374

C(AC)
C(Y)
product

C(AC)=Ol 17

C(MQ)=4770

2764
x7624
77301403

C(AC)
C(Y)
(-00476374)

C(AC)=7660

C(MQ)=4770

3.3.4 Full-Word Logic
In each of these Boolean functions, the operation is performed between corresponding bits of the AC and the
operand, independent of the other bits in either word.
BCL

Bit Clear ({3-Class)

BCL I {3
1540 + 201 + {3
4.8 µs; 3.2 µs. when I= 1 and {3 = 00
For each bit of the operand that is a 1, the corresponding bit of the AC is cleared to 0. For
each operand bit that is a 0, the corresponding AC bit is unchanged. The operand is not
changed. The following truth table gives the relationship between the corresponding bits, with
the results of the comparison.

Form:
Octal code:
Execution time:
Operation:

0~01
C(Yj)

I 0

The Boolean statement of this relation is AC A Y.

Example

ESE

C(AC)=2307
C(Y) =1616
Result:=2 l 0 I

010011000111
001110001110
010001000001

Bit Set ({3-Class)

Form:
Octal code:
Execution time:
Operation:

BSE I {3
1600 + 201 + {3
4.8 µs; 3. 2 µs. when I = 1 and {3 = 00
For each bit of the operand that is a 1, the corresponding bit of the AC is set to 1. For each
operand bit that is 0, the corresponding AC bit is not changed. The operand is not affected.
The truth table for this relation, which is the familiar inclusive OR, is as follows:

3-11

The Boolean statement of this relation is AC VY.
Example

C(AC)=2307

010011000111
001110001110
011111001111

C(Y) =1616

Result:=3717
BCO

Bit Complement ((3-Class)

Form:
Octal code:
Execution time:
Operation:

BCO I (3
1640 + 201 + (3
4.8 µs; 3.2 µ.s. when I= 1 and (3 = 00
For each bit of the operan_d that is a 1, the corresponding bit of the AC is complemented. For
each operand bit that is 0, the corresponding AC bit is unchanged. The operand is not changed.
The truth table for this relation, which is the exclusive OR, is as follows:

The Boolean statement of this relation is AC¥-Y.
Example

C(AC)=2307
C(Y) =1616
Result:=35 I I

010011000111
001110001110
011101001001

3.3.5 Full-Word Comparison
In both of these operations, the next succeeding memory location in the program sequence is skipped if the stated
condition is met. When (3 =I= 00, this presents no unusual circumstance. When (3 = 00, however, the memory location
immediately following the skip instruction contains either the operand itself or its address. When such is the case,
this location is automatically skipped, and the one beyond that is considered to be the next location in the program
sequence. If a skip occurs under these conditions, the program will proceed from the third location following the
skip instruction.
SAE

Skip If Accumulator Equal To Operand ((3-Class)

Form:
Octal code:
Execution time:
Operation:

3-12

SAE I {3
1440 + 201 + (3
4.8 µs; 3.2 µs. when I= 1 and (3 = 00
If the· contents of the Accumulator are equal to the contents of Y (where Y is specified by I
and {3), the next instruction in the program sequence is skipped. Otherwise, the program
continues without skipping. The contents of the AC and of Y are not changed.

Skip and Rotate (~-Class)

SRO

Fann:
Octal code:
Execution time:
Operation:

SRO I {3
1500 + 201 + (3
4.8 µs; 3.2 µs. when I= 1 and {3 = 00
If bit 11 of the operand is 0, the contents of Y (that is, the operand) are rotated right one
place and the next sequential instruction is skipped. Otherwise, the program proceeds without
skipping.

Example:
ADDRESS

OCTAL

0020
0021
0022
0023

1520
3725
0016
0016

P,
Pl,
P2,
P3,

CONTENTS
*20
SRO I 0
3725
NOP
NOP

REMARKS
/THE OPERAND IS IN REG 21
/OPERAND BIT 11=1, SO NO SKIP
/PROGRAM CONTINUES FROM HERE

After the test is performed, the contents of Pl are rotated right one place; the result, which is retained in Pl, is
5752. If the instruction in register P were then to be executed again, the skip would occur, because the new
contents of bit 11 of Pl equal 0. The program would then proceed from register P3, skipping the instruction in P2.
3.3.6 Half-Word Operations
3.3.6.1 Half-Word Addressing - The three instructions, LDH, STH, and SHD, operate on either half of a memory
register, independent of the other half. The addressing scheme is basically that of other (3-class instructions, with
the following difference: whenever bit 0 of the register containing the effective address holds a 0, the left half of
the addressed operand is used; when bit 0 contains a 1, the right half is used. In either case, the data is transferred
or compared between the designated half of the operand and the right half of the AC.
The following examples demonstrate the effects of half-word addressing. The instruction LDH transfers the
designated half of the operand into the right half of the AC; the left half of the AC is cleared.
a. LDH 0
I = 0, (3 = 00. C(R) = 0370. (R is the register following LDH). The effective address is 0370.
Because C(Ro) = 0, the contents of the left half of register 0370 are placed in the right half of the AC, and the left
half of the AC is cleared.
b. LDH 12
I = 0, {3 = 12, C(OO 12) = 43 70. Bit 0 of {3-register 12 contains a 1 ; therefore, the contents of the
right half of register 03 70 are placed in the right half of the AC, and the left half of the AC is cleared.
c. LDH I 0
I = I, {3 = 00. C(R) = 6527. This is a direct reference, so that there is no explicit effective
address. In this case, the left half of the operand in register R is taken. In the example, the quantity 65 is placed in
the right half of the AC, and the left half of the AC is cleared.
d. LDH I 12

I= 1, {3 = 12. C(0012) = 0370.

The effective address (that is, C(0012)) must be incremented before it is used. Instead of 1, however, 4000 is added
to the contents of the {3-register (remember that the half-word indicator is in bit 0). Given the conditions specified
above, the contents of {3-register 12 are first augmented from 0370 to 4370, and the right half of the operand in
register 0370 is taken. If a second LDH I 12 is then executed, the {3-register is again incremented by 4000. The sum,
which leaves C({3 0 )=O, results in a carry out of the high-order bit. The carry causes 1 to be added to the sum,
resulting in a final effective address of 0371. The new operand is then taken from the left half of the new register.
The indexing sequence is thus: left half, right half, left half of the next succeeding register, etc.
Because the basic indexing scheme is operative only over bits 2-11 of the {3-register, half-word addressing proceeds
from the right half of register 1777 to the left half of register 0000, and from the right half of register 3777 to the
left half of register 2000. C({3) are thus incremented from 1777 to 5777 to 0000, and from 3777 to r/77 to 2000.

3-13

NOTE
Another way of looking at the half-word indicator may help clarify this method of
addressing. If the indicator is considered to be just to the right of bit 11, rather than
in bit 0, it becomes apparent that half-word indexing is just like full-word indexing,
with 1 added to the low-order bit (that is, the half-word indicator) each time. You
can, if you like, imagine a binary point between the half-word indicator and bit 11
of the ,B-register, so that successive addresses might be read as 0370, 0370 1/2, 0371,
0371 1/2, 0372, etc. (Or, in octal, 0370.0, 0370.4, 0371.0, 0371.4, 0372.0, etc.)
LDH

Load Half

Form:
Octal code:
Execution time:
Operation:

STH

Store Half

Form:
Octal code:
Execution time:
Operation:

SHD

LDH I ,B
1300 + 201 + ,B
4.8 µs; 3.2 µs when I= 1 and ,B = 00
The contents of the designated half of register Y (where Y is specified by I and C(jJ)) are
placed in the right half of the Accumulator. The left half of the AC is cleared. The previous
C(AC) are lost. The contents of Y are not changed.

STH I ,B
1340 + 201 + ,B
4.8 µs; 3.2 µs when I= 1 and ,B = 00
The contents of the right half of the Accumulator are stored in the designated half of register
Y. The contents of the AC and of the other half of Y are not disturbed.

Skip If Half Differs

Form:
Octal code:
Execution time:
Operation:

SHD I ,B
1409 + 201 + ,B
4.8 µs; 3.2 µs when I= 1 and ,B ~ 00
If the contents of the designf}ted half of register Y are not equal to the contents of the right
half of the AC, the next instruction in the program sequence is skipped; otherwise, the
program proceeds without skipping. The contents of Y and of the AC are not changed. As in
the other ,B-class skips (SAE, SRO), the register immediately following the SHD is
automatically passed over when (3 = 00.

3.3. 7 a-Class Operations
Each of these instructions uses the registers 0000-0017 in a unique way. A third a-class instruction, DIS, is
described in Paragraph 3.4, CRT Display.
SET

Set a-Register

Form:
Octal code:
Execution time:
Operation:

SET I a
0040 + 201 +a
6.4 µs; 4.8 us when I = 1
The contents of the a-register specified by bits 8-11 of the SET instruction are replaced by the
operand, whose location is determined by the state of the I-bit, as follows:
If I = 1, the operand is in the register immediately following that containing the SET
instruction.

3-14

If I = 0, the effective address of the operand is in the register immediately following that
containing the SET instruction.
SET always requires two successive locations; the program always continues from the second
register following, as in this example:
Address

Contents

SET I 15
2537

p+l
p+2

Action
/THE OPERAND IS IN REGISTER p+ 1
/OPERAND 2537 IS STORED IN REGISTER 15
/PROGRAM CONTINUES FROM THIS REGISTER

The previous contents of the a-register are lost. The AC is not disturbed, and the contents of the register containing
the operand are not changed.

XSK

Index and Skip

Form:
Octal code:
Execution time:

XSK I a
0200 + 201 +a
3.2 µs

Operation:

If I = 1, the contents of the designated a-register are incremented by 1, using 10-bit two's
complement addition as in ~class indexing. If I = 0, a is left undisturbed. Then if the contents
of bits 2-11 of the a-register are equal to 1777, the next instruction in the program sequence is
skipped. Otherwise, the skip does not occur.

When C(a) are incremented, the two high-order bits are not affected. Thus, 1777 is incremented to 0000, 3777 to
2000, etc.
3. 3. 8 Program Control

IMP Jump
Form:
Octal code:
Execution time:
Operation:

JMP y
6000+Y
3.2 µs when Y -=I= 0000; 1.6 µs when Y = 0000
The quantity Y is placed in PC 2 _1 i , and the next instruction is taken from register Y. The
program proceeds from that point.

If Y -=I= 0000, the 10-bit address of the register immediately following the JMP instruction (i.e., the contents of the
Program Counter) is stored in location 0000 of the Instruction Field as a JMP instruction. This permits the JMP to
be used not only as an unconditional transfer of program control, but also as a subroutine calling instruction. If Y =
0000, the jump is executed, but nothing is stored in register 0000. JMP 0 is used to return from a subroutine, as
shown in the example.

3-15

Example
ADDRESS

OCTAL

0000

0001

0000

0175
0176
0177

0016
0000
0000

0242
0243
0244

6000
0000
0000

0572
0573
0574
0575

CONTENTS

0000,

6175
0017
0000
0000

*0000
0000

*0175
NOP

REMARKS

/WILL CONTAIN 6573 AFTER JMP 175 IS
/EXECUTED

/START OF LINEAR SUBROUTINE WHICH
/CONTAINS NO JMP INSTRUCTIONS

*0242
JMP 0

/RETURN FROM SUBROUTINE

*0572
JMP 175
NOP

/JUMP TO SUBROUTINE AT REGISTER 0175
/SUBROUTINE RETURNS TO THIS LOCATION

When JMP 175 is executed, C(PC 2 - 11 ) = 0573. This, combined with 6000 (the octal code for JMP), is placed in
register 0000. When the subroutine has finished, JMP 0 transfers program control to register 0000, where JMP 573
is executed, returning control to the calling program. (At the same time, JMP 1 is stored in register 0000, but that
is incidental to the actions of interest here.)
When a new Instruction Field has been selected (see paragraph 3.3.14. Memory Address Control), the first JMP Y
(Y =/:= 0000) following the field selection performs the actual switching of the field; the target register of the JMP is
in the new field, and the return jump is stored in register 0000 of the new Instruction Field. JMP 0 has no effect on
the field registers.
3.3.9 Shift and Rotate Operations
These instructions rotate the contents of the Accumulator left or right, or shift them right (scaling), propagating
the sign bit. A single instruction can cause a shift of up to 17 8 bit positions, or 1-1 /2 times the length of the AC.
On shifts or rotations right, the MQ is treated as a 12-bit extension of the AC, so that bits shifted out of AC 11
enter MQ 0 , as shown in Figures 3-7 and 3-8. In all these operations, the Link is included when I = 1 and excluded
when I= 0. Execution times depend on the number of positions shifted.

ROL

Rotate Left

Form:
Octal code:
Execution time:
Operation:

3-16

ROLIN
0240 + 20I + N, 0 ~ N -s;;;; 17 8
1.6 - 6.4 µs
The contents of the AC are rotated left N places. If I = 1, the Link is included. The rotation
scheme is shown in Figure 3-6. The contents of the MQ are not affected.

I= 1

Figure 3.6. Rotate Left

ROR

Rotate Right

Form:
Octal code:
Execution time:
Operation:

ROR I N
0300 + 20I + N, 0 < N < 17 8
1.6 - 6.4 µs
The contents of the AC are shifted right N places. Bits shifted out of AC 11 enter MQ 0 , and are
shifted down the MQ. Bits shifted out of MQ 11 are lost. If I = 1, the Link is included in the
rotation. The scheme is shown in Figure 3-7.

I=O
L

D
LOST

LOST

12-0116

Figure 3-7. Rotate Right

3-17

SCR

Scale Right

Form:
Octal code:
Exe cu ti on time:
Operation:

SCR I N
0340 + 201 + N, 0 ~ N ~ 17 8
1.6 - 6.4 µs
The contents of the AC are shifted right N places. The sign bit (contents of AC 0 ) is not
changed, and is placed in the N bits to the right of AC 0 . Bits shifted out of AC 11 enter MQ 0 ,
and are shifted down the MQ. Bits shifted out of MQ 11 are lost. If I= 1, bits shifted out of
AC 11 also enter the Link, so that, at the completion of the operation, C(L) = C(MQ 0 ). If I= 0,
the Link is unaffected. The shifting scheme is shown in Figure 3-8.

Example:

C(AC) = 4371

C(MQ) = 0000

Instruction:

SCR I 6

Because I = 1, the Link will receive the contents of AC 11 at each
shift. The result of the operation:
C(AC) = 7743

The sign bit, which was 1, is loaded in
the vacated bits (AC 1 _6 )

C(MQ) = 7100

Bits shifted out of the AC entered the
MQ at the high-order end.

C(L) =I

The last bit shifted out of AC 1 1 was a
1. Check: C(L) = C(MQ 0 ).

I=O
L

D
LOST

I =1

LOST

Figure 3-8. Scale Right

3-18

3.3.10 Skips
These instructions test the states of various registers, flip-flops, and external inputs. In every case, the next
succeeding instruction in the program sequence is skipped if
(1)

I = 0 and the condition is met

or
(2)

I = 1 and the condition is not met

Otherwise, the program proceeds without skipping.
The skip instructions (with the exception of the unconditional skip instruction, SKP) have an associated "skip
condition", such as a register being cleared or one of the external digital inputs ("external levels") being asserted. If
the skip condition is met (e.g., the register is cleared or the external level is asserted) at the time the instruction is
executed, a skip occurs. This means that the next instruction is taken from the second location following the skip
instruction, rather than from the usual location. Normally, the skip instruction is followed by a single-word
instruction that is skipped or executed according to whether or not the tested condition was met. No distinction is
made between single- and double-word instructions; if the skip instruction were followed by a double-word
instruction, control would be transferred to the second word of the instruction if a skip occurs. Generally skip
instructions should not be followed by double-word instructions. In the skip instructions discussed here, (but not
in the "addressable" skips: SHD, SAE, and SRO), the i bit inverts the sense of the skip. That is, if the i bit is zero,
the instruction skips only if the skip condition is met. If the i bit is a one, the skip occurs only if the condition is
not met.

APO

Accumulator Positive

Form:
Octal code:
Execution time:
Condition:

AZE

Accumulator Zero

Form:
Octal code:
Execution time:
Condition:

LZE

AZE I
0450 + 201
1.6 µs
The contents of the AC equal 0000 (+0) or 7777 (-0).

Link Zero

Form:
Octal code:
Execution time:
Condition:

QLZ

APO I
0451+201
1.6 µs
The sign bit (contents of AC 0 ) is 0, that is, C(AC) is a positive number.

LZE I
0452 + 201
1.6 µs
The contents of the Link equal 0.

MQ Low-Order Bit Zero

Form:
Octal code:
Execution time:
Condition:

QLZ I
0455 + 201
1.6 µs
The contents of MQ 11 equal 0. (This is identical to the LINC-8 instruction, ZZZ.)

3-19

FLO

Overflow

Form:
Octal code:
Execution time:
Condition:

SKP

FLO I
0454 + 201
1.6 µs
The FLOW flip-flop is set to 1. When overflow occurs as the result of an addition (ADD, ADA,
ADM, or LAM), the FLOW flip-flop is set to 1. If overflow does not occur as a result of the
above instructions, the FLOW flip-flop is cleared.

Skip Unconditionally

Form:
Octal code:
Execution time:
Condition:

SKP I
0456 + 201
1.6 µs
The next instruction is skipped unconditionally. (In LINC-8 and early PDP-12 assembly
programs SKP was defined as 466.)

The following skips test for various external input conditions.

IBZ

LINCtape Inter-Block Zone

Form:
Octal code:
Execution time:
Condition:

SNS

0453 + 201
1.6 µs
If the selected LINCtap> unit is in one of the inter-block zones and the tape is moving, the
next instruction is skipped. This instruction will sense an IBZ only if the tape is in motion (i.e.,
only after a tape instruction with "I = 1").

Sense Switch

Form:
Octal code:
Execution time:
Condition:

SXL

IBZ I

SNS I N
0440 + 201 + N, 0 < N < 5
1.6 µs
Sense Switch N on the Operator's Console is set to 1. If I= 1, the skip will occur when the
selected switch is set to 0.

Skip On External Level

Form:
Octal code:
Execution time:
Condition:

SXL I N
0400 + 201 + N, 0 < N < 17 8
1.6 µs
An external input level is +3v. If I= 1, the skip will occur when the external level is at ground
(OV). In the basic PDP-12, only three of these levels have been defined; the others are available
for the user's options. When nothing is connected to the External Level Lines, they are
preloaded to +3V. These external levels are digital inputs to the 1/0 bus, and should not be
confused with the analog inputs to the A-D Converter.
NOTE

The connection for the External Level lines is made via the 1/0 Bus cables (see
Chapter 5).

3-20

The three defined levels and their mnemonics are:
SXL
SXL
SXL
KST

I
I
I

15 (KST)
16 (STD)
17 (TWC)

Key Struck (See below)
Tape Instruction Done (See Paragraph 3.6.9)
Tape Word Complete (See Paragraph 3.6.14)

Key Struck

Form:
Octal code:
Execution time:
Condition:

KST I
0415 + 201
1.6 µs
A key has been struck on the ASR-33 keyboard, the character code has been assembled in the
Teletype buffer, and the Keyboard flag is raised. (The flag is cleared when the character is read
into the AC.)

3.3.11 Miscellaneous
These instructions perform various tasks. All are self-contained and require no memory references.

HLT

Halt

Octal code:
Execution time:
Operation:

CLR

Clear

Octal code:
Execution time:
Operation:
COM

0017
1.6 µs
The contents of the AC are complemented. Bits containing Os are changed to contain 1s, and
vice versa. No other registers are affected.

No Operation

Octal code:
Execution time:
Operation:
QAC

0011
1.6 µs
The AC, MQ, and Link are cleared to zero. No other registers or flip-flops are affected.

Complement AC

Octal code:
Execution time:
Operation:
NOP

0000
1. 6 µs to fetch and decode
The computer stops. The contents of the AC, MQ, Link, and other active registers and
flip-flops are not affected. The Program Counter contains the address of the register
immediately following the HLT. If the operator presses CONTINUE, the program resumes
from the point indicated by the C(PC).

0016
1.6 µs
None. Nothing happens. NOP provides a 1.6-µs delay, and is often used to hold a place in the
program for instructions which might be changed or added during the course of execution.

Place MQ in AC

Octal code:
Execution time:
Operation:

0005
1.6 µs
The contents of MQ 0 _1 0 are placed in AC 1 - 11 • AC 0 is cleared. This instruction provides access
to the low-order bits of a fractional product. Figure 3-9 shows the transfer path.

3-21

SET TO
ZERO

Figure 3-9. QAC Transfer Path
To obtain all 12 bits of the MQ, the following program sequence may be used:
INSTRUCTION

OCTAL CODE

REMARKS

* 0020
0005
0241
0475
6026
1620
0001

QAC
ROL I
QLZ
JMP .+3
BSE I
0001

/C(MQ0-10) PLACED IN ACI-11
/ROT ATE C(AC) LEFT 1 PLACE, WITHOUT LINK.
/SKIP IF C(MQl 1) = 1
/C(MQl 1) = 0. JUMP TO THIRD REGISTER BEYOND.
/C(MQl 1) = 1. SET ACl l EQUAL TO 1.
/OPERAND TO SET ACl l

(QAC is identical to the LINC-8 instruction, ZTA.)

3.3.12 Console Switches
These instructions provide access to the states of the switches in the Left and Right Switch Registers on the
Operator's Console. The I-bit has no effect in these instructions.

LSW

Left Switches

Octal code:
Execution time:
Operation:

RSW

0517
1.6 µs
The contents of the Left Switches Register on the Console are placed in the AC. The previous
C(AC) are lost.

Right Switches

Octal code:
Execution time:
Operation:

0516
1.6 µs
The contents of the Right Switches Register are placed in the AC. The previous C(AC) are lost.

3.3.13 Mode Control

PDP

Switch To The 8 Mode

Octal code:
Execution time:
Operation:

3-22

0002
1.6 µs
Beginning with the next succeeding instruction, the central processor will operate in the 8
mode; all subsequent instructions are interpreted as PDP-8 operations. A similar instruction,
LINC ( 6141 ), in the PDP-8 mode instruction set, causes a switch to LINC mode.

3.3.14 Input/Output Bus
In addition to the input and output devices controlled directly by LINC instructions (see Paragraphs 3.4, 3.5, and
3 .6), the LINC mode program also has direct access to any device connected to the PDP-12 I/O Bus. By using the
special two-word enabling instruction, IOB, any 8 mode IOT instructions can be included within a LINC program
sequence.

JOB

1/0 Bus Enable

Form:
Octal code:
Execution time:
Operation:

IOB (first word) IOT (second word)
0500 (first word)
5.9 µs
The IOT timing chain is activated by the second word of this instruction. Bits 3-11 of this
second word are interpreted as a PDP-8 IOT command; bits ~2 have no effect.

Example 1:
The following sequence may be used to read and store a character from the high-speed tape reader:

IOB
RRB
STA 14

/ENABLE I/O BUS
/READ TAPE READER BUFFER
/STORE IN REGISTER SPECIFIED BY C(0014)

Example 2:
The following sequence waits for the high-speed reader flag and then reads the character buffer
OCTAL CODE

INSTRUCTION

REMARKS

0500
6011
6020
0500
6016

*0020
IOB
RSF
JMP .-2
IOB
RRB

/ENABLE I/O BUS
/SKIP IF HIGH-SPEED READER FLAG IS SET
/NOT SET. GO BACK TWO SPACES
/FLAG IS SET. ENABLE THE BUS, AND ...
/READ THE CHARACTER

Note that, in the skip loop, the program must jump back two locations, because the IOB must be executed each time.

Several IOB/IOT pairs are used in LINC Memory Address Control and Program Interrupt operations.

3-23

3.3.15 Memory Address Control
The two memory Fields used by a LINC program are program-selectable. The assignments are made by setting the
two 5-bit Memory Field Registers, which can address any of 32 1024-word memory segments. Considered with
respect to the physical configuration of memory, the three high-order bits of each Field Register determine which
4096-word memory bank is to be used, while the two low-order bits specify one of the four segments within that
bank. The two LINC memory Fields need not be adjacent, or in any particular order. Normally, however, they
would not be assigned to the same segment.
In addition to the Instruction Field (IF) and Data Field (DF) Registers described in Chapter 1, the PDP-12 Memory
Control contains two other registers of interest to the LINC mode programmer.
3.3.15.1 Instruction Field Buffer (IB) 5 Bits - This register holds the number specifying a new Instruction Field.
Once loaded, its contents are transferred to the IF at the occurrence of the next JMP Y instruction.
3.3.15.2 Save Field Register (SF) 10 Bits - Whenever the Instruction Field is changed, either by programmed
action or by a program interrupt or trap, the contents of the IF and DF are placed in the Save Field Register. From
the SF, the Contents of the IF and DF can be restored, so that execution of an interrupted program, for example
may be resumed. The contents of the SF may be read into the AC. (See also the Program Interrupt discussion in
Paragraph 3.3.15.4.) For historical reasons the SF is also called Interrupt Buffer in some places.

3.3.15.3 Memory Control Programming - The Instruction Field and Data Field registers can be loaded directly,
using LINC mode instructions.

LIF

Load LINC Instruction Field Buffer

Form:
Octal code:
Execution time:
Operation:

LIF N
0600 + N, 0 ~ N ~ 37 8
1.6 µs
The five-bit quantity N is placed in the Instruction Field Buffer (IB). The present contents of
the IF and DF are transferred to the Save Field Register (SF). When the next JMP Y
instruction (Y =I= 0000) is executed, N is transferred from the IB to the Instruction Field
Register. The return JMP is stored in location 0000 of the new Instruction Field, and program
control is transferred to register Y of the new Instruction Field.
The automatic saving of the IF and DF in the Save Field Register is especially useful when
subroutines are called across memory fields; that is, when a called subroutine is located in a
memory field other than the current one. The subroutine may pick up the field information
needed in obtaining arguments and generating subroutine returns by interrogating the Save
Field Register.
The execution of the LIF instruction will internally inhibit the execution of a Program
Interrupt even if ION has been given. This Interrupt Inhibit lasts from the LIF instruction until
the first LINC mode JMP instruction is fetched and executed in the newly selected Instruction
Field. This allows the Save Field Register to be used for cross field subroutine linkage in
programming which uses the Program Interrupt.

Because LINK Instruction Trap (see Paragraph 3.3.17) also uses the Save Field Register for program linkage, an instruction which will be trapped must not be given between an LIF and the next JMP Y (Y f= 0000) if the cross field
reference will ultimately need the Save Field Register linkage information.

3-24

Example:

The program is operating in Field 2. Control is to be transferred to location 1000 of Field 5.
Address

Action

LIF 5

p+k

JMP 1000

Contents

/ 5 IS PLACED IN THE IB
/C(IF) AND C(DF) ARE PLACED IN THE SF

/C(IB) ARE TRANSFERRED TO THE
/IF. JMP P + K + 1 IS STORED IN REGISTER
/0000 OF FIELD 5, AND THE PROGRAM
/PROCEEDS FROM REGISTER 1000 OF FIELD 5

JMP 0 has no effect on the Memory Field registers. If it is used to return to a calling program in a different field,
the change of field is effected by the JMP instruction stored in register 0000 of the subroutine's field.
(LIF replaces the LINC-8 instruction, LMB)

LDF

Load LINC Data Field Register

Form:
Octal code:
Execution time:
Operation:

LDF N
0640 + N, 0 ~ N ~ 37 8
1.6 µs
The 5-bit quantity N is placed in the Data Field Register. All subsequent indirect references to
the Data Field are made to the newly selected field. The previous C(DF) are lost. The contents
of the other Memory Control registers are not affected.

(LDF is identical to the LINC-8 instruction, UMB)
The contents of the Memory Field Registers can be examined by using the following IOB/IOT pairs.

JOB
RIF

.Q..ead Instruction Field

Octal code:
Execution time:
Operation:

0500
6224
5.9 µs
The contents of the Instruction Field Register are ORed into bits AC 6 _1 0 . The remaining AC
bits are unaffected, and the contents of the IF are unchanged.

NOTE
When executed in LINC mode, the three IOT instructions, RIF, RDF, and RIB, are
the only cases where an IOT has a slightly different function than when executed in
8 mode. For these instructions, all five bits of the IF and/or DF are read into the AC
when in LINC mode, while only the most significant three bits of each are used in 8
mode.

3-25

IOB
RDF

Read Data Field

Octal code:

0500
6214
5.9 µs
The contents of the Data Field Register are ORed into bits AC 6 _ 1 0 . The remaining AC bits are
unaffected, and the contents of the DF are not changed.

Execution time:
Operation:

3.3.15.4 Program Interrupt In LINC Mode - To facilitate the handling of data being transmitted to and from
several peripheral devices, the PDP-12 includes a Program Interrupt Facility. When an external device is ready for
servicing, a signal (flag) associated with that device is set. With Interrupt enabled, the following sequence of events
will occur when a flag is set:
1. The instruction being executed at the time of the interrupt request is completed.
2. The contents of the Program Counter are stored in register 0040 of memory field 0 (regardless of the
current Instruction Field assignment).
3. The contents of the Memory Field registers are placed in the Interrupt Buffer (Save Field Register).
4. Program execution proceeds from register 0041 of Memory Field 0.
The normal procedure from this point calls for the interrupt service routine beginning in location 0041 to
determine which device flag caused the interrupt request, perform the appropriate tasks, restore the Memory Field
registers, re-enable the interrupt, and jump back to the interrupted program at the point where the Program
Interrupt occurred.
Whenever a change of LINC Instruction Field occurs, the Program Interrupt is inhibited (between Steps 1 and 2
above) until the first JMP is executed in the new field. This allows the programmer to obtain and save the contents
of the SF after the Field change, before a waiting interrupt request destroys the contents of the SF.
The interrupt control instructions and related memory field instructions are all IOB/IOT pairs.
JOB

ION

Interrupt On

Octal code:
Execution time:
Operation:

0500
6001
5.9 µs
The Interrupt Facility is enabled immediately after the next succeeding instruction (following
the ION) is executed. From that point on, any interrupt request will cause the sequence of
events described above. If a device flag is already raised when the Interrupt is enabled, the
waiting request is serviced immediately. The one-instruction delay before enabling the
interrupt ensures that the interrupt service routine can return to an interrupted program before
a new request is honored without losing its place.

JOB

!OF Interrupt Off
Octal code:
Execution time:
Operation:

3-26

0500
6002
5.9 µs
The Interrupt is disabled. The facility is disabled immediately; subsequent requests will not
cause an interrupt until the facility is enabled again.

The next two instructions are related to the Save Field Register, wherein the original contents of the IF and DF are
stored whenever the contents of the IF are being changed, by an LIF instruction, or as the result of an Interrupt
request or a Program Trap.
INST. FIELD
BUFFER

4 - - JMP AFTER LIF

DATA FIELD

- - - INTERRUPT, TRAP, LI F

ACCUMULATOR
12-0118

Figure 3-10. Data Path: IB, IF, DF, and AC

JOB
RIB

Read Interrupt Buffer

Octal code:
Execution time:
Operation:

0500
6234
5.9 µ.s
The contents of the Interrupt Buffer (Save Field Register) are ORed into bits AC 0 - 1 and
AC 4 - 11 , as shown in Figure 3-10. AC 2 - 3 and the contents of the SF are unchanged.
RIB is most commonly used immediately after a change of instruction field or a program trap,
to save the record of the origin fields while the Program Interrupt is inhibited. (If inhibit were
not provided, a waiting interrupt request could destroy the contents of the Save Field Register.
The first JMP instruction executed after a trap or change of Instruction Field reenables the
Interrupt.)

JOB
RMF

Restore Memory Fields

Octal code:

0500

Execution time:
Operation:

5.9 µs, including IOB
The contents of SF 5 - 9 are placed in the Data Field Register, and the contents of SF o-4 are
placed in the Instruction Field Buffer. At the next occurrence of a JMP Y instruction (Y =I=
0000), the contents of the IB are transferred to the IF, effecting a return to the proper field
after servicing an interrupt request. The data transfer path is shown in Figure 3-11.

624~

3-27

INSTRUCTION FIELD

I I

DATA FIELD REGISTER

(JMPY)

(RMF)

I I
2

SAVE FIELD REGISTER

Figure 3-11. Data Path, RMF Instruction
DJR

Disable JMP Return

Octal code:
Execution time:
Operation:

0006
1.6 µs
DJR sets a flip-flop, preventing contents of location 0000 from being changed when the next
and only the next LINC mode JMP is given. The DJR instruction is used when returning from
Program Interrupt or Trap service routines. The DJR should be given prior to the ION
instructions. This is useful because an interrupt can occur within a LINC mode subroutine that
uses Location 0000 of its IF to retain the subroutine return; hence, it must not be destroyed.

Example:

A program operating in Field 7 is interrupted while the instruction in register 0531 is being executed.
( 1) C(PC) are stored in location 0040 of Field 0.

(2) C(DF) and C(IF) are placed in the SF, as shown in Figure 3-10.

(3) Program execution resumes in location 0041 of Field O; in other words, 00 is placed in the IF, and 0041
in PC 2 - 11 •
( 4) The interrupt is disabled.
The interrupt service routine must do three things. First, it sets up a return jump enabling the program to get back
to the point of the break. Next, it identifies the cause of the request and services the condition. Finally, it restores
the conditions prevailing at the time the interrupt occurred and returns to the main program. The following
sequence shows how these tasks may be accomplished.

3-28

ADDRESS OCTAL

CONTENTS

0040
0041
0042
0043

0532
4000
2040
1620

*0040
0532
STC ACSAV
ADD 0040
BSE I

0044
0045

6000
4071

6000
STC RTN

0046

0000

0047
0050
0051
0052
0053
0054
0055
0056
0057
0060

0000
0000
0000
0016
0016
0016
0016
0000
0000
0500

/CONTENTS OF PC AT TIME OF INTERRUPT
/SAVE C(AC), THEN CLEAR AC
/SAVED ADDRESS (0532) TO AC
/MAKE JMP INSTRUCTION: C(AC)
/V C(0044)
/OCTAL CODE OF JMP INST.
/STORE JMP 532 AT END OF SERVICE
/ROUTINE
/MAIN PART OF SERVICE ROUTINE, IF
/NECESSARY
/OTHER ACTIVE REGISTERS (MQ,L,ETC)
/SHOULD BE SAVED ALSO

NOP
NOP
NOP
NOP

/THE REST OF THE ROUTINE

0061

6244

0062
0063
0064
0065
0066

4076
2000
0006
0000
0000

0067
0070
0071
0072
0073
0074
0075
0076

0500
6001
6532
0000
0000
0000
0000
0000

REMARKS

IOB

/EXIT SEQUENCE, ENABLE IOT TIMING
/CHAIN
RMF
/ ... AND RESTORE MEMORY FIELDS,
/(07 TO IB)
STC TEMP
/CLEAR AC WITHOUT DISTURBING MQ AND L
ADDACSAV /RESTORE ORIGINAL C(AC)
DJR
/SET PROCESSOR SO THAT NEXT JMP INST
/WILL NOT STORE IN LOCATION ZERO OF
/MEMORY BANK TO WHICH JMP AT "RTN"
/WILL GO
IOB
ION
/RE-ENABLE INTERRUPT
JMP 0532
/JMP TO ORIGINAL FIELD

RTN,

TEMP,
RMF=6244
ION=6000

0000

3.3.16 Special Functions
A set of six Special Functions allows the LINC programmer to establish any of five operating states, or generate an
1/0 PRESET pulse. The special functions are determined by AC 2 - 7 , as shown in Figure 3-12.

I I I I
1

INSTRUCTION
TRAP

I I }
7

1/0 PRESET
PULSE
DISABLE
TELETYPE
INTERRUPT

TAPE
TRAP

FAST
SAMPLE

CHARACTER
SIZE

Figure 3-12. Special Functions

3-29

These functions have the following characteristics:
1. Instruction Trap Enable - Causes an immediate program interrupt to register 0141 when an undefined
LINC instruction code is encountered.
The instruction trap is described in detail in Paragraph 3.3.17.
2. Tape Trap - When this function and Instruction Trap Enable are both set, a program interrupt to register
0141 will occur whenever a LINCtape instruction or one of the other trapped codes is encountered. The LINCtape
instruction is not executed. Tape Trap is described in detail in Paragraph 3.6.13.
3. Character Size - This function determines the size of a character displayed on the CRT by the DSC
instruction. It is described in detail in Paragraph 3.4.1.
4. Fast Sample - This function reverses the order of events of the SAM instruction; i.e., read the converter
buffer and initiate a new conversion, then continue without pausing (see Paragraph 3.5.1 ).
5. Disable Teletype lnterrnpt - Interrupt requests from the ASR-33 Keyboard or Printer are inhibited. No
program interrupt will occur when either TTY flag is set even if the Interrupt Facility is enabled (see Chapter 6).
6. Generate 1/0 Preset - If this bit is set when the enabling instruction (ESF) is executed, an I/O PRESET
pulse is generated clearing all device flags, disabling the Interrupt, clearing the Tape Extended Operations Buffer,
and generating the TAPE PRESET pulse. Other Special Functions are cleared, or in the case of CHARACTER
SIZE, set to full size. The active registers of the Central Processor are not affected, and the system continues to
operate with RUN on. Any or all of these functions may be enabled at the same time, except that they are
effectively nullified if I/O PRESET is given. All the Special Functions except I/O PRESET are controlled by
flip-flops set from the designated AC bits; the states of these flip-flops may be examined at any time.

ESF

Enable Special Functions

Octal code:
Execution time:
Operation:

SFA

0004
1.6 µs
The contents of AC 2 - 6 are placed in their respective flip-flops, as shown in Figure 3-12. For
each AC bit set to 1, the corresponding function is enabled. For each AC bit set to 0, the
corresponding function is disabled. If AC 7 is set to 1, the I/O PRESET pulse is generated. All
Special Function bits are cleared (except ESF 04, Full Size Character, which is set to a 1) by
I/O PRESET, either from the console or program control.

Place Special Function Flip-Flops in AC

Octal code:
0024
Execution time: 1.6 µs
Operation:
The contents of the Special Function flip-flops are placed in their respectively designated AC
bits, as shown in Figure 3-12. AC 0 - 1 and 7 - 1 1 are cleared.
3.3.17

Instruction Trap

Several sets of operation codes in the LINC repertoire are undefined. The LINC programmer can make use of these
codes without having to hard-wire them, by means of subroutines and the Instruction Trap. When the Trap is
enabled (ESF with C(AC 2 ) = I), any undefined LINC codes will cause a program trap. When the undefined code is
encountered, program control is transferred to register 0141 of Memory Field 0, regardless of the current setting of
the IF. The contents of the Program Counter are placed in register 140, and the contents of the IF and DF are
placed in the Save Field Register. The subroutine beginning at 0141 can examine the trapped code (using the
information stored in 0140 and the SF) to determine what program-defined operations are to be performed. (Also,
see Paragraphs 3.3.15.3 and 3.3.15.4 for interaction with Program Interrupt.
These are the undefined LINC codes which cause a program trap:
Operate class
Execute class
Undefined
Undefined

3-30

501-515, 521-535
740-747
540-577
1700-1737

The LINC codes 1700-1737 are considered as j3-class instructions. Therefore, when either a 1700 or 1720
instruction is encountered, the address contained in location 140 is the address of the trapped instruction
incremented twice (trapped instruction address +2). All other undefined codes will cause location 140 to contain
the address of the trapped instruction incremented once (trapped instruction + 1).
Probably the most common use of the Instruction Trap is in the execution of programs written for the LINC-8. A
LINC-8 Trap Simulator is provided in the basic PDP-12 software package. Close study of this program will be most
helpful for the programmer wishing to use the Trap facility. The Trap facility is further useful for developing
device-independent software.
3.3.17. l Tape Trap - When both the Tape Trap and Instruction Trap functions are enabled, the LINCtape
instructions (codes 700-737) are trapped also. This is useful if the programmer wishes to substitute another
external storage device, such as a Disk, for the LINCtape.
3.3.17.2 Program Interrupt and Instruction Trap - If the interrupt is enabled when an Instruction Trap occurs, the
interrupt is inhibited until the execution of the first JMP after the trap. This permits the trap program to store the
contents of the Save Field Register immediately after the trap, so that the record of where the trap took place is
not destroyed by an interrupt request, which also causes the contents of the IF and DF to be placed in the SF (also
see Paragraphs 3.3.15.3 and 3.3.15.4).
3.4 CRT DISPLAY, TYPE VR 12
The 6.5 inch x 9 inch rectangular screen of the PDP-12 CRT Display Type VR12 has a total display area of 58.5
square inches. Grid dimensions are 512 x 512 points. The horizontal distance between points is 0.0176 inches; the
vertical distance is 0.0127 inches. The (0,0) grid point is at the midpoint of the left side of the screen, as shown in
the schematic representation in Figure 3-13. Grid co-ordinates are given in octal.

o,+377 - - - - - - - 111, +377

0,0

1----------11 777,0

0,-377 - - - - - - - 777,-377

Figure 3-13. CRT Grid

The display system is fully buffered. Coordinates are held in two 9-bit buffers; during the execution of DSC, the
pattern word is retained in a 12-bit Pattern Intensification Register. Either of two multiplexed intensification
channels can be specified. A switch on the VR 12 front panel allows either or both channels to be displayed.

Below the channel selector is a variable knob which allows the user to change the intensity of the displayed points.
A level control located within the VRl 2 presets the maximum brightness level, preventing spot burns.
A 24-contact connector on the Data Terminal Panel allows the user to connect an auxiliary scope (VR-l 2A CRT
Display, Tektronix 561, or similar unit) for remote display of the same information sent to the main screen. The
channel selectors can be independently set so that each scope displays one of the channels, thus allowing
independent simultaneous displays on two scopes.
A complete set of connection points for the VC12/VR12 display system is shown in Appendix G.

3-31

The output drive capability of the D-A converters is Ov to -5.85v capable of driving a load resistance of 1 kQ
connected to ground. This allows up to 200 feet of cable for a remote VR-12. The absolute values of the D-A
outputs are not held closer than ±0.3v but are stable to within 3.0%. The D-A converters are loaded by jam
transfer. The D-A used to drive the scope is also available as a single-ended output to drive external devices. The Ov
D-A point is equivalent to the lower left hand corner of the display screen.
The LINC display instructions allow the programmer to display single grid points or a small array of points. In
either case, the full buffering allows the program to proceed after the display operation has been initiated. If a
subsequent display instruction is encountered before the previous display operation has been completed, the
program will pause until the display control is free, then execute the new instruction.
3.4.1 Point Displays
DIS

Display (a-Class)
DIS I a

Form:
Octal code:
Execution time:

0140 +a, 0 ~a~ 17 8
3.2 µs; 23 µs for completion of display
A single point on the screen is intensified. The vertical coordinate is specified by AC 3 _1 1 ; the
horizontal coordinate by bits 3-11 of the designated a-register. If bit 0 of the a-register is set to
0, the point will be displayed on Channel O; if C(a 0 ) = I, the point will be displayed on
Channel 1.
If I = 0, the contents of a are taken as is. If I = 1, C(a) are first incremented by I, using 10-bit,

two's complement addition. Bits 0 and I are not affected.

3.4.2 Character Displays
DSC

Display Character ({J-Class)

Form:
Octal code:
Execution time:
Operation:

DSC I f3
1740 + 201 + {3, f3 ~ 2 ~ 17 8
4.8 µs when I= 1, f3 = 00; 6.4 µs when I= 0 or {3=t 00 Control completion time 20-56 µs.
A vertical 2 x 6 array of points is displayed according to a pattern word stored in register Y (Y
is defined as with other ~-class instructions). For each bit of the pattern that is a 1, the
corresponding point is intensified; for each bit that is a 0, the corresponding point is left dark.
In Figure 3-14, the circles represent the points of array; the small numbers refer to the
corresponding bit positions of the pattern word. The small arrows show the order in which the
pattern bits are examined and displayed. As with DIS, the vertical coordinate is held in the
Accumulator. The horizontal coordinate is held in register 0001; for this reason, register 0001
cannot be used as a 13-register with DSC. The character may be displayed in either of two sizes:
full size, in which the spacing between points in both directions is four grid positions, and
half-size, in which the spacing is two positions. The following description assumes full-size
characters.
When a DSC instruction is executed, the following events occur:
( 1) The intensification pattern is transferred from Y to the display control Intensification
Buffer.
(2) The contents of AC 3 - 6 are placed in the display control Y-buffer; AC 7 - 11 are set to 30 8 •
The contents of register 0001, the X-coordinate, are incremented by 108 , and transferred to
the display control X-buffer.

3-32

The foregoing operations take 4.8 or 6.4 µs to do their work, after which the central processor
is free to resume program execution. The remaining operations are performed by the display
control.
(3) The pattern word is examined in the order shown in Figure 3-14. The time required to scan
and display the points varies according to the number of points to be intensified. Reaching the
first point requires 20 µs, then 1 µs for each point to be left dark and 3 µs for each point to be
displayed. This action continues until all points are intensified.
Because of the manner in which the Y-coordinate is used, full-size character arrays may start
only at coordinates which are multiples of 40s; e.g., 000, 040, 100, -100. Since the array itself
is only 30s points high, this gives the programmer an automatic vertical spacing of 1Os points
between the bottom of one line and the top of the one immediately below it.

,.,
•, ~'

X+I09 {FULL SIZE)
X+ 49 (HALF SIZE)

I
2·0030

Figure 3-14. Display Pattern for DSC
3.4.3 Half-Size Characters
If the programmer clears the CHARACTER SIZE bit of the Special Function Register [ESF with C(AC 4 ) = 0), all
increments are by two grid positions, rather than four. AC 3 _7 provides the initial Y coordinate; after the two
coordinates have been transferred to the display control's buffers, the contents of AC 8 - 11 will be 14s, and the X
coordinate in register 0001 will be incremented by 4 instead of by I Os. Vertical spacing is likewise halved; arrays
may start at intervals of 20 8 points, with 4 points between lines. I/O PRESET sets this bit of the Special Function
Register to a 1 (full-size characters).

3 .4 .4 Character Set
Any character that can be represented on a 4 x 6 grid (24 points) can be displayed by using two DSC instructions,
with two consecutive storage words providing the complete 24-bit character pattern. Table 3-1 lists the display
patterns for the ASR-33 character set. Nondisplayed characters have patterns of all zeros. The table entries, each
consisting of two words, are arranged in order of ASCII codes.

3-33

Table 3-1. ASR-33 Character Set Display Pattern
External
ASCII

Internal
Code

Character

Pattern
Words

External
ASCII

Internal
Code

Character

Pattern
Words

245

274

246

275

211

TAB

276

250

(

277

251

)

301

252

302

253

303

254

304

255

305

256

306

257

307

260

310

261

311

262

312

263

313

264

314

265

315

266

316

267

317

270

320

271

321

272

322

273

3114
0643
5166
0526
0000
0000
3600
0041
4100
0036
2050
0050
0404
0437
0500
0006
0404
0404
0001
0000
0601
4030
4136
3641
2101
0177
4523
2151
4122
2651
2414
0477
5172
0651
1506
4225
4443
6050
5126
2651
5122
3651
2200
0000
4601
0000

323

0412
2100
1212
1212
0021
1204
4020
2055
4477
7744
5177
2651
4136
2241
4177
3641
4577
4145
4477
4044
4136
2645
1077
7710
7741
0041
4142
4076
1077
4324
0177
0301
3077
7730
3077
7706
4177
7741
4477
3044
4276
0376
4477
3146
5121
4651

3-34

'
-

Table 3-1. ASR-33 Character Set Display Pattern (cont)

External
ASCII

Internal
Code

Character

Pattern
Words

External
ASCII

Internal
Code

324

335

325

326

327

4040
4077
0177
7701
0176
7402
0677
7701
1463
6314
0770
7007
4543
6151
4177
0000
0204
1020

330

331

332

333

[

334

Character

Pattern
Words

]

336

212

LINE
FEED

0000
7741
0000
0000
0000
0000

240

SPACE

241

242,

215

RETURN

244

0000
0000
7500
0000
7000
0070
0000
0000
4731
4275

3.5 DATA TERMINAL

The Data Terminal provides analog inputs and relay-controlled outputs for use by LINC mode programs. The
facility includes the following:
Analog Inputs
Relays
Auxiliary Scope Connector

Six teen channels
Six relays for external equipment control
24-pin connector for an auxiliary CRT

3.5.1 Analog Inputs

The AD 12 Analog-Digital Converter and Multiplexer consists of 16 input channels, a Sample and Hold, a
multiplexer, and a 10-bit A-D converter. Eight of the channels are for external inputs via phone jacks. These feed
through preamplifiers to the multiplexer. The acceptable voltage range of these inputs is± lv with a sensitivity of
approximately 2 mv/count.
The other eight channels are controlled by continuously variable knobs mounted on the Data Terminal. The knobs
give ten turns stop-to-stop however, 7 turns provide the full 10-bit range to the converter (1-1/2 to 2 turns from
each extreme is beyond the A-D range of -777 8 to +777 8 ). The knobs can be used to control speeds (as in the
continuous display of data from tape), set threshold levels or other test parameters, etc.
A single LINC mode instruction selects the input channel, initiates the conversion, and transfers the contents of the
buffer into the AC.

3-35

SAM

Sample

Form:
Octal code:
Execution time:
Operation:

SAM N
0100 + N, 0 ~ N ~ 17 8 (Basic system); 0 ~ N ~ 37 8 (extended system)
18.2 µs (Normal mode); 1.6 µs (Fast sample mode)
Input channel N is selected. In normal mode, the voltage level present at the input is sampled
and converted to a 10-bit number (including sign), which is assembled in the converter buffer.
When the conversion is complete, the contents of the buffer are transferred into AC 3 - 11 • 'The
sign is placed in AC 0 - 2 •
When the FAST SAMPLE Special Function is selected [ESF with C(AC 5 ) = 1], the order of
events is reversed. The current contents of the converter buffer are transferred to the AC. Then
the specified channel is selected and a new conversion is initiated. The results of this new
conversion can be read by a subsequent SAM instruction, unless the KW 12-A Real Time
Interface is selected to mode 4, 5, 6, or 7; in this case only, the KWl 2-A may initiate the
A-D conversion. If a conversion is still in progress when the next SAM is encountered, the processor waits until the conversion is complete before executing the new SAM.

3.5.2 Relays
Six DPDT relays mounted on the Data Terminal can be switched by LINC mode instructions, allowing the user to
control the operation of various pieces of external equipment that are not interfaced directly with the PDP-12. The
states of the relays can be examined at any time. One set of form C contacts for each of the relays is available at
the binding posts on the Analog Input Panel as indicated in Figure 3-15. A second set of contacts is brought out to
split lugs on the relay printed circuit board.

N.C.

N.O.

RELAY

... I ..

0
0

COM

AC BIT

12-0209

Figure 3-15. Relay Terminals and Corresponding AC Bits

3-36

ATR

AC to Relays

Octal code:
Execution time:
Operation:

0014
1.6 µs
The contents of AC 6 • 1 1 are transferred to the Relay Buffer; the state of each relay is
determined as follows:
If the corresponding AC bit is 0, the relay is switched off.
If the corresponding AC bit is 1, the relay is switched on.

RTA

Relays to AC

Octal code:
Execution time:
Operation:

0015
1.6 µs
The contents of the Relay Buffer are transferred into AC 6 - 1 1 . If the relay is off, the
corresponding bit will be O; if it is on, the bit will be 1. Bits AC 0 • 5 are not changed.

3.6 LINCTAPE TYPE TC12
The basic LINCtape system consists of either two DECtape Transports Type TUSS or one DECtape Transport Type
TU56 controlled by a fully buffered subprocessor. A single ten-channel tape head serves for both reading and
writing. Information is redundantly recorded; one line of tape contains five bits, each recorded in two non-adjacent
channels, as shown in Figure 3-16. Three bits are actual data; the other two provide control information for the
tape processor. The Timing track determines the position of each recorded line. Four lines are required to
accommodate a full 12-bit word; the corresponding Mark Track code identifies the nature of the data word. The
recording technique and tape layout are described in detail in the PDP-12 Maintenance Manual.

3.6. l Organization of Data
On a standard-format LINCtape, information is recorded in blocks of 256 12-bit words each, with identifying data
at each end of the block. One reel of Standard format LINCtape has a capacity of 512 blocks, for a total of
131,072 1 0 words of data. (In other formats, this capacity may be extended to 225 ,000 1 0 words.)
The organization of a tape is schematically presented in Figure 3-16. At each end of the tape is a long End Zone
which allows the transport to reverse direction or come to rest without pulling the tape off the reel. Between the
end zones and the terminal blocks, and between blocks, are Interblock Zones which can be sensed by the LINC
instruction IBZ. An interblock zone is 5 words long.
Figure 3-l 6B represents a typical block of 256 data words preceded and followed by control and identifying
information. The serial bit sequence on the Mark Track, is decoded so that the control can determine whether the
adjacent data bits form true data, checksum words, guard words, etc. The symbols BM, CM, GM, etc. (defined
below), refer to these Mark Track bit patterns.

3-37

w
00

532 10 BLOCKS

r
A. FULL
TAPE

~~m1-1 11rrJ
LEADER
(BLANK)

END
ZONE

INTERBLOCK
ZONE

20009

77779

END
MARKS

INTERBLOCK
MARKS
INTERBLOCK
ZONE

IM(5)

.............

GUARD
/WORD

'-y-1

FORWARD
BLOCK NUMBER

..............

109

40009

INTER BLOCK
MARKS

END
MARKS

--......

............

..............

CM CM

·-

256 DATA WORDS

REVERSE
BLOCK NUMBER
,..-....,
.........

4
8
0
4

.........

TIMING TRACK

m
m
m
m -r---.---.,.-----,,.--m--m--m---tf
0

'--v-1

IM (5)

"-v-1J

R
B

---v---.

DATA CHANNEL 1
DATA CHANNEL 2
DATA CHANNEL 3
DATA CHANNEL 1
DATA CHANNEL 2
DATA CHANNEL 3

TRAILER
(BLANK)

............

I
I
I FM
I
I

--......

,,.

C.1 WORD

--......

CHECKSUM
WORD

DATA (3778 DM)

END
ZONE

'-----y----1'-----y-----J

............

ZONE

BN 0-7779

~/~
8. 1 BLOCK

I BN IINTERBLOCK

5~~ USEABLE
BLOCKS
............

'-----y-----J'---y---..J

10131014

1
5
9

MARK TRACK

3
7

6
10

m
t

m ( MARK TRACK
+

TIMING TRACK

TAPE DIRECTION FWD - - - 12-0107

Figure 3-16. Standard LINCtape Format

A block consists of 256 data words preceded and followed by control and identifying information, as shown in the
second drawing in Figure 3-16.
Block Number
(BM)

This identifies the block. On a standard LINCtape, block numbers are
sequential, from 0000 through 0777 8 •

Guard Word

This protects the Block Number from transients when the read/write current
is turned on and off, and allows time for the tape processor to switch from
Search to Read or Write modes.

(GM)

Data Words
(DM,FM)

This is the information recorded on tape from core memory. The final Data
Word is specially identified, to signal the end of the block. When writing a
tape, this signal conditions the tape processor to write the checksum in the
next word position.

Checksum

This is the two's complement of the 12-bit sum of all the data words in the
block plus the constant 7777 8 • The result of adding the data sum to the
checksum should be 0000; this provides a check (hence the name) on the
accuracy of the transfer.

(CM)

Check Words
(CM)

Reverse Block Number
(RBM)

These are dummy words whose Mark Track code is the same as that for the
Checksum. They are provided to insure that the Write current will be turned
off before the Reverse Block Number is encountered. The Guard and Check
words are not of general interest to the programmer except as they affect
timing.
This is the Block Number that identifies the block when tape is being
searched in the reverse direction.

Su bprocessor
The LINCtape processor controls all information transfers between memory and tape. It is fully buffered; once an
operation has been initiated by a LINC mode instruction, it is carried to completion by the tape processor. The
central processor may either wait until the tape transfer is complete, or proceed immediately after the tape
instruction has been initiated, testing at some later time for completion of the operation.
Transfers are effected in either Standard or Extended modes. In Standard mode, transfers are made to and from
fixed memory locations. Extended Operations provide for a flexible addressing facility, program interrupt, and
additional tape units.
As can be seen in Figure 3-17, the tape subprocessor contains seven registers which provide the transmission path
for data and for control information.

Data Path
Read/Write Buffer (RWE), 12-Bits - When reading, the four lines of a data word are assembled in this register, in
the bit positions shown in the third drawing of Figure 3-16. When writing, the contents of the RWB are
disassembled and written on four consecutive lines of tape. Essentially, the RWB is a three-section shift register,
with the three bits of a tape line entering (or leaving) the register at four-bit intervals, as indicated by the arrows in

Figure 3-17.

3-39

SEARCH ONLY
TBN

12 bits

TMA

12 bits

SHIFT
REGISTER

12 bits

ADDER
WRITE
TMA

SETUP

XOB

READ/SEARCH

12 bits

READ/
WRITE

TB+TAC

12 bits

TAC

12 bits

LINCtape
PROCESSOR

AC
CENTRAL
PROCESSOR

>TAPE DATA

_ _ __,_..CONTROL INFORMATION ( 12 BITS)
12-0105

Figure 3-17. LINCtape Processor Information Paths

Tape Buffer (TB), 12 Bits - When reading, the assembled word is transferred from the RWB to the TB, and from
there sent to the MB in the central processor. When writing, the direction is reversed; information from the MB
enters the TB, and from there is placed in the RWB for disassembly onto the tape.
Tape Accumulator (TAC), 12 Bits - As each data word is read or written, the data sum is accumulated in the TAC.
When reading, this sum is added to the Checksum read from tape, to determine whether the transfer was completed
accurately. When writing, the data sum is complemented when the final data word signal is received, and the
resulting Checksum is written in the word position following the final data word. The contents of the TAC can be
brought into the central processor AC, using the Linc mode TAC instruction. In searching operations. the TAC also
holds the sum of the desired block number and the last block number read from tape.
Control Registers
In Standard mode operations, these registers are automatically set up; in Extended Operations, the program must
set the XOB and TMA Setup Register.

3-40

Tape Block Number (TBN), 12 Bits - This contains the number of the block to be accessed in a data transfer. As
the tape is searched, the Block Number read from tape is compared with that in the TBN; when the numbers
match, the tape is positioned so that the transfer can begin. During group operations, the TBN contains the number
of the first block to be accessed.
Tape Memory Address (TMA), 12 Bits - This contains the address of the memory location to or from which the
data is being transferred. In extended address mode, TMA is loaded from the TMA Setup Register at the beginning
of a tape instruction; in Standard mode, the MBLK and TBLK information in the second tape instruction word are
used to determine the initial contents of TMA. The TMA is incremented by I for each data word transferred.
TMA Setup Register, 12 Bits - In Extended Address mode, the register retains the first memory address of the data
to be transferred. If the transfer is not successful, the contents of TMA Setup are placed in the TMA, and the
operation is repeated. The TMA Setup Register is loaded from the AC, using the TMA instruction.
Extended Operations Buffer ( XOB) 12 Bits - The contents of this register determine which of the various
extended tape operations are in effect. These include extended memory addressing, tape interrupt, the no-pause
condition, hold motion, and extended units.

3.6.2 Programming

The tape transfer operations are the same for both Standard and Extended Operation modes. Data may be read or
written in single blocks or groups of contiguous blocks (in the extended address mode, only single blocks are
transferred), with or without error-checking. Step-by-step searches can be performed, and block numbers can be
identified without reading or writing data.
All LINCtape instructions require two words. The first word specifies the operation to be performed, one of two
tape units, and the motion of tape at the end of the operation. The second word gives the tape block number and
in Standard mode also gives the memory block number. The structure of the two words is shown in Figure 3-18.

FIRST WORD

1 2 1 3

I I I I I I
4

INSTRUCTION CODE

MOTION

I I I
0

j 10

I ,, I

t t '- OPER~TION

LUNIT

BLOCK NUMBER (EXTENDED ADDRESSING}

MUST BE =O

SECONOWORO

MEMORY BLOCK
NUMBER
(MBLK)

TAPE BLOCK NUMBER (TBLK)

12-0119

Figure 3-18. LINCtape Instruction Format

3-41

First Word

The general instruction code for the LINCtape class is 0700. The particular
operation to be performed is specified by bits 9-11 of the first word. In the
basic system, one of the two TU55 units is selected by bit 8. If this bit is 0,
the unit dialed to 0 is selected; if this bit is a 1, unit 1 is chosen. Bit 7 (the
I-bit) is used to determine the state of the unit's motion when the operation
is completed. See Paragraph 3.6.3 below.

Second Word

In Standard Addressing, bits 3-11 of the second word specify the number of
the tape block to be accessed. Bits 0-2 specify one of four blocks of a LINC
Memory Field to or from which data is to be transferred. These memory
blocks are assigned to specific addresses in each field. There are four blocks
in each LINC field, each being 256 words (1 tape block) long. The blocks are
assigned as follows:

Memory
Block Number
(MBLK)
0

1
2
3
4
5
6
7

LINC
Memory Field

LINC
Field Addresses

Instruction Field
Instruction Field
Instruction Field
Instruction Field

0000-0377
0400-0777
1000-1377
1400-1777

Data Field
Data Field
Data Field
Data Field

2000-2377
2400-2777
3000-3377
3400-3777

In Standard Mode addressing, the contents of a tape block and a memory block correspond exactly. All
single-block transfers are effected between the tape block and the memory block specified by the second word of
the tape instruction. In group transfers, where several contiguous blocks are transferred, the second word is
interpreted in a slightly different way. (See description of RCG and WCG instructions in Paragraph 3.6.4.) The two
non-transfer instructions, MTB and CHK, use the second word in still different ways.

3.6.3 Tape Motion
Tape is read or written in the forward direction. It may be searched in either the forward or backward direction.
Bit 7 of the first word of a LINCtape instruction determines the motion of the tape when a LINCtape operation
has been completed.
If bit 7 (the I-bit) is set to a 1, the tape is left moving in the direction in which it was going at the completion of
the operation. Except for searches backward, this will usually be the forward direction.
If bit 7 is set to a 0, the tape processor enters the Turnaround State at the completion of the operation, which is
the end of the Checkword State. When a block mark is encountered, the tape stops, leaving the Turnaround State
and entering the Idle State. If a subsequent tape instruction occurs while the tape processor is in the Turnaround
State, searching begins with the tape moving forward.

3-42

If the tape has stopped, a subsequent tape instruction will begin with tape motion in the backward direction. It will
search backwards until a block number has been encountered. This first block number is used to determine the
required direction to complete the instruction.
NOTE
The foregoing discussion applies only to tape motion at the completion of an
instruction. It should not be confused with the NO PAUSE Extended Operation,
which affects central processor action after a tape operation has begun.

3.6.4 LINCtape Instructions
In the subsequent instruction descriptions, the following terms are used:

Data sum

two's complement sum of all 256 data words in a block

Checksum

two's complement of (Data sum + 7777 8 )

Transfer check

Data sum + Checksum + 7777 8
If the transfer is successful, the transfer check= 7777 8
If not, the transfer check =f=. 7777 8

MBLK, TBLK

As shown in Figure 3-18
NOTE
It is assumed that Extended Address and NO PAUSE are

not used in the following discussion.

RDE

Read Tape

Form:
Octal code:
Execution time:
Operation:

RDC

Read and Check

Form:
Octal code:
Execution time:
Operation:

RCG

RDE I U
0702 + 201 + IOU
3.2 µs
Block TBLK is read from tape into memory block MBLK. The transfer check is left in the
TAC and AC. The contents of the tape are unchanged.

RDC I U
0700 + 201 +IOU
3.2 µs
Block TBLK is read from tape into memory block MBLK. If the block is transferred correctly,
the transfer check is left in the TAC and AC; otherwise, the operation is repeated. The
information on tape is unchanged.

Read and Check Group

Form:
Octal code:
Execution time:
Operation:

RCG I U
0701 + 20I +JOU
3.2 µs
Block TBLK is read from tape into the memory block designated by the three low-order bits
of TBLK; e.g., tape block 773 is read into memory block 3, tape block 027 into memory block
7. The next consecutive tape blocks are read into successive memory blocks. Tape block 000
follows tape block 777, and memory block 0 follows memory block 7. MBLK is the number of
additional consecutive blocks to be transferred.
3-43

Example: Transfer blocks 202-205 from unit 1 to memory, leaving the unit in motion at the end.
Instruction

Octal

RCG I
3202

0731
3202

/READ AND CHECK GROUP INST
/MBLK = 3, THE NUMBER OF ADDITIONAL BLOCKS
/TBLK = 202.

Data is transferred from tape block 202 into memory block 2, then from 203 to memory block 3, 204 to memory
block 4, and 205 to memory block 5.
Each block transfer is checked. If the transfer is successful, the transfer check (7777) is left in the TAC; otherwise,
that block is repeated. If the entire group is transferred successfully, 7777 is left in the TAC and AC at the end of
the operation.
WR!

Write Tape

Form:
Octal code:
Execution time:
Operation:

WRC

WRC I U
0704 + 20I + IOU

3.2 µ.s
The contents of memory block MBLK are copied into block TBLK. If the transfer is
successful, the transfer check (7777) is left in the TAC and PAC; otherwise, the operation is
repeated.

Write and Check Group

Form:
Octal code:
Execution time:
Operation:

3-44

3.2 µ.s
The contents of memory block MBLK are copied into block TBLK; the transfer check is left in
the TAC. The contents of memory are unchanged.

Write and Check

Form:
Octal code:
Execution time:
Operation:

WCG

WRI I U
0706 + 201 + IOU

WCG I U
0705 + 20I + IOU
3.2 µs
MBLK is the number of additional consecutive memory blocks whose contents are written on
tape. The low-order digit of TBLK specifies the first memory block to be accessed. The
contents of this block are copied into block TBLK of tape. The contents of the next MBLK
memory blocks are copied into the next successive tape blocks. Memory block 0 follows
memory block 7, and tape block 000 follows block 777. The scheme is identical with that for
RCG. If the transfer is successful, the transfer check (7777) is left in the TAC and AC;
otherwise, the operation is repeated.

The following two instructions do not transfer data.

MTB

Move Toward Block

Form:
Octal code:
Execution time:
Operation:

CHK

MTB I U
0703 + 201 + lOU
3.2 µs
Subtract the first tape block number encountered (or reverse block number, if the tape is
moving backwards) from TBLK, leaving the difference in the TAC and AC. If I = 0, the tape
stops. If I= 1, the tape is left moving forward if the difference is positive or 0, and backward if
negative. If motion = 0 when this instruction is given, it starts moving backward; otherwise it
continues in the direction in which it had been going. The MBLK bits of the second word are
ignored.

Check one Tape Block

Form:
Octal code:
Execution time:
Operation:

CHK I U
0707 + 20I + IOU
3.2 µs
Find block BN, form its transfer check and leave it in the TAC and AC. The information on
tape and the contents of memory are unchanged.

The contents of the Tape Accumulator can be examined by using the following instructions.

TAC

Tape Accumulator to AC

Octal code:
Execution time:
Operation:

0003
1.6 µs
The contents of the Tape Accumulator are placed in the central processor AC. The previous
C(AC) are lost; C(TAC) are unchanged. This instruction is used to verify transfer Checksums
for NO PAUSE tape operations. Because this instruction uses the tape ADDER data path, 11.
must not be given while a tape operation is in progress.

3.6.5 Extended Operations
LINCtape Extended Operations give the programmer a more flexible addressing scheme for information transfers,
additional control functions, and a tape processor maintenance facility. These operations are controlled by the
contents of the Extended Operations Buffer, defined as shown in Figure 3-19. The XOB can be loaded from the AC
and vice versa. The function of these bits is described in Paragraphs 3.3.6 through 3.6.12.

EXTENDED OPERATIONS BUFFER (XOB)

·:=~~~ r ,
MARK
CONDITION

~XTENDED
UNITS

HOLD
UNIT
MOTION

ENABLE
TAPE - - - - - - - - - - - '
INTERRUPT

MAINTEN~~~ - - - - - - - - - - - - '

....___ _ _ _ _

DO NOT
DURING

~USE

EXECUTION

.__________

ENABLE
~~6~~g~o

MOOE

Figure 3-19. Extended Operations Buffer Bit Assignments
3-45

AXO

AC to XOB

Octal code:
Execution time:
Operation:

XOA

0001
1.6 µs
The contents of the AC are placed in the Extended Operations Buffer. The previous C(XOB)
are lost; C(AC) are unchanged. Changing these states while a tape operation is in progress may
cause incorrect execution.

XOB to AC

Octal code:
Execution time:
Operation:

0021
1.6 µs
The contents of the Extended Operations Buffer are placed in the AC. The previous C(AC) are
lost; C(XOB) are unchanged.
This instruction must not be given when the tape is in progress because the data path includes
the tape ADDER.

3.6.6 Extended Address Format
;

This facility releases the programmer from the limitation of block-to-block transfers, as described previously.
Instead, a block transfer may begin in any register of any memory field, regardless of the settings of the Memory
Field Registers. The first memory address affected in the data transfer is placed in the TMA Setup Register by the
program, using the instruction TMA. When the Extended Address Mode is enabled (by setting bit 7 of the XOB to
1), all subsequent tape transfers are executed as follows. At the occurrence of a tape transfer instruction, the
contents of the TMA Setup Register are placed in the TMA. The second word of the instruction is taken as an
11-bit block number, and placed in the TBN. The transfer is effected between tape and the designated area of the
4096-word memory bank specified by bits 0-2 of the XOB. The transfer is thus independent of the LINC Memory
Field assignments.
As in all extended memory operations, whether with tape or not, the transfer will not cross 4096 1 0 memory field
bank boundaries; address 7777 is followed by address 0000.
NOTE
The group transfer instructions RCG and WCG cannot be used in extended address
mode.

TMA

Load TMA Setup Register

Octal code:
Execution time:
Operation:

3-46

0023
1.6 µs
The contents of the AC are placed in the Tape Memory Address Setup Register. The previous
contents of TMA Setup are lost; C(AC) are unchanged. This instruction must not be given
when the tape is in progress because the data path includes the tape ADDER.

Example:

Read the contents of block 365 of unit 0 into memory, beginning at absolute location 105408
(0540 8 in the second 4096 10 -word bank of memory).

Instruction

Octal
Code

LDA
0540
TMA
LDA
1020
AXO

1020
0540
0023
1020
1020
0001

/LOAD AC WITH STARTING ADDRESS
/STARTING ADDRESS OF TARGET AREA
/PLACE STARTING ADDRESS IN TMA SETUP
/LOAD AC WITH EXTENDED OPERA TIO NS BITS
/BANK 1; ENTER EXTENDED ADDRESS MODE
/LOAD XOB FROM AC

RDC
0365

0700
0365

/READ AND CHECK FROM UNIT 0
/BLOCK 365

Action

The data will be read into registers 0540 8 - 1137 8 of the second 4096 10 -word bank of memory.

3.6.7 Extended Units
The two Extended Units bits (XOB 1 0 - 11 ) may be thought of as an extension of the unit bit of a LINCtape
instruction (bit 8). Taken together, the three bits can select one of up to eight transports which may be attached to
the TC 12 tape control. The logical unit numbers are assigned by rotating the dials on the transports; they
correspond to the unit select bits as follows:
Extended Unit
Bits (XOB)
11
10
0
0
0
0

0
0

Instruction
Unit Bit
8
0
I
0
I
0

Transport
Selected
0
I
2

3
4
5

6
7

3.6.8 Tape Interrupt Enable
When this bit (XOB 5 ) is set, a program interrupt will occur whenever INTERRUPT is enabled and the TAPE DONE
flag is set (i.e., the tape operation is completed). As with other LINC interrupts, control is transferred to register
0041 of memory field O; the contents of the PC are stored in register 0040. (If the central processor is in the 8
mode, the interrupt uses registers 0001 and 0000.) TAPE DONE is set by the completion of a tape instruction and
cleared by the execution of a new tape instruction or the tape maintenance instruction LMR (IOT 6151) with
AC 4 (1). (See Paragraph 3.6.9 and Appendix E.)

3-47

3.6.9 No Pause Condition
Normally, the central processor waits until a tape operation is finished before proceeding. Such delays may be
eliminated by setting the NO PAUSE condition bit (XOB 8 ). When this condition is enabled, the processor
continues with the program as soon as the LINCtape instruction has been interpreted and the operation initiated.
Subsequently, the program can monitor the Tape Done flag to determine when the operation has finished. The
Tape Done flag is set when a tape operation has been completed and is cleared at the beginning of the next tape instruction. The flag can also be sensed and cleared by the following instructions. When in the no pause condition, a
second tape instruction should not be used until the previous tape instruction has been completed.

JOB
LMR

Load Maintenance Register

Execution time:

0500
6151
5.9 µs (LINC mode)

Operation:

The maintenance IOT (see Appendix E) is used to test and clear the TAPE DONE flag.

Octal code:

(AC 0 5 = 1) Skip if Tape Done Flag is set.
(AC 04 = 1) Clear Tape Done Flag
Do not have other AC bits on a 1, as this instruction has many additional functions.
STD

Skip if Tape Done

Form:
Octal code:
Execution time:
Operation:

STD I
0416 + 20I
1.6 µs
If I = 0, skip the next instruction if no tape operation is in progress; otherwise, execute the
next instruction. If I = 1, skip if an operation is still in progress. This instruction is identical to
SXL I 16.
Used in conjunction with the tape flag and tape interrupt, the NO PAUSE condition can save
considerable amounts of time in central processor programming. When NO PAUSE is set, the
Transfer Check is not placed in the accumulator at the end of tape instruction. The instruction
TAC (see Paragraph 3.6.4) should be used to recover the Transfer Check.

3.6.10 Hold Unit Motion
Normally, a tape transport stops as soon as another unit has been selected. When XOB 9 is set, however, the
transport will continue in the direction it has been moving when the unit is deselected. This is a useful feature for
certain operations involving several units, and must be used with caution. Note that it is not the same as the motion
bit of a LINCtape instruction, which determines the motion state of a unit at the completion of an instruction
only.
NOTE
With the Hold Unit Motion and No Pause bits both set, it is impossible to do two backto-back tape instructions and enable both units 0 and 1 for simultaneous motion.
3.6.11 MARK Condition
This bit (XOB 4 ) is used in conjunction with the MARK switch on the operator's console to allow the MARK 12
program (see Chapter 7 on Program Library) to record Timing and Mark tracks on a new tape. The interaction
between the switch and the XOB is designed to minimize the possibility of accidentally destroying a tape by
enabling the MARK flip-flop. The flip-flop can be set only when the MARK switch is held down while an AXO
instruction is being executed with AC 4 set to 1.
3-48

3.6.12 Maintenance Mode
When XOB 6 is set, all timing signals and data are prevented from entering the tape control registers from the
reader-writers. Instead, signals generated by IOT instructions are used as input to the tape control, in order to
simulate the functions of the tape head and the tape processor. The Maintenance Mode is designed for diagnostic
purposes and is not intended for general use. See Appendix E for a list of Maintenance Mode tape control
instructions.

3.6.13 Tape Trap
Whenever the TAPE TRAP and INSTRUCTION TRAP Special Functions are enabled (ESF with AC 2 - 3 set),
LINCtape instructions are not executed. When one is encountered, a program trap to register 0140 of memory field
O occurs. The Tape Trap is intended primarily for use with LINC-8 programs and the I/O Handler (LINC-8 Trap
Simulator) to ensure compatibility. Also, device-independent software can make use of Tape Trap to substitute
other mass storage devices, such as disks for LINCtape.
3.6.14 Tape Word Skip
TWC

Skip on Tape Word Complete

Form:
Octal code:
Execution time:
Operation:

TWC I

0417 + 201
1.6 µs
fhis instruction is used when formatting a tape using the MARK 12 Program.

3-49/3-50

CHAPTER 4
8 MODE PROGRAMMING

8-mode programming of the PDP-12 is covered in this chapter, which is divided into six sections: Organization of
Memory, Memory Addressing Methods, PDP-8 Instructions, Program Interrupt, Extended Arithmetic Element, and
'
Extended Memory.

4.1 ORGANIZATION OF MEMORY

4.1.1 Organization
In the 8 mode, the basic 4096-word memory is divided into 32 pages of 128 words each for addressing purposes
Within one of these pages, operands may be addressed directly by memory reference instructions. Access to
operands across page boundaries (except for Page 0) requires indirect addressing.
Executable programs may be stored in any page of memory, and program sequences may extend across several
pages. The program counter is indexed over all 12 bits in the 8 mode, so that a straight-line program sequence will
pass from the last word of a page to the first word of the next. A programmed jump across page boundaries,
however, requires an indirect reference. The organization of one memory field in 8 mode is shown in Figure 4-1.

4.1.2 Page 0
The first page of memory (addresses 000-1 77) contains several registers reserved for special use, which the
,programmer must take into account. These are:

Address

Use

0000
0001

During a program interrupt, holds C(PC).
Contains the first instruction to be executed after a
program interrupt.
Automatic index registers (see Paragraph 4.2.2).

0010-0017

4-1

PAGE (OCTAL)

2
3
4
5
6

7
10
11

12
13
14
15
16
17
20
21

22
23
24
25
26
27
30
31
32

33
34
35
36
~7

ADDRESSES

0000-0177
0200-0377
0400-0577
0600-0777
1000-1177
1200-1377
1400-1577
1600-1777
2000-2177
2200-2377
2400-2577
2600-2777
3000-3177
3200-3377
3400-3577
3600-3777
4000-4177
4200-4377
4400-4577
4600-4777
5000-5177
5200-5377
5400-5577
5600-5777
6000-6177
6200-6377
6400-6577
6600-6777
7000-7177
7200-7377
7400-7577
7600-7777

12-0121

Figure 4-1. Organization of Memory, 8 Mode
4.1.3 Extended Memory
Additional 4K memory fields are organized in the same manner as the basic field. The Memory Field registers
determine the assignment of fields (see Paragraph 4.6).

4.2 MEMORY ADDRESSING METHODS

4.2.1 Direct Addressing
In the 8 mode, all memory reference instructions have the same structure, which is shown in Figure 4-2.

4-2

Note that only seven bits (5-11) are available for use as an address. This is just sufficient to give access to 128
registers, or exactly one page. The state of bit 4 of the instruction determines which of two possible pages the 7-bit
page address references. If this bit is 1, the page address is on the current page; that is, the one in which the
instruction itself is stored. If bit 4 is 0, the page address is on Page 0. Thus, a memory reference instruction has
direct access to a total of 256 registers of memory; the 128 locations of Page 0, and those of the current page.

Examples:
To store the contents of the AC in register 150 of the current page:
DCA 350

Octal code: 3350. The page address is 150; bit 4 (Page bit) set to 1 gives a total octal
value of 350 for the address.

To store the contents of the AC in register 150 of Page 0:
DCA 150

Octal code: 3150. With the page bit set to 0, the complete octal address is 150.

As one can see from these examples, it is useful to think of page addresses running from 000-1 77 on Page 0, and
from 200-377 on the current page.

4.2.2 Indirect Addressing
To gain access to registers outside of Page 0 or the current page, indirect addressing must be used. If bit 3 of a memory reference instruction is set to 1 (see Figure 4-2), the contents of the register designated by bits 5-11 are taken
as the "effective" address of the operand. This is a full 12-bit number which gives the absolute address of any register in the 4K memory field.

OPERATION
COOE

MEMORY
PAGE

r"-....

I I
4

'-yJ

INDIRECT
ADDRESSING

PAGE
ADDRESS
12-0122

Figure 4-2. Memory Reference Instruction Format

4-3

In the following examples, as in normal 8 mode programming, the letter I is used as a mnemonic to represent the
presence of a 1 in bit 3.
Examples:
a. To store the contents of the AC in register 100 of page 10 (absolute address 2100), using an effective
address stored on the current page:
Absolute
Address

Contents

0410

DCA I 300

0500

2100

Action
/OCTAL CODE: 3700. THE
/EFFECTIVE ADDRESS IS
/CONTAINED IN REGISTER 500,
/(PAGE ADDRESS 300)

b. To store the C(AC) in register 2100, using an effective address stored in Page 0:
Absolute
Address

Contents

0050

2100

0410

DCA I 50

Action
/EFFECTIVE ADDRESS, STORED
/ON PAGE 0
/OCTAL CODE: 3450. (BIT 4 = 0)

Table 4-1. Summary of Addressing Methods in 8 Mode

Bit 3

Bit 4

Effective Address

The operand is in Page 0 at the address specified by
bits 5 through 11.
The operand is in the current page at the address
specified by bits 5 through 11.

The absolute address of the operand is taken from
the contents of the location in Page 0 designated
by bits 5 through 11.
The absolute address of the operand is taken from
the contents of the location in the current page
designated by bits 5 through 11.

4.2.3 Autoindexing
The eight registers in locations 10-17 of Page 0 have a special function when indirectly addressed. The contents of
such a register are first incremented by 1; the result is taken as the effective address of the operand. This
autoindexing feature allows the programmer to address a series of contiguous locations without extra address
modification, as shown in the following example.

4-4

Example:
To obtain the sum of 100 numbers stored in registers 1000-1077.
Address
Labe1

Instruction

GO,

CLA
TAD LIST

/CLEAR THE AC
/PUT 777 IN AC (ADDRESS-I OF THE TABLE OF NUMBERS)

DCA
TAD
DCA
TAD

/DEPOSIT IN AUTOINDEX REGISTER 10. (CLEARS AC)
/PUT-I 00 IN AC (COUNT OF ADDENDS IN TABLE)
/DEPOSIT IN REGISTER FOR COUNTING
/C( 10) INCREMENTED BY 1, THEN USED AS
/EFFECTIVE ADDRESS TO GET ADDEND FROM TABLE

LOOP,

COUNT
INDEX
I 10

Operation

END,

IMP LOOP
HLT

/INCREMENT COUNT. IF RESULT IS 0000, SKIP
/THE NEXT INSTRUCTION.
/IF NOT FINISHED, GO BACK TO GET NEXT ADDEND
/WHEN FINISHED, STOP; AC CONTAINS THE SUM

LIST,
COUNT,
INDEX,

777
-100
0000

/ADDRESS-I OF TABLE OF ADDENDS
/COUNT OF TABLES ENTRIES
/HOLDS COUNT DURING EXECUTION OF PROGRAM

ISZ INDEX

When register 10 is first accessed, its contents are incremented from 777 to 1000, then used as the effective address
to obtain the first addend. The next time around the loop, C( 10) is again incremented by 1, to 1001, for the next
operand. At the end of the sequence, C(l 0) = 1077.

4.3 8 MODE INSTRUCTIONS (See Appendix B)

4.3. l Memory Reference Instructions
There are six memory reference instructions: DCA, TAD, AND, ISZ, JMP, and JMS. All may use either direct or
indirect addressing. When indirect addressing is specified, 1.6 microseconds is added to the execution time.

DCA

Deposit and Clear Accumulator

Form:
Octal code:
Execution time:
Operation:

TAD

DCA Y
3000 + y
3.2 µs
The contents of the AC are deposited in register Y; the AC is then cleared to 0000. The
previous C(Y) are lost.

Two's Complement Add to Accumulator

Form:
Octal code:
Execution time:
Operation:

TAD v
1000 + y
3.2 µs
The contents of Y are added to the contents of the AC, using two's complement addition. If
there is a carry out of bit 0, the Link is complemented; otherwise, the Link is unchanged. The
previous contents of the AC are lost; the contents of Y are not changed.
·

4-5

AND

Logical AND to Accumulator

Form:
Octal code:
Execution time:
Operation:

AND Y
0000 + y
3.2 µs
The contents of the AC and the contents of Y are combined according to the Boolean AND
relation, with the result left in the AC. The operation is performed on corresponding bits of
each operand, independent of the other bits in the two operands. The truth table for the AND
relation is shown below:

0
0

When corresponding bits of AC and Y are both 1, the result is 1. Otherwise, the result is 0. The
previous C(AC) are lost; the C(Y) are unchanged.
ISZ

Increment And Skip If Zero

Form:
Octal code:
Execution time:
Operation:

JMP

Jump

Form:
Octal code:
Execution time:
Operation:

JMS

ISZ Y
2000 + y
3.2 µs
The contents of Y are incremented by 1. If the result is 0000, the next instruction in sequence
is skipped; otherwise, the next instruction is executed. The contents of the AC are not
affected.

JMP Y
5000 + y
1.6 µs
The address Y is placed in the PC, and the next instruction is taken from register Y; the
program continues from that point. The contents of the AC are not affected.

Jump to Subroutine

Form:
Octal code:
Execution time:
Operation:

JMS Y
4000 + y
3.2 µs
The contents of the PC are stored in Y. The address Y + 1 is placed in the PC, and the program
continues from Y + 1. The contents of the AC are not affected. To return from the subroutine
to the point at which the JMS was given (i.e., to the register immediately following the JMS),
the instruction JMP I Y is executed. The contents of Y are taken as the effective address;
since Y contains the PC stored at the time of the JMS, control returns to the calling program.

4.3.2 Operate Class Instructions
This class is divided into two groups, I and II. Group I instructions include miscellaneous operations on the
Accumulator and Link. Group II instructions include skips, program halt, and access to the console switches.

4-6

Operate class instructions are microprogrammable; they may be combined to provide several operations within a
single instruction. However, combinations can be made only within a group; operations from different groups
cannot be combined. To ease this restriction, the operation CLA (Clear the AC) is available in both groups. All
Operate Class instructions require 1.6 microseconds for execution.

4.3.2.1 Operate Class: Group I - The microprogram structure of Group I instructions is shown in Figure 4-3. Any
combination of these functions can be made, but the programmer must be aware of the order in which the
operations are performed when the instruction is executed. This order is as follows:
1. CLA, CLL
2. CMA, CML
3. IAC
4. RAR,RAL,RTR,RTL
Certain combinations of Group I operations are common enough to be assigned separate mnemonics. These are
described in Paragraph 4.3.2.2.

OPERATION
CODE 7

CLA

CMA

ROTATE1
ROTATE POSITION IF 0,
AC AND L 2 POSITIONS
RIGHT
IF 1

I I I I I I I I
'-yJ
'-y-J
'-y-J
'-y-J
'-y-J
3

CONTAINS
0 TO
SPECIFY
GROUP 1

CLL

CML

ROTATE
AC AND L
LEFT

IAC

Figure 4-3. Group I Operate Class Instruction Format
NOP

No Operation

Octal code:
Operation:

CLA

Clear Accumulator

Octal code:
Operation:
CLL

7200
The contents of the AC are cleared to 0000.

Clear Link

Octal code:
Operation:
CMA

7000
None. This instruction may be used to provide short delays ( 1.6 microseconds per instruction),
or to hold a place for instructions to be inserted by the programmer.

7100
The content of the Link is cleared to 0.

Complement Accumulator

Octal code:
Operation:

7040
The one's complement of the contents of the AC replaces the original contents of the AC.
Each bit that is 0 becomes 1, and vice versa.
4-7

CML

Complement Link

Octal code:
Operation:

!AC

Increment Accumulator

Octal code:
Operation:

RAR

7012
The contents of the AC and Link, taken as a 13-bit register, are rotated two positions to the
right. (See Figure 4-4.) This is the equivalent of two RAR instructions.

Rotate Accumulator Left

Octal code:
Operation:

RTL

7010
The contents of the AC and Link, taken as a 13-bit register, are rotated right one position. A
bit rotated out of AC 11 enters the Link~ the bit rotated out of the Link enters AC 0 . (See
Figure 4-4.)

Rotate Two Places Right

Octal code:
Operation:

RAL

7001
The contents of the AC are incremented by 1, using two's complement arithmetic. A carry out
of bit 0 complements the Link.

Rotate Accumulator Right

Octal code:
Operation:

RTR

7020
The content of the Link is complemented.

7004
The contents of the AC and Link, taken as a 13-bit register, are rotated one place to the left. A
bit leaving AC 0 enters the Link; a bit leaving the Link enters AC 1 1 . (See Figure 4-4.)

Rotate Two Places Left

Octal code:
Operation:

7006
The contents of the AC and Link, taken as a 13-bit register, are rotated two positions left. (See
Figure 4-4.) This is equivalent to two RAL instructions.

~
0

~
Figure 4-4. Rotation Scheme for RAR, RTR, RAL, RTL

4.3.2.2 Combined Operations: Group I - The following combined operations have been given separate mnemonics
for programming convenience.

4-8

STA

Set Accumulator (CLA + CMA)

Octal code:
Operation:
STL

Set Link (CLL + CML)

Octal code:
Operation:
CIA

7120
Clear, then complement the Link. Resulting C(L) = 1.

Complement and Increment Accumulator (CMA +/AC)

Octal code:
Operation:

GLK

7240
Clear, then complement the AC. Resulting C(AC) = 7777.

7041
Complement the AC, then increment the result by 1. This gives the two's complement of the
original C(AC). The two's complement of a number is defined as the one's complement plus 1.

Get Link (CLA + RAL)

Octal code:
Operation:

7204
Clear the AC, then rotate one place left, thus putting the contents of the Link into AC 11 . This
instruction is useful in multiple precision arithmetic.

Other Useful Combinations - The programmer can place a number of selected constants in the AC by combining
Group I operations as shown:

Combination

Octal Code

7201
7326
7325
7307
7327
7344
7346
7330
7332
7333

CLA
CLA
CLA
CLA
CLA
STA
STA
CLA
CLA
CLA

IAC
STL
STL
CLL
STL
CLL
CLL
STL
STL
STL

RTL
IAC
IAC
IAC
RAL
RTL
RAR
RTR
IAC

Resulting C(AC)

RAL
RTL
RTL

RTR

0001
0002
0003
0004
0006
7776 (-2)
7775 (-3)
4000
2000
6000

4.3.2.3 Operate Class: Group II - The microprogram structure of Group II operations is shown in Figure 4-5. Any
of these operations may be combined, but the programmer must be aware of the sequence of events. In addition,
the sense of the skip instruction determines the manner in which combined skips are interpreted. If bit 8 is a 0, the
logical OR of the tested conditions will cause a skip; if this bit is a 1, the logical AND of the conditions will cause
the skip. In the first case, this means that the skip will occur if any one of the conditions tested is true; in the
second case, the skip will occur only if all the conditions tested are true. The various combinations are described in
Paragraph 4.3.2.4.
The sequence of events in a Group II instruction is as follows:
1. Skips
2. CLA
3. OSR
4. HLT occurs after all other specified operations have been performed.

4-9

OPERATION
CODE 7

;

CLA

SNA
OR
SZA

DETERMINES
SENSE
OF SKIP

HLT

I 4 I I I I I I 10 I ,,
'-y-1
'-y-1
3

'-y-'

CONTAINS 1
TO SPECIFY
GROUP 2

SMA
OR
SPA

SNL

SZR

'-y-'

'-y-1

OSR

CONTAINS 0
TO SPECIFY
OPERATE*
CLASS

THIS BIT DISTINGUISHES GROUP JI OPERATE CLASS INSTRUCTIONS FROM THE
OPTIONAL EAE INSTRUCTION SET, IN WHICH THIS BIT IS SET TO 1.

Figure 4-5. Group II Operate Class Instruction Format

CLA

ClearAC

Octal code:
Operation:
SKP

Skip Unconditionally

Octal code:
Operation:
SNL

7450
The contents of the AC are not equal to 0000.

Skip On Minus Accumulator

Octal code:
Skip condition:

4-10

7440
The contents of the AC equal 0000.

Skip On Non-Zero Accumulator

Octal code:
Skip condition:
SMA

7430
The contents of the Link equal 0.

Skip On Zero Accumulator

Octal code:
Skip condition:
SNA

7420
The contents of the Link equal 1.

Skip On Zero Link

Octal code:
Skip condition:
SZA

7410
The next instruction in the program sequence is unconditionally skipped.

Skip On Non-Zero Link

Octal code:
Skip condition:
SZL

7600
Clear the AC

7500
The contents of AC 0 equal 1. By convention, a negative number is one in which the most
significant digit is 1. Thus, all numbers between 4000 and 7777, inclusive, are negative. The

two's complement of such a number is its positive counterpart. In this sense, 7777 is
equivalent to -1; 4000 is equivalent to -4000. The two's complement sum of a number and its
two's complement is always zero.

SPA

Skip On Plus Accumulator

Octal code:
Skip condition:

OSR

7510
The contents of AC 0 equal 0. By the convention described above, a number is positive if its
most significant digit is 0.

OR Switch Register With Accumulator
7404
The contents of the console switch register (Right Switches) are combined with the contents
of the AC by the logical Inclusive OR reiation; the result is left in the AC.

Octal code:
Operation:

If either bit of a corresponding pair is set to 1, the result is 1. The result is 0 only if both AC
and SR bits are 0. This instruction is normally used with CLA to obtain the actual status of the
Switches (see below).

HLT

Halt

Octal code:
Operation:

LAS

7402
The processor stops. The PC contains the address of the register following the HLT instruction.
The contents of the other processor registers are not affected.

Load Accumulator From Switches ( CLA + OSR)

Octal code:
Operation:

7604
Clear the AC, then OR the contents of the Right Switches with C(AC). This places the status
of the switches in the AC. If the switch is set to 1, the corresponding AC bit is set to 1.

4.3. 2.4 Combined Skips In Group 11 - The possible skip combinations are listed, with the conditions for a skip to
occur.

Combination
SZA
SZA
SMA
SZA

SNL
SMA
SNL
SMA

SNL

Octal Code

A skip will occur if

7460
7540
7520
7560

C(AC)=OOOO, or C(L)= 1, or both
C(AC)=OOOO, or C(AC 0 )= 1, or both
C(AC 0 )=1, or C(L)= 1, or both
C(AC)=OOOO, or C(AC 0 )=1, or C(L)=l, or
any, or all of these.
A skip will occur if and only if

SNA
SNA
SPA
SNA

SZL
SPA
SZL
SPA

SZL

7470
7550
7530
7570

C(AC)=i=O and C(L)=O
C(AC)#O and C(AC 0 )=0
C(AC 0 )=O and C(L)=O
C(AC)#OOOO and C(AC 0 )=0 and
C(L)=O

If CLA is combined with any skip, the AC is cleared after the conditions have been tested.
4-11

4.3.2.5 Input/Output Transfer Class - These instructions, all of which have the basic operation code of 6000, are
used to service peripheral devices, enable and disable the program interrupt, operate the memory extension control,
change from 8 to LINC programming mode, and provide maintenance operations for the LINCtape subprocessor.
Most of these instructions are described in Chapter 6 with their associated devices. The program interrupt and
memory extension control are discussed with their respective instructions in Paragraphs 4.4 and 4.6 of this chapter.

Mode Control - To change operating mode from 8 to LINC, the following IOT instruction is used.
LINC

Switch to LINC Mode

Octal code:
Execution time:
Operation:

6141
4.25 µs
Starting with the next succeeding instruction, the central processor will operate in LINC mode.

4.4 PROGRAM INTERRUPT

4.4.1 Operation
To facilitate the handling of data transfers and the checking of peripheral device status, provision is made for
interrupting a program when a given condition exists. In general, an interrupt occurs when a peripheral device flag
is raised (i.e., when the device is available for service, when an operation has been completed, or when a specific
condition, such as an alarm, occurs within the device).

The Program Interrupt (PI) is enabled or disabled by the program. When it is disabled, a device flag must be sensed
by means of a skip; the program is not interrupted. When the interrupt is enabled, any device flag that is connected
to the interrupt system will cause the following sequence of events to occur when that flag is raised:
1. The instruction in progress at the time of the PI request is completed.
2. The contents of the program counter are stored in register 0000, and 0001 is placed in the PC.
3. Processing continues, beginning with the instruction in register 0001.
4. The PI facility is disabled.
The two IOT instructions which control the PI facility are described below.

ION

Interrupt On

Octal code:
Execution time:
Operation:

4-12

6001
4.25 µs
The PI facility is enabled immediately after the instruction following the ION has been
executed. If a PI request is waiting at the time of the ION, the interrupt will occur after the
next instruction has been completed. The enabling is delayed in this manner so that a PI
service routine can return to the interrupted program before a subsequent PI request destroys
the contents of register 0000.

/OF

Interrupt Off

Octal code:
Execution time:
Operation:

6002
4.25 µs
The PI facility is disabled. Subsequent requests will not cause a Pl, although any flag causing a
request may be sensed in the usual manner with an IOT skip.

4.4.2 Using the Program Interrupt
Normally, when a PI occurs, the instruction in register 0001 is a JMP to a PI service routine, which examines the
expected flags to determine which device or condition caused the request. The appropriate routine is then called to
service the device. During this time, the PI facility is disabled. When the device service routine is completed, control
normally returns to the PI handling routine for restoring the PI facility and exiting to the main program. The last
two instructions of such a routine would be:
ION
JMP I 0

/ENABLE PI FACILITY
/RETURN TO MAIN PROGRAM AT THE ADDRESS
/STORED IN REGISTER 0000

The PI is not enabled until the JMP I 0 has been executed, so that the return to the main program is completed
before a waiting request can cause another PI.
NOTE
Refer to Paragraph 3.3.15 for the discussion of additional aspects of Program
Interrupt during LINC mode programming.
4.5 EXTENDED ARITHMETIC ELEMENT TYPE KE12
4.5.1 Operation
The Extended Arithmetic Element (EAE), Type KE 12, adds a complete automatic multiplication and division
facility to the PDP-12. Programming is provided by a class of 8 mode instructions. The AC and MQ are used to
accommodate full 24-bit products and dividends, and the remainder and quotient after a division. Shifting,
normalizing, and register setup instructions are included. All operands are treated as unsigned integers; the
programmer must establish his own sign conventions. The normalizing instruction facilitates the writing of
floating-point subroutines.
4.5.2 EAE Instructions
The EAE instruction set has a basic operation code of 7401; some functions are microprogrammable, as in Operate
Class instructions. The microprogram structure of the EAE class is shown in Figure 4-6.

OPERATION
CODE 74

MQA

MQL

CONTAINS
1 TO
SPECIFY
EAE GROUP

I I"-y--1I I
"-y--1
4

CLA

SCA

I· I I
v
9

1=SCL
2•MUY 3=DVI
4•NMI 5 .. SHL
6=-ASR 7=LSR

Figure 4-6. EAE Instruction Format
4-13

As with other microprogrammed instructions, EAE operations are performed in a given order. Operations can be
combined in a single instruction, except that operations occurring at the same time cannot be combined with
meaningful results.
The order of events is as follows:
1. CLA
2. MQA, MQL, SCA
3. SCL, MUY, DVI, NMI, SHL, ASR, LSR
CLA

ClearAC

Octal code:
Execution time:
Operation:
CAM

Clear AC and M Q

Octal code:
Execution time:
Operation:
MQA

7601
1.6 µs
Clear the AC. The MQ and Link are unaffected.

7621
1.6 µs
The AC and the MQ is cleared.

Place MQ in AC

Octal code:
Execution time:
Operation:

7501
1.6 µs
The contents of the MQ are ORed into the AC. The C(MQ) are unchanged.
NOTE

All twelve bits are transferred; this is not identical to the LINC mode QAC
instruction (Paragraph 3.3.11 ).
MQL

Load MQ/rom AC

Octal code:
Execution time:
Operation:
SCA

7421
1.6 µs
The MQ is cleared. The contents of the AC are placed in the MQ. The previous C(MQ) are lost.
The AC is cleared at the end of the instruction.

Step Counter to AC

Octal code:
Execution time:
Operation:

7441
1.6 µs
The contents of the step counter are ORed inclusively with the contents of AC7-l l; the result
is left in the AC. To obtain the actual step count, SCA is combined with CLA (combined operation code: 7641).

All other EAE instructions, except NMI, require two words: the first contains the operation to be performed, the
second contains the operand. In the following descriptions, the notation p + 1 designates the register containing the
operand.
SCL

Load Step Counter

Octal code:
Execution time:
Operation:

4-14

7403
3.2 µs
The complement of the contents of bits 7-11 of p + 1 is placed in the SC.

MUY

Multiply

Octal code:
Execution time:
Operation:

DVI

Divide

Octal code:
Execution time:
Operation:

NM!

7405
9.0 µs
The number in the MQ is multiplied by the number in register p + 1. At the conclusion of this
instruction the Link contains a 0. The most significant 12 bits of the product are in the AC
and the least significant 12 bits are in the MQ.

7407
4.0 µs to 10.0 µs
The 24-bit dividend is held in the AC (most significant part) and MQ (least significant part);
the divisor is in register p + 1. At the conclusion of the division, the quotient is in the MQ, and
the remainder in the AC. If the division was carried out, the Link is left clear. If either
dividend or divisor is zero, the operation ends after one step and the Link is set to 1, to
indicate that a divide overflow occurred.

Normalize

Octal code:
Execution time:
Operation:

7411
1.6 µs + 0.40 µs/step
The AC and MQ are treated as a single 24-bit register. The combined contents of the AC and
MQ are shifted left until C(AC 0 ) differs from C(AC 1 ) or until 6000 0000 is contained in the
combined AC and MQ. Bits shifted out of AC 0 enter the Link; bits shifted out of the Link are
lost. Zeros enter MQ 11 and are shifted up the registers. At the end of the operation, the SC
contains the number of shifts performed, which is the exponent of the normalized floating
point fraction. The shift pa th is shown in Figure 4-7.

LOST

Figure 4-7. Shift Path for NMI, SHL

SHL

Shift Left

Octal code:
Execution time:
Operation:

7413
3.2 µs + 0.40 µs/step
The combined contents of the Link, AC and MQ are shifted left N + I places, where N is the
number contained in bits 7-11 of register p + 1. Bits shifted out of the Link are lost; zeros are
shifted into MQ 11 and up the registers. The shift path is identical to that for NMI, as shown in
Figure 4-7.
4-15

ASR

Arithmetic Shift Right

Octal code:
Execution time:
Operation:

7415
3.2 µs + 0.40 µs/step
The combined contents of the AC and MQ are shifted right N + 1 places, where N is the
number contained in bits 7-11 of register p + 1. The sign bit (AC 0 ) is reproduced in all vacated
bit positions, and is also placed in the Link. Bits shifted out of MQ 11 are lost, as is the
previous C(L). The shift path is shown in Figure 4-8.

LOST
12-0108

Figure 4-8. Shift Path for ASR

LSR

Logical Shift Right

Octal code:
Execution time:
Operation:

7417
3.2 µs + 0.40 µs/step
The combined contents of the AC and MQ are shifted right N + I places, where N is the
number contained in bits 7-11 of register p + 1. Bits shifted out of the MQ 11 are lost; zeros are
shifted into the Link and down the register. The shift path is shown in Figure 4-9.

LOST

Figure 4-9. Shift Path for LSR

4.5.3 EAE Programming
4.5.3.1 Multiplication - Multiplication is performed as follows:
I. Load the AC with the multiplier using the TAD instruction.
2. Transfer the contents of the AC into the MQ using the MQL command.
4-16

3. Give the MUY command.
Note that steps 2 and 3 can be combined into one instruction.
The contents of the MQ are then multiplied by the contents of the next successive core memory location (p + 1).
At the conclusion of the multiplication the most significant 12 bits of the product are held in the AC and the least
significant bits are held in the MQ. This operation takes 9.0 microseconds; at the end of this time, the next
instruction is executed.
The following program examples demonstrate the operation of the EAE during multiplication:
a. Multiplication of 12-bit Unsigned Numbers
Enter with a 12-bit multiplicand in AC and a 12-bit multiplier in core memory. Exit with high order half of
product in a core memory location labelled HIGH, and with low order half of product in the AC. Program
time is approximately 13 microseconds.
MQL MUY
MLTPLR,

0000
DCA HIGH
MQA

/LOAD MQ WITH MULTIPLICAND, INITIATE
/MULTIPLICATION
/MULTIPLIER
/STORE HIGH ORDER PRODUCT
/LOAD AC WITH LOW ORDER PRODUCT

b. Multiplication of 12-Bit Signed Numbers, 24-Bit Signed Product
Enter with a 12-bit multiplicand in AC and a 12-bit multiplier in core memory. Exit with signed 24-bit
product in core memory locations designated HIGH and LOW.

CLL
SPA
CMACMLIAC
MQL
TADMLTPLR
SPA
CMACMLIAC
DCAMLTPLR
RAL
DCA SIGN
MUY
MLTPLR,

0000
DAC HIGH
TAD SIGN
RAR
MQA
SNL
JMP LAST
CLLCMA IAC
DCA LOW
TAD HIGH
CMA
SZL

LAST,

/MULTIPLICAND POSITIVE?
/NO. FORM TWO'S COMPLEMENT
/LOAD MULTIPLICAND INTO MQ
/MULTIPLIER POSITIVE?
/NO. FORM TWO'S COMPLEMENT
/SA VE LINK AS SIGN INDICATOR
/MULTIPLY
/MULTIPLIER
/LOAD LINK WITH SIGN INDICATOR
/IS PRODUCT NEGATIVE?
/NO, MULT DONE, EXIT
/YES
/COMPLEMENT RESULT
/LINK USED TO COUPLE CARRY
/FROM BIT 12 TO BIT 11
/OF DOUBLE-LENGTH PRODUCT

IAC
DCAHIGH
SKP
DCALOW
4-17

4.5.3.2 Division - Division is performed as follows:
1. Load the least significant 12 bits of the dividend into the AC using the TAD instruction, then transfer the
contents of the AC into the MQ using the MQL command.
2. Load the most significant 12 bits of the dividend into the AC.
3. Give the DVI command.
The 24-bit dividend contained in the AC and MQ is divided by the 12-bit divisor contained in the next successive
core memory location (p + 1). This operation takes a maximum of 10.0 microseconds; when complete, a 12-bit
quotient is held in the MQ, the 12-bit remainder is in the AC, and the Link holds a 0 if divide overflow did not
occur. To prevent divide overflow, the divisor in the core memory must be greater than the 12 bits of the dividend
held in the AC. When divide overflow occurs, the Link is set and the division is concluded after only one cycle.
Therefore, the instruction following the divisor in core memory should be an SZL microinstruction to test for
overflow. The instruction following the SZL may be a jump to a subroutine that services the overflow. This
subroutine may cause the program to type out an error indication, rescale the divisor or the dividend, or perform
other mathematical corrections, then repeat the divide routine.
The following program examples demonstrate the use of the EAE in division.
a. Division of 24-Bit Unsigned Numbers
Enter with the low order 12 bits of the dividend in the AC and the high order 12 bits of the dividend in
memory location labeled HIGH 12. The divisor is in memory location labeled DIVISOR upon entry. Exit
with the quotient in the AC and the remainder in location labeled REMAIN.
CLL
MQL
TAD HIGH 12
DVI
DIVISOR, ( 12 BIT DIVISOR HERE)
SZL
JMP EXIT
DCA REMAIN
MQA

/CLEAR LINK FOR OVERFLOW CHECK.
/LOAD MQ WITH LOW ORDER DIVIDEND
/LOAD AC WITH HIGH ORDER DIVIDEND
/INITIATE DIVIDE
/OVERFLOW?
/YES - EXIT
/NO - STORE REMAINDER
;AND LOAD AC WITH QUOTIENT

b. Division of 24-Bit Signed Numbers
Enter with the low order 12 bits of the dividend in memory location labeled LOW 12 and the high order
12 bits of the dividend in memory location labeled HIGH 12. The 12 bit divisor is in location labeled
DIVISOR. Exit with the unsigned remainder in location labeled REMAIN, and the signed quotient in the
AC.
CLA CU
TAD HIGH 12
SMA CLA
JMP .+12
TAD LOW 12
CMA IAC
DCA LOW 12
TAD HIGH 12

4-18

/CLEAR AC AND LINK
/LOAD AC WITH HIGH ORDER DIVIDEND
/DIVIDEND NEGATIVE?
/NO - SKIP NEGATION
/YES - LOAD AC WITH LOW ORDER DIVIDEND
/NEGATE IT AND
/STORE IT BACK
/LOAD AC WITH HIGH ORDER DIVIDEND

CMA
SZL
IAC
DCA HIGH 12
CLL CML
TAD DIVISOR
SPA
CMA CML IAC
DCA DIVISOR
SNL
CMA
CLL
DCA SIGN
TAD LOW 12
MQL
TAD HIGH 12
DVI
DIVISOR, (DIVISOR STORED HERE)
SZL
JMP EXIT
DCA REMAIN
MQA
ISZ SIGN
CMA IAC

/NEGATE IT
/WAS THERE A CARRY FROM LOW ORDER?
/YES - INCREMENT HIGH ORDER
/AND STORE IT BACK
/SET LINK TO 1 FOR SIGN CHECK
/LOAD AC WITH DIVISOR
/IS IT POSITIVE?
/NO - NEGATE IT
/AND STORE IT BACK
/CHECK LINK FOR SIGN OF RESULT
/POSITIVE - STORE -1 IN SIGN
/NEGATIVE - STORE 0 IN SIGN
/GET LOW ORDER DIVIDEND
/STORE IT IN MQ
/LOAD AC WITH HIGH ORDER DIVIDEND
/DIVIDE
/OVERFLOW?
/YES - EXIT ON OVERFLOW
/NO - STORE UNSIGNED REMAINDER
/LOAD AC WITH QUOTIENT
/SHOULD QUOTIENT BE NEGATIVE?
/YES - NEGATE IT

4.6 EXTENDED MEMORY
When additional 4096-word memory banks are attached to the PDP-12, the Memory Extension Control provides
access to the additional storage, both for programs and data. The registers of the Control are already built into the
PDP-12; they are described in Paragraph 3.3.15 in relation to LINC mode memory control. In the 8 mode, the
functions of these registers are the same, but only a portion of each register is used. The Instruction Field (IF),
Data Field (DF), and Instruction Field Buffer (IB) registers are each five bits long; the two low-order bits of the
5-bit total pertain only to LINC mode programming operations. In 8 mode the Save Field register (Interrupt
Buffer) uses only six bits; the four low-order bits are unused.
4.6.1 Registers
4.6.1. l Instruction Field Register (IF), 3 Bits - These three bits serve as an extension of the PC for determining
the 4096-word field from which executable instructions are to be taken. All direct memory references are made to
registers in the Instruction Field. With one exception, all JMP and JMS instructions, whether direct or indirect, are
to registers within the Instruction Field. The exception is the first JMP or JMS executed after a CIF instruction is
given. This causes the field to change.
4.6.1.2 Data Field Register {DF), 3 Bits - These three bits serve as an extension of the Memory Address register
for determining which memory field contains the operands to be accessed by the memory reference instructions
AND, TAD, DCA, and ISZ when indirect addressing is used. The Data Field and Instruction Field may be set to the
same field.
4.6.1.3 Instruction Field Buffer (IB), 3 Bits - This serves as an input buffer for the IF. Except for a direct transfer
from the console switches, all transfers into the IF must pass through the IB. When a CIF or RMF instruction is
executed, information going to the IF is first placed in the IB. At the next occurrence of a JMP or JMS, the
contents of the IB are transferred to the Instruction Field register, and programming continues in th~ new field,
starting in the target register ·of the jump.
4-19

4.6.1.4 Save Field Register (SF), 6 Bits - Also called the Interrupt Buffer. When a program interrupt occurs, the
contents of the IF and DF are stored in the Save Field register, as shown in Figure 4-10. After the PI has been
serviced, an RMF instruction will cause the contents of the SF to be restored to the DF and IB. The SF can be
examined by using the RIB instruction.
4.6.1.5 Break Field Register (BF), 3 Bits - When an external device requires extended memory for the transfer of
data using the Data Break Facility, the contents of the BF specify the memory field to be accessed.

4.6.2 Instructions
All Extended Memory IOT instructions require 4.3 microseconds for execution.

----,
I

...__ _ _ _ _... - - -

- .J

I
~--.......- _....._ _ _ _ _"""'T"_ -

r-------------1

L - - - - - - - - - - - - - -

L--""--..__....__ _,__ _..__.AC

12-0113

Figure 4-10. Data Path to SF and AC

CDF

Change Data Field

Octal code:
Operation:

CIF

62Nl, O~N~7
The quantity N is transferred to the Data Field register. All subsequent indirect memory
references by AND, TAD, ISZ, and DCA are to the new field.

Change Instruction Field

Octal code:
Operation:

61N2, O~N~7
The quantity N is transferred to the Instruction Field Buffer. At the occurrence of the next
JMP or JMS instruction, whether direct or indirect, the contents of the IB are transferred to
the IF. The effective address of the jump is placed in the PC, and the program continues from
that address in the new Instruction Field.

In both CIF and CDF, the number N occupies bits 6-8 of the instruction code.

RDF

Read Data Field

Octal code:
Operation:

4-20

6214
The contents of the Data Field register are ORed into AC 6 _8 • The other bits of the AC are
unaffected.

RIP

Read Instruction Field
6224
The contents of the Instruction Field register are ORed into AC 6 - 8 . The other bits of the AC
are unaffected.

Octal code:
Operation:

RIB

Read Interrupt Buffer
6234
The contents of the Save Field register (Interrupt Buffer) are transferred to the AC, as follows:
Bits 0-2 (IF) are ORed into AC 6 - 8 ; bits 3-5 (DF) are ORed into AC9 - 11 .

Octal code:
Operation:

RMF

Restore Memory Field
6244
The contents of the Save Field register are placed in the Instruction Field Buffer and DF as
follows: Bits 0-2 (original Instruction Field) are transferred to the IB; bits 3-5 (original Data
Field) are restored to the Data Field register. This instruction is used to restore the Memory
Field registers after a program interrupt has been serviced. Normally, the next instruction after
the RMF would be JMP I O; the address of the interrupted program, stored in register 0000 of
field 0, is placed in the PC, and the contents of the IB are placed in the Instruction Field
register; the program thus returns to the main program with the Memory Fields restored to
their original values.

Octal code:
Operation:

4.6.3 Programming
All instructions, effective addresses, and directly-addressed operands are taken from the field specified by the
contents of the Instruction Field Register. All indirectly-addressed operands are taken from (or are stored in) the
field specified by the contents of the Data Field Register. The following chart shows the results of the four possible
addressing combinations, when the IF and DF designate different memory fields.
Instruction Bits
Indirect
Page
0

0
0

Fields
IF DF

Effective
Address

The operand is in Page 0 of Field m at the address
specified by instruction bits 5-11.

The operand is in the current page of Field m.

The effective address of the operand is in Page 0 of
Field m at the location specified by instruction bits
5-11 . The operand is in Field n, in the location
specified by the contents of the effective address.

The effective address is taken from the current
page of Field m, at the location specified by
instruction bits 5-11. The operand is in Field n, in
the location specified by the contents of the
effective address.

4-21

4.6.3. l Autoindexing - When any memory field is used as an Instruction Field, registers 10-17 of that field have
autoindexing properties, just as the corresponding locations in field 0 do. This is necessary so that a program can
operate correctly regardless of the actual memory field assigned by the IF. When an autoindex register is indirectly
addressed, the resulting effective address is used to obtain the operand from the Data Field specified by the DF.

Example:
C(IF) = 2.

C(DF) = 4.

In field 4:
In field 2:

C(4326)= 1107
C(0012) = 4325

The instruction TAD

C(AC) = 0.

12 is executed in field 2.

C(OOl 2) + 1 ~ C(OOl 2). Resulting effective address is 4326.
C( 432q) in field 4 are added to the AC.
C(AC) = 1107 when the instruction is completed.
4.6.3.2 Calling A Subroutine Across Fields - The problem is to let the subroutine know which field contains the
calling program, so that it can return to the proper point when it's finished. This is most easily done by setting the
DF to the same field as the IF, then setting the IF to the field containing the subroutine, anct executing a JMS to
read the subroutine. The subroutine uses the DF to indirectly obtain data from the calling field, then transfers the
C(DF) back to the IF Buffer to return to the calling program. The following example shows a general procedure for
doing this.
/CALLING PROGRAM IN FIELD 2, SUBROUTINE IN FIELD 4
/CURRENT DATA FIELD IS 1
/CALLING SEQUENCE SAVES CURRENT DF, PUTS IF IN DF, CALLS
/SUBROUTINE. ON RETURN, ORIGINAL DF IS RESTORED

RESDF,

CLA
TAD KCDF
RDF
DCA RESDF
TAD KCDF
RIF
DCA SETDF
0000
CIF 40
JMS I SUBADR
0000

/CDF INSTRUCTION TO AC
/C(DF) TO AC 6-8 FORMS CDF IO (6211)
/STORE IN SEQUENCE TO RESTORE DF
/CDF TO AC
/C(IF) TO AC 6-8 FORMS CDF 20 (6221)
/STORE IN SEQUENCE TO SET DF
/SETS DF TO CURRENT IF
/SET IF BUFFER TO SUBROUTINE FIELD 4
/JUMP TO SUBROUTINE IN FIELD 4
/RESTORES ORIGINAL DF (FIELD 1)

SUBADR,
KCDF,

SUBRTN
CDF

/ABSOLUTE ADDRESS OF SUBROUTINE
/CONSTANT

SETDF.

/IN FIELD 4, THE SUBROUTINE HAS THE FOLLOWING GENERAL FORM
SUBRTN,

0
TAD KCIF
RDF
DCA RESIF

/C(PC) FROM CALLING PROGRAM
/CIF INSTRUCTION TO AC
/C(DF) TO AC 6-8 FORMS CIF 20 (6222)
/STORE IN SEQUENCE TO RESTORE CALLING FIELD

RESIF,

<WOO

/SETS IF BUFFER TO RESTORE CALLING FIELD

4-22

KCIF,

JMP I SUBRTN
CIF

/JUMP BACK TO CALLING PROGRAM
/CONSTANT

The original contents of the IF, placed in the DF by the calling program, are used to form a CIF instruction which
is placed in the subroutine program sequence just before the exit, to restore the original calling field.
4.6.3.3 Program Interrupt - If, when the PI facility is enabled, a PI request occurs, the contents of the IF and DF
are saved in the Interrupt Buffer. The contents of the PC are stored in register 0000 of Field 0, and the next
instruction is taken from register 0001 of Field 0. Regardless of the states of the Memory Field register, a PI always
transfers control to Memory Field 0. When the interrupt has been serviced, the RMF instruction is used to restore
the Memory Field registers to their original states. The last three instructions of a general interrupt service routine
should be as follows:

RMF
ION

JMP I 0

/RESTORES DF, PUTS ORIGINAL IF IN IF BUFFER
/ENABLE INTERRUPT
/SETS IF FROM IF BUFFER, AND RETURNS TO
/MAIN PROGRAM.

4-23/4-24

CHAPTER 5
INPUT/OUTPUT BUS DESCRIPTION

Because the processing power of a computer depends largely upon the range and number of peripheral devices that
can be connected to it, the PDP-12 has been designed to interface readily with a broad variety of external
equipment. This chapter defines the interface characteristics of the computer thus allowing the user to design and
implement any electrical interfaces required to connect 1/0 devices to the PDP-12.
The simple 1/0 technique of the PDP-12, the availability of DEC's FLIP CHIP logic circuit modules, and DEC's
oolicy of giving assistance wherever possible allow inexpensive, straightforward device interfaces to be realized.
hould questions arise relative to the computer interface characteristics, the design of interfaces using DEC
modules, or installation planning, customers are invited to telephone any of the sales offices or the main plant in
Maynard, Massachusetts. Digital Equipment Corporation makes no representation that the interconnection of its
circuit modules in the manner described herein will not infringe on existing or future patent rights. Nor do the
descriptions contained herein imply the granting of licenses to use, manufacture, or sell equipment constructed in
accordance herewith.
The PDP-12 contains a central processor and core memory composed of Digital's M Series TTL circuit modules.
These circuits have an operating temperature range exceeding the limits of 50° F to 110° F, so air-conditioning is
not required. Standard 11 SV, 50/60-Hz power operates an internal solid-state power supply that produces all
required voltages and currents. High-capacity, high-speed 1/0 capabilities of the PDP-12 allow it to operate a variety
of peripheral devices in addition to the standard Teletype keyboard/printer, tape reader, and tape punch. DEC
options, consisting of an interface and normal data processing equipment, are available for connecting into the
computer system. These options include a random access disk file, card equipment, line printers, magnetic tape
transports, magnetic drums, analog-to-digital converters. CRT displays, and digital plotters. The PDP-12 system can
also accept other types of instruments or hardware devices that have appropriate interfaces. Up to 61 devices
requiring three programmed command pulses, or up to 183 devices requiring one programmed command pulse can
be connected to the computer. The interface of any device to the computer does not require any modification to
the central processor, and thus can be achieved in the field.
Control of some kind is needed to determine when an information exchange is to take place between the PDP-12
and peripheral equipment, and to indicate the location(s) in the computer memory which will accept or yield the
data. Either the computer program or the 1/0 device can exercise this control. Transfers controlled by the
computer, hence under control of its stored program, are called programmed data transfers.
Transfers made under control of the external 1/0 devices through the data break facility are called data break
·ansfers.

5-1

Programmed Data Transfers

The majority of 1/0 transfers occur under program control. To transfer and store information under program
control takes about six times as much computer time as under the data break facility. In terms of real time, the
duration of a programmed transfer is rather small, due to the high speed of the computer, and is well beyond that
required for laboratory or process control instrumentation.
To realize full benefit of the built-in control features of the PDP-12, programmed 1/0 transfers should be used in
most cases. Controls (or devices using programmed data transfers are usually simpler and less expensive than
controls for devices using data break transfers. Using programmed data transfer facilities, simultaneous operation of
devices is limited only by the relative speed of the computer with respect to the device speeds, and the search time
required to determine the device requiring service. Analog-to-digital converters, digital-to-analog converters, digital
plotters, line printers, message switching equipment, and relay control systems typify equipment using programmed
data transfers.

Data Break Transfers

Devices which operate at very high rates of speed or which require very rapid response from the computer use the
data break facilities. Use of these facilities permits an external 1/0 device to insert or extract words from the
computer core memory, almost arbitrarily bypassing all program control logic. Because the computer program has
no cognizance of such transfers, programmed checks of input data are made prior to use of information received in
this manner. The data break is particularly well suited for devices that transfer large amounts of data in block form;
e.g., random access disk file, high-speed magnetic tape systems, high-speed drum memories, or CRT display systems
containing memory elements.

Program Interrupt
It is sometimes very useful for a program to be able to initiate operation of an I/O device and then continue with

execution of programming which is not immediately related to the input-output operation, rather than wait for the
device to become ready to transfer data. In this mode of operation, the device itself, through use of the PDP-12
Program Interrupt facility, initiates execution of the programming to transfer data to or from the computer. When
the device requires service (i.e., when the device is ready to transfer data), it transmits an interrupt request signal to
the computer. This signal causes the execution of the program currently underway to be interrupted, and program
control to be transferred to a specific memory location. The contents of the program counter are stored in this
location, and subroutine for servicing the I/O device beginning in the next core memory location is executed. After
completion of the data transfer, the interrupted program is resumed by returning to the location specified by the
contents of the program counter, which were saved when the interrupt occurred. The program interrupt hardware
is designed so that interrupt requests from devices may be ignored if the program so desires.

Logic Symbols
The PDP-12 uses TTL logic internally. In order to discuss some of the internal logic pertaining to interfacing, it is
necessary to understand the TTL symbology used in the PDP-12. The logic symbols are shown in Figure 5-1.

Signal Names

All signals not originating at a flip-flop output are true when the line is at the level indicated by the suffix H (high)
or L (low). Thus, a line labeled IOP 1 His high when the pulse is being generated, and at all other times is ground.
Similarly, AC CLEAR Lis at ground for assertion, and positive otherwise.

5-2

-0
-0
DD-

+3V INPUT
CLOCK PULSE WILL CAUSE
DATA INPUT TO APPEAR
AT "1" OUTPUT

DATA-----'

GND INPUT

Ir= :~SEC

~SEC

TAPPED DELAY

+3V OUTPUT

ADJUSTABLE

GND OUTPUT

DELAY

SINGLE SHOT WITH
COMPLEMENTARY OUTPUTS

LOGICAL AND GATE
FOR POSITIVE SIGNAL
WITH POSITIVE OUTPUT

GENERAL
PURPOSE
FILTER

LOGICAL OR GATE
FOR POSITIVE SIGNALS
WITH POSITIVE OUTPUT

AMPLIFIER
(OR LEVEL CONVERTER)

LOGICAL NANO GATE (AND)
POSITIVE SIGNALS

LOGICAL NOR GATE FOR
GNO SIGNALS

12-0125

Figure 5-1. Logic Symbols
Signals originating at flip-flops are defined in terms of the flip-flop state. The following table illustrates the
convention.
Signal Name
MB 03 (0) H
MB 03 (0) L

State of MB Flip-Flop
0
0

Signal Voltage
+3V

ov
ov

MB 03 (1) L
MB 03 (1) H

+3V

NOTE
The line MB 03(0)H is the same line as MB 03(1)L, and MB 03(1)H is the same line
as MB 03(0)L.

5-3

5.1 PROGRAMMED DATA TRANSFERS AND 1/0 CONTROL
The majority of 1/0 transfers take place under control of the PDP-12 program, taking advantage of control
elements built into the computer. Although programmed transfers take more computer and actual time than data
break transfers, the timing discrepancy is insignificant, considering the high speed of the computer with respect to
most peripheral devices. The maximum data transfer rate for programmed operations of 12-bit words is 148 kHz
when status checking (end, transfer check, etc.) is not done. This speed is well beyond the normal rate required for
typical laboratory or process control instrumentation.
The PDP-12 is a parallel-transfer machine that distributes and collects data in bytes of up to twelve bits. All
programmed data transfers take place through the accumulator, the 12-bit arithmetic register of the computer. The
computer program controls the loading of information into the accumulator (AC) for an output transfer, and for
storing information in core memory from the AC for an input transfer. Output information in the AC is power
amplified, and supplied to the interface connectors for bussed connection to many peripheral devices. Then the
program-selected device can sample these signal lines to strobe AC information into a control or information
register. Input data arrives at the AC as pulses received at the interface connectors from bussed outputs of many
devices. Gating circuits of the program-selected device produce these pulses. Command pulses generated by the
device are connected to the input/output skip facility (IOS) to sample the condition of I/O device flags.
The IOS allows branching of the program based upon the condition or availability of peripheral equipment,
effectively making programmed decisions to continue the current program or jump to another part of the program,
such as a subroutine to service an 1/0 device.
The bussed system of input/output data transfers imposes the following requirements on peripheral equipment:
a. Each device must be able to sample the select code, generated by the computer during an IOT instruction*,
and, when selected, must be able to produce sequential IOT command pulses in accordance with the
computer-generated IOP pulses. Circuits which perform these functions in the peripheral device are called
Device Selectors (DS). Figure 5-2 shows the decoding of the IOT instruction.

OPERATION
CODE

IOP GENERATOR
CONTROL

,-J---..,

DEVICE
SELECTION

CODE
12-0039

Figure 5-2. IOT Instruction Decoding

b. Each device rece1vmg output data from the computer must contain gating circuits at the input of a
receiving register capable of strobing the AC signal information into the register when triggered by a
command pulse from the DS. Gating is also recommended at the input to the peripheral device in order to
minimize loading on the BAC signal lines.

*Appendix C provides a listing of IOT instructions.

5-4

c. Each device sending input data to the computer must contain gating circuits at the output of the
transmitting register capable of sampling the information in the computer output register and supplying a
pulse to the computer input bus when triggered by a command pulse from the DS.
d. Each device should contain a Busy/Done flag (flip-flop) and gating circuits that can pulse the computer I/O
skip bus (IOS) upon command from the DS when the flag is set in the binary 1 state, to indicate that the
device is ready to transfer another byte of information.
Figure 5-3 shows the information flow within the computer which effects a programmed data transfer with I/O
equipment. All instructions stored in core memory as a program sequence are read into the memory buffer register
(MB) and the instruction register (IR) for execution. The transfer of the operation code in the three most
significant bits (bits 0, 1, and 2) of the instruction into the instruction register (IR) takes place and is decoded to
produce appropriate control signals. The computer, upon recognition of the operation code as an IOT instruction,
enters a 4.25-microsecond expanded computer cycle and enables the IOP generator to produce time-sequenced IOP
pulses as determined by the three least significant bits of the instruction (bits 9, 10, and 11 in the MB). These IOP
pulses and the buffered output of the select code from bits 3-8 of the instruction word in the MB are bussed to
device selectors in all ~eripheral equipment.

BITS

0-2
12-BIT
- - - - - . INSTRUCTION
WORD
CORE
MEMORY

INSTRUCTION
REGISTER
(IRl

IR
DECODER

IOT
INSTRUCTION
IOP
GENERATOR

IOP PULSES

BITS 9-11
MEMORY
BUFFER
REGISTER
(MB)

BITS 3-8

ACCUMULATOR
REGISTER
(AC)

CONNECTIONS
TO INPUT I OUTPUT
DEVICE

INPUT OUTPUT
SKIP
FACILITY
!IOS)
PROGRAM
,.......P-RO_G_R-AM--. INTERRUPT
INTERRUPT
REQUEST
FACILITY
-----(Pl)

81·0119

Figure 5-3. Programmed Data Transfer Interface Block Diagram

5-S

STMT al
IIO CYCLE
:
I
:.---750·950 na

. .H. P!!
'

+:sv
9TI I ClllWLILf

lO DlvtCEI

I1
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:
~
I
II
;~g :: ---t------------------------------+!I

;.----..,;

!. . . .

I
:

CTO DIV1Cll

-.j 1--500- 600 na --1

.-------.

700- 850 ..

_J
~

+SY I

t--

!
i

:50-450na _ ,

t---500-600

3!50-450 na ~

llO • . . , .

500- 600 ··~

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r
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:""'-----------------------------~!-

(TO lllVICf:I

*
I

___J

+3\1 I

ITI I IAllllllLAkE
TO 0€\t!Cll
tllO

ENO CW
I/O CYCLE
I

400 " ' ,

1+-850

··----l

,.-

··=1 }----

850 •• _ ,

I
I

1.0 >''

2.0 ,Ill

3.0 )U

4.0 ,Ill
12-0128

Figure 5-4. Programmed Data Transfer Timing

Figure 5-4 indicates the timing of programmed data transfers.
Devices which reqµire immediate service from the computer program, or which require too much computer time to
discontinue the main program until transfer needs are met, can use the program interrupt (Pl) facility. In this mode
of operation, the computer can initiate operation of I/O equipment and continue the main program until the device
requests servicing. A signal input to the PI requesting a program interrupt causes storing of the conditions of the
main program and initiates a subroutine to service the device. At the conclusion of this subroutine, the main
program is reinstated until another interrupt request occurs.
5.1.l Timing and IOP Generator
When the IR decoder detects an operation code of 6000 8 , it identifies an IOT instruction and the computer
generates a slow cycle. The Slow Cycle signal is ANDed with TP4 to generate I/O Start and sets the I/O PAUSE
flip-flop. The logic of the IOP generator consists of a re-entrant delay chain which generates three time states.
These time states are gated with MB bits 11, 10, and 9 to generate IOP 1, IOP 2, and IOP 4, respectively. Note that
an IOP is generated only if the corresponding MB bit is set although the 1/0 timing remains constant. At the end of
each IOP, the state of the 1/0 interface is sampled by an I/O strobe pulse.
Following the end of IOP 4 time, the PAUSE flip-flop is reset and the normal timing chain is restarted.

5-6

Unlike PDP-8/1, the PDP-12 does not make a timing distinction between internal 1/0 functions and normal 1/0,
thus all 1/0 instructions cause the slow cycle.
Instruction
Bit

IOP
Pulse

IOT
Pulse

Event
Time

11
10

IOP 1
IOP 2
IOP 4

IOT 1
IOT 2
IOT4

1
2
3

Used Primarily For,
But Not Restricted To
Sampling Flags, Skipping.
Clearing Flags, Clearing AC.
Reading Buffers, Loading Buffers and Clearing
Buffers.

5.1.2 Device Selector (OS)
Bits 3 through 8 of an IOT instruction serve as a device or subdevice select code. Bus drivers in the processor buffer
the 1 and 0 output signals of MB 3 _8 and distribute them to the interface connectors for bussed connection to all
device selectors. Each DS is assigned a select code and is enabled only when the assigned code is present in the MB.
When enabled, a DS regenerates IOP pulses as IOT command pulses and transmits these pulses to skip, input, or
output gates within the device and/or to the processor to clear the AC.
Each group of three command pulses requires a separate DS channel, and each DS channel requires a different
select code (or 1/0 device address). Therefore, one 1/0 device can use several DS channels. Note that the processor
produces the pulses identified as IOP 1, IOP 2, and IOP 4 and supplies them to all device selectors. The device
selector produces pulses IOT 1, IOT 2, and IOT 4, which initiate a transfer or effect some control. Figure 5-5 shows
generation of command pulses by several DS channels.

IOT 6341 H
IOT 6341 L

6 LINES FOR
SELECT CODE
34

DEVICE
SELECTOR
34

IOT 6342 H
IOT 6342 L
IOT 6344 H
IOT 6344 L
DEVICE 34 SELECTED

6 LINES FOR
SELECT CODE
33

DEVICE
SELECTOR
33

'-y-J
12
BMB
LINES

IOP LINES
(BUSSED TO ALL
DEVICE SELECTORS)

12-0124

Figure 5-5. Generation of IOT Command Pulses by Device Selectors

5-7

The logical representation for a typical channel of the DS, using channel 34, is shown in Figure 5-6. An 8-input
AND gate is wired to receive the appropriate signal outputs from the MB 3 - 8 for select code 34, which. activates the
channel. In the DS module, 6 input pins are connected to the complementary outputs of MB 3 - 8 , and 2 are open to
receive subdevice or control condition signals as needed. Either the 1 or the 0 signal from each MB bit is connected
to the AND gate when establishing the select code. The positive output of the AND gate indicates when the IOT
instruction ~election selects the device, and can, therefore, enable circuit operations with the device. This output
also enables three' power NAND gates, each of which produces a ground output pulse if the corresponding IOT
pulse occurs. The ground output from each gate is an IOT command pulse identified by the select code and the
number of the initiating IOP pulse. Three inverters receive the negative IOT pulses to produce complementary IOT
output pulses.

IOT 6344 H

B lOP 4 H - - - - - - t

IOT 6342 H

BMB03 (O)H

B IOP 2 H - - + - - - - - t

BMB04 (1) H
IOT 6341 H

BMB05 (1) H
B IOP 1 H --4-------t
BMB06 (1) H
BMB07 (0) H
BMBOB (0) H

AVAILABLE FOR {
SUB-DEVICE
ENCODING

634XH
!DEVICE SELECT LINE
USED FOR BAC
INPUT GATING)

!U-0111

Figure 5-6. Typical Device Selector (Device 34)

An amplifier module can be connected in each channel of the DS to provide greater output drive.

5.1.3 Input/Output Skip (IOS)
Generation of an IOS pulse can be used to test the condition or status of a device flag, and to continue to or skip
the next sequential instruction based upon the results of this test. This operation is performed by a 2-input AND
gate in the device connected as shown in Figure 5-7. One input of the skip gate receives the status level (flag output
signal), the second input receives an IOT pulse, and the output drives the computer skip (designated SKIP BUSL)
to ground when the skip conditions are fulfilled. The state of the skip bus is sampled at the end of each IOT. If the
bus has been driven to ground, the contents of the program counter are incremented by 1 to advance the program
count without executing the instruction at the current program count. In this manner, an IOT instruction can
check the status of an I/O device flag and skip the next instruction if the device requires servicing. Programmed
testing in this manner allows the routine to jump out of sequence to a subroutine that services the device tested.

5-8

PDP-12

BUILT-IN LOADS RECEIVER

Si<iPBiJS L

STATUS
FLIP-FLOP

M623 SECTION
(PWR "AND" GATE
WITH OPEN COLLECTOR)

er -0101

Figure 5-7. Use of IOS to Test the Status of an External Device

Assuming that a device is already operating, a possible program sequence to test its availability is:
100,
IOI,
102,

6342
5100
5XXX

/SKIP IF DEVICE 34 IS READY
/JUMP.-1
/ENTER SERVICE ROUTINE FOR DEVICE 34.

When the program reaches address I 00, it executes an instruction skip with 6342. The skip occurs only if device 34
is ready when the JOT 6342 command is given. If device 34 is not ready, the flag signal disqualifies the skip gate,
and the skip pulse does not occur. Therefore, the program continues to the next instruction, which is a jump back
to the skip instruction. In this example, the program stays in this waiting loop until the device is ready to transfer
data, at which time the skip gate in the device is enabled and the skip pulse is sent to the computer IOS facility.
When the skip occurs, the instruction in location 102 transfers program control to a subroutine to service device
34. This subroutine can load the AC with data and transfer it to device 34, or can load the AC from a register in
device 34 and store it in some known core memory location.
5.1.4 Accumulator
The binary 1 output signal of each flip-flop of the AC, buffered by a bus driver, is available at the interface
connectors. These computer data output lines are bus-connected to all peripheral equipment receiving programmed
data output information from the PDP-12. The 1/0 bus input on each flip-flop of the AC is connected to the
interface connectors for bussing to all peripheral equipment supplying programmed data input to the PDP-12. An
IOP that drives the input bus terminal to ground sets the corresponding AC flip-flop. Output and input connections
to the accumulator appear in Figure 5-8.
The status of the link bit is not available to enter into transfers with peripheral equipment (unless it is rotated into
the AC). A bus driver continuously buffers the output signal from each AC flip-flop. These buffered accumulator
(BAC) signals are available at the interface connectors.

5-9

BAC01( I) L

AC BUS DRIVER

0
ACO,

110 STROBE
(OCCURS AT END
OF EACH IOP)

110 ENABLE (ASSERTED BY ALL IOP's)

AC01 !OH

AC CLEAR BUS
(FROM 110 INTERFACE)

AC 01 BUSL
(FROM 1/0 INTERFACE)

11-0112

Figure 5-8. Accumulator Input or Output
5.1. 5 Input Data Transfers

When a device is ready to transfer data into the PDP-12 accumulator, it sets a flag. The program senses the ready
status of the flag and issues an IOT instruction to read the contents of the external device buffer register into the
AC. If tlie AC CLEAR BUS Lis not asserted, the resultant word in the AC is the inclusive OR of the previous word
in the AC and the word transferred from the device buffer register. The AC CLEAR BUSL may also be used as an
1/0 AC clear by activating only this line from a separate IOT.
The illustration in Figtire 5-9 shows that the accumulator has an input bus for each bit flip-flop. Setting a 1 into a
particular bit of the accumulator necessitates grounding of the interface input bus by the standard interface gate. In
the illustration, the 2-input AND gates set various bits of the accumulator. In this case an IOT pulse is AND
combined with the flip-flop state of the external device to transfer into the accumulator. (The program need not
include a clear AC command prior to loading in this manner.)

5-10

Following the transfer (possibly in the same instruction) the program can issue a command pulse to initiate further
operation of the device and/or clear the device flag.
ACOO

ACOl

AC02

110
CONTROL

PDP-12

AC CLEAR BUS L

ACOO BUSL

ACOI BUSL

At:.02 BUSL

TRANSFER !OT 1-U- l --------+-----t>------+---.-------t---~---------t---

PWR "ANO" GATES

4--- WITH OPEN COLLECTORS
M623 OR EQUIVALENT

OMIT THIS GATE
IF "ONES TRANSFER"
DESIRED

I
81 ·011,

Figure 5-9. Loading Data into the Accumulator from an External Device

5.1.6 Output Data Transfers
The AC is loaded with a word (e.g., by a CLA TAD instruction sequence); then the IOT instruction is issued to
transfer the word into the control or data register of the device by an IOT pulse (e.g., IOP 2), and operation of the
device is initiated by another IOT pulse (e.g., IOP 4). The data word transferred in this manner can be a character
to be operated upon, or can be a control word sampled by a status register to establish a control mode. The BAC
lines should be gated by the select code at each device to prevent excessive loading. A special module, the MlOl, is
provided for this purpose.
Since the BAC interface bus lines continually present the status of the AC flip-flops, the receiving device can strobe
them to sense the value in the accumulator. In Figure 5-10, a strobe pulse samples six bits of the accumulator to
transfer to an external 6-bit data register. Since this is a jam transfer, it is not necessary to clear the external data
register. The gates driving the external data register are part of the external device and are not supplied by the
computer. The data register can contain any number of flip-flops up to a maximum of twelve. If more than twelve
flip-flops are involved, two or more transfers must take place. Obviously the strobe pulse shown in Figure 5-10
must occur when the data to be placed in the external data register is held in the accumulator. This pulse,
therefore, must be under computer control to effect synchronization with the operation or program of the
computer.

5.1. 7. Program Interrupt (Pl)
When a large amount of computing is required, the program should initiate operation of an 1/0 device, then
continue the main program, rather than wait for the device to become ready to transfer data. The program
interrupt facility, when enabled by the program, relieves the main program of the need for repeated flag checks by
allowing the ready status of 1/0 device flags to automatically cause a program interrupt. When a program interrupt
occurs, program control transfers to a subroutine that determines which device requested the interrupt, and
initiates an appropriate service routine.

5-11

DATA REGISTER OF
EXTERNAL DEVICE

0
FF

IOT (FROM Ml03)
(STROBE PULSE)
M111 INVERTERS
(IF NEEDED)

M101 INPUT GATES

DEVICE SELECT LINE _ __.~--'----____,..__-+.----..._---1----_._-+-----_.--+------'
(FROM 103)

BAC INPUTS
FROM COMPUTER

12-0198

Figure 5-10. Loading a Six-Bit Word into an External Device from the Accumulator

In the example shown in Figure 5-11, a flag signal from a device status flip-flop operates a standard gate with no
internal load. When the status flip-flop indicates the need for device service, the Program Interrupt Request bus is
driven to ground and requests a program interrupt.

INTERRUPT
BUS

M623 OR EQUIVALENT GATE
GATE IS ACTIVATED WHEN
FLIP-FLOP IS SET

DEVICE FLAG
OR STATUS
FLIP- FLOP

0
I
FLIP-FLOP

IOT TO
CLEAR FLAG
12-0135

Figure 5-11. Program Interrupt Request Signal Origin
If only one device is connected to the PI facility, program control can be transferred directly to a routine that
services the device when an interrupt occurs. This operation occurs as follows (example in 8 mode):

Tag

Address

Instruction

Remarks

JMP SR

/MAIN PROGRAM
/MAIN PROGRAM CONTINUES
/INTERRUPT REQUEST OCCURS
/INTERRUPT OCCURS
/PROGRAM COUNT (PC= 1003) IS
/STORED IN 0000
/ENTER SERVICE ROUTINE

1000
1001
1002
0000
0001

5-12

SR,

2000

3001
3002
3003
3004
1003
1004

RMF
ION
JMP I 0000

/SERVICE SUBROUTINE FOR
/INTERRUPTING DEVICE AND
/SEQUENCE TO RESTORE AC, AND
/RESTORE .LINK IF REQUIRED
/RESTORE MEMORY FIELDS
/TURN ON INTERRUPT
/RETURN TO MAIN PROGRAM
/MAIN PROGRAM CONTINUES

In most PDP-12 systems, numerous devices are connected to the PI facility, so the routine beginning in core
memory address 0001 must determine which device requested an interrupt. The interrupt routine determines the
device requiring service by checking the flags of all equipment connected to the PI and transfers program control to
a service routine for the first device encountered that has its flag in the state required to request a program
interrupt. In other words, when program interrupt requests can originate in numerous devices, each device flag
connected to the PI must also be connected to the IOS.

DEVICE 2
FLAG

INTERRUPT
BUS

SKIP
BUS
81-0106

Figure 5-12. Multiple Inputs to IOS and PI Facilities

5-13

5.1. 7.1 Multiple Use of IOS and Pl - In common practice, more than one device is connected to the PI facility. In
the basic PDP-12, the teletype flags are already connected. Therefore, since the computer receives a request that is
the inclusive OR of requests from all devices connected to the PI, the IOS must identify the device making the
request. When a program interrupt occurs, a routine is entered from address 0001 in 8 mode (0041 in Linc mode)
to sequentially check the status of each flag connected to the PI and to transfer program control to an appropriate
service routine for the device whose flag is requesting a program interrupt. Figure 5-12 shows JOS and PI
connections for two typical devices.
The following program example illustrates how the program interrupt routine determines the device requesting
service (example in 8 mode):
Tag

Instruction

Address

Remarks

1000
1001
1002

/MAIN PROGRAM
/MAIN PROGRAM CONTINUES
/INTERRUPT REQUEST OCCURS
INTERRUPT OCCURS

0000
0001

JMP FLGCK

FLGCK,

JOT 6341
SKP
JMP SR34
IOT 6441
SKP
JMP SR44
JOT 6541
SKP
JMP SR54

/STORE PC (PC= 1003)
/ENTER ROUTINE TO DETERMINE
/WHICH DEVICE CAUSED INTERRUPT
/SKIP IF DEVICE 34 IS REQUESTING
/NO - TEST NEXT DEVICE
/ENTER SERVICE ROUTINE 34
/SKIP IF DEVICE 44 IS REQUESTING
/NO - TEST NEXT DEVICE
/ENTER SERVICE ROUTINE 44
/SKIP IF DEVICE 54 IS REQUESTING
/NO - TEST NEXT DEVICE
/ENTER SERVICE ROUTINE 54

Assume that the device that caused the interrupt is an input device (e.g., tape reader). The following example of a
device service routine might apply:
Tag

Instruction

SR,

DCA TEMP
IOTXX
DCA I 10
ISZ COUNT
SKP
JMPEND

TAD TEMP

RMF
ION
JMP I 0

5-14

Remarks
/SAVE AC
/TRANSFER DATA FROM DEVICE BUFFER TO AC
/STORE IN MEMORY LIST
/CHECK FOR END
/NOT END
/END. JUMP TO ROUTINE TO HANDLE
/END OF LIST CONDITION

/RESTORE LINK AND OTHER STATUS IF REQUIRED
/RELOAD AC
/RESTORE MEMORY FIELDS
/TURN ON INTERRUPT
/RETURN TO PROGRAM

If the device that caused the interrupt was essentially an output device (receiving data from computer), the IOT then - DCA I 10 sequence might be replaced by a TAD I 10 - then - IOT sequence.

5.2 MULTI-LEVEL AUTOMATIC PRIORITY INTERRUPT
The KF12B Multi-Level Automatic Priority Interrupt is designed to reduce the central processor overhead during
the servicing of program interrupts. It is prewired in the EP section of the PDP-12 in racks P and R and utilizes approximately 55 M series modules. There are three major services provided automatically by the KFl 2B.
a.

Automatic determination of device priority and vectoring of interrupt service routines.

Automatic saving and restoring of all major registers and machine status which include the following:
PC, AC, IF, DF, MQ, LINK, FLOW, UF, MODE and the current processor level.

Automatic stacking of the saved parameters permitting multiple levels of interrupts.

Storing, or stacking, of parameters is called Pushing and restoring the CP to its original status prior to an interrupt
is called Popping. The CP is in the break state for the duration of each operation. It takes five break cycles for each
Push and five break cycles for a Pop. This does not affect the normal operation of the data break facility in the
PDP-12. One data break device can be handled without the addition of a multiplexer. The KF 12B has the lowest
priority on the bus and break requests from another device are acknowledged during push and restore operations.
The KF 12B control has its own timing generator and is asynchronous with computer timing. A free running 5 mHz
oscillator provides the various clocking pulses. An MISS decoder provides the enable levels to enable data on the
bus.

5.2. I Interrupts
Up to 15 levels of interrupts can be accommodated with each level having a two-word vector address. The interrupts can be accepted from a prewired option or from up to six external devices. A priority is assigned to each interrupt by a jumper module, M905 at location RI 6. Level 0 has the highest priority. Interrupts of a higher priority
can occur after executing the first instruction in the interrupt service routine. When the KFI 2B is not enabled (API
ON (0)), interrupts are processed through the interrupt cycle in the normal manner. The "TRAP" feature has not
been modified by the KFl 2B, but caution should be exercised when using this feature.

5.2.2 Push
When the level of the device requesting an interrupt is greater than the current machine level a Push operation is
performed. The Push and Break Req flip-flops are set and the processor enters the Break cycle. The active registers
and status levels are stored (pushed) in five consecutive memory locations specified by the contents of the STACK
register. (Refer to Table 5-1.) The starting location of the stack is specified by the program (IOT 6776) and is automatically incremented during the push operation. The stack increments and decrements across field boundaries.
The CP is always in 8 MODE at the completion of an interrupt-push operation. If the CP is in LINC mode when a
Push occurs it is returned to LINC mode at the completion of a Restore command.

5-15

Table 5-1. STACK Register
Location

Data Stored

AC 0-11

P+l

PC 0-11

P+2

MODE o; FLOW 1; LINK 2; MACHINE LEVEL 8-11

P+3

MQ 0-11

P+4

UF 1; IF 2-6; DF 7-11

P =Initial STACK address.
NOTE: the subscript indicates the corresponding memory bits.

5 .2.3 Restore-"POP" (REST-IOT 6771)
Every interrupt subroutine should be terminated with a Restore command. This restores the major registers and
machine status from the stack and resumes programming at the memory location specified by the program counter.
For every Push operation performed a Pop (restore) must be performed; however, the two operations do not have
to occur in any particular sequence (see Figure 5-13). The Restore command should not be issued when the CP is
in a non-interruptable state because an Interrupt Inhibit is set due to the LIP or CIF instruction, or SAVE PC is not
set due to a DJR instruction.

E1
EO

/
CORE {
MEMORY
1. AN EMPTY STACK

2. PUSHING A DATUM ONTO
THE STACK

&-i

EB
4. ANOTHER PUSH

3. PUSHING ANOTHER DATUM
ONTO THE STACK

E3
E2

bd
5. POP

EB
6. PUSH

bd
7, POP
12-0297

Figure 5-13. Illustration of Push and Pop Operations

5.2.4 Vectoring
Each of the 15 interrupt levels has an associated vector address to specify the appropriate interrupt service routine.
The vector address is transferred to the PC during the Push operation, as shown in Figure 5-14. Vector bits 0, 1,
and 2 specify the memory field and are set with AC bits 3, 4, and S by an IOT. Vector bits 3 through 9 specify the
seven most significant bits of the MA (0-6) and are set with AC bits 0-6 by an IOT. The interrupt level specifies
memory address bits 7 through 10 with level "O" setting these bits to zero. A vector address is always an even number address; therefore, each interrupt level is allotted two memory locations.

5-16

The following are the vector address assignments, which can reside in any memory field. Vector bits 3 through 9
(MA0-6) are set to 1s by the SVEC instruction:
Level

Address

Level

Address

0
0

7740
7741
7742
7743
7744
7745
7746
7747
7750
7751
7752
7753
7754
7755
7756
7757

8
8
9
9

7760
7761
7762
7763
7764
7765
7766
7767
7770
7771
7772
7773
7774
7775

2
2
3
3
4
4
5
5
6
6
7
7

MEMORY
FIELD

10
10

11
11
12
12
13
13
14
14

MEMORY ADDRESS BITS

VECTOR REGISTER

IOT

3-5

INTERRUPT
LEVEL

IOT

12-0298

Figure 5-14. Vector Flow Diagram

5.2.5 Maintenance Logic
The maintenance logic included in the KF 12B provides the capability of checking the major portion of the option
for proper operation. Two JOT instructions simulate the 15 interrupt level inputs to check the priority logic and
initiate the Push operation.

5-17

Instruction

Function

IOT 6051

AC0-11 to LEVELS 0-11
( 1s transfer)

IOT 6052

AC 9, 10, 11 to LEVELS 12, 13, 14
( 1s transfer)

The levels remain set for only one computer cycle. This feature allows enough time to initiate a Push function
when the selected level has priority and API is enabled.
The KFl 2B features a new two-word instruction called push jump (PUSHJ, IOT 676X). This instruction permits
jumping to subroutines across field boundaries in both Linc and PDP-8 Modes. The instruction causes the stacking
of the active registers and machine status and automatically jumps to the memory location specified by the 15-bit
address associated with the PUSHJ. The instruction code is (IOT) 676X and is similar to an IOT except that X defines the new memory field and the following location (P+ 1) specifies the 12-bit memory address of the subroutine.
The PC, which is saved on the stack during the execution of the PUSHJ, points to the location following the twoword instruction as shown in the following example:
Address

Instruction

Octal Code

15432
15433
15434*

PUSHJ
1000
CLA

6760
1000
7200

01000 - Programming is transferred to this memory location.

* Field and PC saved on stack. The program is resumed at this
location following a Restore.

5. 2 .6 Programming
The following is a typical example of a program to service a Teletype interrupt, which is level 5.
START/CLA
TAD FLDLEV
SMLV
CLA
TAD STACK
SSTK
CLA
TAD VEC
SVEC
APION
NOP
JMP. -1

* 6412/JMS TTYR
* 6413/REST

5-18

/set stack and vector fields
and machine level
/set stack

/set vector
/enable KF 12
/wait for interrupt
/go to teletype reader subroutine
/restore to status prior to push

*VECTOR ADDRESSES
/return address saved here

TTYR/XXXX

CLA
KRS
DCA I SAVE

/read keyboard buffer
/save word
/clear reader flag
/return to restore

KCC
JMPITTYR
FLDLEV/0017
STACK/7000
VEC/6400

5.2.7 Programming Restrictions
The REST and PUSHJ commands should not be issued when the processor is in a non-interruptable state due to the
following conditions:
a.

"Interrupt Inhibit" being set due to the execution of a CIF or LIF instruction;

The DJR instruction is being executed or Save PC is not set due to the previous execution of a DJR
instruction.

If the REST command is issued and the CP is not in an interruptable condition, the Restore operation will not be
performed until the condition becomes satisfactory. If the PUSHJ command is issued and the CP is not in an interruptable condition, the second word of the instruction is treated as a new instruction, and when the condition becomes satisfactory, the PUSHJ operation will not be properly executed. The ESF Disable Teletype instruction is not
effective when the KF 12B is enabled (API ON (1)); the TIY and DP 12 interrupts will always be acknowledged.
When the KF l 2B is not enabled (API ON (0)), the ESF instruction functions in the normal manner. Location zero
is not saved on the stack; therefore, caution should be exercised when using this location in conjunction with a LINC
JMP instruction.

5.2.8 Instruction List
Function

Octal

ION

Enable software interrupt system

6001

IOF

Disable all interrupts

6002

APION

Enable API (KF 12B) system
Disable software interrupt
The next instruction will be executed before an interrupt
is processed.

6006

PUSH-J

PUSH JUMP to 15 bit address

Instruction

676X
(P+l)

(XXXXX)

xxxx

REST

Restore machine to previous level

6771

SMLV*

Set current machine level to AC 8-11. If AC7= 1, set
stack field to AC0-2 and vector field to AC3-5.

6772

..:-_;,.~~..~:..ti--.

*The KFl 2B must be deselected to execute these instructions (i.e., API ON (0)).
5-19

Instruction

Function

Octal

RFLD

Read stack field into AC0-2, vector field into AC3-5,
current level into AC8- I l (Read in complement form)

6773

RSTK

Read least significant 12 bits of current stack pointer address (Read in complement form)

6774

RVEC

Read vector bits 3-9 into AC bits 0-6, Trial levels into
AC bits 7-10 (Read in complement form)

6775

SSTK*

Set the least significant 12 stack bits to AC0-11

6776

SVEC*

Set bits 309 of the vector address (MA0-6) to AC 0-6

6777

Note: When the above instructions are given in LINC mode they should be preceded by an IOB instruction.
*The KF l 2B must be deselected to execute these instructions (i.e., API ON (0)).
5.2.9 DM12
The DMl 2, which is prewired' in the PDP-12, provides the capability of operating up to three data break devices in
either three-cycle or single-cycle data break. Both three-cycle and single-cycle devices can be simultaneously controlled by the DM 12. The KF l 2B is a prerequisite for the DM 12 because the KF l 2B and DM 12 use the same timing
and control signals, which originate in the KF l 2B. The DM 12 uses M series positive logic; all signals are clamped at
0Vand+3V.
Because both options use the control and timing of the KF l 2B, the theory of operation is similar. When an external
device issues a break request, the corresponding Level flip-flop is set. The three level flip-flops and the API flip-flop
are decoded to determine priority. Either PRO, PR 1, or PR2 is generated and the appropriate Data Address and control signals are enabled on the bus. The EN BRK flip-flop corresponding to the device that has been decoded is set at
TPl, allowing the B BREAK signal to go to the device that has control of the bus. The B BREAK signal is used to
control the data on the bus for transfer between memory and the external devices.
Both options use the same IOTs; thus, when testing the DM 12 the KF l 2B must be disabled using jumpers that allow
only the DM 12 priorities to be enabled.
The DM 12 priorities are determined by cable location. Two cables from each device are used for the data address,
data bits, and status signals. The cables from the device having the highest priority are inserted in locations P20 and
P2 l as illustrated in Figure 5-15.
COAXIAL CABLES TOTAL LENGTH ON BUS 45ft. MAX.

EM12

BAC
EP 12

BMB

DEVICE 0

I /0 BUS*
KFl2
OM 12
P20
P21
P22

DEVICE

HIGHEST
PRIORITY

DATA ADDRESS
DATA BITS
DATA ADDRESS

DEVICE 2

LOWEST
PRIORITY

DATA BITS
P23
P.N

DATA ADDRESS
DATA BITS

P25
12-0299

COAXIAL CABLES -MAX, LENGTH 25 ft.
*If the priority interrupt system is used in the KF12B this cable is connected separately from each device.
(ref. BS-KF12-CAB).

Figure 5-15. DM12 Cable Diagram

5-20

5.3 DATA BREAK TRANSFERS
The Data Break facility allows an I/O device to transfer information directly with the PDP-12 core memory on a
cycle-stealing basis. The Data Break is ~articularly well suited for devices which transfer large amounts of
information in block form, and can be expanded to accommodate more than one device by using the DMOI or
DM04 multiplexers. The DMOI will multiplex up to seven devices and is a negative bus option. The DM04 (positive
bus) will multiplex three devices and up to three DM04s may be added for a total of nine devices.

Peripheral 1/0 equipment operating at high speeds can transfer information with the computer through the data
break facility more efficiently than through programmed means. The combined maximum transfer rate of the data
break facility is 6.5 million bits per second. Information flow to effect a Data Break transfer with an I/O device
appears in Figure 5-16.
MEMORY
EXTENSION
CONTROL
TYPE MCl2

EXTENDED DATA
ADDRESS 11 BIT)

MEMORY
ADDRESS
REGISTER
(MAI

DATA ADDRESS
(12 BITS)

CORE
MEMORY
MEMORY
BUFFER
REGISTER
!MBI

DATA INFORMATION
112 BITS IN)
DATA INFORMATION
(12 BITS OUT)
ADDRESS
ACCEPTED
WORD COUNT
OVERFLOW
BREAK STATE

DATA
BREAK
FACILITY

..--

CONNECTIONS TO
INPUT I OUTPUT
DEVICE

......-

~BREAK REQUEST

TRANSFER
t-_ DIRECTION (IN l
~CYCLE SELECT

--- +

CA INHIBIT

_ INCREMENT MB
I"'"
12-0123

Figure 5-16. Data Break Transfer Interface Block Diagram
In contrast to programmed operations, the Data Break facilities permit an external device to control information
transfers. Therefore, Data Break device interfaces require more control logic circuits, causing a higher cost than
programmed-transfer interfaces.
Data Breaks are of two basic types: single-cycle and three-cycle. In a single-cycle Data Break, registers in the device
(or device interface) specify the core memory address of each transfer and count the number of transfers to
determine the end of data blocks. In the three-cycle Data Break, two computer core memory locations perform
these functions, simplifying the device interface by omitting two hardware registers.

5-21

In general terms, to initiate a Data Break transfer of information, the interface control must do the following:
a. Specify the affected address in core memory.
b. Provide the data word by establishing the proper logic levels at the computer interface (assuming an input
data transfer), or provide input gates and storage for the word (assuming an output data transfer).
c. Provide a logical signal to indicate direction of data word transfer.
d. Provide a logical signal to indicate single-cycle or three-cycle break operation.
e. Request a Data Break by supplying a proper signal to the computer data break facility.

5 .3 .1 Single-Cycle Data Breaks

Single-cycle Data Breaks are used for input data transfers to the computer, output data transfers from the
computer, and memory increment data breaks. Memory increment is a special Data Break in which the content of a
memory address is read, incremented by 1, and rewritten at the same address. It is useful for counting iterations or
external events without disturbing the computer program counter (PC) or accumulator (AC) registers.

5.3.2 Input Data Transfers
Figure 5-17 illustrates timing of an input transfer data break. The address to be affected in core is normally
provided in the device interface in the form of a 12-bit flip-flop register (data break address register) which has
been preset by the interface control by programmed transfer from the computer.
External registers and control flip-flops supplying information and control signals to the Data Break facility and
other PDP-12 interface elements are shown in Figure 5-18. The data register (DR in Figure 5-18) holds the 12-bit
data word to be written into the computer core memory location specified by the address contained in the address
register (AR in Figure 5-17).
Appropriate output terminals of these registers are connected to the computer to supply ground potential to
designate binary 1s. Since most devices that transfer data through the Data Break facility are designed to use either
single-cycle or three-cycle breaks, but not both, the Cycle Select signal can usually be supplied from a stable source
(such as a ground connection or a +3v clamped load resistor), rather than from a bistable device as shown in Figure
5-18.
Other portions of the device interface, not shown in Figure 5-18, establish the data word in the input buffer
register, set the address into the address register, set the direction flip-flop to indicate an input data transfer, and
control the break request flip-flop. These operations can be performed simultaneously or sequentially, but all
transients should occur before the data break request is made.
When the Break Request is recognized, the computer completes the current instruction, generates an Address
Accepted pulse (at TPl, the beginning of the break cycle) to acknowledge receipt of the request, then enters the
Break state to effect the transfer. The Address Accepted pulse can be used on the device interface to clear the
BREAK REQUEST flip-flop, increment the content of the address register, etc. If the Break Request signal is
removed before TP2 time of the data break cycle, the computer performs the transfer and returns to programmed
operation.

5-22

TP2

+3
BREAK REQUEST SIGlllAL
lllllPUT TO PROCESSOR)

BREAK SYlllC FLIP FLOP
llNTERlllALI

TP:S

TP4

TP5

COMPUTER TIME

Tl'Z

TI'S

SAMPLED AT OFF-PAUSE
BY PROCESSOR**

----•I
D-------------'
SET AT SAMPLE TIME

TP4

TPI

TP2

TP:S

SIGlllAL MUST GO TOH\/ AT START Of" AOOMSS ACCEPT PULSE IF NEXT CYCLE IS TO IE A BREAK

----+
SAMPLE
AT TPI

____..I

3 CYCLE
CYCLE SELECT
!SAMPLE TO PROCESSOR I

TPI

PREVIOUS
ClCLE-..... - - - - - - - - I M t E A K CYCLE - - - - - - - - . - - N E X T CYCLE

USED TO SELECT BREilK CYCLE AT TP I

I
SAMPLED AT TPI
t-"-TYPICALLY HARDWIRED FOR A GIVEN DEVICE

1 CYCLE

8-BREAK SIGlllAL
IOUTPUT TO 110 OE\/ICEl

Ett«l OF llM:AIC CYCLE ____,

DATA ADDRESS
INPUT LEVELS
(INPUT TO PROCESSOR)

EXT.MEM.
ADDRESS
READ

READ AT
TP I BY
PROCESSOR

EARLIEST TIME POSSIBLE TO REMOVE AOORESS IS AT START OF BREilK CYCLE

TPI -TP:S

ADDRESS ACCEPT PULSE
!OUTPUT TO I 10 DEVICE I
GND
IN (+311)
TRANSFER DIRECTION
I INPUT TO PROCESSOR)

lllUST BE SET UP AT TP2

SIGNAL INPUT TO MB
*DATAlllllPUT
TO PROCESSOR)

- -----

AVAIL (+3\1)
LATEST POSSIBLE TIME TO SPECIFY
INPUT DATA IS TP2

NOT AVAIL (GND)
"Ou TPUT DATA AVAILABLE IN MB
!OUTPUT TO 110 DEVICE)

r...----CANCHAlllG£ ANYTIME AFTER TP:S

~----------------------

OUT(GND)

SAMPLED AT TP:S BY PROCESSOR

lllVAIL(+3V)
AVAILABLE AT TP 3

TIME DURING WHICM DATA MUST !IE STllOllED BY 1/0 OE\/ICE

NOT AVAIL (+3\1) - - - - - - - - - - - - - - - - - - - - - - - - - - - '

BTS5
!OUTPUT TO 110 DEVICE I

BTS2
!OUTPUT TO 110 DEVICE)

G:: --------~~L------------------'~~-------------~+3\/
GNO

*WORD COUNT OVERFLOW
!OUTPUT TO l/ODE\/ICEl

+3\1 - - - - - - - - - - - - - - - - - - - - - - - - - - .

OCCURS If' MEMORY INCREMENT IS FIEOUESTEO
AlllD THE WORD COUNT OVERFLOWS

GNO
* SIGNAL NOT USED FOR INPUT TRANSFERS
SHOWN FOR REFERENCE ONLY

**OFF-PAUSE OCCURS 200n1 BEFORE TP5. IF
OFF IOP SAMPLES BREAK REQUEST.

IOP INSTRUCTION IN PROCESS,

12-0130

Figure 5-17. Single Cycle Data Break Input Transfer Timing Diagram
5.3.3 Output Data Transfers
Timing of operations occurring in a single-cycle output Data Break is shown in Figure 5-19. Basic logic circuits for
the device interface used in this type of transfer are shown in Figure 5-20. Address and control signal generators are
similar to those discussed previously for input data transfers, except that the Transfer Direction signal must be at
ground potential to specify the output transfer of computer information. An output data register (OB in Figure
5-20) is usually required in the device interface to receive the computer information. The device must supply strobe
pulses for all data transfers out of the computer (programmed or data break) since circuit configuration and timing
characteristics differ in each device.

5-23

ADDRESS 0 L

0
ARO

ADDRESS 1 L

0
AR1

ADDRESS 11 L

0
AR11

BREAK REQUEST L

ADDRESS ACCEPTED (FROM

GROUND TO REQUEST BREAK CYCLE

TO PDP-12

PDP-12 l

DATA 0 L

0
ORO

DATA 1 L

0
DR1

DATA It L

0
DR11

DIRECTION (+3 FOR INPUT)

CYCLE SELECT

NOTE:
AR=ADDRESS
DR= DATA REGISTER
D= TRANSFER DIRECTION (FLIP-FLOP)
BR= BREAK REQUEST(FLIP-FLOP)

Figure 5-18. Device Interface Logic for Single-Cycle Data Break Input Transfer
5-24

12-0300

COMPUTER TIM[

TP3

T'f

'"'2

TPI

TPS

I
~~ous.!.
,.....-----------------------------I

MEAi< CYCLE - - - - - - -.....--NEXT CYCLE

+3
BREAK REQUEST SIGNAL
(INPUT TO PROCESSOR!

BREAK SYNC FLIP FLOP
(INTERNAL)

SIGNAL MUST GO TO UV AT STMT Of' AOOM:SS ACCEPT PULSE IF NEXT CYCLE IS TO BE A MEA1

----1

0-----------SET AT SAMPLE TIME

SAMPLE
AT TPI

USED TO SELECT BREAK CYCLE AT TP I

3 CYCLE
CYCLE SELECT
!SAMPLE TO PROCESSOR!

8-BREAK SIGNAL
(OUTPUT TO 110 DEVICE I

DATA ADOllESS
INPUT LEVELS
llNPUT TO PROCESSOR)

1 CYCLE
+3V

-----------------~

START Of' llREAll CYCLE

GNO

+3V
GN0-------

EXT. MEM
ADDRESS
READ

READ AT
TP I BY
PROCESSOR

EARLIEST TIME POSSIBLE TO 11£MOVE AOOll£SS IS AT START Of llllEAll CYCLE

+3V
TPI -TP3

ADDRESS ACCEPT PULSE
!OUTPUT TO 110 DEVICE!
GNO
IN (+3V)
TRANSFER DIRECTION
!INPUT TO PROCESSOR)
S!GfjAL INPUT TO MB
*DATA(INPUT
TO PROCESSOR!

LATEST l"OSSlllLE TIME IS TP2

. .- - - - C A N 0tAHGE AHYTllllE AFTER TP 3

OOT(GNDI
AVAIL (+5Vl

HOT AVAIL (GNO)
OUTPUT DATA AVAILABLE IN MB
!OUTPUT TO 110 DEVICE)

.....IL(·HV)
AVAILABLE AT TP 3

TIME DlA'llNG WHICH DUA llJST Bf STR08£D BY 110 DEVICE

NOT A\AllL {+311)
Mii INCREMENT REQUEST
llNPUT TO PROCESSOR I

NO REQU£ST{+3V)
MUST OCCUR EARIER THAN TP 2
REQUEST (GNO)

BTS 5
!OUTPUT TO 110 DEVICE I

~Hit,£1/J

},.m>.
......*1...._M_u_s_T_oc_c_UR_o_N_LY_WHE
__
,. _a_BRE_All_·_·_...

....
kR,..,E,._.oy
...

TPI

+311
GRN

BTS 2
!OUTPUT TO l/D DEVICE)

+3V
&NO

+3\1
*WORD COUNT OVERFLOW
(OUTPUT TO !10 DEVICE l

OCCUflS IF MEMORY INCREMENT IS REQUESTED
ANO THE WORD COUNT OVERFLOWS
GND
*SIGNAL NOT USED FOR OUTPUT TRANS FE RS
SHOWN FOR REFERENCE ONLY

OCCURS 200ns BEFORE TP5. IF IOP
** OFF-PAUSE
OF< IOP SAMPLES BREAK REQUEST.

1~5TRUCTION

11' PROCl'SS,

12-0IZ9

Figure 5-19. Single-Cycle Data Break Output Transfer Timing Diagram

5-25

ADDRESS 0 L

AR Ill

ADDRESS I L

AR 1

ADDRESS

11 L

AR 11

BREAK REQUEST

0
+3v
BR

' - - - - - - - - - - - - - - - - - - - - - - - - - - ADDRESS ACCEPTED L

OB~

BREAK

ENABLE

BTS5
B BREAI<
BMBllJ

OBI
DIRECTION
(0 FOR OUTPUT!

0
BMBI

DIRECTION

NOTE:
OB' OUTPUT BUFFER
AR,ADDRESS REGISTER
BR' BREAK REQUEST
(FLIP-FLOP)

0811

BMBll

STROBE

BTS 2

+3 - - - - - - - - - CYCLE

SELECT

Figure 5-20. Device Interface Logic for Single-Cycle Data Break Output Transfer

5-26

When the Break Request is recognized the computer completes the current instruction and generates an Address
Accepted pulse as it enters the Data Break cycle. At TPl time, the address supplied to the PDP-12 is loaded into
the MA, and the Break state is entered. Not more than 900 nsec after TP 1 (at time TP3), the contents of the
device-specified core memory address are read and available in the MB. (This word is automatically rewritten at the
same address during the last half of the Break cycle, and is available for programmed operations when the Data
Break is finished.) Data Bit signals are available as static levels of ground potential for binary Os and +3v for binary
ls. The MB is changed at time TP3 of each computer cycle, so the data word is available in the MB for
approximately 1.6 microseconds to be strobed by the device interface.
Generation of the strobe pulse by the device interface can be synchronized with computer timing through use of
timing pulses BTS2 or BTS5, which are available at the computer interface. In addition to a timing pulse (delayed
or used directly from the comput~r), generation of this strobe pulse should be gated by condition signals that occur
only during the Break cycle of an output transfer.' Figure 5-20 shows typical logic circuits to effect an output data
transfer. In this example, BTS5 and B BREAK set the BREAK ENABLE flip-flop, which remains set for one
computer cycle (unless successive cycles are requested). This enabling signal loads the buffered MB lines into the
data inputs of a D type flip-flop. At BTS2 time, the data will be clocked into the Output Buffer flip-flops. Note
that BTS2 can generate a strobe pulse only during a BREAK ENABLE cycle. Interface input gates are MlOl;
output bus drivers are M6 23.
By careful design of the input and output gating, one register can serve as both the input and the output buffer
register. Most DEC options using the Data Break facility have only one data buffer register with appropriate gating
to allow it to serve as an output buffer when the Transfer Direction signal is at ground potential or an input buffer
when the Transfer Direction signal is +3v.

5.3 .4 Memory Increment
In this type of Data Break the contents of core memory at a device-specified address are read into the MB, are
incremented by 1, and are rewritten at the same address within one 1.6-microsecond cycle. This feature is
particularly useful in building a histogram of a series of measurements, such as in pulse-height analysis applications.
For example, in a computer-controlled experiment that counts the number of times each value of a parameter is
measured, a Data Break can be requested for each measurement, and the measured value can be used as the core
memory address to be incremented (counted).
Signal interface for a memory increment Data Break is similar to an output transfer Data Break except that the
device interface generates an Increment MB signal and does not generate a strobe pulse (no data transfer occurs
between the PDP-12 and the 1/0 device). Timing of memory increment operations appear in Figure 5-21.

5-27

COMPUTER TIME

TP2

TP3

TP4

TP5

Tl'I

I PREVIOUS

Tl'!

Tl'll

T""'

T,.,

T"I

TP2

TP3

CYCLE-•..,..
....- - - - - - - B M A I C CYCLE

--+
M

+3
BREAK REOUEST SIGNAL
(INPUT TD PROCESSOR)

--------1+
...

--NEXT CYCLE

~-----------------------------SIGNAL MUST GO TO+:W AT START CW AOOllESS "4:CEPT PULSE IF NEXT CYCLE IS TO Bf A BREAK

SAMPLED AT OFF- PAUSE BY PROCESSOR

GND - - - - - - - - - - - - - - ' ' - - - - - ' " ' " '
SAMPLE_..,:
:

BREAK SYNC FLIP FLOP
(INTERNAL I

3 CYCLE
CYCLE SELECT
!SAMPLE TO PROCESSOR)

B-BREAK SIGNAL
!OUTPUT TO 110 DEVICE)

DATA ADDRESS
INPUT LEVELS
(INPUT TO PROCESSOR)

USED TO S£LECT MCAii CYCLE AT TP I

_::SE~T~A~T_S:'.A~M'._'.:P.:_L.:_E...!,T_!!IM~E;_-====:::!~ AT TP I

~SAMPLED AT TPI

TYPICALLY HARDWIRED FOR A GIVEN DEVICE

1 CYCLE

I---

+3V -----------------~
GNO
.. 311
GNO-------

XT.MEM.
ADDRESS
READ

READ AT

-+ TP I BY

START Of' BREAK CYCLE

ENO OF MUK CYCLE ___,

EAltLl[ST TIME POSSIBLE TO REMOVE AOOR£SS IS AT START Of MEAll CYCLE

PROCESSOR

+3V
ADDRESS ACCEPT PULSE
IOUTPUT TO I 10 DEVICE)

TP I -TP 3
GND
IN (+311)

TRANSFER DIRECTION
!INPUT TD PROCESSOR)
SIGNAL INPUT TO MB
*DATA(INPUT
TO PROCESSOR)

LATEST POSSllU: TIME IS Tl"2

OUT(GNO)

LATEST POSSIBLE TIME TO SPECll'Y
INPUT DATA IS TP2

f'K>T AVAIL (GNO)
*OUTPUT DATA AVAILABLE IN MB
!OUTPUT TO 110 DEVICE)

. . - - - - - C A N OWtlGE AH'ITlllilE AFTER TP!

A\IAIL (+3Vl

AllAIL(+3V)
AVAILABLE AT TPI

TlllilE DlltlNG MOCH DATA ailJST IE STllOIED IY l/O DEVICE

NOT AVAIL (+3V) - - - - - - - - - - - - - - - - - - - - - - - - - _ .
Mii INCREMENT REQUEST
!INPUT TO PROCESSOR)

NO REQUEST(+3Vl
MUST OCCUR QlllLY WHEN a llflEAll • 1

MUST FALL EARLIER THArol TP 2
REQUEST (GNO)

BTS S
!OUTPUT TO I 10 OE VICE)

HV
GRN

llTS 2
(OUTPUT TO 110 DEVICE)

+3V

GND

I.____ _ ___,

+3V
II WORD COUNT OVERFLOW
(OUTPUT TO l/OOEVICE)

OCCIMS If lilEMOl'IY INCREM£NT IS lt£0U£STED
ANO THE WOl'O COUNT OVERFLOWS

GND
*SIGNAL NOT USEO
SHOWN FOft REFERENCE OfilLY

OCCURS 200ns BEFORE TP5. IF IOP INSTRUCTION
** OFF-PAUSE
IN PROCESS, OFF IOP SAMPLES BREAK REQUEST.
12-0131

Figure 5-21. Memory Increment Data Break Timing Diagram

An interface for a device using memory increment Data Breaks must supply twelve Data Address signals, a Transfer

Direction signal, a Cycle Select signal, and a Break Request signal to the computer Data Break facility as in an
output transfer data break. In addition, a ground potential increment MB signal must be provided at least 250
nanoseconds before time TP3 of the Break cycle. The signal can be generated in the device interface by ANDing the
B Break Computer Output signal, the output transfer condition of the Transfer Direction signal, and the Condition
signal in the device that indicates that an increment operation should take place. When the computer receives this
Increment MB signal, it forces the MB control element to generate a Carry Insert signal at time TS3 to increment
the contents of the MB.

5-28

5 .3 .5 Three-Cycle Data Breaks

Timing of input or output three-cycle Data Breaks is shown in Figure 5-22. The three-cycle Data Break uses the
block transfer control circuits of the computer. The block transfer control provides an economical method of
controlling the flow of data at high speeds between PDP-12 core memory and fast peripheral devices, e.g., drum,
disc, magnetic tape and line printers, allowing transfer rates in excess of 208 kHz.

T T 'i. T I

TPI

14---

BREAK REQUEST SIGNAL
(INPUT TO PROCESSOR)

BREAK SYNC FLIP· FLOP
(INTERNAL)

CYCLE SELECT
(INPUT TO PROCESSOR)

GND lSAMPLED AT
OFF· PAUSE BY
+ V PROCESSOR*
3

TP2

TP3

TP4

TP5

WORD COUNT STATE

SET AT
SAMPLE TIME

o-------

i---b

TPI

TP2

TP3 T. . TP5

TPI

TP2

TP3

TP4 TP5

TPI

TP2

TP5

TP4 TP5

TPI

I I

-+-

CUAAENT ADOllESS STATE

--+---

llREAK CYCLE

---t

SAMPLW AT TPI

+3V
- - - - - SAMPLED AT TP t
TYPICALLY HARDWIRED FOR A GIVEN DEVICE
GND

EXT. MEM.
ADDRESS
SAMPLED

DATA ADDRESS INPUT LEVELS
(INPUT TO PROCESSOR\

f 4 - SAMPLED AT TPI IF FF REGISTER SUPPLIES THESE INPUTS TIMING IS IDENTICAL TO THAT SHOWN ON FIG 5-13
I

ADORE SS ACCEPTED PULSE
!OUTPUT TO 110 0£\llCE)

GND
TRANSFER DIRECTION
(INPUT TO PROCESSOR)

IN (+-3Vl
OUT(GNDl

L-----------------S-AMP-LE-D-AT-T-P3_0F_8R£-AK_c_vc_LE_~_....I __,

AVAIL.
DATA SIGNAL INPUT TO MB
(INPUT TO PROCESSOR)

LATEST l'OSSIBLE TIME TO SF'ECFY INPUT DlTA IS !!IOO

llEFORE TP

2--:

SAMPLED AT T~! ev PROCESSOR

NOT AVAIL
AVAIL.

OUTPUT DATA AVAILABLE IN MB
!OUTPUT TO l/O DEVICE!

WORD COUNT OVERFLOW
(OUTPUT TO 110 DEVICE I

AVAILABLE AT T"5

LATEST POSSIBLE TIME TO SPECIFY 1. . HIBIT CA
INCREMENT IS 300 NS BEORE TPl

1"4HIBIT CA INCREMENT

!OUTPUT TO PROCESSOR)

TP3

OCCURS ONLY DURING LAST TRANSFER OF A BLOCK TRANSFER

GND

+3V

----9'4

SAlf LED AT TP3 BY PROCESSOR

GND

8 BREAK SIGNAL
!OUTPUT TO 110 OEVICEI

+3v ~-~---~------~~--~---~---.
~-----START OF BREAK CYCLE~---------'r--ENO OF BREAK CYCLE
GND

BTS 5
(OUTPUT TO 110 OEVICEl

BTS 2

!OUTPUT TO 110 DEVICE)

GND _ _ __.

:::1

'---------'

*OFF-PAUSE OCCURS 20001 BEFORE

'---------'

TP5. IF IOP INSTRUCTION IN PROCESS, OFF

nSEFORSAllllPLING
OUTPUT DATA
.___ _ _ _ __,
'--------'

IOP SAMPLES BR'-E-AK_R_E-QU-E-ST-._

__.

'-----

12 ·01!2

Figure 5-22. Three-Cycle Data Break Timing Diagram

The three-cycle Data Break facility provides separate current address and word count registers in core memory for
the connected device, thus eliminating the necessity for flip-flop registers in the device control. When several
devices are connected to this facility, each is assigned a different set of core locations for word count and current
address, allowing interlaced operations of all devices as long as their combined rate does not exceed 208 kHz. The
device specifies the location of these registers in core memory, and thus the software remains the same, regardless
of what other equipment is connected to the machine. Since these registers are located in core memory, they may
be loaded and unlo-dded directly without the use of IOT instructions. In a procedure where a device request to
transfer data to or from core memory, the three-cycle Data Break facility performs the following sequence of
operations:
a. An address is read from the device to indicate the location of the word count register. This address is
always the same for a given device; thus it can be wired in and does not require a flip-flop register.

b. The contents of the specified address are read from memory and I is added before rewriting. If the
contents of this register become 0 as a result of the addition, a WC Overflow pulse will be transmitted to the device.
To transfer a block of N words, this register is loaded with -N during programmed initialization of the device. After
the block has been fully transferred this pulse is generated to signify completion of the operation.
c. The next sequential location is read from memory as the current address register. Although the contents of
this register are normally incremented before being rewritten, an increment CA inhibit(+ I -+ CA Inhibit) signal
from the device may inhibit incrementation. To transfer a block of data beginning at location A, this register is
program initialized by loading with A-1.
d. The contents of the previously read current address are transferred to the MA to serve as the address for
the data transfer. This transfer may go in either direction in a manner identical to the single-cycle Data Break
system. The three-cycle Data Break facility uses many of the gates and transfer paths of the single-cycle Data Break
system, but does not preclude the use of standard Data Break devices. Any combination of three-cycle and
single-cycle Data Break devices can be used in one system, as long as a multiplexer channel is available for each.
Two additional control lines are provided with the three-cycle data break. These are:

Word Count Overflow - A level change from GND to +3V, from TP3 of the cycle requesting the word count to
TP3 of the next cycle is transmitted to the device when the word count becomes equal to zero.
Increment CA Inhibit - When ground potential, this device-supplied signal inhibits incrementation of the current
address word.

In summary, the three-cycle Data Break is entered similarly to the single-cycle Data Break, with the exception of
supplying a ground-level Cycle Select signal to allow entry of the WC (Word Count) state to increment the fixed
core memory location containing the word count. The device requesting the break supplies this address as in the
single-cycle Data Break, except that this address is fixed and can be supplied by wired ground and +3V signals,
rather than from a register. Following the WC state, a Current Address (CA) state is entered, in which the core
memory location following the WC address is read, incremented by one, restored to memory, and used as the
transfer address (by MB-+ MA). Then the normal Break (B) state is entered to effect the transfer.

5.4 INTERFACE DESIGN AND CONSTRUCTION

This section describes the PDP-12 interface techniques, available modules, interface conventions, and interface
connections.

S.4.1 PDP-12 Interface Modules
PDP-12 interfacing is constructed of Digital FLIP-CHIP modules. The Digital Logic Handbook describes more than
150 of these modules, their component circuits, and the associated acessories; i.e., power supplies and. mounting
panels. The user should study this catalog carefully before beginning the design of a special interface.
The interface modules of the PDP-12 are the M111, M906, MS 16, M660, and M623 modules. Interface signals to
the computer use either a combination of the M111 and M906 modules or the MS 16 module. Interface signals from
the computer will originate from a combination of M623 and M906 modules for data signals, and M660 modules
for timing signals.

S.4.1.1 M111/M906 Positive Input Circuit (See Figure 5-23) - The Ml 11 Inverter module is used in conjunction
with the M906 Cable Terminator module, which clamps the input Jo prevent excursions beyond +3 volts and
ground. The M906 also provides the pullup resistors to +5 volts.

5-30

-----------,

I
I
I
I
I
I

OUTPUT SIGNAL TO PROCESSOR

I
I
I
I

M 111
(161NVERTERS)

I
I

-------,

+5V
I
I
M906
I
(t8 CIRCUITS)
I
I Bt POSIT I VE BUS INPUT s I GNAL
I
(FROM EXTERNAL DEVICE)
L __________
_ _j
12-0136

Figure 5-23. Typical Ml l l/M906 Positive Input Circuit

5.4.1.2 M516 Positive Bus Receiver Input Circuit (See Figure 5-24) - Six four-input NAND gates with overshoot
and undershoot clamp on one input of each gate. Pullup resistors connected to +SV are also provided.

-----------,
8'

OUTPUT s I G N AL TO PROCESSOR

I
I
I

(

M5t6
s Ix GATES )

I
I
I
I

D I } USED
~:
INTERNALLY

+5V

I
I
I
I
I
I

I
I
I

I Al POSITIVE BUS INPUT SIGNAL
(FROM EXTERNAL DEVICE)
L __________
_ _j

12-0136

Figure 5-24. Typical MS 16 Positive Bus Receiver Input Circuit

5 .4.1.3 M623/M906 Positive Output Circuit (See Figure S-25) - The M623 Bus Driver module contains twelve
circuits with negative NOR gates. Used in conjunction with the M906 Cable Terminator module, the output is
clamped to prevent excursions beyond +3 volts and ground. Output can drive +5 milliamperes at the high level and
sink 20 milliamperes at the low level.

5-31

,
-- - - - - - - - - - - - ,I
I
M906
(!8 CIRCUITS)
I
I
POSITIVE BUS OUTPUT SIGNALS
I
(TO EXTERNAL DEVIC£)
I

---,
+5V

I
I

Al
81
OUTPUT SIGNALS FROM PROCESSOR

L - - - - - - - - - - - _J

12.-0136

Figure 5-25. Typical M623/M906 Positive Output Circuit

5.4.1.4 M660 Bus Driver Output Circuit (See Figure S-26}° - Three circuits which provide low impedance 100-ohm
tenninated cable driving capability using M Series levels or pulses of duration greater than 100 nanoseconds. The
output can drive 5 ma at the high level and sink 20 ma at the low level, in addition to termination current required
by the G7 l 7 termination module. The M660 module is used in the PDP-12 for the following output signals:

IOP 1, IOP 2, IOP 4, TS 2, TS 5

-----------,
rI
I
POSITIVE BUS OUTPUT SIGNAL
(TO EXTERNAL DEVICE)

I M660
I (3 CIRCUITS)

I
I

I
I
I
I
I
I
I

OUTPUT SIGNAL

L - - FRO:_PROCESSOR -

IZ-0136

Figure 5-26. M660 Terminated Bus Driver Output Circuit

5.4.1.5 Module Selection for Interface Circuits of Peripheral Equipment - Two FLIP-CHIP modules are of
particular interest in the design of equipment to interface with the PDP-12. Complete details on these and other
FLIP CHIP modules can be found in the Digital Logic Handbook.

5-32

5.4.1.6 M103 Device Selector (See Figure 5-27) - The M103 selects an input/output device according to the code
in the instruction word (being held in the memory buffer during the IOT cycle). M103 module includes diode

protection clamps on input lines so that it may be used directly on the PDP-12 positive bus.
H1
J1

LI
N1

E2
F2
H2
J2
K2
L2
N2

>--~-O_;.Ev_1_c_E~S..;;E_L.;;...EC_T..;;E_o_.(') v 2

BMB 03(0)
BMB 04(0)
BMB 05(0)
BMB 06(0)
BMB 07(0)
BMB 08(0)
NOT USED
NOT USED

BIOP 1

IOTI

IOT2
R

2 ~.--B_;.IO.;;...P_2_ _ _ _ _ _ __._---1

L.---IOT 2

IOT4
BIOP 3

s20-~_:_-----------1.__

E
1

___

iOfii

~-----..nF1

FROM

PROCESSOR 110 BUS

Figure 5-27. M103 Device Selector Logic Circuit

TO EXTERNAL DEVICE

IZ-0138

5.4.1.7 M101 Bus Data Interface (See Figure 5-28) - Fifteen two-input NANO gates with one input of each gate
tied to a common line. For use in strobing data off of the PDP-12 1/0 bus. The M 101 module includes diode
protection clamps on input lines so that it may be used directly on the PDP-12 positive bus.

5-33

n-~B_A~C---=-0_7_ _ _- I

DEV ICE SELECTED (FROM M 1031

BAC 00

BAC 01

BAC

09
J2

BAC 02

BAC 10

TO EXTERNAL
DEVICE

BAC 03

BAC 11

BAC 04

P2 n,....._ _ _ ___._-1
M1

BAC

n---------'"-~

BAC 06

U2 n......-------4---1

12-0137

Figure 5-28. MlOl Bus Data Interface Logic Circuit

5 .4.2 M Series Flip Chip Modules

The following is a list of M Series modules available from Digital Equipment Corporation that can be used in
designing special interfaces and special devices. The majority of these modules are described in the Digital Logic
Handbook. For those that cannot be found in the Handbook, contact the nearest Digital representative.

5-34

Table 5-2. M Series Module Summary
Type

Function

Description

M002

15 Loads

Fifteen +3 volt sources each capable of driving ten
unit loads. Can be used for tying off unused inputs.

M040

Solenoid Driver

Output ratings of-70 volts and 0.6 amp allow these
two drivers to be used with a variety of medium
current loads.

M050

50 ma Indicator and
Relay Driver

Output ratings of -20 volts and 50 ma. Allow any
of the twelve circuits on this module to drive a
variety of incandescent lamps. These drivers can
also be used as slow speed open collector PNP level
shifters to -3 volt systems.

MIOI

Bus Data Interface

Fifteen two-input NAND gates with one input of
each gate tied to a common line. For use in
strobing data off of the PDP-8/I or PDP-12 1/0
bus. Pin compatible with M 111.

M103

Device Selector

Similar to W103, but for use with PDP-8/1 and
PDP-12 options. Output pulses are not regenerated
but only buffered.

Mll 1

Inverter

Sixteen inverter circuits with a fan-in of one unit
load and fan-out of ten unit loads.

Ml 12

NOR Gate

Ten positive NOR gates with a fan-in of one unit
load and fan-out of ten unit loads.

Mll3

10 2-Input
NAND Gates

Ten two-input positive NAND gates with a fan-in
of one unit load and fan-out of ten unit loads.

Ml 15

8 3-Input
NAND Gates

Eight three-input positive NAND gates with a
fan-in of one unit load and a fan-out of ten unit
loads.

Ml 17

6 4-lnput
NAND Gates

Six four-input positive NAND gates with a fan-in
of one unit load and a fan-out of ten unit loads.

M119

3 8-Input
NAND Gates

Three eight-input positive NAND gates with a
fan-in of one unit load and a fan-out of ten unit
loads.

Ml21

AND/NOR Gates

Six gates which perform the positive logic function
AB+ CD. Fan-in on each input is one unit load and
gate fan-out is ten unit loads.

5-35

Table 5-2. M Series Module Summary (cont)

5-36

Type

Function

Description

Ml41

NAND/OR Gates

Twelve two-input positive NAND gates which can
be used in a wired OR manner. Gates are grouped
in a 4-4-3-1 configuration, with a fan-in of one unit
load and a fan-out which depends on the number
of gates ORed together.

Ml60

Gate Module

Three general purpose multi-input gates which can
be used for system input selection. Fan-in is one
unit load and fan-out is ten unit loads.

Ml61

Binary to Octal/
Decimal Decoder

A binary-to-eight line or BCD·to-ten line decoder.
Gating is provided so that up to six binary bits can
be decoded using only M 161 s. Accepts a variety of
BCD codes.

Ml62

Parity Circuit

Two circuits, each of which can be used to
generate even or odd parity signals for four bits of
binary input.

Ml69

Gating Module

Four circuits that can be used for input selection.
Each circuit is of an AND/OR configuration with
four two-input AND gates.

M202

Triple J.K.
Flip-Flop

Three J-K flip-flops with multiple input AND gates
on J and K. Versatile units for many control or
counter purposes. All direct set and clear inputs are
available at module pins.

M203

Set-Reset
Flip-Flops

Eight single-input set/reset flip-flops for use as
buffer storage. Each circuit has a fan-in of one unit
load and a fan-out of ten unit loads.

M204

Counter-Buffer

Four J-K flip-flops which can be interconnected as
a ripple or synchronous counter or used as general
control elements.

M206

Six Flip-Flops

Six D-type flip-flops which can be used in shift
registers counters, buffer registers, and general
purpose control functions.

M207

Flip-Flops

Six single-input J-K type flip-flops for use in shift
register, ripple counters, and general purpose
control functions.

M208

Buffer Shift Register

An internally connected 8-bit buffer or shift
register. Provisions are made for gated single-ended
parallel load, bipolar parallel output, and serial
input.

Table. 5-2. M Series Module Summary (cont)
Type

Function

Description

M211

Binary Up/Down
Counter

A six-bit binary up/down ripple counter with
control gates for direction changes via a single
control line.

M212

6-Bit L-R
Shift Register

An internally connected left/right shift register.
Provisions are made for gated single-ended parallel
load, bipolar parallel output, and serial input.

M213

BCD Up/Down
Counter

One decade of 8421 up or down counting is
possible with this module. Provisions are made for
parallel loading, bipolar output, and carry features.

M230

Binary to BCD Shift
Register Converter

One decade of a modified shift register which
allows high speed conversion ( 100 nsec per binary
bit) of binary data to 8421 BCD code. System use
of this module requires additional modules.

M302

One Shot Delay

Two pulse or level triggered one-shot delays with
output delay adjustable from 50 nsec to 7 .5 msec.
Fan-in is 2.5 unit loads and fan-out is 25 unit
loads.

M310

Delay Line

Fixed tapped delay line with delay adjustable in
50-nsec increments from 50 nsec to 500 nsec. Two
digital output amplifiers and one driver are
included.

M360

Variable Delay

Continuously variable delay line with a range of 50
nsec to 500 nsec. Module includes delay line
drivers and digital output amplifiers.

M401

Clock

A gateable RC clock with both positive and
negative pulse outputs. The output frequency is
adjustable from 10 MHz to below 100 Hz.

M405

Crystal Clock

Stable system clock frequencies from 5 kHz to 10
mHz are available with this module. Frequency
drift at either the positive or negative pulse output
is less than 0.01 % of the specified frequency.

M410

Reed Clock

A stable low frequency reed control clock similar
to the M452. Stability in the range 0°C to 70°C is
better than 0.15%. For use with communications
systems and available with only standard teletype
and data set frequencies.

M452

Variable Clock

Provides square wave output of 880 Hz, 440 Hz,
and 220 Hz necessary for clocking the M706 and
M707 in a 110-baud teletype system.

5-37

Table 5-2. M Series Module Summary (cont)

S-38

Type

Function

Description

MSOI

Schmitt Trigger

Provides regenerative characteristics necessary for
switch filtering, pulse shaping, and contact closure
sensing. This circuit can be AND/OR expanded.

M502

Negative Input
Converter

Pulses as short as 3 5 nsec can be level shifted from
-3 volt systems to standard M Series levels by the
two circuits in this converter. This module can also
drive low impedance terminated cables.

M506

Negative Input
Converter

This converter will level shift pulses as short as 100
nsec from -3 volt systems to M Series levels. Each
of the six circuits on this module provides a low
impedance output for driving unterminated long
lines.

M507

Bus Converter

Six inverting level shifters which accept -3 and
GND, as inputs and have an open collecter NPN
transistor at the output. Output rise is delayed by
100 nsec for pulse spreading.

M516

Positive Bus
Receiver

Six four-input NOR gates with overshoot and
undershoot clamps on one input of each gate. In
addition, one input of each gate is tied to +3 volts
with the lead brought out to a connector pin.

M602

Pulse Generator

The two pulse amplifiers in this module provide
standard 50-nsec or 110-nsec pulses for M Series
systems.

M617

6-4 Input NOR
Buffers

Six four-input positive NOR gates with a fan-in of
one unit load and a fan-out of 30 unit loads.

M627

Power Amplifier
Module

Six four-input high speed positive NAND gates
with a fan-in of 2.5 unit loads and a fan-out of 40
unit loads.

M650

Negative Output
Converter

The three non-inverting level shifters on this
module can be used to interface the positive 'levels
or pulses (duration greater than 100 nsec) of Kand
M Series to -3 volt logic systems.

M652

Negative Output
Converter

These two circuits provide high-speed non-inverting
level shifting for pulses as short as 3 5 nsec or levels
from M Series to -3 volt systems. The output can
drive low impedance terminated cables.

M660

Positive Level
Driver

Three circuits which provide low-impedance
100-ohm terminated cable driving capability, using
M Series levels or pulses of duration greater than
100 nsec. Output drive capability is 50 ma at +3
volts or ground.

Table 5-2. M Series Module Summary (cont)
Type

Function

M661

Positive Level
Driver

Three circuits which provide low-impedance
unterminated cable driving. Characteristics are
similar to M660 with the exception that +3 volts
drive is 5 ma.

M730

8/I Bus Positive
Output Interfacer

General Purpose positive bus output module for
use in interfacing many positive level (0 to +20
volt) systems to the PDP-8/I or PDP-12. Module
includes device selector, 12-bit parallel output
buffer, and adjustable timing pulses.

M731

8/I Bus Negative
Output Interfacer

Identical to M730, except outputs are level shifted
for 0 to -20 volt systems to the PDP-8/I or PDP-12.
Module includes device selector, 12-bit parallel
input buffer, and adjustable timing pulses.

M733

8/1 Bus Negative

Identical to M732, except inputs are level shifted
from negative voltage systems.

M901

Flexprint® Cable
Connector

Double-sided 36-pin Flexprint cable connector. All
pins are available for signals or grounds. Pins A2,
B2, U 1, and V 1 have 10 n resistors in series.

M902

Resistor Terminator

Description

Double-sided 36-pin terminator module with 100

n terminations on signal leads. Alternate grounds
are provided as in the M903 and M904.
M903

Connector

Double-sided 36-pin Flexprint cable connector
with alternate grounds for I/O bus cables.

M906

Cable Terminator

18 load resistors clamped to prevent excursions
beyond +3 volts and ground. It may be used in
conjunction with the M623 to provide cable
driving ability.

5.4 .3 Construction of I nterfaces
This section provides the interface designer with information on design procedures, module layout, wiring, and
cable selection. Additional help may be obtained from local DEC sales offices.

5.4.3.1 Physical - The PDP-12 was designed to provide the user maximum ease and flexibility in implementing
special interfaces. External devices and interfaces are constructed and mounted outside of the basic machine,
thereby eliminating the necessity for modifications to the basic processor. All signals to and from the computer are
carried on coaxial or Flexprint cables.

®Flexprint is a registered trademark of Sanders Associates, Inc.

5-39

To implement several devices, the cables parallel-connect each peripheral in a serial type form (see Figure 5-29).
Three dual cables are used for program interrupt cable connections in (or out). Two additional dual cables are used,
for a total of five, when Data Break devices are implemented.

5.4.3.2 Module Layout - In general, module layout is based on the functional elements within a system and is
primarily a matter of common sense.
Digital has, however, layout conventions for 1/0 cabling to extend devices. The interface designer may wish to use
these conventions as a guide. The general rule is DO NOT DEAD END THE 1/0 BUS. This means that parallel
connections should always be made at each device to handle possible future expansion.

3 DUAL PROGRAM
INTERRUPT CABLES

2 DUAL DATA
BREAK CABLES

DEVICE
I

DEVICE

PDP-12

12- 0142

Figure 5-29.\ 1/0 Bus Configuration
Figure 5-30 shows the 1/0 cable connections in an option mounting panel. Module slot locations 1 through 3
(looking at the wiring pin side) are reserved for program transfer cable connections in (or out). Module slot
locations 4 to 5 are reserved for data break cable connections in (or out). Slot 6 is used for Sense lines.
Module slot locations 1 through 6 in the bottom half of the option mounting panel are wired in parallel with the
top module slot locations 1 through 6. To continue the 1/0 cabling to the next device, the bottom slots are used,
and the 1/0 cable connections are exactly the same as mentioned above.

5.4.3.3 Cable Selection - Two types of cables are recommended for 1/0 interface connections.
The first is 9-conductor coaxial cable. This cable protects systems from radiated noise and cross talk between
individual lines. Coax cable used and sold by Digital has the following nominal specs:

z = 95 ± s n
C = 13. 75 pF/foot approx. (unterminated)
L = 124 nH/foot approx.
R = 0.095 Q/foot nominal
Y = 79% of velocity oflight, approx. ( 1. 5 nsec/ft.)

5-40

The second type is a 19-conductor (9 signals and 10 grounds), #30 gauge flat copper Flexprint.
The total length of I/O cabling, from the PDP-12 to the last device, can be a maximum of 50 feet, and can be
composed of 50 feet of coax or a combination of coax and Flexprint, in which case the Flexprint cannot exceed a
total of 15 feet.

5.4.3.4 Connector Selection - Of the many connectors available in the module product line, several have
particular application to I/O connectors. Price and ordering information is available on these and other connectors
in the Digital Logic Handbook. Of particular interest are the M903 and M904 connectors described in the
subsequent paragraphs.

CABLE LOCATION

---

BACOOTO
BAC 11

DATA ADD 00
TO

AC11BUS

DATA ADD 11

BT 53, 1

SKiPB'US

BRK RQST

---

B INITIALIZE

INT RQST BUS

DATA IN

CA INCREMENT

---

MB INCREMENT

---

BMB OOTO
BMB 11

AC CLEAR

BuS

DATAOo

AC 00 BUS
TO

BIOP 1, 2, 4

TO
DATA 11

3 CYCLE

SENSE
LINES

EXT DATA ADD

BADO
ACCEPTED
B BREAK
BWC
OVERFLOW

BRUN
B INITIALIZE

SAME ASSIGNMENTS AS ABOVE

Figure 5-30. 1/0 Cable Connections

5-41

a. M903 Connector - Double sided 36-pin Flexprint cable connector with alternate grounds for I/O bus
cables. (Two Flexprint cables are utilized with this connector module.)
b. M904 Connector - Double-sided 36-pin coaxial cable connector with alternate grounds for I/O bus cables.
(Two coax cables are utilized with this connector module).

( 1) Signals:
Bl, DI, El, HI, JI, Ll, Ml, Pl, SI,
D2, E2, H2, K2, M2, P2, S2, T2, V2
(2) Grounds:

Al, Cl, Fl, Kl, NI, RI, Tl,
C2,F2,J2,L2,N2,R2, U2
Signal Terminating - The G717 module is used for terminating the following signals:
IOP 1, IOP 2, IOP 4, TS 2, TS 5.
This module contains five 1DO.ohm terminating resistors and should be located in the last device of the I/O cabling
scheme.

Wiring Hints - These suggestions may help reduce mounting panel wiring time. They are not intended to replace
• any special wiring instructions given on individual module data sheets or in application notes. For fast, neat wiring,
the following order is recommended:
I. All power wiring (Pins A2, B2, C2, Tl) and any horizontally bussed signal wiring. Use Horizontal Bussing
Strips, Type 933. (Pin-B2 is bussed with -1 SV for modules requiring -1 SV.)
2. Vertical grounding wires interconnect chassis ground with Pins C2 and Tl grounds. Run these wires from
the uppermost mounting panel to the bottom panel. On the first and last blocks of the mounting panel, connect
the grounds to the chassis.
3. All other ground wires. Always use the nearest ground pin, unless a special grounding pin has been provided
in the module.
4. Wire all signal wires in convenient order. Point-to-point wiring produces the shortest wire lengths, goes in
fastest, is easiest to trace and change, and generally results in better appearance and performance than cabled
wiring. Point-to-point wiring is strongly urged.
The recommended wire size for use with H803 mounting blocks and H911 mounting panel is #30. Larger or
smaller wire may be used depending on the number of connections to be made to each lug. Solid wire and a heat
resistant insulation is recommended. The H803 mounting blocks are only available with wire wrap pins which
necessitates the use of a wire wrap tool. (Digital can supply #30 gauge wire in I 000 foot rolls.)
Adequate grounding is essential. In addition to the connections between mounting panels mentioned above, there
must be continuity of grounds between cabinets and between the logic assembly and any equipment with which
the logic communicates.

S-42

When wire wrapping is done on a mounting panel contaimng modules, the wire wrap tool must be grounded, except
when all modules are removed from the mounting panel. This procedure must be followed because, even with tools
isolated from the ac power line, such as those operated by batteries or compressed air, static charges may build to
sufficient amplitudes so that damage to semiconductors may result.

Cooling - The low power consumption of M Series modules results in a total of about 15 watts dissipation in a
typical H9 l l mounting panel containing 64 modules. Convection cooling is sufficient for a few mounting panels,
but forced air cooling should be used when a very large system is built.

5.4.4 IOT Allocations
IOT

Option

00
01
02
03
04
05
06
07
10
11
12
13
14
15
16
17
20
21
22
23
24
25
26
27
30
31
32
33
34
35
36
37
40
41
42
43
44
45

Interrupt
High Speed Reader Type PR 12
High Speed Punch Type PP 12
Teletype Keyboard/Reader
Teletype Teleprinter/Punch
Displays, Types VC8/I and KV8/I
Displays, Types VC8/I and KV8/I
Displays, Types VC8/I, and Light Pen Type 370
Power Fail Option KPl 2
Teletype System Type PT08
Teletype System Type PT08
Real Time Clock Type KW 12
Mode Change (IOT 6141)
Tape Maintenance

Memory Extension Control Option Type MCI 2
Memory Extension Control Option Type MCI 2
Memory Extension Control Option Type MCI 2
Memory Extension Control Option Type MC 12
Memory Extension Control Option Type MC 12
Memory Extension Control Option Type MC 12
Memory Extension Control Option Type MC12
Memory Extension Control Option Type MCI 2
User Interfaces
User Interfaces
User Interfaces
User Interfaces
User Interfaces
User Interfaces
User Interfaces
User Interfaces
Teletype System Type DPl 2
Teletype System Type DP 12
Teletype System Type PT08
Teletype System Type PT08
Teletype System Type PT08
Teletype System Type PT08

5-43

46
47
50
51
52
53

Teletype System Type PT08
Teletype System Type PT08
Incremental Plotter Type XYl 2
Incremental Plotter Type XY 12
Incremental Plotter Type XY 12
General Purpose A/D Converters and Multiplexers, Types AFO 1A, AM02A,
AM03A and AF04A Scanning Digital Voltmeter
General Purpose A/D Converters and Multiplexers, Types AFOlA, AM02A,
AM03A and AF04A Scanning Digital Voltmeter
D/A Converter Type AAOlA
D/A Converter Type AAOlA
D/A Converter Type AAOlA, Sample and Hold Control Type ACOlA and
AF04A Scanning Digital Voltmeter
Random Access Disk File and Control Type DF32 and Synchronous Modem
Interface Type DPOlA
Random Access Disk File and Control Type DF32 and Synchronous Modem
Interface Type DPOlA
Random Access Disk File and Control Type DF32 and Synchronous Modem
Interface Type DPOlA
Card Reader Type CR 12
Synchronous Modem Interface Type DPOlA
Synchronous Modem Interface Type DPOlA
Synchronous Modem Interface Type DPOIA
Card Reader Type CR 12 and Synchronous Modem Interface Type DPO l A
Automatic Mag Tape Type TC5 8
Automatic Mag Tape Type TC5 8
Automatic Mag Tape Type TC58
Automatic Mag Tape Type TC58
Automatic Mag Tape Type TC58

54
55
56
57
60
61
62
63
64
65
66

67
70
71
72
73
74
75

DECtape Control TCOl
DECtape Control TCOl

5.4.5 Interface Connections
All interface connections to the PDP-12 are made at assigned module receptacle connectors in the Processor
Mounting Frame. Capital letters designate vertical rows of modules within a mounting frame. The letters progress
alphabetically from right to left when viewed from the wiring side. Module receptacles are numbered from top to
bottom within a row. Terminals are assigned capital letters from right to left, with the letters G, I, 0, and Q
omitted. Double-sided connectors or modules use the suffix number 1 to designate the top side of a module and
the suffix number 2 to designate the bottom side.
The module receptacles and assigned use for interface signal connections are:

5-44

Receptacle

Use

N13
N14
N15
N16
Nl7
NIB

SENSE LINES
AC, IOP, TIMING OUTPUTS
MB OUTPUTS
AC, SKIP, INT. REQUEST INPUTS
DATA BREAK ADDRESS INPUTS
DATA BREAK DATA INPUTS

Terminals Al, Cl, Fl, Kl, NI, Rl, Tl, C2, F2, 12, L2, N2, R2, and U2 of these receptacles are grounded within
the computer, and terminals Bl, Dl, El, Hl, Jl, Ll, Ml, Pl, Sl, 02, E2, H2, K2, M2, P2, S2, T2, and V2 carry
signals. Terminals A2 and B2 are not used. These terminals mate with either M903 or M904 Cable Connectors.
Interface connection to the PDP-12 can be established for all peripheral equipment by making series cable
connections between devices. In this manner only one set of cables is connected to the computer and two sets are
connected to each device; one receives the computer connection from the computer itself or the previous device,
and one passes the connection to the next device. Where physical location of equipment does not make series bus
connections feasible, or when cable length becomes excessive, additional interface connectors can be provided near
the computer. All logic signals passing between the PDP-12 and input/output equipment are positive voltage levels,
allowing direct TTL logic interface with appropriate diode clamp protection.
Positive level for a low logic state is 0 to 0.4 volts. Positive level for a high logic state is +3.6 volts.
The following table presents cable connections to the PDP-12 I/O Bus. A signal is true when its polarity matches
the suffix character of its name (i.e., 100 BAC 00 (1) H will be high when AC 00 (1) and a program interrupt will
be requested when the line EXT INT RQST BUSL is pulled low).
Table 5-3. Cable Connections to the PDP-12 1/0 Bus
Signal

Connection

Signal

Connection

IOB XL OOH
IOB XL 01 H
IOB XL 02 H
IOB XL 03 H
IOB XL 04 H
IOB XL 05 H
IOB XL 06 H
IOB XL 07 H
IOBXL lOH

Nl3Bl
Nl3Dl
N13El
Nl3Hl
Nl3Jl
N13Ll
N13Ml
N13Pl
Nl3Sl

IOB XL 11 H
IOB XL 12 H
IOB XL 13 H
NOT USED
NOT USED
NOT USED
NOT USED
NOT USED
NOT USED

Nl3D2
N13E2
N13H2
N13K2
Nl3M2
Nl3P2
Nl3S2
Nl3T2
Nl3V2

100 BAC 00 (1) H
JOO BAC 01 (1) H
JOO BAC 02 (1) H
100 BAC 03 (1) H
100 BAC 04 (1) H
100 BAC 05 (1) H
JOO BAC 06 (1) H
JOO BAC 07 (1) H
100 BAC 08 (1) H

Nl4Bl
Nl4Dl
N14El
N14Hl
N14Jl
Nl4Ll
N14Ml
Nl4Sl

100 BAC 09 (1) H
100 BAC 10 (1) H
lOOBAC 11 (l)H
100 BIOP 1 H
100 BIOP 2 H
100 BIOP 4 H
100 BTS 5 (1) H
JOO BTS 2 (1) H
100 BA INITIALIZE H

Nl4D2
Nl4E2
N14H2
Nl4K2
Nl4M2
Nl4P2
Nl4S2
Nl4T2
Nl4V2

JOO BMB 00 (1) H
JOO BMB 01 (1) H
100 BMB 02 (1) H
JOO BMB 03 (0) H
100 BMB 03 (1) H
100 BMB 04 (0) H
JOO BMB 04 (1) H
JOO BMB 05 (0) H
JOO BMB 05 (1) H

Nl5Bl
NlSDl
N15El
NISHI
NI SJ I
NlSLl
Nl5Ml
Nl5Pl
Nl5Sl

JOO BMB 06 (0) H
JOO BMB 06 (1) H
JOO BMB 07 (0) H
JOO BMB 07 (1) H
100 BMB 08 (0) H
100 BMB 08 (1) H
100 BMB 09 (1) H
JOO BMB 10 (1) H
100 BMB 11 (1) H

Nl5D2
Nl5E2
N15H2
N15K2
Nl5M2
Nl5P2
NISS2
Nl5T2
Nl5V2

~14Pl

5-45

Table 5-3. Cable Connections to the PDP-12 I/O Bus (cont)
--

Signal

Connection

Signal

Connection

EXT IO BUS 00 L
EXT IO BUS 01 L
EXT IO BUS 02 L
EXT IO BUS 03 L
EXT IO BUS 04 L
EXT IO BUS OS L
EXT IO BUS 06 L
EXT IO BUS 07 L
EXT IO BUS 08L

N16Bl
N16Dl
N16El
N16Hl
N16Jl
N16Ll
N16Ml
N16Pl
N16Sl

EXT IO BUS 09L
EXT IO BUS 10 L
EXT IO BUS 11 L
EXT SKIP BUS L
EXT INT RQST BUS L
EXT AC CLEAR BUS L
IOO B RUN (0) H
NOT USED
NOT USED

N16D2
Nl6E2
Nl6H2
Nl6K2
Nl6M2
N16P2
N16S2
N16T2
Nl6V2

EXT DATA ADD 00 L
EXT DATA ADD 01 L
EXT DATA ADD 02 L
EXT DATA ADD 03 L
EXT DATA ADD 04 L
EXT DATA ADD 05 L
EXT DATA ADD 06 L

N17Bl
N17Dl
N17El
N17Hl
Nl7Jl
N17Ll
Nl7Ml

Nl7D2
Nl7E2
Nl7H2
Nl7K2
Nl7M2
N17P2

EXT DATA ADD 07 L
EXT DATA ADD 08 L

N17Pl
N17Sl

EXT DATA ADD 09 L
EXT DATA ADD 10 L
EXT DATA ADD 11 L
EXT BREAK RQST L
EXTDATAINH
IOO BREAK (0) H
IOOADD
ACCEPTED (0) H
EXT INCREMENT MB L
IOO BB INITIALIZE H

EXT DATA 00 L
EXT DATA 01 L
EXT DATA 02 L
EXT DATA 03 L
EXT DATA 04 L
EXT DATA OS L
EXT DATA 06 L
EXT DATA 07 L
EXT DATA 08 L

Nl8Bl
N18Dl
N18El
Nl8Hl
Nl8Jl
N18Ll
N18Ml
N18Pl
Nl8Sl

EXT DATA 09 L
EXT DATA IO L
EXT DATA 11 L
EXT 3 CYCLE L
IOB CA INCREMENT H
IOO WC OVERFLOW (0) H
EXT EXTEND DATA ADD 02 L
EXT EXTEND DATA ADD 01 L
EXT EXTEND DATA ADD 00 L

Nl8D2
Nl8E2
Nl8H2
Nl8K2
N18M2
N18P2
N18S2
N18T2
N18V2

546

Nl7S2
N17T2
N17V2

CHAPTER 6
PERIPHERAL DEVICES

INTRODUCTION

This chapter contains descriptions of all the standard prewired I/O bus options which are available with the
PDP-12. It describes the peripheral logic expander, BAI 2, and options contained within the panel, as well as the
most commonly used PDP-8 and PDP-12 family of I/O bus options. In general, most PDP-8 family of options can
be operated without modification on the PDP-12 1/0 bus. The reader, therefore, should refer to the DEC Small
Computer Handbook ( 1970) for additional information.
Prewired options and options contained in the BAI 2 Peripheral Expander panel derive their power from the
PDP-12 power supply. The Peripheral Expander contains the necessary buffering to provide the isolation and
current driving requirements for 1/0 devices. The control logic for these options is contained in plug-in modules;
therefore, when one of these options is added, wiring changes or additions are not needed. Separate power supplies
are normally included with all the other options.

Option Groupings
a. Pre wired
Teletype Model 33 ASR
Additional Teletype or Dataphone
Real-Time Interface
Fixed Interval Clocks
LINCtape to DECtape format converter
Digital Plotter and Control
Power Fail

Option Type Number

DPI 2-A,B
KW12-A
KW12-B,C
TC12-F
XY12
KP12

b; Peripheral Expander Type BAI 2
4-Station TTY Control
Line Printer
High-speed Paper Tape Reader/Punch
Standard or Mark Sense Card Reader
Data Buffers

DC02-D,E
LP12
PC12, PP12, and PR12
CR12, CM12
DBI 2-P, N

6-1

Option Groupings

Option Type Number

c. 1/0 Bus Stand Alone Peripherals
32 Station TTY Control
I- and 2-Station TTY Control
Line Printer
Magnetic Tape Control
Magnetic Tape Transport
Disk Fixed Head, 3 2K
Disk Fixed Head, 256K
Disk Movable Head BOOK
A-D Converter
D-A Converter

DC02-F,G
PT08
LP08
TC58
TU20
DF32, DS32
RF08, RS08
RK8, RKOl
AFOIA
AAOIA

The above groupings represent the physical organization of the PDP-12; however, the options will be described in
the following order:

6-2

Option Descriptions

Page Number

Teletype Controls (TTY)
Real-Time Interface and Clocks
Disks
Tapes
Line Printers
Card Readers
Plotters
High-Speed Paper Tape
Data Buffers
Power Fail/Restart
A-D Converter
D-A Converter

6-3
6-18
6-27
6-45
6-59
6-63
6-68
6-71
6-73
6-74
6-76
6-82

6.1 TELETYPE
6. 1.1 Model 33 ASR
The Teletype Model 33 ASR is the standard Teletype device offered with the PDP-12. It may be used to type in or
print out information at a rate of up to ten characters per second, or to read in or punch out perforated-paper tape
at ten characters per second. Signals transferred between the Model 33 ASR and the control logic are standard,
serial, 11-unit code, Teletype signals. The signals consist of marks and spaces which correspond to idle and bias
current in the Teletype, and to zeros and ones in the teletype control and computer. The start mark and
subsequent eight-character bits are one-unit-of-time duration, and are followed by the stop mark, which occupies
two units. The 8-bit code used by the Model 33 ASR Teletype unit is the American Standard Code for Information
Interchange (ASCII) modified. To convert the ASCII code to Teletype code, add 200 octal (ASCII + 200 8
Teletype). Bits are numbered from right to left, from 1 through 8, with bit 1 having the least significance.
Figure 6-1 illustrates the relationship between paper tape information and the AC.
SPROCKET
FEED HOLES

TAPE HOLE AND
CHANNEL NUMBERS

0
......._PAPER TAPE

AC BIT LOCATION-+ 4

NOTE:
AC BITS 0-3 ARE NOT USED.
12-0193

Figure 6-1. Relationship Between Paper Tape and Accumulator
The character (number) four (4) as it would be punched on paper tape is shown in Figure 6-2.
The Model 33 ASR set generates all assigned codes except 340 through 374 and 376. Generally codes 207, 212,
215, 240 through 337, and 377 are sufficient for Teletype operation. The Model 33 ASR detects all characters, but
does not interpret all of the codes that it can generate as commands. The standard number of characters printed per
line is 72. The sequence for proceeding to the next line is a carriage return followed by a line feed (as opposed to a
line feed followed by a carriage return). Appendix F lists the character codes for the Teletype.
6.1.2 Model 33 KSR
This Teletype model is similar to the 33 ASR, except that it does not have either a paper tape reader or punch. The
control logic, however, is the same as that used with the 33 ASR.

6-3

SPROCKET FEED HOLE
TAPE CHANNEL

1
0
0
'---..,,---'

BINARY CODE
{t=PUNCH)
OCTAL CODE

4
12-0193

Figure 6-2. Punched Paper Tape Format for the Number 4

6.1.3 Model 35 KSR
This unit is functionally the same as the 33 KSR. It is designed for heavy duty use and extended reliability. The
control logic, however, is the same as that used in the 33 ASR.

6.1.4 Model 37 KSR
This Teletype is offered as part of the LT37-AD, AE (50 Hz) option. It has an expanded character set (i.e., upper
and lower case) and control functions, and operates at 15 characters per second, both transmitting and receiving.
The LT3 7-AD option has a front panel switch which can effectively convert the unit to operate as a 33 ASR. Only
upper case characters would then be received or transmitted. The LT37 option provides the following programmed
operations:
a. Horizontal tab set and clear
b. Motor control; on and off
c. Vertical tab; set and clear at full line increments
d. Ribbon color shift
e. Reverse linefeed; full and half line increments

The LT37 is useful for the preparation of formal reports, business forms and graphical plots.
Table F-3 in Appendix F provides the character and control codes for each mode of operation.

6.1.S Teletype Controls
The basic programmed operation of the following devices is similar:
Console Teletype
Prewired Dataphone Option, Type DPl 2-A, B
Add-on Single and Dual TTY Control, Type PT08-B, C
They all transmit and receive asynchronous, full-duplex, bit-word information. These devices use control modules
M706 (Receiver) and M707 (Transmitter), which are positive logic modules, or W706 (Receiver) and W707

6-4

(Transmitter), which are the negative equivalent logic control modules. These modules are fully described in the
Digital Logic Handbook. The main differences in these options being controlled are:
a.

Source of data (e.g., Dataphone, keyboard/display terminal, Teletype, etc.)

Speed of operation
Slow speed devices such as Teletype are driven by the stabilized RC oscillator clock module (M452).
Higher speed requires a high stability of the selected frequency; therefore, a crystal-controlled clock
module (M4QS) is used. The frequency of operation must be specified for each separate device.

Voltage level of inputs
Typically, DEC equipment will interface directly with EIA RS-232-B industry standard devices or the
standard 0, 20 mA Teletype current loop (sometimes referred to as 0, +3V logic level). As the console
Teletype is typical of the three different controls discussed in this section, it will be described in detail.
The differences which are noteworthy in the PT08 and DPl 2 will be further discussed.

6.1.5.1 PDP-12 Console Teletype Control - The Teletype control uses the standard M706 receiver, M707
transmitter, and M452 clock modules for basic logic. It will drive any one of the previously discussed Teletype
models (the KSR-37 requires a slight adjustment of the clock to operate at 15 characters per second).
Serial information read or written by the Teletype unit is assembled or disassembled by the Teletype control for
parallel transfer to the accumulator (AC). The control also provides the program flags that cause a program
interrupt or an instruction skip depending on the availability of the Teletype and the processor.
In all programmed operation, the Teletype unit and control are considered ~s a Teletype in (TTI) for input data
from the keyboard or the perforated-tape reader, and as a Teletype out (TTO) for computer output information to
be printed and/or punched on tape. Therefore, two device select codes are used. Select code 03 initiates operations
associated with the keyboard/reader (TTI) and select code 04 performs operations associated with the
teleprinter/punch (TTO). Parallel input and output functions are performed by corresponding IOT pulses produced
by the two device selectors. Pulses produced by the IOPl pulse trigger skip gates; pulses produced by the IOP2
pulse clear the control flags and/or the accumulator; and pulses produced by IOP4 initiate data transfers to and
from the control.

6.1.5.2 Keyboard Reader - The keyboard and tape reader control contains an 8-bit shift register (TTI) which
assembles and holds the code for the last character struck on the keyboard or read from the tape. Teletype
characters from the keyboard/reader are received serially by register TTL The code of a Teletype character is
loaded into the TTI so that spaces correspond to binary zeros and holes (marks) correspond to binary ones. Upon
program command, the contents of the TTI are transferred in parallel to the accumulator.
When a Teletype character starts to enter the TTI, the control de-energizes a relay in the Teletype unit to release
the tape feed latch. When released, the latch mechanism stops tape motion only when a complete character has
been sensed, and before sensing of the next character is started. A keyboard is set when an 8-bit computer
character has been assembled in the TTI from a Teletype character. The program must sense the condition of this
flag with a KSF instruction, and, if the flag is set, issue a KRB instruction which clears the AC, clears the keyboard
flag, transfers the contents of the TII into the AC, and enables advance of the tape feed mechanism. Program
interrupt can be controlled by the LINC mode instruction ESF (0004) (refer to Paragraph 3.3.16). This instruction
either enables or inhibits interrupts when either the TTI or TIO flag is set.
6.1.5.3 Instructions - Instructions for use in supplying data to the computer from the Teletype are as follows:

6-5

KSF

Skip on Keyboard Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

KCC

4.25 µs
If the keyboard flag is set, the contents of the PC are incremented by one so that the next
sequential instruction is skipped.
If Keyboard Flag= 1, then PC+ I -+ PC

Clear Keyboard Flag

Octal code:
Event time:
Execution time:
Operation:

Symbol:

KRS

6031

6032
2
4.25 µs
The AC and the keyboard flag are cleared. If there is tape in the reader and the reader is on,
the character over the read head is loaded into the TTI and the tape advanced one frame. If
there is no tape or the reader is off (STOP or FREE) the character struck on the keyboard is
assembled into the TTL In either case, when the character is completely assembled in the TTI,
the hardware sets the keyboard flag.
0-+AC
0-+ Keyboard flag allowing the hardware to cause:
Keyboard/Tape Character-+ TTI
I -+ Keyboard flag (approximately I 00 ms after issuing the instruction)

Read Keyboard Buffer Static

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6034
3
4.25 µs
The contents of the TTI are transferred into AC 4 - 11 • This is a static command in that neither
the AC nor the keyboard flag is cleared. KRS can be microprogrammed with KCC.
TTI V AC 4 - 11 -+AC4-11
0-+ Keyboard Flag

NOTE
The KRS instruction has been redefined in a later version of the PDP-12 to permit
clearing of the TTI flag without advancing the paper tape and assembling the next
character.

KRB

Read Keyboard Buffer Dynamic

Octal code:
Event time:
Execution Time:
Operation:

Symbol:

6-6

6036
2, 3
4.25 µs
This instruction combines the functions of the KCC and KRS. The AC and keyboard flag are
both cleared and the contents of the TTI are transferred into AC 4 - 11 • Clearing the keyboard
flag allows the hardware to begin assembling the next input character into the TTI (as
described for KCC). When the character is completely assembled in the TTI, the hardware
causes the flag to be set, indicating that TTI again has a character ready for transfer.
0-+ AC
C(TTI) V C(AC4 - 11 )-+ AC 4 - 11
0-+ Keyboard Flag allowing the hardware to cause:
Tape Reader to advance I character
Keyboard/Tape Character -+ TTI
1 -+ Keyboard Flag when down (approximately
I 00 ms after issuing instruction)

KST

Key Strock (LINC mode)

Form:
Octal code:
Execution time:
Condition:

KSTI
0415 + 201
1.6 µs
A key has been struck on the ASR-33 keyboard, the character code has been assembled in the
Teletype buffer, and the Keyboard flag is raised. (The flag is cleared when the character is read
into the AC.)

The program example shown below will read 1 character from the keyboard.
*200
INPUT,

KCC
JMS LISN
DCA STORE
HLT

/CLEAR KEYBOARD FLAG

LISN,

/SKIP ON KEYBOARD FLAG

/READ KEYBOARD BUFFER

STORE,

KSF
JMP.-1
KRB
JMP I LISN
0

The main program begins with KCC. In general, the main program should begin by clearing the flags of all devices
to be used later in the program. If the above program is started at location 200, it will proceed to the KSF, IMP. -1
loop, and stay in this loop endlessly until a key on the Teletype unit is pressed or a paper tape is loaded into the
reader. When the ASCII code for the character is assembled in the keyboard/reader buffer register, the flag will be
set to a 1 and the program will skip out of the loop. The contents of the buffer will be transferred into the
accumulator, and the buffer and flag will be cleared.
6.1.5.4 Teleprinter/Punch - On program command, a character is transferred from the accumulator (AC) to the
output shift register (TTO) for transmission to the teleprinter/punch unit. The teleprinter control generates the
start space, shifts the eight character bits serially into the printer selector magnets of the teletype unit, and then
generates two stop marks. Bit transfer rate from the TTO to the teleprinter/punch unit is at the normal Teletype
rate of 110 baud. A character transfer requires 100 milliseconds for completion. The teleprinter flag is set when the
last bit of the character code is sent to the teleprinter/punch, indicating that the TTO is ready to receive a new
character from the AC. The flag activates either the program interrupt synchronization element or the instruction
skip element. When using instruction skip, the program checks the flag by means of TSF instruction. If the flag is
set, the program must issue a TLS instruction which clears the flag and sends a new character from the AC to the
TTO. AC to TTO transfer time is short compared to the print/punch time, so the program must wait for the flag to
set before issuing another TLS. Instructions for use in outputting data to the teleprinter/punch are as follows:

TSF

Skip on Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation·

6041
4.25 µs
If the teleprinter flag is set, the contents of the PC are incremented by one so that the next

Symbol:

sequential instruction is skipped.
If Teleprinter Flag = 1, then PC + 1 ~ PC

6-7

TCF

Clear Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:
TPC

Load Teleprinter and Print

Octal Code:
Event time:
Execution time:
Operation:

Symbol:

TLS

6042
2
4.25 µs
The teleprinter flag is cleared. Can be microprogrammed with TPC.
0 ~ Teleprinter Flag

6044
3
4.25 µs
AC 4 - 11 are parallel transferred to the TTO, then the hardware starts shifting the character out
to the printer/punch unit. When the transfer is complete (approximately 100 ns), the TTO flag
is set.
C(AC 4 - 11 ) ~ TTO causing:
C(TTO) ~printed and (if punch is on) punched

Load Teleprinter Sequence

Octal Code:
Event time:
Execution time:
Operation:

Symbol:

6046
2, 3
4.25 µs
This is an instruction that combines TCF and TPC. The teleprinter flag is cleared, then the
contents of AC 4 - 11 are parallel transferred to the TTO, where the hardware serially shifts the
character-bits out to the printer/punch unit. When the printer/punch has finished outputting
the character, the hardware sets the teleprinter flag. The whole operation, from the time TLS
clears the flag and TPC starts character transfer until the time the hardware finishes with the
character and again sets the flag, requires 100 ms.
0 ~Teleprinter flag
C(AC4 - 11 ) ~ TTO causing:
C(TTO) ~ Printed and (if punch on) punched
1 ~ Teleprinter flag when done (approximately 100 ns after issuing instruction)

Shown below are several programming examples illustrating the use of the TTO control.
TYPE,

TLS
TSF
JMP .-1
CLA
JMP I TYPE

/LOAD TIO FROM AC AND PRINT /PUNCH
/TEST FLAG SKIP IF = 1
/JMP BACK & TEST FLAG AGAIN AND AGAIN
/CLEAR CHARACTER FROM AC
/EXIT TO MAIN PROGRAM

By rearranging this subroutine, the 100 ms spent waiting for the character to be output and the flag to be set is
used to continue the main program, making more efficient use of program time.

6-8

TYPE,

TSF
JMP .-1
TLS
CLACLL
JMP I TYPE

/TEST FLAG TO SEE IF TELEPRINTER FREE, SKIP IF NOT
/WAIT TILL IT IS BY TESTING AGAIN AND AGAIN
/OUTPUT CHARACTER
/CLEAR CHARACTER FROM AC
/EXIT TO CONTINUE PROGRAM

This subroutine tests the flag first, and waits only if a previous character is still being output. It clears the AC and
exits immediately after sending the character to the TTO, and continues to run the user's program instead of
waiting while the teleprinter (a much slower device) is off typing/punching the last character. The user must
initialize the control by setting the teleprinter flag to a one. Otherwise, the subroutine will "hang-up" the first time
through (in the TSF, JMP .-1 loop). The initialization can be accomplished by issuing a TLS or TPC instruction at
the beginning of the mainline program.
Format Routines
Input and output routines are very often written in the form of subroutines, like the TYPE subroutine in the
previous example. The example below is a carriage return/line feed subroutine that calls the TYPE subroutine to
execute a carriage return and line feed on the printer, thus advancing to a new line for the printing of information.
Carriage Return/Line Feed Subroutine:
CRLF,

K212,
K215,
TYPE,

TAD K212
JMS TYPE
TAD K215
JMS TYPE
JMP I CRLF
212
215
0
TSF
JMP .-1
TLS
CLACLL
JMP I TYPE

/ASCII FOR CARRIAGE RETURN
/ASCII CODE FOR A LINE FEED

Subroutines similar to the one above could be written to tab space the carriage a given number of spaces, or to ring
the bell of Teletype Model 33 ASR by using the respective codes for these nonprinting control characters.
6.1.5.5 Single Teletype Control, Type DP12-A (prewired) - This internal option provides an interface which is
programmed similar to the standard console Teletype. The device select codes are IOTs 40 and 41. Interrupts
caused by either the transmitter or receiver flags can be disabled by the LINC mode instruction ESF (refer to
Paragraph 3.3.16).
6.1.5.6 Dataphone Control, Type DP12-B - This option is a modification of the DP12-A, which permits
communication to most standard Dataphone sets. An extra crystal-controlled clock permits the user to specify a
baud rate from 110 to 1ObK baud in order to provide the necessary frequency stability required at higher baud
rates. In addition, the option is supplied with a 25-ft cable, Type BCOlA-25, which will connect (via a 25-pin
connector) to a Dataphone set. This cable has a card connector (M850), which converts the EIA standard RS-232-B
signals to DEC logic levels of 0 and +3V

6-9

6.1. 5. 7 Single and Dual TTY Control Type PT08 - The PT08 is a serial-to-parallel, parallel-to-serial converter
which provides full-duplex communication between an asynchronous channel and a PDP-12 computer. Two basic
configurations are offered: PT08-B (one full-duplex channel) and PT08-C (two full-duplex channels). Systems may
be expanded up to five duplex channels by stacking PT08 units.
The PT08-B and C are designed to supply transmit and receive keying current that is intended for use with 20 mA,
de-keyed devices. Digital Equipment Corporation's Model 33 or 35 teleprinter units have been modified to be
compatible with the PT08. Devices equivalent to the modified teleprinter units are also compatible with the PT08.
The PT08-B and C are negative bus options (0, -3V) and, therefore, a DW08-A negative-to-positive 1/0 bus
converter must be used when connecting the PT08 to the PDP-12.
The PT08-F option provides EIA standard RS-232-B level conversion as well as a 25-ft cable designed to connect to
a Dataphone set. Another option, the PT08-X, can be installed in any channel for customer selection of character
format and speed. With the PT08-F and PT08-X options combined, the bit rate can be increased to lOOK baud for
driving medium-to-high-speed asynchronous modems. This combination can be used for an economical
intercomputer communication channel, or for interfacing to special equipment with unique asynchronous speeds
and character formats.

Specifications
Performance specifications are summarized in Table 6-1.
Table 6-1. PT08 Specifications
Specifications
Speed
Character Format
Operating Mode
Interface

Transmission Distance

110 baud is standard; up to lOOK (software limited) with PT08-X option.
Standard:
I-unit start; 8 character bits; 2-unit stop.
PT08-X Option: 5 or 8 character bits, 1- or 1.5-unit stop element at user's request.
Full duplex.
Supplies transmit and receive keying current that is intended for
Standard:
use with 20 mA, de-keyed devices.
PT08-F Options: Provides interface that conforms to EIA RS-232-B devices.
1500-ft maximum (environment dependent) for local terminals.
EIA interface transmission distance is limited only by characteristics of modem and
associated communication facility. A 25-ft cable to the modem is supplied.

Figure 6-3 illustrates the various PT08 equipment configurations for both the standard system expansion and
interface provisions.

Programming
IOT instructions test for character-ready conditions and transfer assembled characters to and from the computer's
accumulator. The same basic commands are used for all channels, with individual channels assigned different device
selection codes. For PT08 channel 1, the devices codes are 40 and 41, etc. (See Table 6-2 for complete listings of
PT08 device codes.) It will be noted that channel 1 IOTs are the same as assigned to the internal prewired option
DPl 2-A or B. When channel 1 is implemented, the IOT for channel 1 must be revised to an unused device select
code. This normally would be one of the device codes 30 through 37. The basic mnemonic plus the PT-number
designator identifies the mnemonic for the specific channel.

6-10

PDP-12

(+)

·------,

1W070 ------LOCAL
-I/O
BUS
PTOBB
I TERMINAL
DWOS-A .,....__ _ OR C
L - - - - -

i---

t- - --

-----

l_P_!~B_F

I
1---+

(TELEPRINTER)
(UP TO 1500 FEET
MAXIMUM)
110
BAUD

'EiA Rs-=2120- -l4-+

MAXI MUM OF 5 FULL
DUPLEX LINES (20mA
DC- KEYING) OF
SERIAL-STA RT-STOP CODE

TYPE MODEM

~~~~~N!•!T~)j.....

PTOSB 1
OR C
1---1

CONTINUATION OF
1/0 BUS TO OTHER
PERIPHERALS

I
PTOBB ~- -OR C
1-1 _ __

UP TO
B1 OAOUDK

f"HIGH.:SPEED-i.-.
1
I
1ASYNCHRONOUS
MODEM

PTOs-x' 1PTOBF ----J~E_!:;L_~~~.~~l.Ji....
12-0206

Figure 6-3. PT08 Equipment Configurations
Table 6-2. PT08 Device Codes

Basic
Mnemonic
KSF
KCC
KRS
KRB
TSF
TCF
TPC
TLS

Channel Number
1

6421
KSFPT2
6422
KCCPT2
6424
KRSPT2
6426
KRBPT2
6431
TSFPT2
6432
TCFPT2
6434
TPCPT2
6436
TLSPT2

6441
KSFPT3
6442
KCCPT3
6444
KRSPT3
6446
KRBPT3
6451
TSFPT3
6452
TCFPT3
6454
TPCPT3
6456
TLSPT3

6461
KSFPT4
6462
KCCPT4
6464
KRSPT4
6466
KRBPT4
6471
TSFPT4
6472
TCFPT4
6474
TPCPT4
6476
TLSPT4

6111
KSFPTS
6112
KCCPT5
6114
KRSPT5
6116
KRBPTS
6121
TSFPTS
6122
TCFPT5
6124
TPCPT5
6126
TLSPTS

6301
KSFPTl
6302
KCCPTI
6304
KRSPTl
6306
KRBPTl
6311
TSFPTl
6312
TCFPTI
6314
TPCPTI
6316
TLSPTl

Instructions
The following instructions are used with the PT08:
KSF

Skip on Receive Flag

Event time:
Indicators:
Execution time:
Operation:
Symbol:

IOT, Fetch, Pause
4.25 µs
Causes the program to skip the next instruction if the receive flag is set, indicating that an
assembled character is ready.
If receive flag = 1, PC + 1 -+ PC

6-11

KCC

Clear Receive Flag and AC

Event time:
Indicators:
Execution time:
Operation:
Symbol:

KRS

Read Receive Buffer (Static)

Event time:
Indicators:
Execution time:
Operation
Symbol:

KRB

2
JOT, Fetch, Pause
4.25 µs
Clears the accumulator and the receive flag.
o~Ac, o~ RF

3
IOT, Fetch, Pause
4.25 µs
Transfers an assembled character from the receive buffer to AC 4 - 1 1 . Does not reset AC or
receive flag.
RB~ AC 4 - 11

Read Receive Buffer (Dynamic)

Event time:
Indicators:
Execution time:
Operation:

2, 3
IOT, Fetch Pause
4.25 µs
Performs the functions of KCC and KRS together, so that the receive flag and AC are cleared
before data is transferred from the receive buffer to the AC.

Symbol:

o~Ac, o~RF

RB~ AC 4 - 11

TSF

Skip on Transmit Flag

Event time:
Indicators:
Execution time:
Operation:

TCF

Clear Transmit Flag

Event time:
Indicators:
Execution time:
Operation:
Symbol:

TPC

2
IOT, Fetch, Pause
4.25 µs
Resets the transmit flag.
o~TF

Load Transmit Character

Event time:
Indicators:
Execution time:
Operation:
Symbol:

6-12

I OT, Fetch, Pause
4.25 µs
Causes the program to skip the next instruction if the transmit flag is set, indicating that the
transmit flag= 1, PC+ 1 ~PC

3
IOT, Fetch, Pause
4.25 µs
Loads the transmit buffer from AC4 - 11 and initiates transmission of a character.
AC 4 - 11 ~TB

TLS

Load Transmit Sequence

Event time:
Indicators:
Execution time:
Operation:
Symbol:

2, 3
IOT, Fetch, Pause
4.25 µs
Performs the functions of TCF and TPC together.
0-+TF
AC 4 _11 -+TB

Maximum Data Rates
In transmitting the PT08 provides a full character cycle for the program to deliver new data. In receiving, one bit
time is required to read in necessary data. However, for maximum data transfer rates, the time at which data
transfer can occur is limited to an aperture equal to the stop bit time plus half a bit time. This response time is
measured from the beginning of a stop bit (the time at which the transmit or receive flag is reset), and the midpoint
of the next character's start bit. If the program fails to respond within this time, a character is lost. Timing is
illustrated in Figure 6-4.

STOP BIT TIME

l4-- (BIT TIME X STOP UNITS}

--.i

BIT TIME
( 1/BAUD RATE) ____,

DATA BITS

I
I

START

r-r T- - - - ---iL_j __i_ _l_ _ _ _ _ _I _ !

CHARACTER-----,
TIMING

STOP

:sTA~- -.-DATA ~T~ -

!'_

_L _ _ _ _

LAST TIME TO
RESPOND TO FLAG

I
I
I

I
I

RECEIVE

TRANSMIT OR
FLAG RESET

I
I
I

I
I

81-0075

Figure 6-4. PT08 Program Response Time

For example, at 110 baud (9.09 ms bit time), response time is:
Stop bit time + half a data bit time
= 2 x 9.09 + 9.09/2
= 22.725 ms
Note that the number of bits per character need not be considered.
6.1.5.8 Multiple Teletype Control, Type DC02-E (see Table 6-3) - The DC02-E option, which is prewired in the
BAI 2 Peripheral E~pander, allows the user to add up to four serial-to-parallel, parallel-to-serial asynchronous data
channels. It consists of a DC02-E multiple station control and from one to four DC02-D station interfaces (each
full-duplex). A Type BCOIA-25 cable is available that will connect to most Dataphones via a 25-pin connector and
will convert EIA standard RS-232-B signals to DEC logic levels of 0 + 3 volts.
The control will handle teletypes at their normal baud rate of 110. In addition, higher speed devices may be
operated by using crystal clocks. In this case the baud rate must be specified by the user. Up to two clocks may be
used and may be connected by a jumper module in any combination to control the stations' transmitters and
receivers.

6-13

Table 6-3. DC02-E Specifications
Characteristics

Specifications

Speed
Character Format

110 baud is standard; up to 1OOK baud crystal controlled.
Standard:
I-unit start; 8 character bits; 2-unit stop.
Option:
5 or 8 character bits 1- or 1.5-unit stop element at user's request.
Full duplex.
Standard:
Supplies transmit and receiver keying current that is intended for
use with 20 mA, de-keyed devices.
1500 ft maximum (environment dependent) EIA interface transmission distance is
limited only by characteristics of modem and associated communication facility. A
25-ft cable to the modem is supplied. (BCOlA-25).

Operating Mode
Interface
Transmission Distance

DC02-E Control Instructions
The following instructions are·used with the DC02E control:

MTPF

Multiple Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MINT

6117

1, 2, 3
4.25 µs
Transfer AC 0 _ 3 to selection register (select stations when bit is set).
AC 0 _3 --+ SR

Multiple Keyboard Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6-14

6115

3
4.25 µs
Interrupt on if AC 1 1 is set (interrupt request if any flags).
AC 1 1 --+ Interrupt Enable

Multiple Station Select

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTKF

1, 2
4.25 µs
Transfer status of teleprinter flags to AC 0 - 3 .
Teleprinter flags--+ AC·0 - 3 •
0--+ AC 4 - 11 .

Multiple Interrupt

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTON

6113

6123

1, 2
4.25 µs
Transfer status of keyboard flags to AC 0 - 3 •
KF-+ AC0 - 3
0--+ AC 4 - 11

MINS

Multiple Interrupt and Skip

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTRS

6125
1, 4
4.25 µs
Skip if the interrupt request is active (if interrupt is on and any flag is raised).
If interrupt request is active, PC+ 1 ~PC

Read Station Select Status

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6127
1, 2, 3
4.25 µs
Transfer the status of the selection register to AC 0 • 3 •
SR~ AC 0 • 3
0 ~ AC4-11

DC02-D Instructions

Decoder instructions for the DC02-D are in two basic groups: receiver and transmitter. The receiver instructions are
6111, 6112, 6114, and 6116; the transmitter instructions are 6121, 6122, 6124, and 6126. The "Station Select"
flip-flop is gated with each device select code; therefore, these IOTs are effective only when a particular station is
selected.

MKSF

Skip On Keyboard Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

*MKCC

6111
4.25 µs
Skip if the selected keyboard flag is set.
IfKF= 1, PC+ 1 ~PC

Clear Keyboard Flags

Octal code:
Event time:
Execution time:
Operation:

6112
2
4.25 µ.s
Clear the keyboard flag of the selected station; clear AC. If the paper tape reader is on, the
tape will advance 1 character and the receiver flag will be set approximately 100 ns after
issuing the instruction.

Symbol:

o~KF, o~RF, o~Ac

MKRS

Read Keyboard Register Static

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6114
3
4.25 µ.s
Transfer the keyboard register contents to AC 4 • 11 .
AC 0 • 11 V KR to AC 0 .
11

* On some systems a logic revision has been added which inhibits tape advance and consequent setting of the receiver flag.

6-15

MKRB

Load Keyboard Sequence

Octal code:
Event time:
Execution time:
Operation:

6116
2,3
4.25 µs
Clear the keyboard and reader flags, clear AC; transfer the keyboard register contents to
AC 4 - 11 (MKCC and MKRS combined).

Symbol:

0-* KF
0-* RF
0-* AC
KR --"* AC 4 - 11

MTSF

Skip on Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTCF

6124
3
4.25 µs
Load AC 4 - 11 into the teleprinted register (begin print/punch).
AC 4 - 11 ~TR

Load Teleprinter Sequence

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6122
2
4.25 µs
Clear the teleprinter flag of the selected keyboard station.
0-*TF

Multiple Load Teleprinter Register and Print

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTLS

4.25 µs
Skip if the selected teleprinter flag is set.
If TF = 1, PC + 1 -* PC

Clear Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTPC

6121

6126
2, 3
4.25 µs
Clear the teleprinter flag and load AC 4 - 1 1 into the teleprinter register (MTCF and MTPC
combined).
o~TF

AC 4 - 11 ~TR
Multiple Teletype Control, Type DC02-F
This control is similar to the DC02-E in operation and design. It consists of a double row of logic (10-1 /2" x 19"
nominal rack space) complete with power supplies. This unit will handle up to eight stations. The DC02-F is
designed so that four controls may be connected together in such a way that 32 stations total may be operated. A
jumper module is used to enable selected signals when the system is expanded.
As in the four-station control DC02-E, the high order bits of the' AC are used to select a station. AC 0 - 7 are used to
select the stations within one control and AC 8 - 11 are used to select any one of up to four DC02-F controls. Up to

6-16

three separate clocks may be specified. In addition, two frequency divide registers are available with outputs at
divide-by-8 and divide-by-128. The resultant timing pulses may be connected in any combination with jumper
modules to provide timing for the transmitter and receiver modules of the stations.
The specifications for this control are the same as those of the DC02-E. The program instructions are likewise
identical except for the following.

MTPF

Multiple Teleprinter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTKF

6113

1, 2
4.25 µs
Transfer status of teleprinter flags AC 0 - 7 • AC 8 - 11 selects one of four controls.
Teleprinter flags-+ AC 0 - 7
0-+ ACs-11

Multiple Keyboard Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTON

6123

1, 2
4.25 µs
Transfer status of keyboard flags to AC 0 _7
KF-+ AC 0 _7
0-+ ACs-11

Multiple Teleprinter

Octal code:
Event Time:
Execution time:
Operation:
Symbol:

6117

1, 2, 3
4.25µs
Transfer AC 0 _7 to selection register select stations when bits are set. AC 8 _1 1 selects one of
four controls.
AC 0 _7 -+ SR
0-+ ACa-11

MINS

Multiple Interrupt and SKP

Octal code:
Execution time:
Operation:
Symbol:

MTRS

Multiple Teleprinter Read Status

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6125
4.25 µs
Skip if the interrupt request is active (i.e., if interrupt is on and any flag is raised) AC 8 _1 1
select one of four controls.
0-+ AC 8 - 11

6127

1, 2, 3
4.25 µs
Transfer the status of the selection register to AC 0 - 7 • AC 8 - 1 1 selects one of four controls.
Transfer status of interrupt enable flip-flop to AC 11 . If AC 11 = 1, the interrupt enable is set.
SR-+ AC 0 - 7
Interrupt Enable-+ AC 11
0-+ AC 8 -~ 0

6-17

6.2 REAL TIME CLOCKS
6.2.1 Real Time Interface, Type KW12-A
The KW 12-A (see Figures 6-5 and 6-6) is a prewired PDP-12 option with an input control panel, which mounts
behind the vertical door on the left front of the PDP-12. The Real Time Interface can be used to synchronize the
central processor to external events, count external events, measure intervals of time between events, or provide
program interrupts at programmable intervals from 2.5 µs to over 40 seconds. Some of the above mentioned
operations can be done simultaneously.

Figure 6-5. KW 12-A Real Time Interface

Time Base
The programmable time base provides count pulses to the counter register at any of the following rates derived
from a 400 kHz crystal clock:
400 kHz
100 kHz
10 kHz

6-18

1 kHz
100 Hz

Input channel 1 may be used to enable an external source to drive the counter. This external source may be
switch-selected to be either the power line waveform or an actual signal from a laboratory instrument. The
programmable selection of the rate is accomplished with the three rate-bits of the clock control register.
Input Synchronizers
Three input channels are used to convert external events into a synchronized control and status signal for the clock.
Each input channel consists of an input Schmitt trigger with pulse generator, five flip-flops, and associated control
gating. The Schmitt trigger and pulse generator converts the preselected voltage threshold crossing by an external
signal into a single event (pulse). This Schmitt trigger has level and slope selection controls available on the front
panel. They provide selection of ·any threshold between ±6V and either positive or negative-going slope. The
Schmitt trigger has a hysteresis of 0.3V.

TO AC (12 BITS)

CLOCK BUFFER PRESET REG (12 BITS)
IO BUS

IO AND MODE
CONTROL

(12 BITS)

FROM AC (12 BITS)

START A-0 CONVERTER
PROGRAM
INTERRUPT
AND SKIP

OVERFLOW
LOGIC

COUNT

CLOCK COUNTER (12 BITS)

INPUT 1
CLEAR
CLOCK

(12BITS)

INPUT 2

RATE CONTROL

INPUT 3
CRYSTAL

400 kHz
100 kHz

10kHz

1kHz

100 Hz
12-0110

Figure 6-6. KWI 2-A Organization

The five Input Circuits flip-flops are: INPUT ENABLE, INPUT, PRE-EVENT, EVENT, and ENABLE EVENT
INTERRUPT (see Figure 6-7). Figure 6-8 shows a basic timing of the Input Synchronizer.

I
6-19

Not shown in Figure 6- 7 is the logic which clears the EVENT and PRE-EVENT flip-flops when the CLSA
instruction is given. This logic ensures that events occurring during the execution o'r the present CLSA instruction
are indicated when the next CLSA instruction is given.

Input Enable Flip-Flop - Gates on and off input signals to the clock. It is set and cleared under program control.
Input Flip-Flop - Set by an external signal from the Schmitt trigger input or under program control with the
CLLR instruction. The INPUT flip-flop provides synchronization between external timihg and internal clock
timing.
Pre-Event Flip-Flop - Strobed into the EVENT flip-flop by the strobe 1 signal. This clears the INPUT flip-flop if
EVENT is clear.
Event Flip-Flop - Loaded with the PRE-EVENT flip-flop on the next strobe 1 and set to a 1 by the second strobe
1 following the setting of the INPUT flip-flop. Subsequent to EVENT being loaded, PRE-EVENT is cleared.
Event Enable Interrupt Flip-Flop - Permits external events to cause program interrupts. It is set and cleared by the
CLEN instruction.
The occurrence of strobe 2 with EVENT (0) and PRE-EVENT (1) is the actual single event used by other parts of
the clock logic such as counting and transfers from counter to buffer register.
The status of the EVENT and PRE-EVENT flip-flops is loaded into the AC under program control. When this
transfer occurs, the corresponding INPUT, PRE-EVENT, and EVENT flip-flops are cleared.

If a second input occurs before the EVENT flip-flop is cleared, then both the PRE-EVENT and EVENT flip-flops
will remain set, indicating an error.

INPUT

~NABLE

SYNC
STROBE

EVENT

PRE
EVENT

INTER.
REQ L

ENABLE
EVENT
INTER.

0
12-0194

Figure 6-7. Simplified Input Synchronizer Logic Diagram

6-20

SYNC.

SYNC

STROBE1~
I

100ns
I

1 '

-11-

STROBE 1

:COUNTER
I
I TO
600n s BUFFER

1-IH/

INPUT
FLIP-FLOP

SYNC

__J
COUNTER

----=r--1
_j
!

INCREMENTED

STROBE 2

INPUT
FLIP-FLOP

UUUT

HE RE
PRE-EVENT
FLIP-FLOP ---~

__J

CD
PRE-EVENT
r-----i- - - - 1 f
FLIP-FLOP _ _ ___.
®

.....__ __

EVENT__ll_
FLIP-FLOP
Timing diagram for Channel 1 only if the
rote field equals 6 8 and Channel 1 input
is enabled.

EVENT
FLIP-FLOP ----C-P_....IN_T_E~RRUPT
HERE
NORMAL

ERROR

NOTES:
1 Normally PRE-EVENT is reset.
If however, EVENT was already set,
PRE-EVENT remains set as on error
f I a g ~ ind i cat in g that more than one
input occured between clearing of the
EVENT flip-flop.

may be used to increment the
counter. For this case the
timing diagram is shown below.

3. Error indication that 6135

2. EVENT is cleared only by the CPU using
the 6135 (CLSA) instruction with the
following exception: Inputs to Channel 1

(CLSA) instruction was not
issued soon enough following
an EVENT.

12 -0205

Figure 6-8. KWl 2-A Timing Diagram
Counter Register
The counter register is a 12-bit counter that is loaded from the buffer-preset register or can be transferred into the
buffer-preset register.
The counter may be used to count events, measure intervals of time between events, or provide processor interrupts
at program selected intervals from 2.5 µs to over 40 seconds.
OVERFLOW Flip-Flop - The OVERFLOW flip-flop is set by the most significant bit of the counter register going
from I to 0.
Buffer-Preset Register - Used to buffer the current coum in the clock register at the occurrence of an event when
operating with Mode 1 (1). With Mode 1 (0) and Mode 2 (1), the buffer-preset register holds the number to be
transferred into the counter when overflow occurs. The buffer-preset register can be loaded into the AC or the AC
can be transferred into the buffer-preset register.

6. 2.1.1 Use of Interface with A-0 - With Mode 0 (1 ), the occurrence of overflow is used to start an A-D
conversion if the A-D is in the Fast Sample Mode. With Clock Mode 0 ( 1), the A-D is triggered only by the clock.
When a SAM instruction is given, the result of the last conversion is transferred to the AC, and a new analog
channel is selected for the next conversion to be performed when the clock overflows. If the SAM instruction is
given while a conversion triggered by the clock is in progress, the processor waits in timestate TS5 until the
conversion is complete.

6-21

6.2.1.2 KW12-A Input Panel - The input panel for the clock is located behind the door on the left side of the
front of the PDP-12. External signals (from up to three instrument/sources) are connected to the Input jacks on the
front panel (see Figure 6-5) via standard 3-conductor telephone plugs. Each Input and Output jack is wired in
parallel to permit convenient connection of the external input signals to the KW 12-A and, if desired, the
Analog-to-Digital Converter. The input is differential, ±5V range, input resistance greater than 10,000 ohms, and
protected against inputs up to ±50V. A level control and a slope control are associated with each input. The level
control selects the threshold voltage at which the trigger pulse is generated. The slope determines the polarity of
the input signal causing a trigger pulse. The trigger pulse sets the associated input flip-flop of the clock if that input
channel is enabled.
6.2.1.3 KW12-A Real Time Interface Instructions - The KW12-A is controlled by PDP-12 IOT instructions. These
instructions can be used from either 8 or LINC mode. Execution time for the IOTs is 4.25 µs when in 8 mode and
5 .9 µs when in LINC mode (using IOB).
CLSK

Skip On Clock Interrupt

Octal code:
Event time:
Execution time:
Operation:

6131
4.25 µs
Skip if clock interrupt condition exists. The interrupt conditions are as follows:
a. Enable Event l Interrupt (1) and Event 1 (l ).
b. Enable Event 2 Interrupt ( 1) and Event 2 ( 1).
c. Enable Event 3 Interrupt (1) and Event 3 (l ).
d. Enable Overflow Interrupt ( 1) and Overflow ( 1).

CLLR

Load Clock Control Register

Octal code:
Event tjme:
Execution time:
Operation:

6132
2
4.25 µs
The contents of the AC are transferred to the clock control register. Three bits are used to
provide simulated data input to each of the three Event input channels. The AC is unchanged.
Bit

Function

Count Rate Register Bit 0
Count Rate Register Bit 1
Count Rate Register Bit 2
Mode Control Register Bit 0
Mode Control Register Bit 1
Mode Control Register Bit 2
Not used
Simulate Input to Channel 1
Not used
Simulate Input to Channel 2
Not used
Simulate Input to Channel 3

02
03
04
05
06
07
08
09
10

6-22

The rate of the counter register input count pulses is determined by the contents of the count rate register.
Count Rate
Register
000
001
010
011
100
101
110
111

Frequency of
Count Pulses
Stop
400 kHz
100 kHz
IO kHz
1 kHz
100 Hz
Rate of Input Channel 1
Stop
NOTE

When Channel 1 is used as the time base for the counter, the Event flag is
automatically cleared and Channel 1 Interrupt Enable would normally be left off.
Also the clock counter is advanced one count each time an IO PRESET is performed
either manually or under program control.
The contents of the mode control register determine the method by which the clock system operates.
Program Example
The following program rings the teleprinter bell once for every 10 inputs ( 60 Hz) on external channel three. If the
source knob is turned to line frequency the Teletype bell will ring once/per second on computers connected to 60
Hz power lines.
/PSEUDO TO LAP6 DIAL ASSEMBLER
PM ODE
/CLEAR AC
CLA
BEGIN,
/CLEAR ALL MODES
CLLR
/CLEAR ENABLES
CLEN
/NO. OF COUNTS
TAD K74
CIA
/FORM 25 COMP
/LOAD PRESET REG
CLAB
CLA
/CLEAR AC
TAD KOIOO
/SET AC05=1
CLLR
/GENERATE CLEAR COUNTER
/CLEAR STATUS AND POSSIBLE OVERFLOW
CLSA
CLA
/CLEAR AC
TAD K0320
/LOAD AC
CLEN
/LOAD BUFFER INTO COUNTER, ENABLE INTERRUPT ON OVERFLOW,
AND ENABLE IN
PUT CHAN 1
CLA
/CLEAR AC
TAD K6100
/LOAD AC
CLLR
/START CLOCK BY ENABLING RATE
LOOP,
CLSK
/SKIP ON CLOCK FLAG
JMP LOOP
/WAIT
CLSA
/CLEAR STATUS
CLA
/CLEAR AC
TAD K207
/LOAD AC
TLS
/RING TELEPRINTER BELL
JMP LOOP
/RETURN TO WAIT LOOP
K74,
74
/CONSTANTS
KOIOO,
100
K0320,
320
K6100,
6100
K207,
207

6-23

Mode Control Register
000

Free-run
Counter runs selected rate. Overflow occurs every 4096 counts. The overflow flag remains
set until cleared with CLSA instruction.

001

Preset Time
Counter runs at selected rate. When overflow occurs, the contents of the Clock
Buffer-Preset register are transferred automatically to the Counter which continues. The
Overflow flag remains set until cleared with a CLSA instruction. When Mode is changed
from XOO to XO 1, the clock counter is zeroed.

010

Time Base (measures intervals between events)
Counter runs at selected rate. On the occurrence of an Input Event, the contents of the
counter are transferred automatically to the Buffer Preset register, and the counter
continues to count.

011

Time Base (measures intervals between events)
This is identical to Mode 10, except that the Clock Counter register is cleared after its
contents have been transferred to the Buffer Preset register on Event 3. Events 1 and 2
remain only to cause transfer from the clock counter to the Buffer Preset register.

100
101
110
111

When Mode bit 0 is set to a l, the occurrence of Overflow is used to trigger the A-D
converter if A-D control also has the FAST-SAMPLE flip-flop set. This allows
analog-to-digital conversions to take place under the automatic timing control of the
clock. In this mode, A-D conversions are triggered only by the clock counter overflow.
The SAM instruction reads the result of the previous conversion and sets the channel
number for the next conversion. For details of the Analog-to-Digital converter, see
Paragraph 6.11. The remaining two Mode Control bits are decoded exactly as above.

CLAB

AC to Buffer Preset Register

Octal code:
Event time:
Execution time:
Operation:

CLEN

Load Clock Enable Register

Octal code:
Event time:
Execution time:
Operation:

6-24

6133
2
4.25 µs
Transfer AC to Buffer Preset register. The previous contents of the Buffer Preset registers are
lost and the AC is unchanged.

6134
3
4.25 µs
The contents of the AC are transferred to the Clock Enable register. The function of each bit is
given below:

Function

Bit
00
01

02
03
04
05
06
07
08

09
10
11

CLSA

Clock Status to AC

Octal code:
Event time:
Execution time:
Operation:

6135
1,3
4.25 µs
This instruction interrogates the CLOCK INPUT and OVERFLOW STATUS flip-flops. The
clock status information is inclusive ORed into the AC. Then the AC status bits which are set
are cleared. This ensures that only one occurrence of an EVENT will be transferred to the
program.
AC Bit

Status Condition

00
01

OVERFLOW Flip-Flop
Not used
Not used
Not used
Not used
Not used
Event 1
Pre-Event I
Event 2
Pre-Event 2
Event 3
Pre-Event 3

02
03
04
05
06
07
08

09
10

CLBA

Buffer Preset Register to AC

Octal code:
Event time:
Execution time:
Operation:

CLCA

Not used
Not used
Not used
Not used
Inclusive OR Clock Buffer into counter if mode= XOI and overflow= 0
Enable Interrupt when overflow ( 1)
Enable Interrupt on Event 1
Enable Input Channel 1
Enable Interrupt on Event 2
Enable Input Channel 2
Enable Interrupt on Event 3
Enable Input Channel 3

6136
2,3
4.25 µs
The AC is cleared and the contents of the Clock Buffer Preset register are transferred into the
AC.

Counter to AC

Octal code:
Event time:
Execution time:
Operation:

6137
1,2,3
4.25 µs
The AC is cleared and the contents of the Clock Counter are transferred to the
BUFFER-PRESET register. Then the contents are transferred into the AC.

6.2.2 KW12-B and KW12-C Fixed-Interval Clocks
The KWl 2-B provides a means of interrupting the CP at intervals determined by a variable RC Oscillator. The
KWl 2-C is similar to the KWl 2-B except that the RC oscillator is replaced by a crystal oscillator with a single fixed
frequency. The KWl 2-B or KWl 2-C may be turned on or off under program control. However, variations in
frequency require physically altering or changing the oscillator.

6-25

Instruction Set
The KWl 2-B and KWl 2-C are controlled by IOT instructions. These instructions can be used from either mode.
Execution time for the Simple Clock IOTs is 4.25 µs when in 8 mode and 5.9 µs when in LINC mode (using IOB).

CSOF

Skip on Clock Flag

Octal code:
Execution time:
Operation:

CTOC

6131
4.25 µs
Skip if clock flag is set.

Turn Off Clock

Octal code:
Execution time:
Operation:

6132
4.25 µs
Turn off the clock, clear the clock flag, and disable the clock interrupt.

CTON Turn On Clock
Octal code:
6134
4.25 µs
Execution time:
Turn the clock on and clear the flag.
Operation:
CRUN

Clock Running

Octal code:
Execution time:
Operation:

6135
4.25 µs
Turn on the clock, enable the clock interrupt, clear the clock flag, skip if the clock flag was set
when the instruction was issued.

Frequency Range
KW12-B

KW12-C

6-26

The KW 12-B uses the M401 variable clock in slot F 18 for a time base. The frequency may be
varied with a range by adjusting a potentiometer on the module. Five frequency ranges are
available. The KW 12-B is nominally set to the 1. 7 5 kHz-to- I 7. 5 kHz frequency range by
jumpering Fl8N2 to Fl8T2. Other frequency ranges may be achieved by removing the jumper
from Fl 8T2 and attaching as shown below. The exact frequency may be checked by observing
the signal on Fl 8D2 with an oscilloscope.

Frequency Range

Interconnections Required

17.5 kHz to 50 kHz
1.75 kHz to 17.5 kHz
175 Hz to 1. 7 5 kHz

F18N2 - Fl8S2
F 18N2 - F 18T2 (nominal setting)
F18N2 - F18P2

The KW 12-C uses the M405 crystal clock in slot F 18 for a time base. The frequencies are fixed
by a series resonant crystal oscillator to obtain a frequency stability of .01 percent of the
specified value between 0°C and +55°C. The frequencies available are in the range of 5 kHz to
50 kHz .and must be specified in advance by the customer.

6.3 DISK STORAGE

6.3.1 Random Access Disk File, Types DF/0$32 and DF/DS32-D
The DF32 and DF32-D operate through the three-cycle data break facility to provide 32, 768 13-bit words (12 bits
plus 1 parity bit) of storage, and are economically expandable to 131,072 13-bit words using the respective
expander disk, DS3 2 or DS3 2-D.
The DF32 and DF32-D comprise two basic assemblies: the storage unit containing the read/write circuits and the
computer interface logic. The storage unit contains a nickel cobalt plated disk driven by a hysteresis synchronous
motor. Data is recorded on a single disk surface by 16 read/write heads in fixed positions. The disk motor,
read/write data heads, and photocell assembly (on DF32) are all mounted on a rack assembly that permits sliding
the unit in and out of a DEC 19-inch Standard Cabinet.
The following table summarizes the DF32 and DF32-D:
DF32

DF32-D

60Hz

SOHz

60Hz

SO Hz

Data Transfer rate
(microseconds per word)

Average Access Time
(milliseconds)

16.67

Same

Timing and Address Track
"Start & Finish" Sensing

Photo-electric reflective
marker on disk outer
perimeter

Special Start and Finish
coding and decoding on
timing track

Type of Logic

Negative

DF32DP - Positive
DF32DN - Negative

Instructions
The DF32 and DF32-D disk systems share the following instruction set:

DCMA

Clear Disk Memory Address Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6601
4.25 µs
Clears Memory Address Register, parity error, and completion flags. This instruction clears the
disk memory request flag and interrupt flags.
0 ~ completion flag
0 ~error flag

6-27

DMAR

Load Disk Memory Address Register and Read

Octal code:
Event time:
Execution time:
Operation:

Symbol:

DMA W

1,2
4.25 µs
The contents of the AC are loaded into the disk memory address register and the AC is cleared.
Begins to read information from the disk into the specified core location. Clears parity error
and completion flags. Clears interrupt flags.
AC 0 - 11 ~ DMA 0 - 11
0 ~ completion flag
0 ~ error flag

Load Disk Memory Address Register and Write

Octal code:
Event time:
Ex ecu ti on time:
Operation:

Symbol:

DCEA

6603

6605
1,3
4.25 µs
The contents of the AC are loaded into the disk memory address register and the AC is cleared.
Begins to write information onto the disk from the specified core location. Clears parity error
and completion flags. Clears interrupt flags. Data break must be allowed to occur within 66
microseconds after issuing this instruction.
ACo-11 ~ DMAo-11
0 ~ completion flag
0 ~ error flag

Clear Disk Extended Address Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6611

4.25 µs
Clears the Disk Extended Address and Memory Address Extension register.
0 ~ Disk Extended Address Register
0 ~ Memory Address Extension Register

DSA C Skip on Address Confirmed Flag
Octal code:
Event time:
Execution time:
Operation:
Symbol:

6612
2
4.25 µs
Skips next instruction if address confirmed Flag is set. Flag is set for 16 µs (AC is cleared).
If address confirmed flag = 1, then
PC+l~PC

DEAL

Load Disk Extended Address

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6-28

6615
1,3

4.25 µs
The disk Extended Address and Memory Address Extension registers are cleared and loaded
with the track address data in the AC.
AC 6 - 8 ~Core Memory Extension
AC 1-s ~Disk Address Extension 32K, 64K, 96K, l 28K
AC 0 9 - 1 1 used in DEAC instruction
(See NOTE on opposite page)

DEAC

Read Disk Extended Address Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6616
2,3
4.25 µs
Clear the AC then load the contents of the disk Extended Address register into the AC
allowing program evaluation. Skip next instruction if address confirmed flag is set.
Disk Address Extension 32K, 64K, 96K, 128K--+ AC 1 -s
Core Memory Extension --+ AC 6 - 8
Photo-cell sync mark--+ AC0 (Available 200 µs)
Data Request Late flag --+ AC 9
Non-Existent or Write Lock switch on--+ AC 10
Parity Errors --+ AC 1 1
NOTE

For the DEAL and DEAC instructions, refer to the diagrams shown below.

BITS 1-5
(DEAL INST)

ACCUMULATOR
(LOW ORDER 12 BITS)
0-11 of DMAW or DMAR

DISC
ADDRESS
(17 BIT)

CELL 7751
(CURRENT ADDRESS)

CURRENT ADDRESS
(MEMORY) ADDRESS
(15 BIT)

FIELD BITS
6-8

(DEAL INST)

DFSE

Skip on Zero Error Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

DFSC

6621

4.25 µs
Skips next instruction if parity error, data request late, and write lock switch flag are clear.
Indicates no errors.
If Parity Error flag = 1
and Data Request Late flag= 1,
and Write Lock Switch flag = 1, then PC + 1 --+ PC

Skip on Data Completion Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6622
2

4.25 µs
Skips next instruction if the completion flag is set. Indicates data transfer is complete.
If Completion flag = 1, PC + I --+ PC

6-29

DMA C

Read Disk Memory Address Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6626
2,3
4.25 µs
Clears the AC then loads contents of the Disk Memory Address register into the AC allowing
program evaluation. During read, the final address is the last one transferred.
DMAo-11 ~ ACo-11

The computer can handle 12 bits; therefore, the high order bits for Disk and Memory addresses are manipulated by
the DEAL and DEAC instructions. Low order bits are manipulated in the accumulator (AC).
The Disk address is a 17-bit value. Bit 1 of the DEAL and DEAC instructions is the most significant bit. The
Memory address is a 17-bit value. Bit 6 of the DEAL and DEAC instructions is the most significant bit.
Note that the Word Count 7750 is the two's complement of the number of words to be transferred and that the
Disk address is the desired starting address. The Memory or Current address (7751) is the desired address-I.

NOTE
Write Lock Switch status is true only when the disk module contains write
instructions. The nonexistent disk condition will appear following the completion of
a data transfer during read, where the address acknowledged was the last address of a
disk and the next word to be addressed falls within a nonexistent disk. The
completion flag for the data transfer is set by the nonexistent disk condition 16
microseconds following the data transfer.

6.3.2 Disk Memory System Type RF/RS08
The RF08 control and RS08 disk combine as a fast, low-cost, random access bulk storage package for the
PDP-l 2A. One RS08 and RF08 provide 262, 144 13-bit words (12 bits plus parity) of storage. Up to four RS08
disks can be added to the RF08 control for a total of 1,048,576 words of storage.
Data transfer rate on 60 Hz power is 16.2 microseconds per word or 20 microseconds per word on 50 Hz. Data
transfer is accomplished through the three-cycle data break system of the PDP-l 2A.
Average access time with a 60 Hz disk is 16.67 milliseconds, or 20 milliseconds at 50 Hz power. Worst case access
time is 33 milliseconds on 60 Hz power, or 40 milliseconds on SO Hz power.
The RS08 disk unit contains a nickel-cobalt plated disk driven by a hysteresis synchronous motor. Data is recorded
on a single disk surface by 128 fixed read/write heads. The RF08 and RS08 are designed for mounting in a
standard 19-inch DEC cabinet.
The input-output transfer instructions for the RF /RS08 Disk Mem9ry system are identical with the input-output
transfer instructions for the Type DF32 Random Access Disk file (Table 6-4).

Instructions
The RF/RS08 has the following DF32 Programming Compatibility:

DCMA

Clear Disk Memory Address Register

Octal code:
Event time:
Execution time:
Operation:

6-30

6601
4.25 µs
Clear the Disk Memory Address register, and all other disk and maintenance flags except
interrupt enable.

DMAR

Load Disk Memory Address Register and Read

Octal code:
Event time:
Execution time
Operation:

6603
1,2
4.25 µs
Load the low order 12 bits of the Disk Memory Address with information (initial address) in
the accumulator. Then clear the AC. Begin to read information from the disk into the specified
core location. Clear parity error and completion flags. Clear interrupt flags.
During Read, the final address status is the last address transferred+ 1.
When reading the last address of the last available disk the nonexistent disk flag is raised in
coincidence with the completion flag.

DMA W Disk Memory Address Register and Write

Octal code:
Event time:
Execution time:
Operation:

6605
1,3
4.25 µs
Load the low order 12 bits of the Disk Memory Address register with information (initial
address) in the accumulator (AC). Then clear the AC. Begin to write information onto the disk
from the specified core location. Clear parity error and completion flags. Clear interrupt flags.
During Write, the final address status is the last address transferred.
Write Lock Switch status is true only when disk module contains a Write Command.

PROCESSOR
ACCUMULATOR

DISK ADDRESS
REGISTER
LOW ORDER BITS - - - - - - - - - - - - - - - - - - - - LEAST SIGNIFICANT BITS
It

The DF32 maintenance instruction IOT 663X is not assigned to the RF08 system.
DCIM

Clear Interrupt Enable and Core MA Extension Registers

Octal code:
Event time:
Execution time:
Operation:
DSAC

6611
4.25 µs
Clears the disk interrupt enable and core memory address extension registers.

Skip on Confirmed Flag

Octal code:
Event time:
Execution time:
Operation:

6612
2
4.25 µs
Maintenance Instruction Skip next instruction if the Address Confirmed flag is a I. (AC is
cleared.)
6-31

DIML

Clear Interrupt Enable and MA Extension Register and Load

Octal code:
Event time:
Execution time:
Operation:

6615
1,3
4.25 µs
Clears the interrupt enable, and memory address extension register. Then loads the interrupt
enable and memory address extension registers with data held in the accumulator. Then clears

AC.

INT
ENB
CLOCK
INT
ENB
ERR

MEM

INT
ENB
COM PL

MEM
EX
MEM

~
PROCESSOR
ACCUMULATOR

RF08
STATUS REG

DIMA

Clear AC and Load from Status

Octal code:
Event time:
Execution time:
Operation:

6616
2,3
4.25 µs
Clears the accumulator. Then loads the contents of the status into the accumulator to allow
program evaluation

PROCESSOR
ACCUMULATOR

RF08
STATUS REG

DFSE

Skip on Zero Error Flag

Octal code:
Event time:
Execution time:
Operation:

6-32

6621

1
4.25 µs
Skips the next instruction if there is a Parity Error, Data Request Late, Write Lock Status, or
Nonexistent Disk flag set.

DFSC

Skip on Data Completion Flag

Octal code:
Event time:
Execution time:
Operation:

DISK

6622
2

4.25 µs
Skips next instruction if the Completion flag is a 1 (data transfer is complete).

Skip on Error or Completion Flag

Octal code:
Event time:
Execution time:
Operation:

6623
1,2
4.25 µs
Skips next instruction if either the Error or Completion flags or both are set.

DMAC Read Disk Memory Address Register
Octal code:
Event time:
Execution time:
Operation:

DCXA

4.25 µs
Clears the accumulator. Then loads the contents of the Disk Memory address register into the
accumulator to allow program evaluation. This instruction must be issued when the
completion flag is set.

Clear Address Register

Octal code:
Execution time:
Operation:

DXAL

6626
2,3

6641
4.25 µs
Clears the high order 8-bit disk address register.

Clear Address Register and Load from AC

Octal code:
Execution time:
Operation:

6643
4.25 µs
Clears the High Order 8 bits of the disk address register. Then loads the disk address register
from the data held in the accumulator. Then clears the AC.

PROCESSOR
ACCUMULATOR

RF08

DISK SELECT
LEAST SIGNIFICANT BITS _______,.

DXA C

12-0114

Clear AC and Load

Octal code:
Execution time:
Operation:

6645
4.25 µs
Clears the accumulator, then loads the contents of the High Order 8-bit disk address register
into the accumulator.

6-33

PROCESSOR
ACCUMULATOR

RF08
LEAST SIGNIFICANT BITS ---1~-

DMMT

12-0109

(Maintenance Instruction)

Octal code:
Execution time:
Operation:

6646
4.25 µs
For maintenance purposes only, with the appropriate maintenance cable connections and the
disk disconnected from the RS08 logic, the following standard signals may be generated by
IOT's 646 and associated AC bits. AC is cleared. The maintenance register is initiated by
issuing an IOT 601 command.
AC 11 (1)
AC100)
AC 9 (1)
AC 7 (1)
AC6 (1)
AC 0 (1)

Track A Pulse
Track B Pulse
Track C Pulse
DATA PULSE (DAT A HEAD #0)
+ 1 Photocell
+lDBR

Setting DBR to a 1 causes Data Break Request in computer.

NOTE
TAP must be generated to strobe Track B signal into address comparison network.

Disk Address Register - 20 bits

!sfmTj
r-B~S

+·

TRACK
POSITION

.,..

a:+s

TRACK
SELECT

Bl~S

DISK EXTENDED
MEMORY ADDRESS
8 BITS

DISK
MEMORY ADDRESS
12 BITS

I
.,
~

Programming Example
A programming example that writes a block of data onto the disk is shown below. For simplicity, the example
assumes that all data and instructions are within the same page, but in actual practice this may not be true.

6-34

Table 6-4. DF32 Instructions Compared with RF/RS08 Instructions
DF32
Mnemonic

Octal
Code

RF08
Mnemonic

RF08 to DF32
Comparison

DCMA

6601

same

Identical functions.

DMAR

6603

same

Identical functions.

DMAW

6605

same

Identical functions.

DCEA

6611

DCIM

Clears interrupt enable, does not clear EMA. On both
units, clears memory address extension.

DSAC

6612

same

Identical functions.

DEAL

6615

DIML

Similar, except functions transmitted from the AC
are different. EMA information not transmitted. See
DXAL.

DEAC

6616

DIMA

Similar, except that functions transmitted to the AC
are different. See DXAC.

DFSE

6621

same

Instruction is skip on error, rather than skip-no error.
NXD added as an error.

DFSC

6622

same

Identical function.

(none)

6623

DISK

New instruction. Skips on error or data completion,
or both. (DFSE and DFSC combined.) Skip enabled
at IOP 2.

DMAC

6626

same

Identical functions.

(none)

6641

DCXA

Clears EMA.

(none)

6643

DXAL

Clear and load EMA with information in the
accumulator.

(none)

6645

DXAC

Clear accumulator and load address in EMA into the
accumulator.

(none)

6646

DMMT

Maintenance instruction. See description.

6-35

SUB,

/CALLING SEQUENCE
JMS WRT
0
0

0
0

xxx
WRT,

/WRITE SUBROUTINE
0
TAD IWRT
DCAWC
ISZ WRT
TAD IWRT
DCACA
ISZ WRT
TADIWRT
DIML
ISZ WRT
TAD IWRT
DXAL
ISZ WRT
TAD IWRT
DMAW

DISK
JMP .-1
DFSE
JMP .+2
JMP ERR
ISZWRT
JMP I WRT

/JUMP TO WRITE SUBROUTINE
/CONTAINS WORD COUNT
/CONTAINS INITIAL CORE MEMORY ADDRESS
/CONTAINS TRACK AND UNIT NUMBER
/CONTAINS TRACK ADDRESS
/CONTINUE WITH MAIN PROGRAM
/ENTER WRITE SUBROUTINE
/FETCH WORD COUNT
/DEPOSIT IN WORD COUNT REGISTER
/INCREMENT POINTER
/FETCH INITIAL CORE MEMORY ADDRESS
/DEPOSIT INTO CURRENT ADDRESS REGISTER
/INCREMENT POINTER

/FETCH TRACK AND UNIT NUMBER
/DEPOSIT INTO REGISTER IN RF08 CONTROL
/INCREMENT POINTER
/FETCH TRACK ADDRESS
/TRACK ADDRESS TO DMA IN DISK;
/START WRITE OPERATION
/WRITE OPERATION
/FOR ERROR OR COMPLETE
/NO, WAIT
/ANY ERRORS?
/NO, SKIP OVER ERROR EXIT
/YES, TO ERROR SUBROUTINE
/INCREMENT POINTER TO EXIT ADDRESS
/EXIT PROGRAM
NOTE

This coding assumes no live interrupts.
The calling subroutine must be set up so that the subsequent locations to SUB (SUB+ I, SUB+2, etc) contain the
parameters as shown in the comments column.
The JMS WRT instruction causes a subroutine jump location WRT with the contents of the PC-I (which contains
symbolic address SUB-1) deposited into location WRT. Since location WRT now contains SUB+l, the first
instruction of the subroutine (TAD I WRT) loads the AC with the contents of SUB+l or the word count. The word
count is then deposited into the WC (Memory Address 7750) register. Similarly, the initial address is deposited into
the CA (Memory Address 7751) register. The program then proceeds to set up the EMA and OMA registers and
starts the write operation. After the OMAW instruction is issued, the data transfer operation begins and continues
independently of the program; it operates under control of the data break facility to transfer data. When the
transfer is complete, the DCF (Data Complete Flag) comes up and, when sensed by the DFSC control, passes to the
DFSE instruction. DFSE then senses for errors; and if any are detected, control jumps to an error or diagnostic
(not shown) routine. If no errors are found, control exits from the subroutine back to the main program to resume
main processing.
It should be noted that, since the data transfer operates independently of the program, the subroutine could be

exited following the DMAW instruction. An interrupt subroutine could handle the post data transfer processing,
since the DCF and ERROR FLAGS generated an interrupt.

6-36

An identical program could handle data transfers for a read operation, except that the DMAW instruction is
replaced by the DMAR instruction.
Specifications:
Storage Capacity

Each RS08 stores 262, 144 13-bit words (12 plus one parity bit).

Disks

Four RS08s may be controlled by one RF08 for 1,048,576 words.

Data Transfer Path

Three-Cycle Break

Address Locations
7750 Word Count
77 51 Memory Address

Data Transfer Rate

60 Hz Power
16.2 µs per word

50 Hz Power
20 µs per word

Minimum Access Time

258 µs

320 µs

Average Access Time

16.9 ms

20.3 ms

Maximum Access Time

33.6 ms

40.3 ms

Program Interrupt

33 ms Clock Flag
Data Transmission Complete Flag
Error Flag

Write Lock Switches

Eight switches per disk capable of locking out any combination of eight 16,384
word blocks in address 0 to 131,071.

Data Tracks

128

Words Per Track

2048

Recording Method

NRZI

Density

1100 BPI Maximum

Timing Tracks

3 plus 3 spare

Operating Environment

Recommended temperature 65° to 90°F. Relative humidity 20% to 80%. No
condensation during storage or operating.

Vibration/Shock

Good isolation is provided. Vibrating, shaking, or rocking of the cabinet with
large, low frequency displacements can cause data errors. For example, hand fork
lift trucks operating on wooden floors cause excessive vertical displacements
which could cause errors. The RS08 is not designed for aircraft or shipboard
mounting.

Heat Dissipation

RF08: 150 watts
RS08: 500 watts

AC Power Requirements

115 ± 10 Vac, single phase, 50 ± 2 or 60 ± 2 Hz

RS08

Motor start 5.5 amps for 20 ± 3 sec. Motor run 4.0 amps continuous.

6-37

Line Frequency Stability

Maximum line frequency drift 0.1 Hz/sec. A constant frequency motor-generator
set or static ac/ac inverter should be provided for installations with unstable
power sources.

Reliability

Six recoverable errors and one nonrecoverable error in 2 x 10 9 bits transferred. A
recoverable error is defined as an error that occurs only once in four successive
reads. All other errors are nonrecoverable. On-off cycling of the RS08 is not
recommended. The RS08 motor control operates independently of the computer
power control, thus eliminating on-off cycling except for power failures.

Cabinet

A H950 cabinet is designed to accommodate one RF08, up to two RS08s, and
power supplies. Two additional RS08s can be mounted in a second H950. Other
equipment should not be mounted in disk cabinets.

6.3.3 RKB Disk Cartridge Memory System
The RK08 Control and RKOl Disk Drive (RK8) are low cost, random access, removable disk storage devices. One
RK08/RKO 1 provides 831,488 13-bit (12 bits plus parity) words of storage. Up to four RKO 1 disks can be
operated by the RK08 Control for a total of 3,325,952 words of storage.
The removable cartridge utilized is an IBM 2315 disk pack or equivalent with a single aluminimum disk platter
coated on both sides with magnetic oxide. Average access time is 154 milliseconds with the read/write head at
random positions. Data transfer rate is 16. 7 microseconds via the PDP-12 single-cycle data break facility. The
RK8-P will operate off the positive I/O bus. An RK8-N is also available for connection to a negative I/O bus.
Instructions
DLDC

Load Command Register

Octal code:
Operation:

6732
Loads the Command Register from the AC, clears the AC.

COMMAND
REGISTER
ENABLE CHANGE IN
INTERRUPT STATUS
DOUBLE
DENSITY

ENABLE PROGRAM
INTERRUPT ON
TRANSFER DONE
EXTENDED
MEM
ADDRESS

ENABLE INTERRUPT
ON ERROR

DISK
FILE
NUMBER

UNUSED

SEEK TRACK a
SURFACE ONLY

ENABLE READING OR
WRITING OF 2
HEADER WORDS
LOGICAL 1 =FUNCTION TRUE

6-38

12-020"3

*DLDR

Load Disk Address and Read

Octal code:
Operation:

*DLDW

Load Disk Address and Write

Octal code:
Operation:

*DCHP

6733
Loads track, surface, and sector address from AC, then clears AC and starts to read data from
disk if Command Register bit 4 = 0.

6735
Loads track, surface, and sector address from AC, then clears AC. Starts to write on disk if
Command Register bit 4 = 0.

Load Disk Address and Check Parity

Octal code:
Operation:

6737
Loads track, surface, and sector address from AC, then clears AC. Reads data and checks
parity if Command Register bit 4 = 0.

TRACK ADDRESS
REGISTER

SURFACE /SECTOR
ADDRESS

L-__,1,--'--~-'----'-....L.-...L...-..._jr--"-.....a..-----REGISTER

'-----y----'
TRACK
ADDRESS

SECTOR
ADDRESS
SURFACE
BIT
12-0199

*-If command register bit 4 = 1, instruction will be executed only to seek track and surface. These three instructions
start all disk operations.

6-39

DRDA

Read Disk Address

Octal code:
Operation:

6734
Clears AC and then reads Track Address Counter and surface/sector counter into AC.

DRDC Read Disk Command Register
Octal code:
Operation:

DRDS

6736
Clears AC then reads Command Register into the AC.

Read Disk Status Register

Octal code:
Operation:

6741
Clears the AC and then reads the Status Register into the AC.

STATUS
REGISTER

ERROR
TRANSFER DONE
CONTROL BUSY
ERROR
TIME OUT ERROR
PARITY OR
TIMING ERROR
DATA RATE ERROR
TRACK ADDRESS
ERROR
SECTOR NO GOOD
ERROR
WRITE LOCK ERROR
TRACK CAPACITY
EXCEEDED ERROR
SELECT ERROR
BUSY
LOGICAL 1= FUNCTION TRUE

DCLS

Clear Status Register

Octal code:
Operation:

6-40

6742
Clears the Status Register.

12-0201

DMNT Load Maintenance Register
Octal Code:
Operation:

6743
Loads Maintenance register from AC and carries out the operation specified. Bits will remain
set until DMNT is issued with AC bits= 0.

MAINTENANCE
REGISTER
LOGICAL 1 =FUNCTION TRUE
12-0202

AC Bit
0
I

2
3
4
5
6
7
8
9-11

DLDA

Load Disk Address (Maintenance Only)

Octal code:
Operation:

DSKD

Loads the disk address register with the content of AC.

6745
Skips next instruction if the Transfer Done Flag is a 1.

Skip on Error Flag= 1

Octal code:
Operation:

DCLA

6731

Skip on Transfer Done Flag= 1

Octal code:
Operation:

DSKE

Transfer contents of Track address Register to Track counter Register.
Transfer Data Register to Serial Register.
Transfer Serial Register to Data Register.
Oear AC and Read Data Register into AC.
Shift a "1" into the Serial Register.
Shift a "O" into the Serial Register.
Unformatted Disk
Sector Pulse.
Index Pulse.
Not used.

6747
Skip when Error flag is equal to 1.

Clear All

Octal code:
Operation:

6751

Clears selected Disk to Track 000. Then clears all control registers and flags except disk
selection. Transfer done set when disk positioned on Track 000.

6-41

DRWC

Read Word Count Register

Octal Code:
Operation:

DL WC

6753
Loads Word Count register from AC, then clears the AC.

Load Current Address Register

Octal code:
Operation:

DRCA

Clears AC, then reads the contents of the Word Count register into the AC.

Load Word Count Register

Octal code:
Operation:

DLCA

6752

6755
Load Current Address register from AC; then clears the AC.

Read Current Address Register

Octal code:
Operation:

6757
Clears the AC then reads the contents of the Current Address register into the AC.

Example of 1/0 Subroutine
DISKIO,

0
TAD CNT
DLWC
TAD CUR
DLCA
TAD 0000
DLDC
TAD ADR
DLDR

DSKD
JMP .-1
DSKE
JMP I DISKIO
JMP ERR
CNT
CUR
ADR

0
0
0

/SUBROUTINE ENTRY POINT
/FETCH# OF WORDS TO BE READ
/LOAD WORD COUNT REGISTER
/FETCH ADD OF MEMORY BUFFER
/LOAD CUR ADDR. REGISTER
/PUT COMMAND IN ACCUMULATOR
/LOAD COMMAND REGISTER
/FETCH TRACK, SURF ACE, & SECTOR
/LOAD DISK ADR AND READ DATA
/DLDW WOULD HAVE WRITTEN
/DONE WITH TRANSFER?
/NO - GO BACK 1
/YES - IS THERE AN ERROR?
/NO ERROR - RETURN
/GO TO ERROR SUBROUTINE
/#WORDS TO BE READ
/BEG. ADDR. OF MEMORY BUFFER
/DISK ADDRESS

Models*
RK8-P

Positive Bus System; includes RKOl and RK08-P

RK8-N

Negative Bus System; includes RKOl and RK08-N

RKOl

Consists of disk drive, interface and removable cartridge {up to 4 per RK8 system)

RK08-P

Positive Bus disk control

RK08-N

Negative Bus disk control

* See RK8 Manual for details.
6-42

Specifications
Disks

Four RKOls per RK08 for 3,325,952 words.

Storage Capacity

Each RKO 1 stores 831,488, 12-bit words.

Data Transfer Rate

16. 7 µs per word

Transfer Pa th

Single-cycle Data Break

Minimum Access Time

2.35 ms

Average Access Time

154 ms

Maximum Access Time

477 ms

Settle Time

37 ms

Program Interrupt

Transfer Done Flag

Write lock

Two words at the beginning of each track contain status information that is
automatically checked for write lock of sectors. Also total disk can be
write-locked.

Data Tracks

200 plus 3 spare

Words per Track

4096 (2048 on each of two sides)

Sectors

16 per track

Words per Sector

256

Min. Block Size

256 words

Max. Block Size

4096 words

Recording Method

Double Frequency-Time plus Data

Density

1026 bits/inch max.

Speed

1500 rpm

Environmental Requirements
Operating Temp

+65°F to 90°

Operating Humidity

20% to 80% excluding all conditions which would cause condensation.

Heat Dissipation

RK08 - 150 watts
RKOl per drive; 700 watts, 1 KW, surge

AC Power Requirements

115 ±10 VAC, 60 ±Yi Hertz
230 ±20 VAC, 60 ±Yi Hertz

6-43

Mechanical Package

One standard DEC cabinet will accommodate the RK08 and one RKOI. A
second cabinet will house two RKO I units. A third cabinet will house a fourth
RKOl.

6.3.4 Disk Software

Mass Storage LAP6-DIAL-MS, commonly referred to as DIAL-MS or DISK-DIAL, is a modified version of
LAP6-DIAL that may use a disk for the LAP6-DIAL System and/or user programs. The minimum hardware
configuration required is 8K of core storage and two LINCtape transports. LAP6-DIAL-MS will support one of the
following:
a. One or two DF32 or FD32D Disks
b. One to four RF08 Disks
c. One RK8 Disk.
LAP6-DIAL-MS will use only one of the above; for example, the RK8 rather than a DF32, or a RK8 rather than a
RF08, if more than one are installed in the system. It is not possible to operate a DF32 and a RF08 in the same
system as the IOT instructions are similar.
A brief description of LAP6-D IAL-MS is provided in Paragraph 7.1.1.

6-44

6.4 MAGNETIC TAPE
6.4.1 Automatic Magnetic Tape Control, Type TC58
Functional Description
The Type TC58 will control the operation of a maximum of eight digital magnetic tape transports, Types TU20
and TU20A. The Type TC5 8 interfaces with the PDP-12 three-cycle data break facility, which it uses for data
transfer directly between system core memory and magnetic tape. The tape transports offer industry compatibility
(or IBM compatibility) in both 7- and 9-channel tape transports with the following characteristics:

Transport

Tape Speed
(ips)

Densities
(bpi)

TU20 (7-channel)
TU20A (9-channel)

45
45

200/556/800
800

Transfers are governed by the memory word count (WC) and current address (CA) registers associated with the
assigned data channel (memory locations 32 8 and 33 8 ). Since the CA is incremented before each data transfer, its
initial contents should be set to the desired initial address minus one. The WC is also incremented before each
transfer and must be set to the two's complement of the desired number of data words to be transferred. In this
way, the word transfer which causes the word count to overflow (WC becomes zero) is the last transfer to take
place. The number of IOT instruction required for the TYPE TC58 is minimized by transferring all necessary
control data (unit number, function, mode, direction, etc) from the PDP-12 accumulator (AC) to the control using
IOT instructions. Similarly, all status information (status bits, error flags, etc) can be read into the AC from the
control unit by IOT instructions.
During normal data reading, the control assembles 12-bit computer words from successive frames read from the
information channels of the tape. During normal data writing, the control disassembles 12-bit words and distributes
the bits so they are recorded on successive frames of the information channels.
Instructions
The instructions for the Magnetic Tape Control System are as follows:

MTSF

Skip on Error Flag or Magnetic Tape Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTCR

4.25 µs
The status of the error flag (EF) and the magnetic tape flag (MTF) are sampled. If either or
both are set, the contents of the PC are incremented by one, skipping the next instruction.
If MTF or EF = I, PC + I --+ PC

Skip on Tape Control Ready

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6701

6711
.}

4.25 µs
If the tape control is ready to receive a command, the PC is incremented by one, skipping the
next instruction.
If Tape Control Ready, PC + 1 --+ PC

6-45

MTTR

Skip on Tape Transport Ready

Octal code:
Event time:
Execution time:
Operation:
Symbol:
MTAF

Symbol:

6724
3
4.25 µs
Inclusively OR the contents of the command register into AC 0 - 11 .
AC V command register-+ AC 0 - 11

Inclusive OR Contents of Accumulator

Octal code:
Event time:
Execution time:
Operation:
Symbol:

MTLC

6712
4.25 µs
Clears the status and command registers, and the EF and MTF if tape control is ready. If tape
control is not ready, clears MTF and EF flags only.
If tape control is ready, 0-+ MTF, 0-+ EF,
0-+ command register
If tape control not ready, 0 -+ MTF, 0 -+ EF

Inclusive OR Contents of Command Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:
MTCM

4.25 µs
The next sequential instruction is skipped if the tape transport is ready.
If tape unit ready, PC+ 1 -+PC

Clear Regi.sters, Error Flag and Magnetic Tape Flag

Octal code:
Event time:
Operation:

MTRC

6721

6714
3
4.25 µs
Inclusively OR the contents of ACo-s ,9 - 11 into the command register: JAM transfer bits 6, 7,
8 (command function).
AC 0 - 5 , AC 9 - 11 V command register-+ command register
AC 6 - 8 -+ command register bits 6-8

Load Command Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6716

2,3
4.25 µs
Load the contents of AC 0 - 11 into the command register.
AC 0 - 11 -+command register

Inclusive OR Contents of Status Register
Octal code:
Event time:
Execution time:
Operation:
Symbol:

6-46

6704
3
4.25 µs
Inclusively OR the contents of the status register into AC 0 - 1 1
Status Register V AC-+ AC0 - 11

MTRS

Read Status Register

Octal code:
Event time:
Execution time:
Operation:
Symbol:
MTGO

Mag Tape GO

Octal code:
Event time:
Execution time:
Operation:
Symbol:
MCLA

6706
2,3
4.25 µs
Read the contents of the status register into AC 0 - 1 1
Status Register-+ AC 0 - 11

6722
2
4.25 µs
Set GO bit to execute command in the command register if command is legal.
None

Clear the AC

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6702
2
4.25 µs
Clear the accumulator.
0-+AC

Although any number of tapes may be rewinding simultaneously, data transfer may take place to or from only one
transport at any given time. In this context, data transfer includes these functions: read or write data, write EOF
(end of file), read/compare, and space. When any of these functions is in process, the tape control is in the not
ready condition. A transport is said to be not ready when tape is in motion, when transport power is off, or when it
is off line.
Data transmission may take place in either parity mode, odd-binary or even-BCD. When reading a record in which
the number of characters is not a multiple of the number of characters per word, the final characters come into
memory left-justified.
Ten bits in the magnetic tape status register retain error and tape status information. Some error types are
combinations, such as lateral and longitudinal parity errors (parity checks occur after both reading and writing of
data), or have a combined meaning, such as illegal command, to allow for the maximum use of the available bits.
The magnetic tape status register reflects the state of the currently selected tape unit. Interrupts may occur only
for the selected unit. Therefore, other units which may be rewinding, for example, will not interrupt when done.
A special feature of this control is the Write Extended Inter-Record Gap capability. This occurs on a write
operation when Command Register bit 5 is set. The effect is to cause a 3-inch inter-record gap to be produced
before the record is written. The bit is automatically cleared when the writing begins. This is very useful for
creating a gap of blank tape over areas where tape performance is marginal.
Magnetic Tape Functions
For all functions listed below, upon completion of the data operation (after the end-of-record character passes the
read head), the MTF (magnetic tape flag) is set, an interrupt occurs (if enabled), and errors are checked.
No Operation - A NO OP instruction defines no function in the command register. A MTGO instruction with NO
OP will cause an illegal command error (set EF).

6-47

Space - There are two instructions for spacing records, SPACE FORWARD and SPACE REVERSE. The number
of records to be spaced (two's complement) is loaded into the WC. CA does not need to be set. MTF (magnetic
tape flag) is set, and an interrupt occurs at WC overflow, EOF (end of file), or EOT (end of tape), whichever occurs
first. When issuing a space instruction, both the density and parity bits must be set to the density and parity in
which the records were originally written.

Load Point or Beginning of Tape (BOT) detection during a backspace terminates the function with the BOT bit set.
If a SPACE REVERSE instruction is given when a transport is set at BOT, the instruction is ignored, the illegal

command error and BOT bits are set, and an interrupt occurs.
Read Data - Records may be read into memory in the forward mode only. Both CA and WC must be set; CA to
the initial core address minus one, WC to the two's complement of the number of words to be read. Both density
and parity bits must be set.
If WC is set to less than the actual record length, only the desired number of words are transferred into memory. If
WC is greater than or equal to the actual record length, the entire record is read into memory. In either case, both
parity checks are performed, the MTF is set, and an interrupt occurs when the end-of-record mark passes the read
head. If either lateral or longitudinal parity errors or bad tape have been detected, or an incorrect record length
error occurs (WC not equal to the number of words in the record), the appropriate status bits are set. An interrupt
occurs only when the MTF is set.

To continue reading without stopping tape motion, MTAF (clear MTF) and MTGO instructions must be executed.
If the MTGO command is not given before the shut down delay terminates, the transport will stop.
Write Data - Data may be written on magnetic tape in the FORWARD DIRECTION ONLY. For the WRITE
DAT A function, the CA and WC registers and density and parity bits must be set. WRITE DATA is controlled by
the WC in such a way that, when the WC overflows, data transfer stops, and the EOR (end of record) character and
IRG (inter-record gap) are written. The MTF is set after the EOR has passed the read head. To continue writing, a
MTGO instruction must be issued before the shut-down delay terminates. If an error occurs, the EF will be set
when the MTF is set.
Write EDF - The Write EOF instruction transfers a single character ( 17 8 ) record to magnetic tape and follows it
with the EOR character; CA and WC are ignored for WRITE EOF. The density bits must be set, and the command
register parity bit should be set to even (BCD) parity. If it is set to odd parity, the control will automatically
change it to even.

When the EOF marker is written, the MTF is set and an interrupt occurs. The tape transport stops, and the EOF
status bit is set, confirming the writing of EOF. If odd parity is required after a WRITE EOF, it must be specifically
requested through the MTLC instruction.
Read/Compare - The READ/COMPARE function compares tape data with core memory data. It can be useful for
searching and positioning a magnetic tape to a specific record, such as a label or leader, whose content is known in
core memory, or to check a record just written. READ/COMPARE occurs in the forward direction only; CA and
WC must be set. If there is a comparison failure, incrementing of the CA ceases, and the READ/COMPARE error
bit is set in the status register. Tape motion continues to the end of the record; the MTF is then set, and an
interrupt occurs. If there has been a READ/COMPARE error, examination of the CA reveals the word that failed to
compare.
Rewind - The high speed REWIND instruction does not require setting of the CA or WC. Density and parity
settings are also ignored. The REWIND instruction rewinds the tape to loadpoint (BOT) and stops. Another unit
may be selected after the instruction is issued and the rewind is in process. MTF is set, and an interrupt occurs (if
the unit is selected) when the unit is ready to accept a new instruction. The selected unit's status can be read to
determine or verify that REWIND is in progress.

6-48

Continued Operation
a. To continue operating the same mode, the MTGO instruction is given before tape motion stops. The order
of instructions required for continued operation are as follows:
( 1) MTLC, if the instruction is to be changed.
(2) MTAF, clears only MTF and EF flags, since tape control will be in a Not Ready state.
(3) MTGO, if MTLC requested an illegal condition; the EF will be set at this time.
b. To change modes of operation, either in the same or opposite direction, the MTLC instruction is given to
change the mode and a MTGO instruction is given to request the continued operation of the drive. If a change in
direction is ordered, the transport will stop, pause, and automatically start up again.
c. If the WRITE function is being performed, the only forward change in command that can be given is
WRITEEOF.
d. If no MTGO instruction is given, the transport will shut down in the inter-record gap.

NOTE
Flags will not be set when the control or the transport becomes ready, except if the
REWIND instruction is present in the command register and the selected drive
reaches BOT and is ready for a new instruction.

e. If a WRITE (odd parity) instruction is changed to WRITE EOF, the parity is automatically changed to
even.

NOTE
Even parity will remain in the command register unless changed by a new command
instruction, MTLC, which clears and loads the entire command register.

Status or Error Conditions
Twelve bits in the magnetic tape status register indicate status or error conditions. They are set by the control and
cleared by the program.

6-49

The magnetic tape status register bits are:
Bit

Function (When Set)

Error flag (EF)
Tape rewinding
Beginning of tape (BOT)
Illegal command
Parity error (Lateral or Longitudinal)
End of file (EOF)
End of tape (EOT)
Read/Compare error
Record length incorrect
WC= 0 (long)
WC=:F= 0 (short)
Data request late
Bad tape
Magnetic tape flag (MTF) or job done

2
3
4
5
6
7
8

9
10
11

The register bits are equivalent in position to the AC bits (i.e., SR 0 = AC 0 , etc).

MTF (SR 11) - The MTF flag is set under the following conditions:

a. Whenever the tape control has completed an operation (after the EOR mark passes the read head).
b. When the selected transport becomes ready following a normal REWIND function. These functions will
also set the EF if any errors are present.

EOF (SR5) - End-of-file (EOF) is sensed and may be encountered for those functions which come under the
heading of READ STATUS FUNCTION; i.e., SPACE, READ DATA, or READ/COMPARE and WRITE EOF.
When EOF is encountered, the tape control sets EOF = 1. MTF is also set; hence, an interrupt* occurs and the EOF
status bit may be checked.

EOT (SR6) and BOT (SR2) - End-of-tape (EOT) detection occurs during any forward instruction when the EOT
reflective strip is sensed. When EOT is sensed, the EOT bit is set, but the function continues to completion. At this
time the MTF is set (and EF is set), and an interrupt occurs.

Beginning-of-tape (BOT) deflection status bit occurs only when the beginning-of-tape reflective strip is read on the
transport that is selected.
When BOT detection occurs, and the unit is in reverse, the function terminates. If a tape unit is at load point when
a REVERSE instruction is given, an illegal command error bit is set, causing an EF with BOT set. An interrupt then
occurs.

*All references to interrupts assume the tape flags have been enabled to the interrupt (command register bit 9 = 1)
and the unit is selected.

6-50

Illegal Command Error (SR3) - The illegal command error bit is set under the following conditions:
a. A command is issued to the tape control with the control not ready.
b. A MTGO instruction is issued to a tape unit which is not ready when the tape control is ready.
c. Any instruction which the tape control, although ready, cannot perform; e.g.:

( 1) WRITE with WRITE LOCK condition
(2) 9-channel tape and incorrect density
(3) BOT and SPACE REVERSE

Parity (SR4) - Longitudinal and lateral parity checks will occur in both reading and writing. The parity bit is set
for either lateral or longitudinal parity failure. A function is not interrupted, however, until MTF is set.
Maintenance panel indicators are available to determine which type of parity error occurred.
Read Compare Error (SR 7) - When READ/COMPARE function is underway, SR7 is set to 1 for a
READ/COMPARE ERROR (see earlier section on READ/COMPARE for further details).
Bad Tape (SR 10) - A BAD TAPE ERROR indicates detection of a bad spot on the tape. Bad tape is defined as
three or more consecutively missing characters followed by data, within the period defined by the READ
SHUTDOWN DELAY. The error bit is set by the tape control when this occurs. MTF and interrupt do not occur
until the end of the record in which the error was detected.
Record Length Incorrect (SR8) - During a read or read/compare, this bit is set when the WC overflow differs from
the number of words in the record. The EF flag is set.
Data Request Late (SR9) - This bit can be set whenever data transmission is in progress. When the DATA FLAG
causes a break cycle, the data must be transmitted before a write pulse or a read pulse occurs. If it does not, this
error occurs, and data transmission ceases. The EF flag and bit 9 of the status register are set when the MTF is set.
Error Flag (SRO) - The ERROR FLAG (EF) is set whenever an error status bit is present at the time that MTF is
set. However, when an ILLEGAL COMMAND is given, the EF is set and the MTF is not set.
Command Register Contents

PARITY
O•EVEN

WRITE
EXTENDED
INTERR~CORO GAP
(3 OF BLANK
TAPE BEFORE
RECORD)

1•000

'yJ
FLAGS
O•DISABLE
1 •ENABLE

6-51

Unit Selection

Unit

Bits
1

0
0

0
1

1
2

3
4
5
6
7

Density

200 bpi
556 bpi
800 bpi
800 bpi
9 channel

1
0
0

0
1
0

Density Selection
Bits

Command Selection
Bits
Command

NOOP
Rewind
Read
Read/Compare
Write
Write EOF
Space Forward
Space Reverse

0
0
0
0

0
0

1
0
0

Magnetic Tape Function Summary
LEGEND

6-52

CA= Current Address Register= 33 8
WC= Word Count Register= 328
F =Forward
R =Reverse
DS = Density Setting
PR = Parity Setting
EN = Enable Interrupt

0
1
0

Function

Characteristics

Status of Error Types

NO-OP

CA: Ignored
WC: Ignored
DS: Ignored
PR: Ignored
EN: Ignored

Illegal
BOT
Tape Rewinding

SPACE FORWARD

CA: Ignored
WC: 2's comp. of number
of records to skip
DS: Must be set
PR: Must be set
EN: Must be set

Illegal
EOF
Parity
Bad Tape
MTF, BOT,
EOT

SP ACE REVERSE

Same as SPACE FORWARD

READ DATA

CA: Core Address - 1
WC: 2's comp. of number of
words to be transferred
DS: Must be set
PR: Must be set
EN: Must be set

WRITE DATA

Same as READ DATA

WRITE EOF

CA: Ignored
WC: Ignored
DS: Must be set
PR: Must be set
EN: Must be set

READ/COMPARE

Same as READ DATA

REWIND

CA: Ignored
WC: Ignored
DS: Ignored
PR: Ignored
EN: Must be set

Illegal
EOF
Parity
Bad Tape
BOT
MTF
Illegal
EOF
Parity
Bad Tape
MTF
EOT
Data Request Late
Record Length
Incorrect
Illegal
EOT
Parity
MTF
Bad Tape
Data Request Late
Same as WRITE
DATA plus EOF

Illegal
EOF
Read/Compare Error
Bad Tape
MTF
EOT
Data Late
Record Length Incorrect
Illegal
Tape Rewinding
MTF
BOT

6-53

6.4.2 Magnetic Tape Transports
The following paragraphs describe some of the Magnetic Tape Transports that are available for the PDP- l 2A. These
machines are also compatible with the automatic Tape Control Type TC58.
6.4.2.1 Magnetic Tape Transport, Type TU20 (7-Channel) - The Type TU20 is a digital magnetic tape transport
designed to be compatible with the Type TC58 Magnetic Tape Control. The transport operates at a speed of 45
inches per second, and has three selectable densities: 200, 556, and 800 bpi. The maximum rate is 36,000 six-bit
characters per second. Standard seven-channel IBM-compatible tape format is used. The specifications for the unit
are as follows:
Format: NRZI. Six data bits plus one parity bit. End and loadpoint sensing compatible with IBM 729 I-VI.
Tape: Width 0.5 in., length 2400 ft. ( 1.5 mil.). Reels are 10.5 in. in diameter, IBM-compatible, with file protect
(WRITE LOCK) ring.
Head: Write-read gap 0.300 in., Dynamic and skew is less than 14 microseconds.
Tape Specifications: 45 ips speed. Start time is less than 5 milliseconds. Start distance is 0.080 in. (+0.035, -0.025
in.). Stop time is less than 1.5 milliseconds. Stop distance is 0.045 in. (±0.05 in.).
Density: 200, 556, and 800 bpi. Maximum transfer rate is 36 kHz.
Transport Mechanism: Pinch roller drive; vacuum column tension.
Controls: ON/OFF, ON LINE, OFF LINE, FORWARD, REVERSE, REWIND, LOAD, RESET.
Physical Specifications: Width 22-1 /4 in., depth 27-1 /6 in., height 69-1 /8 in., weight 600 lbs.
Read (Read/Compare) Shutdown Delay: 3.6 milliseconds.
Write Shutdown Delay: Approximately 4.5 milliseconds.
9-Track Operation
9- and 7-track transports may be intermixed on the Type TC58 control. When a transport is selected, it
automatically sets the control for proper operation with its number of tracks.
Control of 9-track operation is identical to 7-track, except as noted below:

Write: A word in memory is written on tape with the following format:

fl
BIT

CHARACTER I

4 ---------------------------11

X- THESE BITS ARE IGNORED

6-54

LATERAL PARITY BIT OF CHARACTER I

Read - A word is read into memory from tape with the following format:

x
BIT

Ix I
2

LATERAL PARITY BIT OF CHARACTER I

CHARACTER I

4-----------------------------11

Read/Compare - A direct comparison of the characters on tape is made with those in memory. The parity bit is
ignored, as are bits 0-3 in each memory word.
Core Dump Mode - This mode is used only with 9-track transports. It is entered by setting bit 4 of the command
register.
Core dump mode permits the dumping of complete memory words in the form of two six-bit characters. The
format is:

BIT

CHARACTER I

CHARACTER 2

0--------------------5

6 --------------------11
12-0143

This is accomplished by utilizing only 7 of the 9 tracks on the tape.
Tape written in CORE DUMP MODE must be READ (READ/COMPARE) in this same mode. These operations are
the same as for a 7-track transport.
6.4.2.2 Magnetic Tape Transport, Type TU20A (9-Channel) - The Type TU20A is a digital magnetic tape
transport designed to be compatible with the Type TC58 Magnetic Tape Control. The transport operates at a speed
of 45 inches per second, and a density of 800 bpi. The maximum transfer rate is 36,000 eight-bit characters per
second. Standard nine-channel IBM-compatible tape format is used. The specifications for the unit are as follows:

Format: NRZI. Eight data bits plus one parity bit. End and loadpoint sensing compatible with IBM.
Tape: Width 0.5 in., length 2400 ft. (1.5 mil.). Reels are 10.5 in. in diameter, IBM-compatible, with file protect
(WRITE LOCK) ring.
Heads: Write-read gap of 0.150 in. Dynamic and static skew is less than 14 microseconds.
Tape Specifications: 45 ips speed. Rewind time is less than 5 milliseconds. Start distance is 0.080 in. (+0.035,
-0.025 in.). Stop time is less than 1.5 milliseconds. Stop distance is 0.045 in. (±0.015 in.).
Density: 800 bpi. Maximum transfer rate is 36 kHz.
Transport Mechanism: Pinch roller drive; vacuum column tension.
Controls: ON/OFF, ON LINE, OFF LINE, FORWARD, REVERSE, REWIND, LOAD, RESET.
Physical Specifications: Width 22-1/4 in., depth 27-1/6 in., height 69-1/8 in. Weight 600 lbs.
Read (READ/COMPARE) Shutdown Delay: 3.6 milliseconds.
Write Shutdown Delay: Approximately 4.5 milliseconds.

6-55

6.4.2.3 Magnetic Tape Transport, Type TU20C
General Description
The TU20C connects to the PDP-12 via the TCS 8 Automatic Magnetic Tape Control. IOT instructions, issued by
the PDP-12, control the operation of the tape transport; these instructions are decoded within the tape control unit
to specify the type of tape transport operation. To write on tape, the tape control unit sends a motion-forward
instruction and a write-enable instruction, and, for each character to be recorded, a record data pulse. For spacing
and reading tape, the tape control unit sends the required motion instruction. Therefore, regardless of the
operation, the tape is always being read and the data is always being transmitted to the tape control unit; this
information is used for detecting end-of-record to terminate operation. The TU20C operates at 45 inches per
second, and has the capability of recording in three densities, 200, 556, and 800 bpi; maximum transfer rate is,
therefore, 800 x 45 = 36,000 six-bit characters per second. Standard seven-channel IBM-compatible tape format
is used.
A nine-channel IBM-compatible version of the TU20C, designated TU20B, is also available; remaining
characteristics of the TU20B are essentially the same as those for the TU20C.
Operation
Either version of the Tape Transport (TU20C, TU20B) may be operated in the local mode from the control panel
or in the remote mode from the PDP-12. Local operation is selected by depressing the front panel OFF LINE
control; this action causes the FORWARD, RESET, REVERSE, and REWIND switches to become operable. If
either the FORWARD, REVERSE, or REWIND control is depressed, the tape moves in the specified direction until
RESET is depressed, the beginning of the tape is detected for rewind, or the end of the tape is detected for
FORWARD. Activating the front panel ON-LINE control places the Tape Transport in the remote mode, wherein it
is controlled by the PDP-12; the Tape Transport must, however, be selected by the TC58 Tape Control.

Switches
The following switches are located on the control panel:

Switch

6-56

Function

POWER

Applies power to the tape transport.

ON LINE

Selects programmed (remote) operation by the
computer.

OFF LINE

Selects local operation by the control panel.

FWD

In local operation, spaces the tape in the forward
direction.

REV

In local operation, spaces the tape in the reverse
direction.

REWIND

In local operation, rewinds the tape at high speed.

RESET

In local operation, terminates the space forward,
space reverse, or rewind operation.

LOAD

Loads the tape into the tape column.

Unit Select Switch

Selects the tape transport unit by number. This
number is used in the program to select the tape
transport.

Indicators
The following indicators are provided on the control panel:
Indicators

Meaning When Illuminated

SELECT

The tape transport is selected by the tape control
(or program).

READY

The tape transport is ready (vacuum on, and
settle-down delay complete), no motion.

LOAD POINT

The tape is at load point.

ENDPOINT

The tape is at end point (end of tape).

WRITE LOCK

The write lock-out ring is missing from the tape
reel, which prevents the write function.

WRITE STATUS

The program has enabled the write function in the
tape transport.

This transport is a 9-track type.

This transport is a 7-track type.

REWIND

The tape transport is in the rewind operation.

LOAD

The vacuum is on and the tape is loaded into the
vacuum columns.

REV

Reverse operation is specified.

RESET

No motion (forward, reverse, or rewind) is
specified.

FWD

Forward motion of the tape is specified.

LOCAL

Local operation by the control panel.

REMOTE

Remote operation by the computer.

POWER

Power is applied to the tape transport.

6.4.3 LINCtape Option TC12-F
The TCI 2-F option (prewired) in conjunction with the PRTCl 2-F program extends the TCI 2 LINCtape control to
read and write DECtapes formatted on the PDP-8, PDP-9, PDP-10, and PDP-15 computers. It will operate on a
standard PDP- l 2A system. Tape units 0 through 7 are selectable under program control. Description document
DC-12-YIYA-D explains the differences between the LINCtape and DECtape formats and describes the PRTC12-F
program.

6-57

Data is transferred between the tapes and the computer on the 1/0 bus. Two status flags enable the program to
identify the information on tape. The BLOCK flag is set, indicating that a block mark was encountered on tape and
the Block Number (BN) is in the tape accumulator. This number is then read into the PDP-12 AC and is processed
to determine if the desired block has been found, or to initiate the necessary adjustments to access the desired
block.
The WORD flag is set after four lines of data have been assembled and are ready to store in memory when reading
from the tape. When writing data on tapes, the flag indicates that a 12-bit word has been written on tape and the
control is ready to accept another word from the computer.
The system program PRTCI 2-F no. DC-12-YIYA-PB for this option is contained on the standard LAP6-DIAL
system tape.
NOTE
This option does not permit the user to execute tape operations using DEC tape
instruction subroutines.

Instructions
IOT6152

Octal code:
Event time:
Execution time:
Operation:

6152
2
4.25 µs
As shown below:

AC Bit

Function

5 (1)
5 (1)
6 (1)
7 (1)
9 (1)
10 (1)

Clear Block FF
Set Backward
Select unit l
Set forward
Set motion
Select DECtape & AC 11 write

SWD 0457
STB 0414
TAPE PRESET
TAPE PRESET
TAPE PRESET

6-58

Skip on word flag
Skip on block flag
0 ~ DECtape write
o~ Motion
Deselect DECtape

6.5 LINE PRINTERS
6.5.1 Line Printer and Control, Type LP12
The Line Printer and Control Type LPl 2 allows the PDP-12 computer to output data at up to 600 lines per minute
(depending upon which printer is used). Either the Mohawk Data Sciences Model 4000 or 5000 series line printers
can be used.
Model

Lines Per Minute

Columns Per Line

4000
5000

up to 300
up to 600

132
132

Total number of characters available: 64

A 6-bit line printer code is loaded into the LPl 2 buffer from AC 6 - 1 1 with the instruction Load Printer Buffer
(LLB). The Print (LPR) instruction causes the lineprinter to print the characters in the lineprinter buffer. After the
buffer is filled the LPR instruction should be given to print the contents of the buffer. Two status flags indicate the
line printer conditions. The Error Flag is set when a printer instruction is given if an error status exists, such as
power off, paper supply low, or control circuits not reset. The Done Flag is set by a BUFF AVAILABLE pulse,
generated by the line printer, after the following IOT instructions are given: Load Printer Buffer (LLB) 6654,
Load Format Register and Print (LPR) 6664 and Clear Printer Buffer (LCB) 6662. The BUFF AVAILABLE pulse
indicates that the line printer buffer is ready to receive another character or the lineprinter is ready to print a line.
The Done Flag is cleared by the IOT instruction Clear Line Printer Flags (LCF) 6652 or the status of the Done Flag
can be checked by the IOT instructions. Skip on Line Printer Done Flag (LSD) 6661.
A three-bit format register in the Printer is loaded from AC 9 - 11 during a print command. This register selects one
of eight channels of a perforated tape in the printer to control spacing of the paper.
The Print Flip-Flop is set when the print instruction is given and, when the Print Flip-Flop and the Done Flag are
both set, a program interrupt request is generated, indicating that the printer has finished printing a line. The Print
Flip-Flop can be cleared by an IOT instruction Clear Printer Buffer (LCB). AC 8 is loaded into the Space Flip-Flop
during a print instruction. If the Space Flip-Flop is set, the paper is advanced according to the selected channel of
the format tape in the line printer. If the Space Flip-Flop is clear, the paper advance is inhibited.

LSE

Skip on Line Printer Error Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

LCF

6651
1
4.25 µs
The status of the Printer Error Flag is sensed, and, if it is set, the contents of the PC are
incremented by one, skipping the next sequential instruction.
If Printer Error Flag= 1, then PC+ 1 -+PC

Clear Line Printer Flags

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6652
2
4.25 µs
The Line Printer Error and Done Flags are cleared.
0 -+ Line Printer Error Flag
0 -+ Done Flag

6-59

LLB

Load Printer Buffer

Octal code:
Event time:
Execution time:
Operation:
Symbol:

LSD

Symbol:

6661
4.25 µs
The status of the Line Printer Done Flag is sensed, and, if it is set, the contents of the PC are
incremented by one, skipping the next sequential instruction.
If Line Printer Flag= 1, then PC+ 1 -+PC

Clear Printer Buffer

Octal code:
Event time:
Execution time:
Operation:
Symbol:
LPR

4.25 µs
The contents of AC6 - 11 are loaded into the Printer Buffer.
AC 6 - 11 -+Printer Buffer
AC 8 -+ Space Flip Flop
0-+AC

Skip on Line Printer Done Flag

Octal code:
Event time:
Execution time:
Operation:

LCB

6654
4

6662
2
4.25 µs
The Printer Buffer is cleared.
0-+ Printer Buffer

Load Format Register and Print Character

Octal code:
Event time:
Execution time:
Operation:

Symbol:

6664
4

4.25 µs
The contents of AC9 - 11 are loaded into the line printer format register and the line contained
in the printer buffer is printed. Paper is advanced in accordance with the selected channel of
the format tape.
C (AC 9 - 11 )-+Format Register
AC 8 -+ Space Flip-Flop
Print Line
0-+AC

6.5.2 Line Printer and Control, Type LPOS
The LP08 Line Printer interface allows control of the four models of Data Products Line Printers by the PDP-12 or
positive bus PDP-8 family of computers through the use of IOT instructions. The printers are available in
80-column and 132-column printing widths with either a 64 or 96 visible character set. The device select code for
the LP08 is 66 8 •
The 80-column printer contains a 20-character (24-character in 132 column) buffer and prints 20 characters
simultaneously when either the character buffer is full or a fonpat control character (carriage return, paper feed,
form feed) instruction is given. A paper feed or form feed command must be given to move the paper at the end of
a line or overprinting will result. Characters and commands are given by loading the AC with the appropriate setting
derived from the LP08 Character Code Chart (Appendix F-4) and issuing the IOT 6664 (LPC).

6-60

The three format commands in addition to initiating the print cycle are:
a. Paper Feed - Advances the paper one line. The perforation between pages is automatic.
b. Carriage Return - Returns the print position to the leftmost edge of the paper.
c. Form Feed - Advances the paper to a new page. Nonvisible characters are decoded as spaces if they are not
control characters.
Instructions
LSF

Skip on Demand Character Flag

Octal code:
Operation:
Symbol:
LCF

Symbol:

6664
Load the character into the Print Buffer and print if buffer is full or character was a control
function. This instruction does not clear the AC.
AC-+ Print Buffer

6665
Sets the device interrupt flip-flop to initiate program interrupt when the demand character flag
is set or an error condition exists.
1 -+Int Enable

Load Buffer from AC and Clear Flag

Octal code:
Operation:
Symbol:
LCP

The next instruction is skipped if the error status flag is set. Such errors as out-of-paper, drum
gate open, paper jam, etc. will set error status flag.
If Error Flag = 1, then PC + l -+ PC

Set Program Interrupts Enable

Octal code:
Operation:

LPC

6663

Load Buffer from AC

Octal code:
Operation:

LIN

6662
The line printer character flag is cleared.
0 -+ Character Flag.

Skip on Not Ready

Octal code:
Operation:

LLC

If printer is ready for the next character, this flag accounts for timing required to store
character in buffer, print from buffer, and advance paper.
If Character Flag = 1, then PC + 1 -+ PC

Clear Character Flag

Octal code:
Operation:
Symbol:
LSR

6661

6666
The print buffer is loaded from the AC and the character flag is cleared. Microprogram
cbmbination of LCF and LLC.
AC-+ Print Buffer, 0-+ Character Flag.

Clear Program Interrupt Enable

Octal code:
Operation:
Symbol:

6667
The program interrupt enable is cleared.
0-+ Int Enable

6-61

Print rate
80 column model
64 character

356 Lines/minute, columns 1-80
460 Lines/minute, columns 1-60
650 Lines/minute, columns 1-40
1110 Lines/minute, columns 1-20

96 character

253 Lines/minute, columns 1-80
330 Lines/minute, columns 1-60
478 Lines/minute, columns 1-40
843 Lines/minute, columns 1-20

13 2 column model
64 character

245 Lines/minute, columns 1-13 2
290 Lines/minute, columns 1-110
356 Lines/minute, columns 1-88
460 Lines/minute, columns 1-66
650 Lines/minute, columns 1-44
1110 Lines/minute, columns 1-22

96 character

173 Lines/minute, columns 1-132
205 Lines/minute, columns 1-110
253 Lines/minute, columns 1-88
330 Lines/minute, columns 1-66
4 78 Lines/minute, columns 1-44
843 Lines/minute, columns 1-22

Format

Top-of-form control, single line
advance, and perforation step over.

Paper Feed

One pair of pin-feed tractors for
1/2 inch hole center, edge-punched
paper. Adjustable for any paper
width from 4 inches to 9-7 /8 inches
on the 80 column model; or a
maximum width of 14-7/8 inches
for the 13 2 column model.

Paper slew speed

13 inches per second

6-62

6.6 CARD READERS
6.6.1 Card Reader and Control, Type CR12
The Card Reader and Control Type CRl 2 reads 12-row, 80-column punched cards at a nominal rate of 200 cards
per minute by a photoelectric process. Cards are read by column, beginning with column 1. One select instruction
starts the card moving past the read station. Once a card is in motion, all 80 columns are read. Column information
can be read in one of two program selectable modes, alphanumeric or binary. In the alphanumeric mode, the 12
information bits in one column are automatically decoded and transferred into the least significant half of the AC
as a 6-bit Hollerith code. In the binary mode, the 12 bits of a column are transferred directly into the AC so that
the top row (12) is transferred into AC 00 and the bottom row (9) is transferred into AC 11 . A punched hole is
interpreted as a binary 1, and the absence of a hole is interpreted as a binary 0.
Three program flags indicate card reader conditions. The data ready flag sets and a program interrupt is requested
when a column of information is ready to be transferred into the AC. A read alphanumeric or read binary
instruction must be issued within 1.4 milliseconds after the data ready flag is set to prevent data loss. The card
done flag is set and a program interrupt is requested when the card leaves the read station. A new select instruction
must be issued immediately after this flag is set to keep the reader operating at maximum speed. Sensing of this flag
can eliminate the need for counting columns or, combined with column counting, can provide a check for data loss.
The reader-not-ready flag can be sensed by a skip instruction to provide an indication of card reader power off,
pick failure, a dark check indication, a stacker failure, hopper empty, stacker full, Sync failure, or light check
indication. When the flag is set, the reader cannot be selected and select instructions are ignored. The
reader-not-ready flag is not connected to the program interrupt facility, and cannot be cleared under program .
control. Manual operation is required to clear the reader-not-ready flag. Instructions for the CR12 are:

RCSF Skip on Data Ready
Octal code:
Event time:
Execution time:
Operation:

Symbol:

RCRA

Symbol:

6632
2

4.25 µs
The 6-bit Hollerith code for the 12 bits of a card column is transferred into AC6 - 11 and t}le
data ready flag is cleared.
AC 6 - 11 V Hollerith-+ AC 6 - 1 1
0 -+ Data Ready Flag

Read Binary

Octal code:
Event time:
Execution time:
Operation:

Symbol:

4.25 µs
The status of the data ready flag is sensed, and if it is set (indicating information for one card
column is ready to be read) the contents of the PC are incremented by one skipping the next
sequential instruction.
If Data Ready Flag = 1, then PC + 1 -+ PC

Read Alphanumeric

Octal code:
Event time:
Execution time:
Operation:

RCRB

6631

6634
3

4.25 µs
The 12-bit binary code for a card column is transferred directly into the AC, and the data
ready flag is cleared. Information from the card column is transferred into the AC so that card
rows 12, 11, and 0 enter AC 0 - 2 and card rows I through 9 enter AC 3 - 11 respectively.
0 -+ Data Ready Flag

6-63

RCSD

Skip on Card Done Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:
RCSE

4.25 µs
The status of the card done flag is sensed, and if it is set (indicating that the card has passed
the read station) the contents of the PC are incremented, skipping the next instruction.
If Card Done Flag = 1, then PC + 1 -+ PC

Select Card Reader and Skip if Ready

Octal code:
Event time:
Execution time:
Operation:

Symbol:

RCRD

6671
1

6672

2
4.25 µs
The status of the card reader flag is sensed and if the reader is ready, the PC is incremented
skipping the next sequential instruction, a card is started toward the read station from the
input hopper, and the card done flag is cleared.
If Reader Ready Flag = I, then PC + I -+ PC
0 -+ Card Done Flag

Clear Card Done Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6674
3
4.25 µs
The card done flag is cleared. This instruction allows a program to stop reading at any point in
the card deck.
0 -+ Card Done Flag

A logical instruction sequence to read cards is:
START,

RCSE
JMP NOT RDY

/START CARD MOTION AND SKIP IF READY
/JUMP TO SUBROUTINE THAT TYPES OUT
/"CARD READER MANUAL INTERVENTION
/REQUIRED" OR HALTS

NEXT,

RCSF
JMP DONE
RCRAor
RCRB
DCA I STR

/DATA READY?
/NO. CHECK FOR END OF CARD
/YES. READ ONE CHARACTER OR ONE
/COLUMN AND CLEAR DAT A READY FLAG
/STORE DATA

DONE,

RCSD
JMP NEXT
JMPOUT

/END OF CARD?
/NO, READ NEXT COLUMN
/YES, JUMP TO SUBROUTINE THAT CHECKS
/CARD COUNT OR REPEATS AT START FOR
/NEXT CARD

The CRl 2 does not perform validity checking, although a programmed validity check can be made by reading each
card column in both the alphanumeric and binary mode (within the 1.4 millisecond time limitation), then
performing a comparison check.
The following discussion and controls and indicators deal with the General Design Industries (GDI) Model 100 card
reader. Other card readers can be used and will have similar controls and indicators.

6-64

Before commencing a card reading program, load the input hopper with cards and press Motor Start and Read Start
pushbuttons. The functions of the manual controls and indicators are as follows (as they appear from left to right):
Control or Indicator

Function

A - POWER switch

On/Off toggle switch. Applies power to all circuits
except drive motor.

B - MOTOR START

Momentary action pushbutton, with separate indicator.
Applies power to main drive motor. Motor start is also
used as a reset to clear error indicators, and therefore
will not operate if there is an unremedied condition
such as:
1. Input hopper is empty.
2. Output hopper is full.
3. All photo cells are not illuminated.
4. Internal power supply is not operational.

C - READ START

Momentary action pushbutton, with separate indicator.
Causes ready line to go high, enabling card reading
under control of the external read instructions. If read
co mm and is open or high, card reading begins
immediately at full rated speed.

D-READ STOP

Momentary action pushbutton with indicator. Stops
card reading if depressed without stopping drive motor.
However, READ STOP light can indicate a stopped
motor or a ready line low condition.

E - INDICATORS

Several detection circuits are incorporated in the card
reader. Whenever any red indicator lights, the drive
motor is stopped after completion of the current card
cycle.

1. PICK FAIL Indicator

Lights when a card fails to enter the read station after
two successive pick attempts.

2. DARK CHECK Indicator

After the card enters the read station, a check is made at
the hypothetical 0th and 81 st hole positions to be sure
all photocells are dark. If not, the DARK CHECK
indicator lights and data outputs are immediately
inhibited.

3. STACKER FAIL Indicator

When three cards have passed the read station and none
have been stacked, a STACK FAIL is indicated. Prevents
more than three cards from being in the track at once.

4. HOPPER EMPTY Indicator

Indicates input hopper is empty.

S. STACKER FULL Indicator

When approximately 400 cards are in the stacker
hopper, indicator light lights.

6-65

6. SYNC FAIL Indicator

SYNC FAIL is indicated if the sync signal is lost.
Internal timing signals are derived from an oscillator
which is synced to the track speed.

7. LIGHT CHECK INDICATOR

The photocells must always be illuminated except
during the time a card is being read. The LIGHT
CHECK detector is inhibited each time a card enters the
read station until position (count of) 84 is reached. If a
card fails to leave the read station by this time, a LIGHT
CHECK is indicated.

6.6.2 Optical Mark Card Reader Type CM 12
The GDI Model 100-MS is an optical-mark card reader that reads ( 12-row Hollerith) reflective data cards of various
format designs at a rate of up to 200 cards per minute by a photoelectric process. Cards are read column by
column, beginning with column 1. A single select instruction will cause the reader to feed and read a card. Once a
card is in motion, all columns are read. Column information is read in one of two program-selectable modes,
alphanumeric or binary. In the alphanumeric mode, the 12 information bits in one column are automatically
decoded and transferred into the least significant half of the AC as a 6-bit Hollerith code. In binary mode, all 12
bits of a column are transferred directly into the AC so that the top row (12) is transferred into AC 00 and the
bottom row (9) is transferred into AC 11 • A punched hole or a nonreflective spot (either nonreflective ink or No. 2
pencil) is interpreted as a binary 1, and the absence of a hole or reflective spot is interpreted as a binary 0.
Instructions
The instruction set associated with the optical mark reader is identical to that of the CRl 2 in Paragraph 6.6. l.
Characteristics
Size: The complete unit is 14 in. wide, 18 in. deep, and 18 in. high. The card deck is tilted back at a 45-degree
angle.
Weight: Complete unit weighs 47 lbs.
Card Rate: 200 per minute.
Input Power: 115 VAC ± 10 VAC, 60 ±5 Hz single phase, at 300 VA maximum.
Card Specification: The card reader is designed to read 7-3/8 in. x 3-1/4 in. optical mark cards conforming to the
material and size requirements of EIA Standard RS-292 Media I. Format and printing requirements are specified in
the DEC Mark Sense Card Specification.
Card Capacity: Both input hopper and output stacker hold 450 cards. Cards may be added or removed during
reader operation.
Environment:

Operating:
Storage:

6-66

32° to l 20°F ambient
15% to 80% relative humidity
30° to l 50°F ambient
0% to 100% relative humidity

Controls and Indicators
Power Switch: An alternate action rocker-type switch used to apply AC power to the Card Reader.
Start Switch: A momentary pushbutton switch used to condition the unit to read cards. When it is depressed, the
drive motor will start, and any error indicators will be reset if the error has been cleared. When it is released and the
motor has reached operating speed, the reader may accept a "read command' and process cards.
Stop Switch: A momentary pushbutton switch used to stop the reader. When it is depressed, the motor will stop;
if it is depressed during a time a card is in process, the card cycle will be completed before the motor stops.
Power: A green indicator to verify AC power on; mounted next to the POWER switch.
On Line: A green indicator to verify that the START switch has been depressed and the unit is ready to operate.
Light will remain on until the STOP switch is depressed or an error condition is sensed; mounted next to START
switch.
Cards: A red indicator to identify an input hopper empty or an output stacker full condition.
Feed Error: A red indicator to identify when a card has not been fed from the input hopper to the read station at
the end of a feed cycle.
Stacker Error: A red indicator to identify when a card has not been properly delivered to the output stacker.
Motion Error: A red indicator to indicate a card jam in the read station.
L.D. Error: A red indicator to identify when a Light or Dark Check of the read station was not met.

6-67

6.7 INCREMENTAL PLOTTERS

6.7.1 Incremental Plotter and Control, Type XY12
Calcomp (California Computer Products) Models 563 and 565 available in three step-size models and four models
of the Complot (Houston Instruments) digital plotters can be operated from a Digital Equipment Corporation Type
XY12 Incremental Plotter Control. The characteristics of the recorders are summarized:

Name

Model

Paper Width
(inches)

Speed
(step/minute)

Calcomp

563

12,000

.0 I-in.
.005-in .
. I-mm

565

18,000

.0 I-in.
.005-in .
. 1-mm

DP-1-1
DP-1-5
DP-1-M2
DP-I-Ml

12
12
12
12

18,000
18,000
18,000
18,000

.01-in.
.005-in.
.25-mm
.1-mm

Comp lot

Step Size

The principles of operation are basically the same for each of the recorders. Bidirectional rotary step motors are
employed for both the X and Y axes.
Recording is produced by movement of a pen relative to the surface of the graph paper, with each instruction
causing an incremental step. X-axis deflection is produced by motion of the drum; Y-axis deflection, by motion of
the pen carriage. Instructions are used to raise and lower the pen from the surface of the paper. Each incremental
step can be in any one of eight directions through appropriate combinations of the X and Y axis instructions. All
recording (discrete points, continuous curves, or symbols) is accomplished by the incremental stepping action of
the paper drum and pen carriage. Front panel controls permit single-step or continuous-step manual operation of
the drum and carriage, and manual control of the pen solenoid. The recorder and control are connected to the
computer program interrupt and instruction skip facility.
Instructions for the recorder and control are:
PLSF

Skip on Plotter Flag

Octal code:
Event time:
Execution time:
Operation:

4.25 µs
If the Plotter Flag is set, the contents of the PC are incremented by one so that the next

Symbol:

sequential instruction is skipped.
If Plotter Flag = l, then PC + 1 -+ PC

PLCF

Clear Plotter Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6-68

6501

6502
2
4.25 µs
Clear the AC and Plotter Flag
0-+AC
0 -+ Plotter Flag

PLPU

Pen Up

Octal code:
Event time:
Execution time:
Operation:
Symbol:
PLPR

Pen Right

Octal code:
Event time:
Execution time:
Operation:
Symbol:
PLDU

6511
4.25 µs
Move the plotter pen to the right in either the raised or lowered position.
None

Drum Up

Octal code:
Event time:
Execution time:
Operation:
Symbol:

PLDD

6512
2
4.25 µs
Move the plotter paper drum upward. This instruction can be combined with the PLPR and
PLPD commands.
None

Drum Down

Octal code:
Event time:
Execution time:
Operation:
Symbol:
PLPL

6504
3
4.25 µs
Raise the plotter pen from the paper surface.
None

6514
3
4.25 µs
Move the plotter paper drum downward.
None

Pen Left

Octal code:
Event time:
Execution time:
Operation:
Symbol:
PLUD

4.25 µs
Move the plotter pen to the left in either the raised or lowered position.
None

Drum Up

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6521

6522
2
4.25 µs
Move the plotter paper drum upward. This instruction is similar to the 6512 instruction except
that it can be combined with the PLPL or PLPD instructions.
None

6-69

PLPD

Pen Down

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6524
3
4.25 µs
Lower plotter pen to the surface of the paper.
None

Program sequence assumes that the end location is known at the start of a routine since there is no means of
specifying an absolute pen location in an incremental plotter. Pen location can be preset by the manual controls on
the recorder. During the subroutine, the PDP-12 can track the location of the pen on the paper by counting the
instructions that increment position of the pen and the drum.

6-70

6.8 PAPER TAPE
6.8. l High-Speed Paper-Tape Punch and Reader, Type PC12
The High-Speed Paper-Tape Punch and Reader Type PCl 2 provides the user with a faster means of inputting or
outputting information from paper tape to the PDP-12 than that provided by the standard Teletype tape
reader/punch. The PCl 2 is functionally a PPl 2, High Speed Paper Tape Punch, and a PRl 2, High Speed Paper Tape
Reader, configured mechanically in the same unit. The operating characteristics are discussed in the following
paragraphs.
6.8.2 High-Speed Paper-Tape Punch, Type PP12
The High-Speed Paper-Tape Punch option Type PPl 2 consists of a PC05-P paper-tape punch that perforates 8-hole
fanfold paper-tape at a rate of 50 characters per second. Information to be punched in tape is loaded in an 8-bit
punch buffer (PB) from AC 4 - 1 1 • The punch flag is set at the completion of the punching action, signaling that new
information may be transferred into the punch buffer and punching may be initiated. The control circuitry for this
device is located in the BAl 2 Peripheral Expander. The punch flag is as described for the Teletype unit. The punch
instructions are:

PSF

Skip on Punch Flag

Octal code:
Event time:
Execution time:
Operation:
Symbol:

PCF

Symbol:

6022
2
4.25 µs
The punch flag and the punch buffer are both cleared in preparation for receiving a new
character from the computer.
0 --+ Punch Flag, PB

Load Punch Buffer and Punch Character

Octal code:
Event time:
Execution time:
Operation:
Symbol:

PLS

4.25 µs
The punch flag is sensed, and, if it is set, the contents of the PC are incremented by one,
skipping the next sequential instruction.
If Punch Flag = 1, the PC + 1 --+ PC

Clear Punch Flag

Octal code:
Event time:
Execution time:
Operation:

PPC

6021

6024
3
4.25 µs
An 8-bit character is transferred from AC 4 • 11 into the punch buffer, and then the character is
punched. This instruction does not clear the punch flag or the punch buffer.
AC 4 • 11 --+PB--+ PB

Load Punch Buffer Sequence

Octal code:
Event time:
Execution time:
Operation:

Symbol:

6026
2,3
4.25 µs
The punch flag and punch buffer are both cleared, the contents AC4 • 1 1 are transferred into
the punch buffer, the character in the PB is punched in tape, and the punch flag is set when
the operation is completed. Combines PCF and PPC.
0 --+ Punch Flag, PB
AC 4 • 1 1 --+ PB
I --+Punch Flag when done
6-71

A program sequence loop to punch characters when the punch buffer is "free" can be written as follows:
FREE,

PSF
JMP FREE
PLS
JMP FREE

/SKIP WHEN FREE
/LOAD PB FROM AC AND PUNCH CHARACTER

6.8.3 High-Speed Paper-Tape Reader, Type PR12
The High-Speed Paper-Tape Reader (PC05-R) option Type PR 12 senses data in a 8-hole perforated-paper tape
(unoiled) photoelectrically at 300 characters per second. The reader control requests reader movement, transfers
data from the reader into the reader buffer (RB), and signals the computer when incoming data is present. Reader
tape movement is started by clearing the Reader Flag. Data is assembled into the Reader Buffer from the
perforated tape. The Reader Buffer is transferred into AC 4 -11 under program control. The Reader Flag is
connected to the program interrupt and instruction skip facilities, and is cleared by IOT pulses. Control circuitry
for this device is located in the BA12 Peripheral Expander. Computer instructions for the reader are:

RSF Skip on Reader Flag
Octal code:
Event time:
Execution time:
Operation:
Symbol:

RRB

6011
1
4.25 µs
The status of the Reader Flag is sensed, and, if it is set, the contents of the PC are incremented
by one, skipping the next sequential instruction.
If Reader Flag = I , then PC + 1 ~ PC

Read Reader Buffer

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6012
2
4.25 µs
The contents of the reader buffer are transferred into AC 4 - 11 and the Reader Flag is cleared.
This instruction does not clear the AC.
RB V AC 4 - 11 ~ AC 4 - 11
0 ~ Reader Flag

RFC Reader Fetch Character
Octal code:
Event time:
Execution time:
Operation:
Symbol:

6014
3
4.25 µs
The Reader Flag and the reader buffer are both cleared. A character is loaded into the reader
buffer from tape, and the Reader Flag is set when this operation is completed.
0 ~ Reader Flag, RB
Tape Data~ RB
1 ~ Reader Flag when done.

A program sequence loop to read characters from perforated tape can be written as follows:
LOOK,

6-72

RFC
RSF
JMP LOOK
CLA
RRB
JMP LOOK

/FETCH CHARACTER FROM TAPE
/SKIP WHEN RB FULL

/LOAD AC FROM RB

6.9 DATA BUFFERS
6.9.1 Data Buffer Type DB12-P, N
The DB 12 option is an input/output transfer register, consisting of a 12-bit input bus driver and a 12-bit output
buffer register. The basic logic for this option is contained on an M735 module, which is described in the Logic
Handbook ( 1970). Three DB 12 options are prewired in the BAI 2 Peripheral Expander. The device select gating and
data lines provide the capability for transferring data into or out of the PDP-12 accumulator. The user selects a
device code by inserting jumpers in the M921 Device Code Select Jumper module located in row A, slot 19, of the
BAI 2 Peripheral Expander. Two I/O cables (Flexprint®) terminating in M903 connector modules are provided to
connect the DB 12 to the external I/O device. The output register is buffered to provide either positive (0, +3V) or
negative (0, -3V) logic levels. The option designation is DB12-P (positive) or DB12-N (negative).

® Flexprint is a Registered Trademark of Sanders Associates Inc.

6-73

6.10 POWER FAIL/RESTART

6.10.1 Power Failure Option, Type KP12
General
The KP 12 Power Failure Option protects an operating program upon failure or interruption of the computer's
primary power source. In the event of a power abnormality, a program interrupt is initiated by the KPl 2 and
enables continued operation of the central processor for 1 millisecond. During this interval, the interrupt routine
identifies the power low condition as the initiator of the interrupt. The interrupt routine then stores the contents
of active registers (AC, L, MQ, etc) and the program counter in known core memory locations. Upon restoration of
power, the power low flag is cleared and a routine in the 8 mode beginning at address 0000 8 starts automatically,
restoring the contents of the active registers and the program counter, and then continues the interrupted program.
Operation
A manual RESTART switch enables or disables the automatic restart operation upon restoration of primary power.
When it is ON (down), the program counter is cleared and a signal which simulates the console START key (RCL
ST ART PC) is produced 200 milliseconds after power conditions become satisfactory. Operation is restarted
(always in the 8 mode) by executing the instruction contained in address 0000 8 ; this instruction is a JMP to the
starting address of a subroutine which restores the contents of the active registers and the program counter to the
conditions that existed prior to the power low interrupt. The 200-millisecond delay assures that slow mechanical
devices, such as Teletype equipment, have completed any previous operation before the program is resumed.
When the RESTART switch is OFF (up), the power low flag is cleared upon the return of normal power
conditions, but the program must be manually restarted, possibly after resetting peripheral equipment.
Programming

SPL

Skip on Power Low

Octal code:
Event time:
Execution time:
Operation:

Symbol:

6102

2
4.25 µs
The condition of the power low flag is sampled; if set (indicating a power failure has occurred),
the contents of the PC are incremented by one, skipping the next sequential instruction.
If Power Low Flag = 1, then PC + 1 ~ PC

Figures 6-9 and 6-10 illustrate the Automatic Restart Program Events and Typical Power Failure Program Service
Routine, respectively.

6-74

PROGRAM
IN OPERATION

YES
ENTER DEVICE
"SEARCH"
SUBROUTINE

POWER FAIL SUBROUTINE NOT ENTERED
THE REGISTER CONTENTS ARE NOT
SAVED. PROGRAM. HAS TO BE MANUALLY
RESTARTED FROM BEGINNING.

YES

STOP THE NEXT SEQUENTIAL
INSTRUCTION AND ENTER
KP12 SERVICE ROUTINE

THE PROGRAM CONTINUES FLAG CHECKING.
NOTE WITH REAL TIME APPLICATIONS,
THE TIME REQUIRED FOR
CHECKING REDUCES THE TIME
FOR THE REAL TIME SERVICE
SUBROUTINE POSITION KP 12
INQUIRY NEAR THE BEGINNING.

DCA AC
RAR
DCA LINK
MQA
DCAMQ

6~~ ~gooe
TAD RESTRT X
DCA 00009
HLT

/INTERRUPT WAS CAUSED BY POWER LOSS FLAG
/SAVE AC
/GET LINK
/SAVE LINK
/GET MQ
/SAVE MO
/GET PC
/SAVE PC
/GET RESTART JUMP INSTRUCTION
/DEPOSIT RESTART INSTRUCTION IN 00009
12-0196

Figure 6-9. Automatic Restart Program Events

POWER
RESTORED

YES

PROGRAM MUST BE RESTARTED
MANUALLY.
UPON
REST ART, THE
INSTRUCTION IN
LOCATION 00009
IS PERFORMED

LOCATION

Of JMP X

LOCATION X CONTAINS THE
BEGINNING OF THE RESTART
PROGRAM, WHICH RESTORES
THE CONTENTS OF LINK,AC,PC
AND ANY OTHER INFORMATION
STORED BY PWR FAIL SERVICE
SUBROUTINE.CONTINUATION
OF THE PROGRAM
AUTOMATICALLY OCCURS.

CONTINUE
MAIN PROGRAM
12-0039

Figure 6-10. Typical Power Failure Program Service Routine

6-75

6.11 ANALOG-TO-DIGITAL
6.11.1 General Purpose Multiplexed Analog-to-Digital Converter System, Type AF01-A
The Type AFO 1-A General-Purpose Multiplexed Analog-to-Digital Converter combines a versatile, multipurpose
converter with a multiplexer to provide a fast, automatic, multichannel scanning and conversion capability. It is
intended for use in systems that sample and process analog data from sensors or other external signal sources at
high rates of speed. The AFOl-A is used when greater accuracy than that provided by the standard AD12 A-D
converter is needed. The Type AFO 1-A option is used with the PDP-12 to multiplex up to 64 analog signals and to
convert the signals to binary numbers. Analog data on each of 64 channels can be accepted and converted into
12-bit digital numbers 420 times per second.*
Switching point accuracy in this instance is 99.975 percent, with an additional quantization error of half the analog
value of the least significant bit (LSB).
A/D Converter Specifications
The Type AFO 1-A has a successive approximation converter that measures a 0 to -10 volt analog input signal and
provides a binary output indication of the amplitude of the input signal. The characteristics of the A/D converter
are as follows:
Accuracy and Conversion Times:

See Table 6-6 (includes all linearity and temperature errors)

Converter Recovery Time:

Zero.

Input and Input Impedance:

0 to -1 OV at 10 megohms standard. Input scaling may be
specified using the amplifier or sample and hold options
(see Table 6-5).

Input Loading:

±1 µA and 125 pf for 0 to -IOV input signal.

Output:

Binary number of 6 to 12 bits, with negative numbers
represented in two's complement notation. A OV input gives a
4000 8 ; a -5V input a 0000 8 and a -1 OV (minus 1 LSB) input
gives 3777 8 number.

Provision is made for using the Type A400 Sample and Hold Amplifier (AH02 option) between the multiplexer
output and A/D converter input to reduce the effective aperture to less than 150 ns. The Type A400 may also be
used to scale the signal input to accept ± 1OV, or 0 to + 1OV. The Type A200 amplifier (AH03 option) may be
substituted for the Type A400 to accomplish the same signal scaling without reducing the effective aperture. Both
the AH02 and AH03 options may be used to obtain high input impedance and small aperture. (See Table 6-4.)
Multiplexer Specifications
The multiplexer can include from 1 to 16 Type A 121 Switch Modules. Each module contains four single-pole,
high-speed, insulated gate FET switches with appropriate gating. The Type Al 21 Switches are arranged as a
64-channel group of series-switching single-pole switches with a separate continuous ground wire for each signal
input. The switched signal input wire and the continuous ground for each channel are run as twisted pairs to the
input connectors mounted on the rear panel. The continuous grounds for all channels are terminated at the high
quality ground of the AFOl-A System. Specifications (measured at input connector) are as follows:
*Conversion rate

6-76

= [(35 +2)(10-6)(64)] -1 =420cycles/sec.
= [(9 + 2) (10- 6) (64)] - 1 = 1420 cycles/sec.

Input Operating Signal Voltages:

+lOV to -IOV

Current:

1 mA

On Resistance

500 ohm (max)

Voltage Offset

lµV

"Off Leakage''

10 nA (max)

Capacitance

10 pf (max)

Speed
10% Input to within
1 LSB of output

2 µs

Operate Time

The time required to switch from one channel to another is 2 µ.s
to within 1 LSB of the final voltage. This time is preset within
the control and starts when a set or index command is received.
Table 6-5. Input Signal Scaling

Configuration

Gain

Standard

Input
Signal

Input
Impedance
(ohms)

Input
Output

Option
Designation

0
-5
-10

10 meg.
10 meg.
10 meg.

4000 8
0000 8
3777 8

STD

Sample &
Hold

-1
-1
-1

+5
0
-5

lOK
lOK
lOK

3777g
0000 8
4000 8

AH02

Sample &
Hold

-1/2
-1/2
-1/2

+IO
0
-10

lOK
IOK
lOK

3777 8
0000 8
4000 8

AH02

Amplifier

+l
+l
+l

+5
0
-5

>IOO meg.
>100 meg.
>100 meg.

4000 8
0000 8
3777 8

AH03

+1/2
+1/2
+1/2

+10
0
-10

>IOO meg.
>100 meg.
>100 meg.

4000 8
0000 8
3777 8

AH03

-1
or
-1/2

+5 +10
0 or 0
-5 -10

>IOO meg.
>IOO meg.
>100 meg.

3777 8
0000 8
4000 8

AH03
&
AH02

Amplifier

Amplifier
and Sample
& Hold

NOTE
Unipolar signals (0 to +5, or 0to+1 Ov) may also be specified with either the AH03
or AH02 pption.

6-77

System Operation
The Type AFO 1 System may be operated in either the random or sequential address modes. In the random address
mode, the control routes the analog signal from any selected channel to the A/D converter input. In the sequential
address mode, the multiplexer control advances its channel address by one each time an index instruction is
received. After indexing through the maximum number of channels implemented, the address is returned to 0.
The multiplexer switch settling time is preset within the control to initiate the conversion process automatically
after a channel has been selected in either the random or sequential address mode. A separate A/D Convert I/O
Transfer instruction may also initiate one or more conversions on a currently selected channel.
A/D conversion times are increased by 2 microseconds when multiplexer channels are switched to allow for settling
time of the analog signal at the multiplexer output. Conversion times are increased an additional 3 microseconds
when AH03 is used. These items are added to the conversion times shown in Table 6-6 under selected channel
conversion time, which is the only time required for each successive conversion on a selected channel.
When the Type AH02 Sample and Hold option is required, the multiplexer switch settling time and the sample and
hold acquisition time are overlapped. The total conversion and switching time is increased by 10 microseconds.
(See A400 specifications.)

A/D CONVERTER/MDLTIPLEXER CONTROLS
Designation

Function

WORD LENGTH:

Rotary switch selects digital word length or conversion accuracy. Refer to
Table 6-6 for corresponding conversion times.

POWER ON/OFF:

Applies 117 Vac power to internal power supplies.

CLR:

Clears multiplexer channel-address registers; i.e., selects analog channel O for
conversion.

INDEX:

Advances multiplexer channel-address register by one each time it is
depressed, enabling manual addressing of channels (up to 64) in sequential
mode. Returns address to zero when maximum value is reached.

ADC:

Starts conversion of the analog voltage on the selected channel to a binary
number when depressed.

A/D CONVERTER:

Indicates binary contents of A/D converter register.

MULTIPLEXER:

Indicates binary contents of multiplexer channel-address register.

POWER:

Indicates ON/OFF status.

Programming

Programmed control of the converter/multiplexer by the PDP-12 is accomplished with the IOT instructions listed
below. PDP-12 selects the converter/multiplexer with two device selection codes, 53 8 and 548 , depending upon
whether conversion or multiplexing function is being selected. The converter/multiplexer interprets the device
selection code to enable execution of the IOP command pulse generated by the IOT instruction.

6-78

Table 6-6. System Conversion Characteristics

Word Length
(No. of Bits)

6
7
8
9

10
11
12

Selected
Channel
(A/D)

Random
or
Sequential
(MPX & A/D)

AH03
MPX
A/D

AH02
MPX
A/D

AH02
AH03
MPX &A/D

Max
Switching
Point
Error*

Conversion
Time
(,us)**

Conversion
Time
(µs)**

Conversion
Time
{µs)**

Conversion
Time
(µs)**

±1.6%
±0.8%
±0.4%
±0.2%
±0.1%
±0.05%
±0.025%

9.0
10.5
12.0
13.5
18.0
25.0
35.0

11.0 (9.5)
12.5 (11.0)
14.0 (12.5)
15.5 {14.0)
20.0 {18.5)
27.0
37.0

14.0 (11.0)
15.5 (12.5)
17.0 (14.0)
18.5 {15.5)
23.0 (20.0)
30.0
40.0

19.0 (14.0)
20.5 (15.5)
22.0 (17.0)
23.5 (18.5)
28.0 (23.0)
35.0
45.0

21.0 (18.0)
22.5 (19.5)
24.0 (21.0)
25.5 (22.5)
30.0 (27.0)
37.0
47.0

* ± 1/2 LSB for quantizing error.
**If system is to operate at less than 10 bits continuously, conversion times may be reduced to times shown in
parentheses.

ADSF Skip on A-D Flag
Octal code:
Event time:
Execution time:
Operation:
Symbol:

6531
4.25 µs
The A-D converter flag is sensed, and if it is set (indicating that the conversion is complete) the
contents of the PC are incremented by one, skipping the next instruction.
If A-D Flag= 1, then PC+ 1-+ PC

ADCV Convert Analog Voltage to DigUal Value
Octal code:
Event time:
Execution time:
Operation:

Symbol:

ADRB

Read A-D Converter Buffer

Octal code:
Event time:
Execution time:
Operation:

Symbol:

6532
2
This time is a function of the accuracy and word length switch setting as listed in Table 6-6.
The A-D converter flag is cleared, the analog input voltage is converted to a digital value, and
then the A-D converter flag is set. The number of binary bits in the digital-value word and the
accuracy of the word are determined by the preset switch position.
0-+ A-D Flag at start of conversion, then
1-+ A-D Flag when conversion is done.

6534
3
4.25 µ.s
The converted number contained in the converter buffer (ADCB) is transferred into the AC
left justified; unused bits of the AC are left in a clear state, and the A-D converter flag is
cleared. This instruction must be preceded by a CLA instruction.
ADCB-+AC
0-+ A-D Converter Flag

6-79

ADCC

Clear Multiplexer Channel

Octal code:
Event time:
Execution time:
Operation:

6541
1
4.25 µs
The channel address register (CAR) of the multiplexer is cleared in preparation for setting of a
new channel.

Symbol:

o~CAR

ADSC Set Multiplexer Channel
Octal code:
Event time:
Execution time:
Operation:

6542
2
4.25 µs
The channel address register of the multiplexer is set to the channel specified by AC6 - 11 . A
maximum of 64 single-ended input channels can be used.

ADIC Increment Multiplexer Channel
Octal code:
Event time:
Execution time:
Operation:

Symbol:

6544
3
4.25 µs
The contents of the channel address register of the multiplexer are incremented by one. If the
maximum address is contained in the register when this instruction is given, the minimum
address (00) is selected.
CAR+ 1 ~cAR

The converter/multiplexer may be operated by the program in either the random or sequential addressing mode. In
the random addressing mode, the analog channel is selected arbitrarily by the program for digitizing and the
resultant binary word is read into the accumulator. A sample program for the random addressing mode is as
follows:
TADADDR
ADSC
ADCV
CLA
ADSF
JMP.-1
ADRB

/YES-GET CHANNEL ADDRESS
/AND SEND TO MULTIPLEXER
/CONVERT A TOD
/CLEAR AC
/SKIP ON A/D DONE FLAG
/WAIT FOR FLAG
/AND READ INTO AC

In the sequential address mode, the program advances the multiplexer channel-address register to the next channel
each time an analog value is converted and read into the accumulator.
Should the converter/multiplexer be operated in the interrupt mode, the computer will be signaled each time that a
binary word is ready, enabling the system to use processor time more efficiently.

6-80

Amplifier, Sample and Hold Options for AFOl-A
The AH03 consists of a DEC amplifier (part #1505379-10) mounted on an A990 Amplifier Board with appropriate
scaling networks and gain trim and balance potentiometers.
2 x 10 6
(@ 10 ma) ±1 lV

Open loop gain
Rated output voltage
Frequency response
Unity Gain, small signal
Full output voltage
Slewing rate
Overload recovery

lOMHz
1 MHz
lOOV/µs
50 µs

Input voltage offset
Avg vs temp
Vs supply voltage
Vs time

Adjustable to 0
20 µv/°C
15 µv/%
10 µv/day

Input current
Avg vs temp
Vs supply voltage

50 pAmax
doubles every l 0°C
10 pA/%

Input impedance (ohms)
Between inputs
Common mode

10 1 0 (5 pF shunt c)
10 1 0 (5 pF shunt c)

Input Voltage
Max common mode
Common mode rejection

±l5V
±lOV
50,000V

Power
Voltage
Current at rated load

±15 to 16V
40ma

A400 (standard gain options)
Acquisition time to 0.01 % (fullscale step)
Aperture time
Hold inaccuracy (droop)
Temperature coefficient
Gain (negative)
Input range (volts)
Output Impedance

<12 µs
<150 ns
<l mv/ms
0.1 mv/ms/°C
1.0 or 0.5
±5.0 ±10.0
<1.0 ohm

6-81

6.12 DIGITAL-TO-ANALOG
6.12.1 Digital-to-Analog Converter, Type AA01-A
The general-purpose Digital-to-Analog Converter Type AAO 1-A converts 12-bit binary numbers into analog
voltages. The basic option consists of three channels, each containing a 12-bit digital buffer register and a
digital-to-analog converter (DAC). A common digital input to all three registers is provided by a 12-bit input
channel which receives bussed output connections from the accumulator. Appropriate precision voltage reference
supplies are provided for the converters.
One IOT microinstruction simultaneously selects a channel and transfers a digital number into the selected register.
Each converter operates continuously on the contents of the associated register, providing an analog output
voltage.
Type AAOl-A options can be specified in a wide range of basic configurations; e.g., with from one to three
channels, with or without output operational amplifiers, and with internally or externally supplied reference
voltages. Configurations with double buffer registers in each channel are also available.
Each single-buffered channel is operated by a single IOT command. Select codes of 55, 56, and 57 are assigned to
the AAO 1-A, making it possible to operate nine single-buffered channels or various configurations of
double-buffered channels. A typical instruction for the AAO 1-A is:

DALI

Load Digital-to-Analog Convert 1

Octal code:
Event time:
Execution time:
Operation:
Symbol:

6-82

65 S 1

4.25 µs
The contents of the accumulator are loaded into the digital buffer register of channel 1.
AC-+DACl

CHAPTER 7
PROGRAM LIBRARY

Because of the dual nature of the PDP-12, virtually all PDP-8 classic LINC, and LINC-8 programs will run on the
PDP-12 equipped with the necessary peripherals. The following programs are normally supplied with the PDP-12,
and most will run on just the PDP-12A. There are other programs available from both Digital Equipment
Corporation and from DECUS. These have not been included in the Standard Library. This chapter is divided into
four sections: PDP-12 Programs, PDP-8 Programs, DECUS Programs, and Diagnostic Programs. This list is
representative and subject to change. The Digital Program Library and the DECUS Program Library maintain the
current program lists.
7.1 PDP-12 PROGRAMS
The PDP-12 is delivered to the user complete with an extensive selection of system programs and routines making
the full data processing capability of the new computer immediately available to each user, and eliminating many
commonly experienced initial programming delays.
7.1.1 LAPS-DIAL Display Interactive Assembly Language (DEC-12-SE2D-D)
LAP6-DIAL provides the PDP-12 user with an operatin~ system that includes editing, assembling, and data handling
capabilities. An interactive display permits quick user response; a File Index and Peripheral device Interchange
Program (PIP) facilitate file manipulation. The minimum hardware configuration for using LAP6-DIAL is a 4K
PDP- l 2B system. (The character editing facility is, however, designed primarily around the use of the AD 12
Analog-to-Digital Converter and Multiplexer for the PDP-l 2A.) In addition, the system will utilize an additional 4K
of memory to improve its efficiency significantly.
The LAP6-DIAL system is provided to the user on LINCtape. Each tape contains a reserved area occupied by
LAP6-DIAL, a working area for temporary storage of user programs, and a file area for permanent storage of user
programs. The LAP6-DIAL area of the tape contains the Editor, Assembly and Utility Programs, and a File Index.
The Index stores the name, starting block number, and length of each stored file. User programs are saved as named
files in the tile area of the system tape. The scope is used as a moving window to view source programs in the
working area. Up to 17 lines with up to 40 characters per line can be displayed at a time on the scope (maximum of
256). In the edit mode, any portion of a program in the Working Area can be displayed by an appropriate locate
request.
A LINCtape containing LAP6-DIAL is designated as the system tape, and is assigned to tape unit 0. Some
operations may be performed with only one LINCtape containing LAP6-DIAL, but many procedures, such as
assembling programs, require two tapes. Most efficient operation is achieved when both tapes contain LAP6-DIAL.
7-1

On startup the system automatically enters the edit mode. A source program may be typed in via the TTY
keyboard. The program will reside in the Working Area and will be displayed on the CRT Display
character-by-character as it is entered. The LAP6-DIAL Editor may be used at this time to add, modify, or delete
characters, lines, or large sections of the program. A command may also be issued via the TTY keyboard to the
Monitor. When called, the Monitor writes out its buffer pointers and is replaced by the called program. When the
system program operation is completed, the Monitor is automatically called back into core and it retrieves its
buffer pointers.
The Monitor Commands are summarized in the following table. Items in parentheses are optional; if they are
omitted, the user's program that was most recently manipulated is used.
Functions

Commands
AS
LO
LI
QL
PS
SB
SP
AP
DX
PX
CL
PI
EX
MC

(N, U)
(N, U)
(L, L,)
(L, L,)

Assemble (U = 0, I)
Load Binary
Assemble & List (U - 0, 1)
Assemble & Quick List (U = 0, I)
Print Source
Save Binary
Save Program (Source)
Add Program (Source)
Display Index
Print Index
Clear Working Area
Peripheral Interchange Program
Exit
User's Monitor Command (READS IN
USER PROGRAM FROM FREE AREA)

(N, U)
(N, U)
(N, U)

(L(,L),)
N, U (,M[A])
N, U
(L, L,) N, U or B, U
(, U)
(, U)

X(Y), U

Legend:
N= File Name
U= Tape Unit
L = Line Number

M =Mode (L for LINC or P for PDP-8)
A= Address (5 digits-used only if mode is specified)
B =Tape Block Number

The assembler processes both LINC mode and 8 mode statements, assembling programs up to BK in length.
Six-character alphanumeric symbols can be defined; source listings, assembly listings, or abbreviated assembly
listings may be optionally obtained on the Teletype or, if provided, the Line Printer. To facilitate the preparation
of system programs and large programs, conditional assembly pseudo-operations are provided along with a facility
to preserve the tag table definitions from one assembly to another assembly (or to several assemblies).
Upon loading, programs may be started automatically in either LINC or 8 mode at any memory location.
A second version of LAP6-DIAL, LAP6-DIAL-MS, provides the user of the PDP-12 (with 8K of memory and a
disk) with a fully-integrated tape-disk system. The additional facilities include:
1. Mass storage capabilities to support DF32, RS08, or RK8 disks (or LINCtape).
2. Monitor commands to clear the Binary Working Area and to merge binary files.
3. 1/0 routines to read, write, or move data.
4. An automatic system built to specialize the system tape··for the user's present configuration.
5. Increased assembler facilities for processing large programs.

7-2

7.1.2 Peripheral Interchange Program (PIP)
The Peripheral Interchange Program provides a flexible means of transferring data among peripheral devices such as
LINCtape, Teletype, High Speed Paper-Tape Reader/Punch, Line Printer, Disk, and Card Reader. Symbolic and
binary files, as well as absolute data, are processed in response to scope-directed operator requests.
7 .1.3 OU ANDA (DEC-12-FISA-D)

QANDA is a subroutine which allows a user to display textual information on the CRT Display, ask questions of
the viewer, allow editing of the input, and receive answers.
7.1.4 DATAM* (DEC-L8-FDAA-D)
The DATAM program retrieves, displays, and stores individual data blocks from LINCtape and provides the user
with a repertoire of mathematical operations for manipulating this data. These operations include high and low pass
filtration, differentiation and integration, attenuation and amplification, inversion, addition of a constant, and
plotting of a bar graph. The data or resulting waveforms are continuously displayed.
7.1.5 GRAPHA* (DEC-L8-UGAA-D)
The G RAPHA program allows data to be retrieved from LINCtape and displayed, and allows a graph to be
composed for this data, with appropriate lettering and axes. The graph is assembled on the display and the finished
product may be photographed, plotted on an incremental plotter, or saved on LINCtape for future reference.
7.1.6 FROANA* (DEC-L8-FANA-D)
The FRQANA program performs a frequency analysis of 512 points of data, and resolves the resulting spectrum
into 64 components. The sine, cosine, and rms spectra are subsequently displayed and can be scaled. A resynthesis
from the spectra can then be performed to provide a comparative display of the original data and the resynthesized
waveform.
7.1.7 MAGSPY (DEC-12-UZSA-D)
The MAGSPY program provides a moving window for scanning data stored on LINCtape. The data is displayed on
the scope and can be scanned at a rate determined by a potentiometer setting. The data is interpreted either as a
binary point plot or as packed ASCII characters depending on a switch setting.
7.1.8 COMPAR* (DEC-L8-EUCA-D)
The COMPAR program compares contents of specified LINCtape blocks on a word by word basis.
7.1.9 SEARCH* (DEC-L8-EUSA-D)
The SEARCH program performs a search of blocks of LINCtape for a specific word. The user may specify the word
to be searched and a mask of bits for comparison.
7.1.10 CONVERT (DEC-12-ESYB-D)
The CONVERT program is used to convert symbolic text from LAP-4 and LAP-6 manuscripts for compatibility
with the LAP6-DIAL Assembler.

*LINC-8 Programs.

7-3

7.1.11 MARK 12 (DEC-12-YITB-D)

The MARK 12 program is used to format tapes to be used with the PDP-12. Several format options are available
and, by using the subroutines within MARK 12, the user can generate a tape of arbitrary format.
7.1.12 L8SIM (DEC-12-Sl1B-D)
The LINC-8 Simulator Trap Processor handles Teletype input and output for LINC-8 and classic LINC programs so
they can be run on the PDP-12 without modifications. It must be loaded into the PDP-12 core memory with any
LINC-8 or classic LINC program which uses the keyboard or the Teleprinter, in order for that program to be run on
the PDP-12.
The trap processor operates by using the PDP-12 Instruction Trap Facility to detect execution of either of the two
LINC-8 Teletype input/output instructions by the user's program. It responds to user's execution of a Teletype
instruction by executing coding to simulate the instruction's LINC-8 or classic LINC effect. After simulation of the
instruction, the trap processor returns control to the user program.
Users may easily adapt the LINC-8 Simulator Trap Processor to handle other devices or for their own purposes.
Explicit instructions for a number of useful adaptations are provided in this document, along with enough
information on the internal operation of the program to permit users to easily implement adaptations of their own
invention.
An important limitation of the trap processor is that it is not interruptible. It may not be operated when the
PDP-12 Program Interrupt facility is enabled.

7.1.13 FRED (DEC-12-FZFA-D)
The File Replacement, Entry, and Deletion subroutine processes the LAP6-DIAL Index for the user, freeing him
from the clerical function of maintaining the file entries. A second version Mildred (DEC-12-FZDA-D) performs
these operations in a disk based system.
7.1.14 PRTC 12-F (DEC-12-YIYA-D)
PRTC12-F is a PDP-12 program to utilize the TC12-F tape hardware option in transferring data between LINCtape
and DECtape. The DECtape may have been formatted on a PDP-8, PDP-8/1, PDP-9, PDP-10, and PDP-15. For a
complete description of the TCI 2-F hardware see Section 6.4.3.
7.1.15 SIGAVG/SINPRE (DEC-12-UZ1A-D/DEC-12-UW4A-D)

SIGAVG is a multisweep signal averager that allows the user to enhance signals with a low signal/noise ratio and
display them on the CRT Display. SIGAVG will sample at rates ranging from 55 to 4095 µs per point per
instrument, supporting a maximum of five instruments. It can take up to 4096 sweeps, and can output averaged
results to LINCtape. SINPRE converts the output of SIGAVG (two-word) to the commonly used one-word format.
7.1.16 CATACAL (DEC-12-UWlA-D)
CAT ACAL is a "boxcar" averager and data manipulation program that acquires data from an external instrument
at rates that range from .2 ms to 35 seconds per point. CAT ACAL is capable of reading and writing on LINCtape; it
can output one or two data files (spectra) to either the CRT display or an X-Y recorder. It can also differentiate,
integrate, edit (strip), and compare data files (spectra), and display the results on the scope. It has the capability of
curve-fitting and deconvolution, using Lorentzian or Gaussian equations.
7. l.17 NMRSIM (Nuclear Magnetic Resonance Simulation) (DEC-12-UW5A-D)

NMRSIM allows the user to calculate theoretical spectra of a wide variety of compounds. The user inputs the
appropriate parameters from the keyboard (such as spin, chemical shifts, and coupling constants), and calculated

7-4

line-spectra are then displayed on the scope. NMRSIM can output spectra to LINCtape and can also read, merge,
and display a series of spectra from LINCtape which effectively simulate large spin systems or mixtures of
compounds.
7.1.18 ADTAPE/ADCON (DEC-12-UW2A-D)
ADTAPE is a data acquisition program that allows the user to: sample simultaneously from 1 to 16 A/D channels
at sampling rates ranging from 1000 points per second to 40 seconds per point; display the output of any two
channels on the CRT display; and output all results to LINCtape in real time. ADTAPE has a setup mode that
allows the user to define a wide variety of sampling schemes using either the keyboard, CRT display or LINCtape.
The program ADCON is utilized upon completion of ADT APE and allows the user to sort the ADTAPE LINCtape
output for a given channel onto contiguous tape blocks for further processing.

7.1.19 TISA (DEC-12-UW3A-D)
TISA can acquire asynchronous (time-independent) or synchronous data simultaneously from up to five
instruments at rates that do not exceed 2 milliseconds per point. TISA stores data on LINCtape and supports up to
32K of core. Data is displayed on the CRT display via a moving window and cursor with X-Y decimal readout.
TISA has a setup mode that allows the user to define a wide variety of parameters using either the keyboard/CRT
display of LINCtape. TISA is capable of acquiring data from instruments that are interfaced via shaft encoders or
potentiometers, or both. With the ability to call any LAP6-DIAL program, TISA is able to interact with all PDP-12
software.
7.1.20 FOCAL 12
FOCAL-12 is an adaptation of the conversational FOCAi..© (FOrmula CALculator) language designed specifically
to optimize use of the PDP-12 computer and its standard peripheral devices. The LINCtape, console switches,
external sense lines, and VRl 2 display can all be utilized effectively through FOCAL-12. Simple data acquisition
and reduction tasks may be quickly programmed using FOCAL-12, and the language can be used to analyze
previously generated data stored on LINCtape. FOCAL-12 requires SK of memory.

7.2 PDP-8 PROGRAMS
The PDP-8 programs available to the user are listed in this section. The programs described in these abstracts come
from two sources, past programming efforts on the PDP-5, 8, 8/S, 8/1, 8/L, and present and continuing
programming effort on these machines plus the PDP-12. Thus the programming system takes advantage of the
many man-years of program development and field testing by Digital computer users. There are over 3500
Family-of-8 systems already in the field.
Although all utility and functional program documentation is issued in a newer format than that introduced with
the Farnily-of-8 computers, in many cases PDP-12 programs originated from previous Family-of-8 computers.
Programs written by users of Family-of-8 computers and submitted to the DECUS library (DECUS - Digital
Equipment Corporation User's Society) are immediately available to PDP-12 users. Consequently, users of all
PDP-12 computers can take full advantage of continuing program developments.

7. 2.1 System Programs
DEC-08-AJAD-D FOCAL - FOCAL (for FOrmula CALculator) is an on-line, conversational service program for
the PDP-8 family of computers, designed to help scientists, engineers, and students solve numerical problems. The
language consists of short imperative English statements which are relatively easy to learn. Mathematical
expressions are typed in standard notation for the most part. No previous programming experience is needed either
to understand the manual or to use FOCAL at the Teletype console. However, the best way to learn the FOCAL
language is to sit at the Teletype and try the commands, starting with the examples given in the Programming
Languages Handbook.

7-5

DEC-D8-SDAB-D Disk Monitor System (8 Mode) - This system consists of a keyboard-oriented Monitor, which
enables the user to efficiently control the flow of programs through his PDP-12, and a comprehensive software
package, including a FORTRAN Compiler, Program Assembly Language (PAL-D), Edit program (EDITOR),
Peripheral Interchange Program (PIP), and Dynamic Debugging Technique (DDT-0) program. Also provided is a
program (BUILDER) for generating a customized monitor according to the user's particular machine configuration
(amount of core, number of discs, etc).
The system is modular and open-ended, permitting the user to construct the software required in his environment,
and allows the user full access to his disk (referred to as the system device) for storage and retrieval of his programs.
By typing appropriate commands into the Monitor, the user can load a program (construct it from one or more
units of binary coding previously punched out on paper tape or written on the disk by the Assembler, and assign it
core locations), save it (write it out, with an assigned starting address, on the system device), and later call it (read
it back into core from the system device) for execution. See Introduction To Programming for further details.
DEC-08-AFCO-D, 4K FORTRAN
The 4K FORTRAN Compiler lets the user express problems in a mixture of English words and mathematical
statements. It reduces the time needed for program preparation and enables users with little or no knowledge of the
computer's organization and operating language to write effective programs.
The 4K FORTRAN language consists of four general types of statements; arithmetic, logic, control, and
input/output. FORTRAN functions include addition, subtraction, multiplication, division, sine, cosine, arctangent,
square root, natural logarithm, and exponentiation.
DEC-08-KFXB-D, 8K FORTRAN
The 8K FORTRAN system translates a source program into relocatable binary code. The relocatable binary code is
output on paper tape and then loaded into the computer for program execution. The 8K FORTRAN system
features: USA Standard FORTRAN syntax; subroutines; two levels of subscripting; function subprograms;
input/output supervisors; relocatable output loaded by the 8K Linking Loader; COMMON statements; I, F, E, A,
X, and H format specifications; and arithmetic and trigonometric library subroutines.
The SK FORTRAN system consists of a one-pass compiler, the 8K SABR Assembler, 8K Linking Loader, and a
comprehensive Library of subprograms. The system requires a PDP-8 Family Computer with at least 8K words of
core memory, an ASR33 Teletype, and a high-speed paper tape reader and punch. 8K FORTRAN utilizes all
available core to 32K. 8K FORTRAN is a modified version of USASI Basic FORTRAN and is further described in
Programming Languages Handbook.
DEC-08-CDDB-D, DDT
The Dynamic Debugging Technique provides a means for on-line program debugging at the symbolic or mnemonic
level. By typing commands on the console teleprinter, memory locations can be examined and changed, program
tapes can be inserted, selected portions of the program can be run, and the updated program can be punched. This
and it's octal counterpart ODT-8 (DEC-08-COCO-D) are described in Introduction To Programming.
D EC-08-Y QYB-D, Floating-Point System
A Basic System (DEC-08-YQlB-PB)
B Interpreter, I/O, I/O Controller (-YQ2B-)
C Interpreter, I/O Functions (-YQ3B-)
D Interpreter, I/O, I/O Controller, Functions (-YQ4B-)

7-6

As described in Programming Languages Handbook this includes Floating-Point Interpreter and 1/0 subsystems.
Allows the programmer to code his problem in floating-point machine language.
Floating-point operations automatically align the binary points of operands, retaining the maximum precision
available by discarding leading zeros. In addition to increasing accuracy, floating-point operations relieve the
programmer of the scaling problems common in fixed-point operations. This system includes elementary function
subroutines programmed in floating-point. These subroutines are sine, cosine, square root, logarithm, arctan, and
exponential functions. Data being processed in floating-point is maintained in three words of memory ( 12-bit
exponent, 24-bit mantissa). An accuracy of six digits is maintained.
DEC-08-AFA2-PB, FORTRAN SYMBOL PRINT

Loaded after the FORTRAN Compiler, this program lists the variables used and where they will be located in core.
It also indicates the section of core not used by the compiled program and data.

7.2.2 Elementary Function Routines
The following routines are described in the Program Library Math Routines Manual (DEC-08-FFAC-D) and in the
Programming Languages Handbook.
Square Root Subroutine-Single Precision

Forms the square root of a single-precision number. An attempt to take the square root of a negative number will
give 0 for a result.
Signed Multiply Subroutine-Single Precision

Forms a 22-bit signed product from 11-bit signed multiplier and multiplicand.
Signed Divide Subroutine-Single Precision

This routine divides a signed 11-bit divisor into a signed 23-bit dividend giving a signed 11-bit quotient and a
remainder of 11 bits with the sign of the dividend.
Double-Precision Multiply Subroutine-Signed

This subroutine multiplies a 23-bit signed multiplicand by a 23-bit signed multiplier and returns with a 46-bit
signed product.
Double-Precision Divide Subroutine-Signed

This routine divides a 23-bit signed divisor into a 47-bit signed dividend and returns with a 23-bit signed quotient
and a remainder of 23 bits with the sign of the dividend.

7-7

Sine Routine-Double Precision
The Double-Precision sine subroutine evaluates the function Sin (X) for -4 < 4 (Xis in radians). The argument is a
double-precision word, two bits representing the integer part and 21 bits representing the fractional part. The result
is a 23-bit fraction -1 < Sin(X) 1.
Cosine Routine-Double Precision
This subroutine forms the cosine of a double-precision argument (in radians). The input range is -4 < X < 4.
Four-Word Floating-Point Package
This is a basic floating-point package that carries data as three words of mantissa and one word of exponent.
Common arithmetic operations are included as well as basic input/output control. No functions are included.
Logical Subroutines
Subroutines for performing the logical operations of inclusive and exclusive OR are presented as a package.
Arithmetic Shift Subroutines
Four basic subroutines, arithmetic shift right and arithmetic shift left at both single and double precision, are
presented as a package.
Logical Shift Subroutines
Two basic subroutines, logical shift right at both single and double precision are presented as a package.
Digital-8-21-F Signed Multiply (Uses EAE) Single Precision
This subroutine forms a 22-bit signed product from an 11-bit signed multiplier and multiplicand using the
Extended Arithmetic Element. It occupies less storage and takes less time to execute than its non-EAE counterpart,
and it has the same calling sequence.
Digital-8-22-F Signed Divide (Uses EAE) Single Precision
This subroutine divides a double-precision signed 22-bit dividend by a signed 11-bit divisor, producing a signed
11-bit quotient and a remainder of 11 bits having the sign of the dividend.
It makes use of the Extended Arithmetic Element instruction set and occupies less storage and takes less time to
execute than its non-EAE counterpart. It has the same calling sequence except that the subroutine name is changed
from DIVIDE to SPDIV.
Digital-8-23-F Signed Multiply (Uses EAE) Double Precision
This subroutine multiplies a 23-bit, signed 2's complement binary number by a 23-bit signed 2's complement
binary number, giving a 46-bit product with two signs on the higher order end. It makes use of the Extended
Arithmetic Element instruction set and, because of this, occupies less storage and takes less time to execute than its
non-EAE counterpart. Its calling sequence is comparable with the non-EAE version.
Digital-8-25-F EAE Floating-Point Package
These packages perform the same tasks as the Floating-Point Packages (DEC-08-YQIB through YQ4B), except that
certain routines have been speeded up by the use of the Extended Arithmetic Element.
For a detailed description of floating-point arithmetic and the interpretive Floating-Point Packages, the reader is
referred to DEC-08-YQYB-D or the Programming Languages Handbook.

7-8

7.2.3 Utility Program
DEC-08-LRAA-D, Read-In-Mode Loader
The RIM Loader is a minimum-sized routine for reading and storing the information in Read-In Mode coded tapes
via the 33 ASR Perforated Tape Reader (also high speed reader version).
DEC-08-LBAA-D, Binary Loader (33 ASR, PR12, MC12 Memory Extension)
The Binary Loader is a routine for reading and storing the information in binary-coded tapes via the 33 ASR
Perforated Tape Reader or by means of the Type PRI 2 High-Speed Perforated Tape Reader.
DEC-08-PMPO-D, RIM Punch
This program provides a means of punching out the information in selected blocks of core memory as (Read-In
Mode) RIM-coded tape via the 33 ASR Perforated Tape Reader or the High Speed Punch PP12.
DEC-08-YXlA, Binary Punch (33 ASR)
DEC-08-YX2A, Binary Punch (PP12)
This program provides a means of punching out the information in selected blocks of core memory as binarycoded tape via the 33 ASR Perforated Tape Punch or the High Speed Punch PP12.
DEC-08-YPPA, Octal Memory Dump
This routine reads the console switches to obtain the upper and lower limits of an area of memory, then types on
the Teletype an absolute address plus the octal contents of the first four words specified; it repeats this until the
block is exhausted, at which time the user may repeat the operation.
Digital-8-11-U Double Precision BCD-to-Binary by Radix Deflation
This subroutine converts a 6-digit BCD number to its equivalent binary value contained in two computer words.
Digital-8-12-U Incremental Plotter Subroutine
This subroutine moves the pen of an incremental plotter to a new position along the best straight line. The pen may
be raised or lowered during the motion.
Digital-8-14-U Binary to Binary-Coded-Decimal Conversion
This subroutine provides the basic means of converting binary data to binary-coded-decimal (BCD) data for
typeout, magnetic tape recording, etc.
Digital-8-15-U-SYM Binary-to-Binary-Coded-Decimal Conversion (Four Digit)
This subroutine extends the method used in Digital-8-14-U so that binary integers from 0 to 4095 in a single
computer word may be converted to four binary-coded-decimal characters packed in two computer words.
Digital-8-17-U EAE Instruction Set Simulator
This routine permits the automatic multiply-divide hardware option to be simulated.

7-9

Digital-8-20-U-SYM Character String Typeout Subroutine
This basic subroutine types messages stored internally as a string of coded characters. All 33 ASR characters are
legal.
Digital-8-21-U-SYM Symbolic Tape Formal Generator
The Format generator allows the user to create PDP-8 symbolic tapes with Formatting. It may be used to condense
tapes with spaces by inserting tabs, or merely to align tabs, instructions, and comments.
Digital-8-22-U-SYM Unsigned Decimal Print, Single Precision
This subroutine permits the typeout of the contents of a computer word as a four-digit, positive, decimal integer.
Digital-8-23-U-SYM Signed Decimal Print, Single Precision
This subroutine permits the typeout of the contents of a computer word as a signed two's complement number. If
bit O of the computer word is a 1, the remaining bits represent a negative integer in two's complement form; if bit 0
equals 0, the remaining bits represent a positive integer. If the number is negative, a minus sign is printed; if
positive, a space.
Digital-8-24-U-SYM Unsigned Decimal Print, Double Precision
This subroutine permits the typeout of a double-precision integer stored in the usual convention for
double-precision numbers (see DEC-08-FF AC-D or Programming Languages Handbook). The one exception is that
all 24 bits are interpreted as magnitude bits (i.e., the bit 0 of the high-order word is not a sign bit). The typeout is
in the form of a seven-digit, positive, decimal integer.
Digital-8-25-U-SYM Signed Decimal Print, Double Precision
11Iis subroutine permits the typeout of the contents of two consecutive computer words as one signed,
double-precision, two's complement number. If bit 0 of the high order word is a 1, the remaining 23 bits
represent a negative integer in two's complement form; if bit 0 equals 0, the remaining bits represent a positive
integer. If the number is negative, a minus sign is printed; if positive, space.
Digital-8-28-U-SYM Single Precision Decimal-to-Binary Conversion & Input (ASR-33) Signed or Unsigned
This routine accepts a string of up to four decimal digits (single precision for the PDP-12) from the Teletype
keyboard and converts it to the corresponding two's complement binary number. The string may contain as legal
characters a sign (+, -, or space) and the digits from 0-9. If the first legal character is not a sign, the conversion is
unsigned.
Digital-8-29-U-SYM Double Precision Decimal-to-Binary Conversion & Input (ASR-33) Signed or Unsigned
This routine accepts a string of up to eight decimal digits (double-precision for the PDP-12) from the Teletyp~
keyboard and converts it to the corresponding two's complement binary number. The string may contain as legal
characters a sign (+, -, or space) and the digits 0-9. If the first legal character is not a sign, the conversion is
unsigned.
7.3 DECUS PROGRAM

DECUS is the Digital Equipment Corporation Users' Society, which collects, files, and distributes user-written
programs for all DEC computers. Below is a partial list of PDP-8 programs available through DECUS. More detailed
lists are available in the periodic DECUS proW.am catalog.

7-10

DECUS No. 5-5, EXPANDED ADDING MACHINE
Expanded Adding Machine is a minimum-space version of Expensive Adding Machine (DEC 5-43-D) using a table
lookup method including an error space facility.
This is a basic version to which additional control functions can easily be added. Optional vertical or horizontal
format, optional storage of intermediate result with reentry, fixed-point output of results within reason, and other
features that can be had in little additional space under switch register control. (Write-up and Listing Only)

DECUS NO. 5/8-9, ANALYSIS OF VARIANCE PDP-5/8
An analysis of variance program for the standard PDP-5/8 configuration.

The output consists of:
A. For each sample:
1. sample number

2. sample size

3. sample mean
4. sample variance
5. sample standard deviation
B. The grand mean
C. Analysis of Variance Table
This is the standard analysis of variance table that can be used with the F test to determine the significance, if any,
of the differences between sample means. The output is also useful as a first description of the data.
All arithmetic calculations are carried out by the Floating Point Interpretive Package DEC-08-YQYB-D described in
Programming Languages Handbook.
DECUS NO. 5/8-18a, BINARY TAPE DISASSEMBLY PROGRAM
Disassembles a PDP-8 program, which is on tape in BIN format. It prints the margin setting, address, octal contents,
and mnemonic interpretation (PAL) of the octal contents. A normal program or a program which uses Floating
Point may be disassembled.

7-11

DECUS NO. S/8-20, REMOTE OPERATOR FORTRAN SYSTEM
Program modification and instructions to make the FOR TRAN OTS version dated 2/12/ 65 operate from remote
stations.

DECUS NO. S/8-21, TRIPLE PRECISION ARITHMETIC PACKAGE
An arithmetic package to operate on 36-bit signed integers. The operations are add, subtract, multiply, divide,
input conversion, and output conversion. The largest integer which may be represented is 2 3 5 -1 or 10 decimal
digits. The routines simulate a 36-bit (3 word) accumulator in core locations 40,41, and 42, and a 36-bit multiplier
quotient register in core locations 43, 44, and 45. Aside from the few locations in page 0, the routines use less core
storage space than the equivalent double-precision routines.

DECUS NO. S-25, A PSEUDO RANDOM NUMBER GENERATOR
The random number generator subroutine, when called repeatedly, will return a sequence of 12-bit numbers which,
though deterministic, appears to be drawn from a random sequence uniform over the interval 0000 8 to 7777 8 .
Successive numbers will be found to be statistically uncorrelated. The sequence will not repeat itself until it has
been called over 4 billion times.

DECUS NO. 8-26a, COMPRESSED BINARY LOADER (CBL)
The CBL (Compressed Binary Loader) format, in contrast to BIN format, utilizes all eight information channels of
the tape, thus achieving nearly 25% in time savings.
Whereas BIN tapes include only one checksum at the end of the tape, CBL tapes are divided into many
independent blocks, each of which includes its own checksum. Each block has an initial loading address for the
block and a word count of the number of words to be loaded.
The CBL loader occupies locations 7700 through 7777.

DECUS NO. 8-26c, XCBL - EXTENDED MEMORY CBL LOADER
XCBL is used to load binary tapes punched in CBL format into any 4K memory field. This loader occupies
locations 7670 through 7777 of any memory field.

DECUS NO. 8-26d, XCBL PUNCH PROGRAM
This program permits a user to prepare an XCBL tape of portions of extended memory through the control of the
keyboard of the on-line Teletype.

7-12

DECUS NO. 5/8-27a, BOOTSTRAP LOADER AND ABSOLUTE MEMORY CLEAR
Bootstrap Loader inserts a bootstrap loading program in page 0 from a minimum of toggled instructions.
Absolute Memory Clear leaves the machine in an absolutely clear state and, therefore, cycling around memory,
obeying an AND instruction with location zero. Should not be used unless one plans to reinsert the loader program.

DECUS NO. 5/8-28a, PAL III MODIFICATIONS-PHOENIX ASSEMBLER
This modification of the PAL III Assembler speeds up assembly on the ASR-33/35 and operates only with this I/O
device. Operation is essentially the same as PAL III, except that an additional pass has been added, Pass 0. This pass
starts in the usual manner but, with the switches set to zero, reads the symbolic tape into a core buffer area.
Subsequent passes then read the tape image from storage instead of from the Teletype.

DECUS NO. 5/8-29, BCD TO BINARY CONVERSION SUBROUTINES
These two subroutines improve upon the DEC-supplied conversion routine.

DECUS NO. 5-30, GENPLOT - GENERAL PLOTTING SUBROUTINE
This self-contained subroutine is for the PDP-5 with a 4K memory and a CALCOMP incremental plotter. The
subroutine can move (with the pen in the up position) to location (x,y), make an x at this location, draw a line
from this present position to location (x,y), and initialize the program location counters.

DECUS NO. 5-31, FORPLOT - FORTRAN PLOTTING PROGRAM
FORPLOT is a general-purpose plotting program for use in conjunction with the CALCOMP 560 Plotter. It is
self-contained and occupies memory locations 0000 to 4177. FORPLOT accepts decimal data inputted on paper
tape in either fixed or floating point formats. Formats can be mixed at will. FORTRAN output tapes are
acceptable directly, and any comments on these are filtered out.

DECUS NO. S/8-32a, PROGRAM TO RELOCATE AND PACK PROGRAM IN BINARY FORMAT
Provides a means to shuffle machine language program around in memory to make the most efficient use of
computer storage.

DECUS NO. 5/8-33, TAPE TO MEMORY COMPARATOR
Tape to Memory Comparator is a debugging program which allows comparison of the computer memory with a
binary tape. It is particularly useful for detecting reader problems, or during stages of debugging a new program.
Presently uses high-speed reader, but may be modified for TTY reader.

DECUS NO. 5/8-35, BCD TO BINARY CONVERSION SUBROUTINE AND BINARY TO BCD SUBROUTINE
(DOUBLE PRECISION)
This program consists of a pair of relatively simple and straightforward double-precision conversions.

7-13

DECUS NO. 5/3-38, FTYPE -FRACTIONAL SIGNED DECIMAL TYPE-IN
Enables a user to type fractions of the form: .582. -.73, etc, which will be interpreted as sign plus 11 bits (e.g., 0.5
µ 2000). Subroutine reads into 300-3177 and is easily relocated, as it will work on any page without modifications.

DECUS NO. S/8-39, DSDPRINT, DDTYPE PACKAGE

DOUBLE-PRECISION SIGNED DECIMAL INPUT-OUTPUT

DSDPRINT, when given a signed 24-bit integer, types a space or minus sign, and then a 7-digit decimal number in
the range -8388608 to +8388607. DDTYPE enables user to type in a signed decimal number in either single or
double precision. These routines are already separately available, but the present subroutine package occupies only
one memory page and allows for more efficient memory allocation. Located in 3000-3177, but will work on any
page.

DECUS NO. S/8-43, UNSIGNED OCTAL-DECIMAL FRACTION CONVERSION
This routine accepts a four-digit octal fraction in the accumulator and prints it out as an N-digit decimal fraction
where N = 12 unless otherwise specified. After N digits, the fraction is truncated. Programs are included for use
with the Extended Arithmetic Element.
Storage requirements: 55 Octal locations for the PDP-5, 47 Octal locations for the PDP-8.

DECUS NO. 8-44, MODIFICATIONS TO THE FIXED POINT OUTPUT IN THE PDP-8 FLOATING POINT
PACKAGE (DEC-08-YQYA-D)
The Floating Point Package (DEC-08-YQYA-D) includes an Output Controller which allows output in fixed point as
well as floating point format. This Output Controller takes the form of a certain number of patches to the "Floating
Output E Format" routine, plus an additional page of coding.
Certain deficiencies were noted in the fixed-point output format, particularly the lack of any automatic rounding off.
For example, the number 9, if outputted as a single digit, appears as 8. Modification attempts to provide automatic
rounding off resulted in the Output Controller being completely rewritten with minor changes in the format.

This new version of the Output Controller is also in the form of patches to the Floating Output with an additional
page of coding, thereby not increasing the size of the Floating-Point Package.

7-14

The following summarizes this new version:
1. The number output is automatically rounded off to the last digit printed, or the sixth significant digit,
whichever is reached first. Floating point output is rounded off to six figures, since the seventh is usually
meaningless.
2. A number less than one is printed with a zero preceding the decimal point (e.g., +0.5 instead of +.5).
3. A zero result, after rounding off, is printed as +O instead of+.
4. The basic Floating Point Package includes the facility to specify a carriage return/line feed after the
number using location 55 as a flag for this purpose. The patches for the Output Controller caused this facility to be
lost. This version restores this facility.

DECUS NO. 8-47, ALBIN - A PDP-8 LOADER FOR RELOCATABLE BINARY PROGRAMS
ALBIN is a simple method for constructing relocatable binary formatted programs, using the PAL III Assembler.
Allocation of these programs can be varied in units of one memory page (128 1 0 registers.). When loading an
ALBIN program, the actual absolute addresses of indicated program elements (e.g., the keypoint of subroutines)
are noted down in fixed program-specified location on page zero. In order to make a DEC symbolic program
suitable for translation into its relocatable binary equivalent, minor changes are required which, however, do not
influence the length of the program. Due to its similarity to the standard DEC BIN loader, the ALBIN loader is also
able to read-in normal DEC binary tapes. ALBIN requires 122 1 0 locations, RIM loader included. Piling-up in core
memory of ALBIN programs stored on conventional or DECtape can be achieved using the same method with some
modifications.

DECUS NO. 5/8-48, MODIFIED BINARY LOADER MKIV
The Mark IV loader was developed to accomplish four objectives:
1. Incorporate the self-starting format described in DECUS 5/8-27, ERC Boot.

2. Select the reader in use automatically, without switch register settings.
3. Enable a newly-prepared binary tape to be checked prior to loading by calculating the checksum.
4. Reduce the storage requirements for the loader so that a special program would fit on the last page of
memory with it.

DECUS NO. 8-49, RELATIVISTIC DYNAMICS
Prints tables for relativistic particle collisions and decay in the same format as the Oxford Kinematic Tables. It can
be used in two ways:

1. Two-particle Collisions - Given the masses of incident, target, and emitted particles, the incident energy,
and center-of-mass angles, the program calculates angles and energies of the emitted particles in the Lab frame. If
the process if forbidden energetically, program outputs E, allowing the threshold energy to be found.
2. Single Particle Decays - By specifying M2 = 0 (target), the problem will be treated as a decay, and tables
similar to the above will be printed.

7-15

DECUS NO. 5/8-50, ADDITIONS TO SYMBOLIC TAPE FORMAT GENERATOR (DEC-8-21-U)

Performs further useful functions by the addition of a few octal patches. By making the appropriate octal patches
via the toggles, the Format Generator can also format FORTRAN tapes, shorten tape by converting space to tabs,
and convert the type of tape.
A short binary tape may be made and added on to the end of 8-21-U to edit an original tape that was punched
off-line.
The rubout character will cause successive deletion of the previous characters until the last C. R. is reached but not
removed. The use of +- will cause the current line to be restarted. Thus an input tape may be prepared off-line
without attention to format spacing, with mistakes corrected as they occur, and finally passed through the Format
Generator to create a correctly formatted, edited, and line-fed on either rolled or fanfold paper tape.

DECUS NO. 5/8-51, CHARACTER PACKING AND UNPACKING ROUTINES

ASCII characters may be packed two to a word and recovered. Control characters are also packable but are
preceded by a 37 before being packed into the buffer. The two programs total 663 1 0 registers.
The program occupies 72 1 0 registers.
DECUS NO. 5/8-54, TIC-TAC-TOE LEARNING PROGRAM - T 3

This program plays Tic-tac-toe, basing its moves on stored descriptions of previously lost games. The main program
is written in FORTRAN. There is a short subroutine written in PAL II used to print out the Tic-tac-toe board. The
program comes already educated with about 32 lost games stored. Requires FORTRAN Object Time System.

DECUS NO. 5/8-56, FIXED POINT TRACE NO. I

A minimum size monitor program which executes the user's program one instruction at a time and reports the
contents of the program counter, the octal instruction, the contents of the accumulator and link, and the contents
of the effective address by means of the ASR-33 Teletype. Storage Requirements: two pages.

DECUS NO. 5/8-57, FIXED POINT TRACE NO. 2

Similar to Fixed Point No. 1, except that the symbolic tape provided has a single origin setting instruction of
(6000). Any four consecutive memory pages can be used, with the exception of page zero, by changing this one
instruction.

DECUS NO. 8-58, ONE-PAGE DECTAPE ROUTINE (522 CONTROL)

A general-purpose program for reading, writing, and searching of magnetic tape. This program was written for the
Type 552 Control. It has many advantages over both of the standard DEC routines and also over, the DECUS No.
5-46. The routines are one page long and can be operated with the interrupt on or off. The DEC program delays the
calling program while waiting for the unit and movement delays to time out. This routine returns control to the
calling program. This saves 1/4 second every time the tape searches forward, and half that time when it reverses. In
addition, it will read and write block 0,. This program is an advantage over the previous one-page routines in that it
allows interrupt operations, doesn't overflow by one location, interrupts the end zone correctly and not as an error,
and provides a calling sequence identical to the DEC program.

7-16

DECUS NO. 8-60, SQUARE ROOT FUNCTION BY SUBTRACTION REDUCTION
A single precision square routine using EAE. This routine is usually faster than the DEC routine and can easily be
modified for double precision calculation at only twice the computation time.

DECUS NO. 8-61, IMPROVEMENT TO DIGITAL 8-9 F SQUARE ROOT
An improved version of the DEC Single Precision Square Root Routine (without EAE). Saves a few words of
storage and execution is speeded up by 12 per cent.

OECUS NO. 8-62, HIGH-SPEED READER OPTION FOR FORTRAN COMPILER
Program modification that allows the PDP-8 FORTRAN Compiler to read source tapes through the high-speed
reader, and punch on the ASR-33. The program is loaded in over the compiler. It can be punched on an extension
of the compiler tape so that, by depressing the CONTINUE key, it can be read in immediately following the
compiler.

DECUS NO. 8-65, A PROGRAMMED ASSOCIATIVE MULTICHANNEL ANALYZER
The program describes the use of a small computer as an associate analyzer with special reference to the PDP-8. The
advantages and limitations of the method are discussed in the write-up, and general program algorithms are
presented.

DECUS NO. 8-68 a LABEL for PDP-8, ALP PROGRAM
The ALP Program punches labels for paper tapes. When a key is stuck on the on-line Teletype keyboard, no echo is
performed, but the computer outputs a few characters to the Teletype punch which form the outline of the
character associated with the key.
The character outlines have a fixed width of 5 lines of tape, followed by 3 blank lines for separation between
characters; all 8 columns of the paper tape are used to provide the maximum height of character outlines.

DECUS NO. 5/8-69, LESQ29 and LESQll
The purpose of the program is to fit the best sequences of parabolas to a given 400-point parabola least squares fit
to approximate a given data curve. Approximately 400 individual parabolas are computed.

DECUS NO. 8-70, EAE ROUTINES FOR FORTRAN OPERATING SYSTEM (DEC-08-CFA3)
These are two binary patches to the FORTRAN Operating System which utilizes the Type 182 EAE hardware for
single precision multiplication and normalization, replacing the software routines in FOSSIL (the operating
system). The binary tape is loaded by the BIN Loader after FOSSIL has been loaded. Execution time of a
Gauss-Jordan matrix inversion is reduced by approximately 30%.
Other Programs Needed: FORTRAN Operating System (DEC-08-CFA3-PB), dated March 2, 1967.

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DECUS NO. 8-72, MATRIX INVERSION - REAL NUMBERS

The program inverts a matrix, up to size 12 x 12, of real numbers. The algorithm used is the Gauss-Jordan method.
A unit vector of appropriate size is generated internally at each stage. Following the Gauss sweepout, the matrix is
shifted in storage, another unit vector is generated, and the calculation proceeds.
Other Programs Needed: FORTRAN Compiler and FORTRAN Operating System.
Storage: This program uses essentially all core not used by the FORTRAN Operating System.
Execution time: Actual computation takes less than 10 seconds. Data read-in and read-out may take up to five
minutes.

DECUS NO. 8-73, MATRIX INVERSION - COMPLEX NUMBERS

The program inverts a matrix, up to size 6 x 6, of complex numbers. The algorithm used is the Gauss-Jordan
method, programmed to carry out complex number calculations. A unit vector of appropriate size is generated
internally. Following the Gauss sweep-out, the matrix is shifted, another unit vector is generated, and the
calculation proceeds. The print-out of the matrices uses the symbol J to designate the imaginary part; e.g., A= a+
jb.
Other Programs Needed: FORTRAN Compiler and FORTRAN Operating System.
Storage: This program uses essentially all core not used by the FORTRAN Operating System.
Execution Time: Actual computation takes less than 10 seconds. Data read-in and read-out may take up to five
minutes.

DECUS NO. 8-74, SOLUTION OF SYSTEM OF LINEAR EQUATION: AX= B, BY MATRIX INVERSION AND
VECTOR MULTIPLICATIONS

This program solves the set of linear algebraic equations AX = B by inverting matrix A, using a Gauss-Jordan
method. When the inverse matrix has been calculated, it is printed out. At that point, the program requests the
B-vector entries. After read-in of the B-vector, the product is computed and printed out. The program then loops
back to request another B-vector, allowing the system to solve many sets of B-vectors without the need to invert
matrix A again. Maximum size is 8 x 8.
Other Programs Needed: FORTRAN Compiler and FORTRAN Operating System.
Storage: This program uses essentially all core not used by the FORTRAN Operating System.
Execution Time: Actual computation is less than 10 seconds. Data read-in and read-out may take up to five
minutes.

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DECUS NO. 8-75, MATRIX MULTIPLICATION - INCLUDING CONFORMING RECTANGULAR MATRICES
This program multiplies two matrices, not necessarily square but which conform for multiplication.
Other Programs Needed: FORTRAN Complier and FORTRAN Operating System.
Storage: This program uses essentially all core not used by the FORTRAN Operating System.
Execution Time: Actual computation takes less than 10 seconds. Data read-in and read-out may take up to five
minutes.

DECUS NO. 8-76, PDP NA VIG 2/2
This program utilizes the output of the U.S. Navy's AN/SRN-9 satellite navigation receiver to obtain fixes. This
program except for some details of input and output, follows very closely NAVIG 2 written for the IBM 1620,
which, in turn, is derived from the TRIDON program written at the Applied Physics Laboratory of Johns Hopkins
University for the IBM 7090.
PDP NA VIG 2/2 is written in PAL III for 4096-core machine using the ASR-33. Floating point numbers using two
12-bit words as mantissa and one 12-bit word as exponent are employed. The accuracy is slightly less than that when
using 7 decimal digits per word.
DECUS NO. 8-77, PDP-8 DUAL PROCESS SYSTEM
The purpose of this system is to expedite the programming of multiprocessing problems on the PDP-8. It maximizes
both the input speed and the portion of real time actually used for calculations by allowing the program to run during
the intervals between issuing I/O commands and the raising of the device flag to signal completion of the command.
The technique also allows queuing of input data or commands so that the user need not wait while his last line is
being processed, and so that each line of input may be processed as fast as possible regardless of its length. The
system uses the interrupt facilities, and has about 0.1 % overhead on the PDP-8.

This method is especially useful for a slower machine where the problem may easily be calculation-limited, but
would, without such a system, become I/O Bound.
The system requires 600 8 registers for two TTY s plus buffer space. Several device configurations are possible.

DECUS NO. 8-78, DIAGNOSE: A VERSATILE TRACE ROUTINE FOR THE PDP-8 COMPUTER WITH EAE
This trace routine will track down logical errors in a program (the sick program). Starting at any convenient
location in the sick program, instructions are executed, one at a time, and a record of all operations is printed out
via the Teletype. To avoid tracing proven subroutines, an option is provided to omit subroutine tracing. The
present routine is significantly more versatile than two other trace routines in the DECUS library (DECUS Nos.
8-56 and 8-57 - Biavati) for the PDP-8 in that it is able to trace sick programs containing floating-point, extended
arithmetical, and a variety of input-output instructions. Diagnose is, however, at a disadvantage compared with

7-19

Biavati's routines in requiring more memory space than his first one (DECUS No. 8-56) (five pages as opposed to
two) and in not possessing the trace-suppression features of his second one (DECUS No. 8-57). The mode of
operation of Diagnose is quite different from that of the trace routines of Biavati.
Minimum Hardware: PDP-8 with EAE
Other Programs Needed: Floating Point Package needed for floating point tracing.
Storage: 5(4) pages of memory.
Miscellaneous: Program is relocatable.
DECUS NO. 8-79, TAC-TAC-TOE (TRINITY COLLEGE VERSION)

This TIC-TAC-TOE game is programmed, using internal logic, so that the computer will either win or stalemate, but
not lose a game. Either the player or the computer may choose to go first. At the termination of a game, the
program restarts for the next game by typing anew the grid code to be followed.

DECUS NO. 8-80, DETERMINATION OF REAL EIGENVALUES OF A REAL MATRIX

This is a two-part program for determining the real eigenvalues of a real-valued matrix. The matrix does not have to
be symmetric. Part I uses the power method of iterating on an eigenvector to determine the largest eigenvalue of
the matrix. Part II then deflates the matrix using the results of part I so as to produce a matrix of order one less
than that solved for in Part I. Part I can then be reloaded, and the next eigenvalue in line may be calculated. In this
manner, all the real eigenvalues may be computed in order.

DECUS NO. 5/8-83A AND B, OCTAL DEBUGGING PACKAGE (WITH AND WITHOUT FLOATING POINT)

This program is an on-line debugger which will communicate with the operator through the ASR-33 Teletype. It
allows register examination and modification, octal dumping, binary punching, multiple and simultaneous
breakpoints, starting a program, and running at a particular location with preset AC link. ODP is completely
relocatable at the beginning of all pages except page zero, and is compatible with the PDP-5, the PDP-8, and the

PDP-8/S.
Requirements: The high version of ODP requires locations 7000-7577. The low version requires locations
0200-0777. All versions will require three pages. Also, location 0002 is used for a breakpoint pointer to ODP.
Equipment: The standard PDP-8 with ASR-33 Teletype is required. A highspeed punch is optional.

DECUS NO. 5/8-85, SET MEMORY EQUAL TO ANYTHING

This program will preset all locations to any desired settings. Thus, combining a memory clear,- set memory equal to
HALT, etc, into a single program. The program is loaded via the switch registers into core.

7-20

DECUS NO. 5/8-126, CUMULATIVE GAUSSIAN DISTRIBUTION CURVE FITTING
This is a curve fitting program that will take a set of any number of points with any spacing describing a cumulative Gaussian distribution and determine the mean and standard deviation by an iterative least squares differentialcorrection technique. The mean square error of the final fitted curve is also computed. The program is coded in
PDP-8 FORTRAN.

DECUS NO. 8-133, FIRST ORDER KINETICS
First order kinetic processes are common in chemistry and in other areas. This program accepts up to 42 data
points, calculates the rate constant and intercept by the method of least squares, and gives therms deviation, the
correlation coeffecient, and an estimate of the error in slope. It permits graphical (CRT) examination of deviations
from the least squares line and iteration to a "best" infinity value. It also provides options for plotting the
deviation between observed and calculated quantities on a CRT, and may be used in other cases in which one
wishes to correlate the natural logarithm of one quantity with another, as in linear free energy relationships.

DECUS NO. 8-134, LSQ: LEAST SQUARES SUBROUTINE
The subroutine calculates the slope and intercept for the equation Yj = mxj + b by the method of least squares. It
also returns the ms deviation of y, the correlation coefficent, and an estimate of the error in the slope. The calculated values of y and the differences between the given and calculated values are also available on return from the
subroutine.
Other Programs Needed: FLOAT, floating point interpreter "C" - (DEC-08-YQ3B-PB)

DECUS NO. 8-136, FOURIER TRANSFORM PROGRAM IN FORTRAN II
The program, written in PDP-8 FORTRAN II, performs the discrete Fourier Transform of a function defined over
N(N<200) evenly spaced points. I/O is via the ASR-33. The program requests the number of function points, then
that number of function values, and then prints out the values of the sine and cosine components of the function at
each defined harmonic. A conventional (not Cooley-Tukey) algorithm is used, since I/O time relative to computing
time is significant.

DECUS NO. 8-143, FFTS-R: FAST FOURIER TRANSFORM SUBROUTINE FOR REAL VALUED FUNCTIONS
This subroutine computes the Fast Fourier Transform (FFT) or its inverse of a data sequence which has been
stored in core. It will accommodate up to 2048 time samples, and will transform that number in under 5 seconds.
Minimum Hardware: PDP-8, PDP-8/I, or PDP-12 with EAE

DECUS NO. 8-144, FFTS-C: FAST FOURIER TRANSFORM SUBROUTINE FOR COMPLEX DATA
FFTS-C enables computation of the Discrete Fourier Transformation in a minimum amount of time. By using the
Cooley-Tukey algorithm, up to 1024 points may be transformed in only 4. 5 seconds, introducing a reduction of 99
percent in computation time.
Minimum Hardware: PDP-8, PDP-8/I, or PDP-12

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DECUS NO. 8-192, TALC (TAYLOR'S ALGEBRAIC LINEAR CALCULATOR)

TALC is a general-purpose calculator designed to evaluate a general algebraic equation, given all quantities involved
in the equation. In effect, TALC turns any of the family-of-eight computers into a powerful desk calculator capable
of evaluating complex algebraic, trigonometric, and logarthmic functions. In addition, TALC utilizes the concept of
"idiot-proofing" to virtually eliminate the possibility of an operator error invalidating the equation. Thus, TALC is
easy to use and presents unlimited possibilities in any field where fast and accurate calculations are required.
Minimum Hardware: 4K PDP-8 or PDP-12 High-Speed Reader, DF32 Disk File, and ASR-33/35

DECUS NO. 8-195, POLY BASIC

POLY BASIC is a compiler and operating stand-alone system designed for the PDP-8 family. It has a total user
program storage of 32K characters in which the disk is utilized. Some of the features of the compiler are:
a. It has all BASIC system commands.
b. It has all BASIC operations.
c. It contains all built-in functions except TAN.
d. Its accuracy is 1 part in 2 2 3 rather than 1 part in 2 3 5 , because of word size difference.
e. Maximum program size is 6144 characters as in regular (Dartmouth) BASIC.
f. Maximum usable statement number 4095 rather than 99999.
g. Maximum array space is 3600 characters, and maximum number of statements is 330; however, these can
be traded off against one another at the rate of 25 array elements per statement.
h. There are no matrix operations.
i. The argument "EDIT resequence" is implemented, and the command "EDID" renumbers the user file from
line number 100 in steps of 10.
j. There is a set of error messages to signal compilation errors and a set for execution errors.

Minimum Hardware: PDP-8 or PDP-12 with DECtape, DF32 Disk, RF08 Disk, or LINCtape

DECUS NO. 8-202, PLOT

PLOT will plot data points on a graph, calculate and plot a linear, least squares regression line, and print out the
coefficient of correlation, the equation of the regression line, and other pertinent parameters.
Minimum Hardware: 4K PDP-8 or PDP-12 with a Houston Instrument Complot Plotter Model 6650, DP-1-1, or
equivalent

7-22

DECUS NO. 12-2, PDP-12 UTILITY AND DATA REDUCTION PROGRAMS

Contains a variety of programs written for the classic LINC or LINC-8 and modified to run in the PDP-12. Included
are data reduction programs which perform autocorrelation, fourier analysis, power spectral analysis, and
convolution. Utility programs allow selected blocks of LINCtape to be searched, compared, or typed out. Also
included are programs which allow the user to convert LAP-4 or LAP-6 manuscripts into LAP6-DIAL or to
disassemble binary code into LAP6 or LAP6-DIAL source. The current version of this tape contains binary and/or
source for the programs listed below. Also listed are the original authors. Documents, but no listings, are available
from DECUS.
FREQAN
AUTOCOR
QAFILTER
FFOURIER
FF SAMPLE
DATAM
FRQANA
TAPEDUMP
SEARCH
COMPAR
COMPARE
LAP4-6
BINLAP6
L8SIMO
LAP4Q+A
DSCTABLE
PARAMS
DIV SUB
SPF LT
QIKDIV
RANDOM
NU INDEX

SIMONS
HANCE
GLAESER
BRYAN
BRYAN
HANCE
ENGEBRETSON
LANAHAN
STEIN
DAVISSON
NICHOLS
BJERKE
BJERKE
LANGBEIN
McDONALD
OVERTON
NICHOLS
STEIN
DILL
HANCE
LEWIS
CLAYTON

DECUS NO. 12-3, 8K OPERATING SYSTEM
This modification of DECUS NO. L-80 adapts it to run on the PDP-12.
DECUS NO. 8-203, ALPHA
ALPHA is used for titling graphs on the plotter. It can be used in conjunction with DECUS NO. 8-202.
Minimum Hardware: 4K PDP-8 with a Houston Instrument Complot Plotter Model 6650, DP-1-1, or equivalent
Storage Requirement: 2, 10, 11, 12, 20-167, 200-3654, 4000-777 is reserved for storage.
Restriction: When used in conjunction with PLOT (DECUS No. 8-202), extended memory is required.
DECUS NO. FOCAL-14, LEAST SQUARES FIT TO A STRAIGHT LINE
This is a program using the principle of least squares to fit a straight line to a set of up to 35 experimental data
points.

7-23

The program requires one pass of the data. At the end of the pass the output gives the values of the slope and the
intercept of the straight line equation. In addition, the calculated values of the experimental data based on the
straight line equation are pointed out. Finally, the program gives the value of R which is a criterion of fitness of
equation to the input data.
DECUS NO. FOCAL-15, LEAST SQUARES FIT TO A CUBIC POLYNOMIAL
This is a program using the method of least squares to fit a cubic polynomial to a set of experimental data. The
program demands two passes of the data for its completion; however, the coefficients of the polynomial are
outputted after the first pass, and, at the end of the second pass, the output gives the value of R which is a criterion
of fitness and gives the calculated values of the experimental data based on the cubic polynomial.
In addition, a section of the program can be used as a self-contained program for solution of a set of N by N linear
equations.
DECUS NO. FOCAL-16, ONE-SAMPLE STATISTICS, TWO-SAMPLE STATISTICS, WELCH PROCEDURE;
ONE-WAY ANALYSIS OF VARIANCE; SHEFFE'S CONTRAST BETWEEN MEANS
A three part program used to perform one-sample and two-sample statistics, Welch Procedure; One-way Analysis of
Variance: and Sheffe's Contrast Between Means, which allows one to investigate more thoroughly the source of the
difference between group means.
DECUS NO. FOCAL-17, FOCAL: HOW TO WRITE NEW SUBROUTINES AND USE INTERNAL ROUTINES
The aim of this document is to help the user to code specific routines in FOCAL so that his dialect of FOCAL can
be applied to his application (without being forced to understand in detail all the working of FOCAL). In this way,
perhaps, each user can make his particular dialect of FOCAL "perfect".
It is assumed that the reader has a basic knowledge of PDP-8 processor instructions and PAL mnemonics, as well as

a familiarity with the Floating Point Package. In addition, he should be familiar with the FOCAL language.
This document is an attempt to explain how user-developed software can be interfaced with the basic FOCAL
package, without requiring the user to spend valuable time trying to understand all of its detailed workings. Section
II deals with a general description of how FOCAL works. Section III is concerned with the philosophy of the
language; and the last few sections are technically oriented toward helping the user actually code his additions.
Several examples and ready-coded routines which may be used to simplify the user's problems are included.

DECUS NO. FOCAL-25, PAYROLL CALCULATIONS (CALIFORNIA, 1968)
This routine is used to calculate payrolls. It is based on the California State Unemployment Insurance rate, FICA
rate, and withholding tax.
This program could be modified easily to fit the rules of any particular state. If some of the pay ranges would not
be used, they could be omitted from the two tables, making more room for other routines, such as providing
running totals on gross pay, deductions, and net pay.

DECUS NO. FOCAL-26, CURVE FITTING
This program finds the best curve of a set of points. There are three types of curves involved:
Exponential Curve Y = AeBX

7-24

The variables solved for are A and B. The function is reduced to linear form by logarithms: LOGY= BX+ LOG A.
A table of values is formed and solved simultaneously to get the values of A and B.
Power Curve Y = AX N
This function is reduced to linear form: LOG Y = N LOG X + LOG A. Once a table of values is made, it is solved
simultaneously for A and N.
Linear Line Y = MX + B
A table is made and solved simultaneously for the value of M and B.

DECUS NO. FOCAL-33, SQUARE MATRIX MULTIPLY
The arduous task of multiplying two square matrices is quickly done by this FOCAL Matrix Multiplication routine.
The user inputs "N", indicating the number of rows and columns each matrix will have. The computer then
requests input of the elements of the two matrices. The result of the multiplication is typed out in an
understandable matrix-like format.
Notable characteristics of this program are:
a. It is expressed in only five lines of FOCAL script so that it loads quickly.
b. It will process matrices of varying dimensions. Size of each matrix is limited only by memory capacity. (In
4K FOCAL the limit is about 6 rows and columns.)
c. Because it inputs and outputs the matrix values in a matrix-like format, input transcription errors are less
likely to occur.

DECUS NO. FOCAL-37, Nth DEGREE POLYNOMIAL DATA POINT FITTING ROUTINE, Nth DEGREE
POLYNOMIAL DAT A POINT FITTING ROUTINE WITH RMS ERROR
a. Nth Degree Polynomial Data Point Fitting Routine - This program accepts the x- and y-coordinates for an
unlimited number of data points and calculates for the equation

the coefficients AN which best fit the equation to the data points. The fitting criterion is "least squares". The
program allows the user to select the degree, N, of the fitting equation. N may be as large as 7.
b. Nth Degree Polynomial Data Point Fitting Routine with RMS Error - This program is the same as Nth
Degree Polynomial Fitting Routine except that it calculates the RMS error between they-coordinates of the data
points and the evaluated fitting equation. It will accept only a limited number of data points and the maximum
equation degree allowed is inversely related to this number.

DECUS NO. FOCAL-40, SIMPLE CHI-SQUARE TEST
The program will type out the data matrix and cell contents. Each cell will contain two values, 0 = xxx.xxx and E =
xxx.xxx. The "O=" number is the "OBSERVED" value which was typed in by the user. The "E=" value is the

7-25

expected value calculated by the program. The program will also type out row sums (RS=) and column sums
(CS=), and the grand total (T= ). The last line of output will be "X2= "and "DF= ". These are the CHI-SQUARE
and degrees of freedom.

DECUS NO. L-11, DATUMS
DATUMS is a revision of an addition to DAT AM by James Hance contained in the general library supplied with the
LINC-8 computer. This program has retained all the features of DA TAM. Some of the original routines have been
changed in order to eliminate undesired features. In addition, DATUM8 has the ability to multiply, subtract, and
display the data with two cursors. The data not included between the cursors can be suppressed, allowing, for
instance, integration between definite limits. The program has been recoded to facilitate future modifications.
Minimum Hardware: LINC (2K) or LINC-8

DECUS NO. L-60, FORTRAN WITH LINCTAPE
The system adapts 4K PDP-8 FORTRAN to make use of the magnetic tape facility of the basic LINC-8 computer.
FORTRAN programs can be called from the left-hand tape (unit 0) by statements in the FORTRAN program in
the core; data can be stored and recalled by WRITE and READ statements, using the right-hand tape (u~it I).
The programs may be called in any order, and may be read in at less than full length in order to leave data in core.
Data can l;>e transferred to and from tape in blocks of any length which may be chosen to correspond with program
variables. Incorporation of the program-calling facility does not involve any sacrifice of core space for program or
data; use of the data transfer facilities uses from half to one page of core.
The system includes a modified, improved version of SYMBOL PRINT, increases the maximum length of the
statement number tables, and corrects some errors in the compiler.
Other Programs Needed: PDP-8 FORTRAN System (DEC-08-AFCO)
Source Language: PAL III

DECUS NO. L-80 AND 12-3, 8K OPERATING SYSTEM
The 8K Operating System was developed at the University of Michigan (Cooley Electronics Lab). It is a
two-tape-resident operating system for the LINC-8 with a special 33ASR reader modification. It allows a user to
enter and edit programs from the Teletype keyboard, store them in files on magnetic tape, assemble or compile
these files into PDP-8 machine language, and run the resulting program. These operations are done entirely from
the Teletype keyboard without the use of paper tapes or manipulation of the switches. One of the language
translators is the DEC 8-K FORTRAN system (February 1969 version).
The 8K Operating System consists of 3 system components: a filing system, a system of loaders for running
programs, and a command language interpreter. A file is a collection of information (which the user generates) in
machine-readable form; for example, it may be the set of characters comprising a FORTRAN program. Using the
filing system, the user may name this set of characters and store it on magnetic tape. To use the file containing the
program (for example, in a FORTRAN compilation) the user need only refer to the file name and the system will
handle all bookkeeping necessary to communicate the file to the FORTRAN compiler. A user may change the
contents of files, destroy files, and copy files from other users' tapes. The assembler processes both LINC mode and
PDP-8 mode statements, assembling programs up to 8K in length. Six character alphanumeric symbols can be
defined; source listings, assembly listings, or abbreviated assembly listings may be (optionally) obtained on the
Teletype or, if present, the Line Printer. To facilitate the preparation of system programs and/or large programs,

7-26

conditional assembly pseudo ops are provided, along with a facility to preserve the tag table definitions from one
assembly to another, or to several others.

Upon loading, programs may be started automatically in either LINC or PDP-8 mode at any memory location
permanent file by means of a "SAVE" command.
The loading system contains two separate loaders, the absolute loader and the relocating loader. These loaders do
not load programs directly into core memory, but rather into a core memory image kept on magnetic tape. (This
intermediate step is necessary because of core space limitations and the flexibility desired of the loaders.) Both
loaders take their binary (and core image) input from the system files; both include provisions for changing and
viewing the contents of various core image locations.
The absolute loader operates on the binary output of either the MACR0-8 of PAL-III assemblers to produce a core
image. It is capable of merging an extant core image into the core image it is building. It will also page-relocate
binary input information to be within a different memory page from that for which it was assembled.
The relocating loader operates on FORTRAN compiler and SABR assembler output. It is the final part of the
3-part FORTRAN/SABR/Relocating Loader package, which allows the programmer to write programs for the
PDP-8 disregarding the memory addressing structure of the machine. After the loading process is complete, the core
image file containing the program is available to the user in -B, and may be saved or run immediately using the
"RUN" command.

The "RUN," command software is also part of the loading system. It allows execution of a program contained in a
core image file.

7.4 DIAGNOSTIC PROGRAMS

PDP-12 PROCESSOR TESTS
Maindec-12-DOAB Tests SKIPs and data handling (LINC mode).
These diagnostics test the LINC mode processor and memory control instructions.
PDP-12 TAPE CONTROL TESTS (TC12)
Maindec-12-D3AC Tests tape control logic and interregister transfers.
These diagnostics make use of the TCI 2 maintenance instructions to thoroughly test the tape control. After all
static tests are performed, data transfers and dynamic characteristics are tested.
PDP-12 DISPLAY TEST (VR12)
Maindec- l 2-D6BA Tests display system using DIS and DSC instructions.
The diagnostic tests both the VC 12 CRT display control and the VRI 2 CRT display oscilloscope.
PDP-12 REAL-TIME INTERFACE TEST (KW12)
Maindec-12-D8CB
This diagnostic thoroughly tests the KW 12-A Real-Time Interface.
PDP-12 A-D TEST (AD12)
Maindec-12-D6CB-Tests A-D converter and calibration.
This test verifies the logic of the AD 12 and allows checking and alignment of all 3 2 channels of the A-D converter.
Maindec-08-D03A-D Basic JMS and JMP Test
This is a diagnostic program for testing the JMP and JMS instructions of the PDP-8/1.

7-27

Maindec-08-D04B-D Random JMP Test
This program tests the JMP instruction of the PDP-12. Most of memory is used as a JUMP field with a random
number generator selecting each JUMP FROM and JUMP TO location.
Maindec-08-DOSB-D Random JMP-JMS Test
This program tests the JMS instruction of the PDP-12. Random FROM and TO addresses are selected for each test.
The JMP instruction is tested in that each test requires a JMP to reach JMS.
Maindec-08-D07B-D Random ISZ Test
This program tests the ISZ instruction of the PDP-12. An ISZ instruction is placed in a FROM location, and a TO
location contains the OPERAND. Part 1 of the program selects FROM, TO, and OPERAND from a random number
generator, with the option of holding any or all constant. Part 2 uses fixed set of FROM, TO, and OPERAND
numbers.
Maindec-08-DOAA-D Instruction Test (EAE) Part 3A
This program tests the Extended Arithmetic Element Type KE 12. The following instructions are tested: MQL,
MQA, SHL, LSR, ASR, NMI, SCA. An attempt is made to detect and isolate errors to their most basic faults and to
the minimum number of logic cards. Multiply and divide are tested by Maindec-08-DOBA-D.
Maindec-08-DOBA-D Instruction Test (EAE) Part 3B
Divide overflow detection hardware and divide and multiply hardware are tested by using a pseudo random-number
generator to produce the parameters for each test. A software simulated divide and multiply are used to test the
results of the hardware divide and multiply.
Maindec-08-D lAC-D Memory Power On/Off Test
This program is a Memory Data Validity Test to be used after a simulated power failure.
Maindec-08-DlLl-D Memory Checkerboard Test Low
Maindec-08-D 1L2-D Memory Checkerboard Test High
Tests memory for core failure on half-selected lines under the worst possible conditions for reading and writing. It
is used primarily for testing the operation of memory at marginal voltages.
Maindec-08-D 1CA-D Extended Memory Control Part 1
This program exercises and tests Extended Memory instructions CDF, CIF, RDF, RIF, RMF, and RIB, for proper
operation. Basically, this program tests the control section of the memory. Data is tested by tests
Maindec-08-D 1L1-D, Maindec-08-D 1L2-D and Maindec-08-D 1DA-D.

Maindec-08-DlDA-D Extended Memory Checkerboard Part 2
This preliminary program tests for core memory failures on half-selected lines under worst-case conditions of
reading and writing. It is used to test memory module X while running the program in memory module Y.

Maindec-08-D2PE-D Teletype Reader Test
This program tests performance of the Teletype Model 33 Perforated Tape Reader, using the reader to scan a
closed-top test page punched with alternating groups of character codes 000 to 377. Each character is tested for

7-28

bits dropped or gained while reading; each group of characters is checked for characters missed entirely or read
more than once.
Maindec-08-D2BA-D Exerciser for the Teletype Paper-Tape Reader
This exerciser program tests for the Teletype Paper-Tape Reader. Test tapes are read in a random start-stop fashion
and errors are reported on the Teletype printer.

Maindec-08-D2CA-D Teletype Punch Test
This program punches a test tape in a predetermined pattern. The tape passes directly from the Teletype punch to
the Teletype reader, which checks the pattern for accuracy.

Maindec-08-D2DA-D Teleprinter Test
This program tests the Teleprinter performance of the Teletype 33 Keyboard Printer. There are two parts to the
test, selectable by the operator. The first part tests keyboard input by immediately causing the character typed to
be printed for comparison. The second part tests continuous operation of the teleprinter by causing a line
consisting of the ASCII character set to be repeatedly printed. The latter also tests for correct functioning of the
interrupt after a character has been printed.
Maindec-08-D2GF-D High Speed Reader Test
This program tests performance of the Type 750 High-Speed Perforated-Tape Reader and control by scanning a
closed-loop tape for transmission accuracy. The reader control is tested for correct operation with the PDP-8
interrupt system.
Maindec-08-D2F A-D High Speed Reader Test (PR 12)
This is a diagnostic program for the Digitronics 2500, the PRl 2, and the PR8/I High-Speed Paper-Tape Readers.
The program is divided into three parts. The first is a test tape generator that punches test tapes for parts two and
three on the high-speed punch. Part two is a series of specific tests with module isolation provided for error
situations. Part three reads a preselected tape pattern with the choice of random or fixed block lengths and stalls
between blocks.
Maindec-08-D2GA-D High Speed Punch Test
This program consists of two separate tests. The first causes the PPl 2 and PP8/I High-Speed Paper-Tape Punch to
produce a tape containing a sequence of pseudo-random character codes. This tape is checked for accuracy, using
either the high-speed reader or the Teletype reader.
In the ~econd test, the character code represented by the setting SR4-l l is punched repeatedly. The switch setting
may be changed while the test is running.
Maindec-08-D6CB-D Calcomp Plotter Test
This program tests the CALCOMP or HOUSTON Plotters and their control. All control and plotting functions are
tested.
PDP-12 JMP SELF MAINDEC-12-DlBA-D
This program tests the ability of the read/write gates to switch rapidly between read and write.

7-29

PDP-12 Instruction Test 1 MAINDEC-12-DOBA
This program tests for the basic overall test of most of the LINC mode instructions.
PDP-12 Address Test (R/W Gate) MAINDEC-12-DlCA

This program tests the ability of the R/W gates to rapidly change addresses. It generates two random addresses,
loads these addresses with jumps to each other, and allows the jump sequence to continue until interrupted.
PDP-12 Memory Data Test (Float ls and Os) MAINDEC-12-DlEB

This program fl.oats a single one then a single zero through all of memory to evaluate data handling.
PDP-12 Memory Checkerboard MAINDEC-12-DlDA

Tests memory for core failure on half-select lines under the worst possible conditions for reading and writing. It is used
primarily for testing the operation of memory.

7-30

APPENDIX A
LINC MODE INSTRUCTIONS

The following table lists all LINC mode instructions and their mnemonics, octal codes, and execution times. Full
instruction descriptions are in Chapter 3.
Table A-1. LINC Mode Instructions
Function

Octal

Time (µs)

2000
1100

LAM

Add memory to AC (full address)
Add memory to AC (index class)
Ad~ AC to memory (sum also in AC)
Add link and AC to memory (sum also in AC)

1140
1200

3.2*
3.2*
3.2*
3.2*

MUL

MULTIPLY
Signed multiply

1240

1000

1300

3.2*
3.2*

4000
1040
1340

3.2
3.2*
3.2*

0240
0300
0340

1.6-6.4
1.6-6.4
1.6-6_.4

Mnemonic

ADD
ADD
ADA
ADM

LOAD

LDA
LDH

Load AC, full register
Load AC, half register
STORE (sum also in AC)

STC
STA
STH

Store and clear AC (full address)
Store AC (index class)
Store half AC
SHIFT/ROTATE

ROLN
RORN
SCRN

Rotate left N places
Rotate right N places
Scale right N places

*See Note at end of table.
A-1

Table A-1. LINC Mode Instructions (cont)

Mnemonic

Function

Octal

Time (µs)

0000
0016
0011
0040
6000
0006
0004
0024
0005

1.6
1.6
1.6
4.8
1.6*
1.6
1.6
1.6
1.6

1540
1600
1640

3.2*
3.2*
3.2*

0017

1.6

1440
1400

3.2*
3.2*

0440+N
0456
0450
0451
0452
0453
0454
0455
0400+N
0415
1500

1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
3.2*

0200

3.2

0014
0015
OIOO+N
0140

1.6
1.6-18.2
1.6**
3.2-23**

OPERATE
HLT
NOP
CLR
SET
IMP
DJR
ESF
SFA
QAC

Halt
No operation
Clear AC and LINC
Set register N to contents or register Y
Jump to register Y
Disable JMP return save
Enable Special Function
Special Function to AC
MQ transfer to AC
LOGICAL OPERATIONS

BCL
BSE
BCO
COM

Bit clear (any combination of 12-bits)
Bit set (any combination of 12-bits)
Bit complement (any combination of
12 bits)
Complement AC
SKIP

SAE
SHD
SNSN
SKP
AZE
APO
LZE
IBZ
FLO
QLZ
SXLN
KST
SRO

XSK

Skip next instruction if:
AC equals memory register Y
Right half AC unequal to specified half
of memory register Y
SENSE switch N is set
Unconditional skip
AC equals 0000 or 7777
AC contains positive number
Link bit equals 0
Between blocks on LINC tape
Add overflow is set
MQ low-order bit zero
External level N is low
Keyboard has been struck
Rotate memory register right one place;
then if bit 0 of Y equals 0, skip next
instruction
Index memory register Y, skip when
contents of Y equal 1777
INPUT/OUTPUT

ATR
RTA
SAMN
DIS
**See Note at end of table.
A-2

AC to relay buffer
Relay buffer to AC
Sample analog chan N
Display point on oscilloscope

Table A-1. LINC Mode Instructions (cont)

Mnemonic

Function

Octal

Time (µs)

DSC

Display character on oscilloscope
(2 x 6 matrix)

1740

4.8-56**

RSW
LSW
IOB

RIGHT SWITCH register to AC
LEFT SWITCH register to AC
bxecute mput/output control through
IO Bus
8 Mode to LINC Mode
MEMORY

0516
0517
0500

1.6
1.6
5.9

6141

4.25

LIP
LDP

Load instruction field buffer with N
Load data field register with N

0600
0640

1.6
1.6

IOB
RIP

Read instruction field

0500
6224

5.9

IOB
RDF

Read data field

0500
6214

5.9

IOB
RIB

Read interrupt buffer (Save Field)

0500
6234

5.9

IOB
RMF

Restore memory fields

0500
6244

5.9

0702
0700
0701
0706
0704
0705
0707
0703
0001
0021
0023
0416
0417

3.2**
3.2**
3.2**
3.2**
3.2**
3.2**
3.2**
3.2**
1.6
1.6
1.6
1.6
1.6

LINC

LINC TAPE
RDE
RDC
RCG
WRI
WRC
WCG
CHK
MTB
AXO
XOA
TMA
STD
TWC

Read one block into memory
Read and check one block
Read and check N consecutive
Write one block on tape
Write and·check one block
Write and check N blocks
Check one block of tape
Move tape toward selected block
AC to Tape Extended Operations Buffer
Extended Operations Buffer to AC
AC to TMA setup register
Skip if tape idle
Skip if tape word complete

*Indicates both direct and indirect addressing; add 1.6 µsec when indirect addressing is used.
**Indicates additional time depenaent on I/O device such as tape (Chapter 3 LINC Mode Instructions.)

A-3/A4

APPENDIX B
8-MODE INSTRUCTIONS

Table B-1. 8-Mode Memory Reference Instructions
Direct Addr.
Mnemonic
Symbol

Operation
Code

Indirect Addr.

States
Entered

Executi on
Time
(µs)

States
Entered

Execution
Time
(µs)

Operation

.ANDY

0000

F,E

3.2

F,D,E

4.8

Logical AND. The AND operation is performed between the
contents of memory location Y
and the contents of the AC. The
result is left in the AC, the original contents of the AC are lost,
and the contents of Y are restored. Corresponding bits of the
AC and Y are operated upon
independently. ACj A Yj ~ ACj

TADY

1000

F,E

3.2

F,D,E

4.8

Two's complement add. The contents of memory location Y are
added to the contents of the AC
in two's complement arithmetic.
The result of this addition is held
in the AC, the original contents
of the AC are lost, and the contents of Y are restored. If there is
a carry from AC0 , the link is
complemented.
AC+Y~AC

B-1

Table B-1. 8-Mode Memory Reference Instructions (cont)
Direct Addr.

Indirect Addr.

Mne-

Opera-

monic
Symbol

tion
Code

States
Entered

Execution
Time
(µs)

States
Entered

Execution
Time
(µs)

ISZ Y

2000

F,E

3.2

F,D,E

4.8

Increment and skip if zero. The
contents of memory location Y
are incremented by one. If the
resultant contents of Y equals
zero, the contents of the PC are
incremented and the next instructfon is skipped. If the resultant contents of Y do not
equal zero, the program proceeds
to the next instruction. The incremented contents of Y are restored to memory. If resultant Y
= 0, PC + 1 ~ PC.

DCA

3000

F,E

3.2

F,D,E

4.8

Deposit and clear AC. The contents of the AC are deposited in
core memory at address Y and
the AC is cleared. The previous
contents of memory location Y
are lost.

Operation

AC~Y

o~Ac

JMSY

4000

F,E

3.2

F,D,E

4.8

Jump to subroutine. The contents of the PC are deposited in
core memory location Y and the
next instruction is taken from
core memory location Y + 1.
PC+ 1 ~Y
Y + 1 ~PC

JMPY

5000

1.6

F,D

3.2

Jump to Y. Address Y is set into
the PC so that the next instruction is taken from core memory
address Y. The original contents
of the PC are lost.
Y~Pc

B-2

Table B-2. 8 Mode Group 1 Operate Microinstructions
Mnemonic
Symbol

Octal
Code

NOP
IAC

7000
7001

RAL

7004

RTL

7006

RAR

7010

RTR

7012

CML
CMA

7020
7040

CIA

7041

2,3

CLL
CLL RAL
CLL RTL
CLL RAR
CLL RTR
STL
CLA
CLAIAC
GLK
CLACLL
STA

7100
7104
7106
7110
7112
7120
7200
7201
7204
7300
7240

I
1,4
1,4
1,4
1,4
1,2
1
1,3
1,4

Sequence

1
2

Operation
No operation. Causes a 1.6 µs program delay.
Increment AC. The contents of the AC are incremented by one
in two's complement arithmetic.
Rotate AC and L left. The contents of the AC and the L are
rotated left one place.
Rotate two places to the left. Equivalent to two successive RAL
operations.
Rotate AC and L right. The contents of the AC and L are
rotated right one place.
Rotate two places to the right. Equivalent to two successive
RAR operations.
Complement L.
Complement AC. The contents of the AC are set to the one's
complement of its current contents.
Complement and increment accumulator. Used to ·form two's
complement number.
Clear L. The Lis cleared to contain a binary zero.
Shift positive number one left.
Clear Link, rotate two left.
Shift positive number one right.
Clear Link, rotate two right.
Set Link, the L is set to contain a binary one.
Clear AC. To be used alone or in OPR 1 combinations.
Set AC= 1.
Get link, Transfer L into AC 1 1 •
Clear AC and L.
Set AC = -1. Each bit of the AC is set to contain a binary one.

Table B-3. 8 Mode Group 2 Operate Microinstructions
Mnemonic
Symbol

Octal
Code

Sequence

Operation

HLT

7402

OSR

7404

SKP

7410
7420
7430
7440
7450

Halt. Stops the program after completion of the cycle in
process. If this instruction is combined with others in the OPR
2 group, the other operations are completed before the end of
the cycle.
OR with Right Switch register. The OR function is performed
between the contents of the RSW and the contents of the AC,
with the result left in the AC.
Skip, unconditional. The next instruction is skipped.
Skip if L=F 0.
Skip if L = 0.
Skip if AC = 0.
Skip if AC =F 0.

SNL
SZL
SZA
SNA

B-3

Table B-3. 8 Mode Group 2 Operate Microinstructions (cont)
Mnemonic
Symbol

Octal
Code

SZA SNL
SNA SZL
SMA

7460
7470
7500

SPA

7510

SMA SNL
SPA SZL
SMA SZA
SPA SNA
CLA
LAS
SZA CLA
SNACLA
SMACLA
SPA CLA

7520
7530
7540
7550
7600
7604
7640
7650
7700
7710

Sequence

Operation

1
2
2,3
1,2
1,2
1,2
1,2

Skip if AC= 0, or L = 1, or both.
Skip if AC =I= 0 and L = 0.
Skip on minus AC. If the AC contains a negative number, the
next instruction is skipped.
Skip on positive AC. If the AC contains a positive number, the
next instruction is skipped.
Skip if AC< 0, or L = 1, or both.
Skip if AC ~ 0 and if L = 0.
Skip if AC ~ 0.
Skip if AC ~ 0.
Clear AC. To be used alone or in OPR 2 combinations.
Load AC with SR.
Skip if AC = 0, then clear AC.
Skip if AC =I= 0, then clear AC.
Skip if AC < 0, then clear AC.
Skip if AC > 0, then clear AC.

Table B-4. 8 Mode Extended Arithmetic Element Microinstructions
Mnemonic
Symbol

Octal
Code

Sequence

Operation

MUY

7405

Multiply. The number held in the MQ is multiplied by the
number held in core memory location PC + 1 (or the next
successive core memory location after the MUY Command). At
the conclusion of this instruction the most significant 12 bits of
the product are contained in the AC and the least significant 12
bits of the product are contained in the MQ.

DVI

7407

NMI

7411

YxMQ~AC,MQ

B-4

Divide. The 24-bit dividend held in the AC (most significant 12
bits) and the MQ (least significant 12 bits) is divided by the
number held in core memory location PC + 1 (or the next
successive core memory location following the DVI instruction). At the conclusion of this instruction the quotient is held
in the MQ, the remainder is in the AC, and the L contains a 0. If
the L contains a 1, divide overflow occured so the operation
was concluded after the first cycle of the division.
AC,MQ ..;- Y ~ MQ.
Normalize. This instruction is used as part of the conversion of
a binary number to a fraction and its exponent for use in
floating-point arithmetic. The combined contents of the AC and
the MQ are shifted left by this one instruction until the content
of AC 0 is not equal to the content of AC 1 , thus forming the
fraction. Zeros are shifted into vacated MQ 11 positions for each
shift.

Table B-4. 8 Mode Extended Arithmetic Element Microinstructions (cont)
Mnemonic
Symbol

Octal
Code

Sequence

SHL

7413

ASR

7415

LSR

7417

Operation
At the conclusion of this operation, the step counter contains a
number equal to the number of shifts performed. The content
of Lis lost.
ACj-+ ACr 1
AC 0 -+ L
MQo-+ AC11
MQj-+ MQj- 1
0-+ MQ 11 until AC0 =I= AC 1
Shift left. This instruction shifts the combined contents of the
AC and MQ to the left one position more than the number of
positions indicated by the contents of the core memory at
address PC + 1 (or the next successive core memory location
following the SHL instruction). During the shifting, zeros are
shifted into vacated MQ 11 positions. Shift Y + 1 positions as
follows:
ACj-+ ACj- 1
AC 0 -+ L
MQ 0 -+ AC 11
MQj-+ MQj- 1
0-+ MQ11
Arithmetic shift right. The combined contents of the AC and
the MQ are shifted right one position more than the number
contained in memory location PC + 1 (or the next successive
core memory location following the ASR instruction). The sign
bit, contained in AC 0 , enters vacated positions, the sign bit is
preserved, information shifted out of MQ 11 is lost, and the L is
undisturbed during this operation. Shift Y + 1 positions as
follows:
AC 0 -+ AC 0
ACj-+ ACj + 1
AC 11 -+ MQo
MQj-+ MQj + 1
Logical shift right. The combined contents of the AC and MQ
are shifted right one position more than the number contained
in memory location PC+ 1 (or the next successive core memory
location following the LSR instruction). This instruction is
similar to the ASR instruction except that zeros enter vacated
positions instead of the sign bit. Information shifted out of
MQ 11 is lost and the L is undisturbed during this operation.
Shift Y + 1 positions as follows:
0-+ AC0
ACj-+ ACj + 1
AC 11 -+ MQ 0
MQj-+ MQj + 1

B-5

Table B-4. 8 Mode Extended Arithmetic Element Microinstructions (cont)
Mnemonic
Symbol

Octal
Code

Sequence

Operation

MQL

7421

SCA

7441

SCL

7403

MQA

7501

CLA

7601

CAM

7621

Load multiplier quotient. This instruction clears the MQ, loads
the contents of the AC into the MQ, then clears the AC.
0--+ MQ
AC-+ MQ
0--+ AC
Step counter load into accumulator. The contents of the step
counter are transferred into the AC. The AC should be cleared
prior to issuing this instruction or the CLA instruction may be
combined with the SCA to clear the AC, then effect the
transfer.
SC V AC-+ AC
Step counter load from memory. Loads complement of bits 7
through 11 of the word in memory following the instruction
into the step counter.
Two's MB 7 - 1 1 --+ SC
PC+ 2--+ PC
Multiplier quotient load into accumulator. The contents of the
MQ are transferred into the AC. This instruction is given to load
the 12 least significant bits of the product into the AC
following a multiplication or to load the quotient into the AC
following a division. The AC should be cleared prior to issuing
this instruction or the CLA instruction can be combined with
the MQA to clear the AC then effect the transfer.
MQV AC--+AC
Clear accumulator. The AC is cleared during sequence 1,
allowing this instruction to be combined with other EAE
instructions that load the AC during sequence 2 (such as SCA
and MQA).
0--+ AC
Clear accumulator and multiplier quotient.
CAM=CLAMQL

B-6

1,2

APPENDIX C
1/0 BUS INSTRUCTIONS

In the 8 mode these instructions are given directly, whereas in the LINC mode they must be preceded by the
instruction IOB (0500).

Table C-1. IOT Instructions
Mnemonic

Octal

Operation

Program Interrupt
ION

6001

IOF

6002

Turn interrupt on and enable the computer to respond to an interrupt
request. When this instruction is given, the computer executes the next
instruction, then enables the interrupt. The additional instruction allows exit
from the interrupt subroutine before allowing another interrupt to occur.
Turn interrupt off; i.e., disable the interrupt.

High-Speed Perforated-Tape Reader and Control Type PR12
RSF
RRB

6011
6012

RFC

6014

Skip if reader flag is a 1.
Read the contents of the reader buffer and clear the reader flag. (This
instruction does not clear the AC). RB V AC 4 - 1 1 _,. AC4 -1 1
Clear reader flag and reader buffer, fetch one character from tape and load it
into the reader buffer, and set the reader flag when done.

High-Speed Perforated-Tape Punch and Control Type PP12
PSF
PCF
PPC

6021
6022
6024

PLS

6026

Skip if punch flag is a 1.
Clear punch flag and punch buffer.
Load the punch buffer from AC 4- 11 and punch the character. (This
instruction does not clear the punch flag or punch buffer).
AC 4 - 11 V PB~ PB
Clear the punch flag, clear the punch buffer, load the punch buffer from
AC 4 - 11 , punch the character, and set the punch flag when done.

C-1

Table C-1. IOT Instructions (Cont)
Mnemonic

Operation

Octal

Teletype Keyboard/Reader
KSF
KCC
KRS

6031
6032
6034

KRB

6036

Skip if keyboard flag is a 1.
Clear AC and clear keyboard flag.
Read keyboard buffer static. (This is a static command in that neither the
AC nor the keyboard flag is cleared.)
TTI V AC4-11 ~ AC4-11
Clear AC, clear keyboard flag, and read the contents of the keyboard buffer
into AC 4 - 1 1.
TTO VAC 4-11 ~ AC4-11

Teletype Teleprinter/Punch

TPC

6041
6042
6044

Skip if teleprinter flag is a 1.
Clear teleprinter flag.
Load the TTO from AC 4 - 11 and print and/or punch the character.

TLS

6046

Load the TTO from AC 4-11 , clear the teleprinter flag, and print and/or
punch the character.

TSF
TCF

Power Fail/Restart Type KP 12
SPL

6102

Skip if power is low.

Memory Extension Control Type MC12

CDF

62Nl

CIF

62N2

RDF
RIF
RIB

6214
6224
6234

RMF

6244

Change to data field N. The data field register is loaded with the selected
field number (0 to 7). All subsequent memory requests for operands are
automatically switched to that data field until the data field number is
changed by a new CDF instruction.
Prepare to change to instruction field N. The instruction buffer register is
loaded with the selected field number (0 to 7). The next JMP or JMS
instruction causes the new field to be entered.
Read data field into AC 6 _8 • Bits 0-5 and 9-11 of the AC are not affected.
Same as RDF except reads the instruction field.
Read interrupt buffer. The instruction field and data field stored during an
interrupt are read into AC 6 - 8 and AC 9 - 11 respectively.
Restore memory field. Used to exit from a program interrupt.

Incremental Plotter and Control Type XY12
PLSF
PLCF
PLPU
PLPR
PLDU
PLDD

C-2

6501
6502
6504
6511
6512
6514

Skip if plotter flag is a 1.
Clear plotter flag.
Plotter pen up. Raise pen off paper.
Plotter pen right.
Plotter drum (paper) upward.
Plotter drum (paper) downward.

Table C-1. IOT Instructions (Cont)
Mnemonic

Octal

Operation

PLPL
PLUD
PLPD

6521
6522
6524

Plotter pen left.
Plotter drum (paper) upward. (Same as 6512).
Plotter pen down. Lower pen to paper.

Random Access Disk File Type DF32
DCMA

6601

OMAR

6603

DMAW

6605

DCEA
DSAC
DEAL

6611
6612
6615

DEAC

6616

DFSE

6621

DFSC

6622

DMAC

6626

Clears memory address register, parity error and completion flags. This
instruction clears the disk memory request flag and interrupt flags.
The contents of the AC are loaded into the disk memory address register and
the AC is cleared. Begin to read information from the disk into the specified
core location. Clears parity error and completion flags. Clears interrupt flags.
The contents of the AC are loaded into the disk memory address register and
the AC is cleared. Begin to write information into the disk from the specified
core location. Clears parity error and completion flags.
Clears the disk extended address and memory address extension register.
Skips next instruction if address confirmed flag is a 1 (AC is cleared).
The disk extended address extension registers are cleared and loaded with
the track data held in the AC.
Clears the AC, then loads the contents of the disk extended address register
into the AC to allow program evaluation. Skips next instruction if address
confirmed flag is a 1.
Skips next instruction if parity error, data request late, or write lock switch
flag is a zero. Indicates no errors.
Skips next instruction if the completion flag is a 1. Indicates data transfer is
complete.
Clears the AC, then loads contents of disk memory address register into the
AC to allow program evaluation.

Disk Control and Disk File Type RF08/RS08
DCMA

6601

DMAR

6603

DMAW

6605

DCIM
DSAC
DIML
DIMA
DFSC
DFSC

6611
6612
6615
6616
6621
6622

DMAC

6626

Clears memory address register, parity error and completion flags. This
instruction clears the disk memory request flag and interrupt flags.
The contents of the AC are loaded into the disk memory address register and
the AC is cleared. Begin to read information from the disk into the specified
core location. Clears parity and completion flags. Clears interrupt flags.
The contents of the AC are loaded into the disk memory address register and
the AC is cleared. Begin to write information into the disk from the specified
core location. Clears parity error and completion flags.
Clears the disk interrupt flag and memory address extension register.
Skips next instruction if address confirmed flag is a 1 (AC is cleared).
Accumulator to interrupt enables and memory extension register.
Status to AC.
Skip on error condition.
Skip next instruction if the completion flag is a 1. Indicates data transfer is
complete.
Clears the AC then loads contents of disk memory address register into the
AC to allow program evaluation.

C-3

Table C-1. JOT Instructions (cont)

Mnemonic

Octal

Operation

Disk Cartridge Memory Type RK8/RKO I
DLDC
DLDR

6732
6733

DLDW

6735

DCHP

6737

DRDA

6734

DRDC
DRDS
DCLS
DMNT

6736
6741
6742
6743

DLDA
DSKD
DSKE
DCLA

6731
6745
6747
6751

DRWC

6752

DLWC

6753

DLCA

6755

DRCA

6757

Loads the command register from the AC and then clears the AC.
Loads the track, surface, and sector address from the AC; the instruction then
clears the AC and starts to read data from the disk if command register bit 4 is
a 0.
Loads the track, surface, and sector address from the AC. The instruction
then clears the AC and starts to write on the disk if command register bit 4 is
a 0.
Loads the track, surface, and sector address from the AC. The instruction
then clears the AC and reads data and checks parity if command register bit 4
is a 0.
Clears the AC and then reads the Track Address Counter and surface/sector
counter into the AC.
Clears the AC and then reads the command register into the AC.
Clears the AC and then reads the status register into the AC.
Clears the status register.
Load maintenance register. This instruction loads the maintenance register
from the AC and carries out the operation specified. The bits will remain set
until DMNT is reissued with all AC bits cleared to 0.
Loads the disk address. This instruction is a maintenance operation.
Skip On Transfer Done flag equal to 0.
Skip when the error flag is set to I.
Clear All. This instruction clears the selected disk to Track 000 and then
clears all the control registers and status flags except the disk selection.
Transfer Done is set when the disk is positioned on Track 000.
Read word count register. This instruction clears the AC, then reads the
contents of the word count register into the AC.
Load word count register. This instruction loads the word count register from
the AC and then clears the AC.
Load current address register. This instruction loads the current address
register from the AC and then clears the AC.
Read current address register. This instruction clears the AC and then reads
the contents of the current address register into the AC.

Real Time Interface Type KW12A
CLSK
CLLR
CLAB
CLEN
CLSA
CLBA
CLCA

6131
6132
6133
6134
6135
6136
6137

Skip if Clock Interrupt condition exists
AC to Clock Control r~gister
AC to Clock Buffer-Preset register
AC to Clock Enable register
Clock Status to AC
Clock Buffer-Preset register to AC
Clock Counter to Buffer Preset register and AC.

Fixed-Interval Clock Type KWl 2-B, C
CSOF
CTOC
CTON

C-4

6131
6132
6134

Skip on clock flag.
Turn off the clock, clears the clock flag and disables the clock interrupt.
Turn the clock on and clears the flag.

Mnemonic

Operation

Octal

Fixed-Interval Clock Type KW12-B,C (cont)
CRUN

6135

Clock running. Turns on the clock, enables the clock interrupt, and clears the
clock flag. If the clock flag was set when the instruction was issued, it will
skip.

Automatic Line Printer and Control Type LP12
LSE
LCF
LLB
LSD
LCB
LPR

6651
6652
6654
6661
6662
6664

Skip if the printer done flag is a 1.
Clear both sections of the printing buffer.
Skip if line printer error flag is a 1.
Clear line printer done and error flags.
Load printing buffer from the contents of AC 6 - 11 and clear the AC.
Clear the format register, load the format register from the contents of
AC 9 - 1 1 , print the line contained in the section of the printer buffer loaded
last, clear the AC, and advance the paper in accordance with the selected
channel of the format tape if the content of AC 8 = 1. If the content of ACs
= 0, the line is printed and paper advance is inhibited.

Line Printer Type LP08
LSF
LCF
LSR

6661
6662
6663

LPC

6664

LIN

6665

LLS
LIF

6666
6667

Skip on character flag.
Clear the character flag.
Skip on error status line. (Error status line monitors interrupts caused by the
printer not being ready; i.e., power error, paper jam, out of paper, etc.)
Load the character into the print buffer and print if buffer is full or character
was a control function. This instruction does not clear the AC.
Set the program interrupts.
Enable
Microprogram combination of LCF and LPC.
Clear the program interrupt flag.

Card Reader and Control Type CRl2
RCSF
RCRA

6631
6632

RCRB

6634

RCSP
RCSE

6671
6672

RCRD

6674

Skip if card reader data ready flag is a 1.
The alphanumeric code for the column is read into AC 6 _11 , and the data
ready flag is cleared.
The binary data in a card column is transferred into AC0 _1 1 , and the data
ready flag is cleared.
Skip if card reader card done flag is a 1.
Clear the card one flag, select the card reader and start card motion towards
the read station, and skip if the reader-not-ready flag is a 1.
Clear card done flag.

Automatic Magnetic Tape Control Type TCS8
MTSF

6701

Skip on error flag or magnetic tape flag. The status of the error flag (EF) and
the magnetic tape flag (MTF) are sampled. If either or both are set to 1, the
contents of the PC are incremented by one skipping the next sequential
instruction.

C-5

Table C-1. IOT Instructions (cont)

Mnemonic

Operation

Octal

Automatic Magnetic Tape Control Type TC58 (cont)
MTCR

6711

MTTR

6721

MTAF

6712

MTRC

6724
6714

MTCM
MTLC
MTRS
MTGO

6716
6704
6706
6722

MCLA

6702

Skip on tape control ready (TCR). If the tape control is ready to receive an
instructionn, the PC is incremented by one skipping the next sequential
instruction.
Skip on tape transport ready (TTR). The next sequential instruction is
skipped if the tape transport is ready.
Clear the status and command registers, and the EF and MTF if tape control
ready. If tape control not ready, clears MTF and EF flags only.
Inclusively OR the contents of the command register into AC 0 - 11 .
Inclusively OR the contents of ACo-s and AC 9 - 11 into the command
register; JAM transfer bits 6, 7, 8 (command function).
Load the contents of AC 0 - 11 into the command register.
Inclusively OR the contents of the status register into AC 0 - 11 .
Read the contents of the status register into AC 0 - 11 .
Set "to" bit to execute instructions in the command register if instruction is
legal.
Clear the accumulator.

General Purpose Converter and Multiplexer Control Type AFO 1A
ADSF
ADVC

6531
6532

ADRB
ADCC
ADSC

6534
6541
6542

ADIC

6544

C-6

Skip if A/D converter flag is a l.
Clear A/D converter flag and convert input voltage to a digital number; flag
will set at end of conversion. Number of bits in converted number
determined by switch setting, 11 bits maximum.
Read A/D converter buffer into AC, left justified, and clear flag.
Clear multiplexer channel address register.
Set up multiplexer channel as per AC 6 - 1 1 . Maximum of 64 single·ended or
32 differential input channels.
Index multiplexer channel address (present address + 1). Upon reaching
address limit, increment will cause channel 00 to be selected.

APPENDIX D
8-MODE PERFORATED - TAPE LOADER

READIN MODE LOADER

The readin mode (RIM) loader is a minimum length, basic, perforated-tape reader program for the 33 ASR. It is
initially stored in memory by manual use of the operator console keys and switches. The loader is permanently
stored in 18 locations of page 3 7.
A perforated tape to be read by the RIM loader must be in RIM format:

Tape Channel
8
7
6

Format

Leader-trail code

Al
A3

A2
A4

Absolute address to contain next 4 digits

0
0

XI
X3

X2
X4

Contents of previous 4-digit address

0
0

I
0

Al
A3

A2
X2

0
0

XI
X3
(Etc.)
0
0

X2
X4

Address

Content
(Etc.)
Leader-trailer code

The RIM loader can only be used in conjunction with the 33 ASR reader (not the high-speed perforated-tape
reader). Because a tape in RIM format is, in effect, twice as long as it need be, it is suggested that the RIM loader be
used only to read the binary loader when using the 33 ASR. (Note that some PDP-12 diagnostic program tapes are
in RIM format.)

D-1

The complete PDP-12 RIM loader (SA= 77 56) is as follows:
Absolute
Address

Octal
Content

7756
7757
7760,
7761,
7762,
7763,
7764,
7765,
7766,
7767,
7770,
7771,
7772,
7773,
7774,
7775,
7776,
7777,

6032
6031
5357
6036
7106
7006
7510
5357
7006
6031
5367
6034
7420
3776
3376
5356
0
5XXX

Tag

Instruction 1 Z

Comments

BEG,

KCC
KSF
JMP-1
KRB
CLL RTL
RTL
SPA
JMP BEG+l
RTL
KSF
JMP-1
KRS
SNL
DCA 1 TEMP
DCA TEMP
JMP BEG
0
JMPX

/CLEAR AC AND FLAG
/SKIP IF FLAG = 1
/LOOKING FOR CHARACTER
/READ BUFFER

TEMP,

/CHANNEL 8 IN ACO
/CHECKING FOR LEADER
/FOUND LEADER
/OK, CHANNEL 7 IN LINK

/READ, DO NOT CLEAR
/CHECKING FOR ADDRESS
/STORE CONTENT
/STORE ADDRESS
/NEXT WORD
/TEMP STORAGE
/JMP START OF BIN LOADER

Manually loading the RIM loader in core memory is accomplished as follows:
1. Set the starting address 7756 in the Left Switches.
2. Set the first instruction (6032) in the Right Switches.
3. Press the FILL Switch and then press the FILL STEP Switch.
4. Set the next instruction (6031) in the Right Switches.
5. Press the FILL STEP Switch.
6. Rep~at steps 4 and 5 until all 16 instructions have been deposited.
7. To ensure that RIM is in core, press Exam. The MA will = 7756, and the MB should = the first RIM
instruction (6032 for low-speed reader).
8. To check sequential core locations, press Step Exam, and observe the contents of the MB.

To load a tape in RIM format, place the tape in the reader, set the Left Switches to the starting address 7756 of the
RIM loader (not of the program being read), press the START LS key, and start the Teletype reader.
Refer to Digital Program Library document Digital-8-1-U for additional information on the Readin Mode Loader
program.
BINARY LOADER (8 MODE)
The binary loader (BIN) is used to read machine language tapes (in binary format) produced by the program
assembly language (PAL). A tape in binary format is about one half the length of a comparable RIM format tape. It
can, therefore, be read about twice as fast as a RIM tape and is, for this reason, the more desirable format to use
with the 10 cps 33 ASR reader or the Type PRl 2 High-Speed Perforated-Tape Reader.
The format of a binary tape is as follows:
LEADER: About 2 feet of leader-trailer codes.

D-2

BODY: Characters representing the absolute, machine language program in easy-to-read binary (or octal)
form. The selection of tape may contain characters representing instructions (channels 8 and 7 not punched)
or origin resettings (channel 8 not punched, channel 7 punched), and is concluded by 2 characters (channels 8
and 7 not punched) that represent a checksum for the entire section.
TRAILER: Same as leader.
BODY: Characters representing the absolute, machine language program in easy-to-read binary (or octal)
form. The selection of tape may contain characters representing instructions (channels 8 and 7 not punched)
or origin resettings (channel 8 not punched, channel 7 punched), and is concluded by 2 characters (channels 8
and 7 not punched) that represent a checksum for the entire section.
TRAILER: Same as leader.
Tape Channel Memory
5
4
6
8
7

0
0

1
0

0
0

1
0

0
0

1
0

Content

leader-trailer code
origin setting
0200

0200

CLA

0201

TAD 277

0
0

0202

DCA 276

0
0

0203

HLT

0
0277

0
0

0
1

0277

origin setting

0053

1007
0

Comments

Location

sum check
leader-trailer code

To load BIN
1. Select the 8 mode.
2. Press the IO Preset switch twice.
3. Put tape in the TTY reader, turn the reader on.
4. Press Start LS (still set to 7756).
5. When tape is read in, turn the reader off and stop the computer by pressing the Stop switch.

D-3

To load binary tapes with the BIN loader
1. Place 7777 in Left Switches.
2. Set bit 0 of Right Switches to 1 for low-speed reader (TTY) or set bit 0 of Right Switches to 0 for
high-speed reader.
3. Press Start LS.
4. Tape is read in and computer halts.
5. If AC unequal to 0000 a checksum error has occurred.
After a BIN tape has been read in, one of the two following conditions exists:
a. No checksum error: halt with AC = 0
b. Checksum error: halt with AC= (computed checksum) - (tape checksum)
Operation of the BIN loader in no way depends upon or uses the RIM loader. To load a tape in BIN format place
the tape in the reader, set the Left Switches to 7777 (the starting address of the BIN loader), set Right Switch
register bit 0 0 up for loading via the Teletype unit or down for loading via the high-speed perforated-tape reader,
then press the START LS key, and start the tape reader.
Refer to Digital Program Library document Digital-8-2-U-RIM for additional information on the Binary Loader

program.

APPENDIX E
TAPE MAINTENANCE INSTRUCTIONS

E.l GENERAL
In the Maintenance Mode, all signals from the tape transport are inhibited and data is simulated under program
control. This mode is especially useful for troubleshooting and checking the operation of the TCl 2 Tape Control
Logic.
E.2 TAPE MAINTENANCE INSTRUCTIONS
E.2.1 IOT 6141
This instruction is used to load the Tape Maintenance Instruction Register (used with IOT 6154) and to provide
data and timing information to the TC 12 tape control unit when it is operating in the maintenance mode. It also
checks the status of the Tape Done flag. This instruction is not to be microprogrammed and it should not be used
to generate timing information during tape transfers, although it can be used to set the Tape Maintenance
Instruction Register at any time.
Any deviation from the above should be carefully checked with the logic diagrams to determine the expected
result. The functions of the AC bits during this instruction are shown in Table E-1.
Table E-1. AC Bit Functions
AC Bit Number
00
01
02
03

04
05

06
07
08
09
10

Function
Load into the Tape Maintenance Register (Bit 0)
Load into the Tape Maintenance Register (Bit 1)
Load into the Tape Maintenance Register (Bit 2)
Load into the Tape Maintenance Register (Bit 3)
Clear the Tape Done Flag
Skip if Tape Done Flag is set
Generate TTO
Generate TT3
Simulate input data Mark Channel
Simulate input data Data Channel 1
Simulate input data Data Channel 2
Simulate input data Data Channel 3

E-1

E.2.2 IOT 6152

This instruction is used to generate various control pulses within the TC 12 Tape control unit. These control signals
are used primarily for maintenance purposes. In special situations these controls are useful for handling
nonstandard tape formats.
The bits of instruction 6152 are gated with individual bits of AC register to generate a specific control function.
These functions are intended to be used singly, and not while a tape instruction is in progress, and this instruction
cannot be microprogrammed. Any deviation from the above should be carefully checked with the logic diagrams to
determine the exact result. The functions of the AC bits during this instruction are shown in Table E-2.

Table E-2. AC Bit Functions
AC Bit Number

Function

00
01
02

Tape Preset
Shift RWB
TB-+ RWB
TB+ TAC-+ TAC
Clear 8 Block
Set Direction Backward
Select Unit number 1
Set Direction Forward
Set Write Sync
Set Motion. Set Direction Forward if motion
was cleared
Select 8 Tape
AC 11 -+ 8 Write Flip-Flop

03
04*
05*
06*
07*
08*
09*
10*
11*
*These Bits are used in the TCl 2-F Tape Control

E.2.3 IOT 6154

This instruction is used to load and examine the various registers of the TCl 2 Tape Control Unit. The action of this
instruction is controlled by the contents of the Tape Maintenance Instruction Register and this action is shown in
Table E-3. This instruction is not to be used during the operation of a tape instruction.
Table E-3. JOT 6154 Effect of Tape Maintenance Instruction
Register Contents
Contents of bits 0, I, 2, & 3

E-2

Binary

Octal

0000
0001
0010
0011
0100
0101

00
01
02
03
04
05

Function Performed

AC-+ TB
AC-+ TBN
AC-+ TAC
AC-+ TMA
TMA Setup -+ AC
TBN-+AC

Table E-3. IOT 6154 Effect of Tape Maintenance Instruction (cont)

Octal

0110
0111
1000
1001
1010
1011
1100
1101
1110
1111

06
07
10

11
12
13
14
15
16
17

Function Performed

TB--+ AC
RWB--+ AC
Mark Window--+ AC
Control States, Timing --+ AC
Units & MTN --+ AC
Tape Inst --+ AC
Misc. Status 1 --+ AC
Misc. Status 2 --+ AC
TMA--+ AC

E.2.4 IOT 6154 Detailed Transfer Information
The Tape Maintenance Instruction Register is decoded to give a count of 00 8 to 17 8 • These count levels generate
the signals necessary to enable the selected data onto the Tape Bus for a 12-bit parallel transfer between the AC
and the Tape Registers. The following tables show the contents of the AC after the instruction associated with each
table is given.
Table E-4. Tape Maintenance Instruction Register Equal I 0 8
Mark Window --+ AC

AC Bit

Data Read into AC

00
01
02
03
04
05
06
07

LWN Wind Shade ( 1)
LWN Wind 00 (1)
LWN Wind 01 (1)
LWN Wind 02 (1)
LWN Wind 03 (1)
LWNEM
LWNCM
LWNGM
LWNDM
LWNFM
LWNBM
LWNIM

08
09
10
11

E-3

Table E-5. Tape Maintenance Instruction Register Equals 11 8
Control States & Timing--+ AC
AC Bit

Data Read Into AC

00
01

TAC= 7777
LCS Idle (1)
LCS Search ( 1)
LCS Block ( 1)
LCS Check Word ( 1)
LCS Tum Around ( 1)
LCS Write (1)
LCS Write Cycle ( 1)
LTD ACIP
LTD TTOK
LTD Timing OK
LTD Tape Fail Delay

02
03
04
05
06
07

08
09
IO
11

Table E-6. Tape Maintenance Instructions Register Equals 12 8
Units & Motion - AC
AC Bit

Data Read Into AC

00
01
02
03
04
05
06
07
08
09
10

LTC Unit 0 (0)
LTC Unit 1 (0)
LTC Unit 2 (0)
LTC Unit 3 (0)
LTC Unit 4 (0)
LTC Unit 5 (0)
LTC Unit 6 (0)
LTC Unit 7 (0)
LMU motion ( 1)
LMU Direction ( 1)
LCS Tape OK (1)
LTC Write EN (1)

Table -E-7. Tape Maintenance Instruction Register Equals 13 8
TINSTR--AC

E-4

AC Bit

Data Read Into AC

00
01
02
03
04
05
06

LIN RDC
LIN RCG
LIN RDE
LINMTB
LINWRC
LINWRG
LIN WRI

Table E-7. Tape Maintenance Instruction Register Equals 13 8 (cont)
TINSTR-AC
AC Bit

Data Read Into AC
LIN CHK
LIN I (1)
LGP GP 0 (1)
LGP GP 1 (1)
LGP GP 2 (1)

07
08
09
10
11

Table E-8. Tape Maintenance Instruction Register Equals 14 8

MSC Status 1
AC Bit

Data Read Into AC

00
01
02
03
04
05
06
07
08
09
10
11

LTS PHASE
LIP IN PROGRESS (1)
LTS LC 00 (1)
LTS LC 01 (1)
Mark Chan Write
Data Chan 1 Write
Data Chan 2 Write
Data Chan 3 Write
LGP GP= GPC (1)
LGP GPCNT 0 (1)
LGP GPCNT 1 (1)
LGP GPCNT 2 (1)

Table E-9. Tape Maintenance Instruction Register Equals 15 8
MSC Status 2
AC Bit

Data Read Into AC

00
01
02
03
04
05
06
07
08
09
10
11

TC12-F WRITE SEL (1)
TC12-F TAPE SEL (1)

Not used

E-5

APPENDIX F
TABLES OF CODES

Table F-1. Model 33/35 ASR/KSR Teletype Code (ASCII) in Octal Form

Character

8-Bit Code

Character

(in octal)

c
D

E
F

G
H
I

J
K
L

M
N

0
p

a
R

s
T

v
w
x
y

301
302
303
304
305
306
307
310
311
312
313
314
315
316
317
320
321
322
323
324
32·5
326
327
330
331
332

(in octal)

!
II

#
$

&
I

{

)

*
+

I
:

<
=

>
?
@

[

\
]

t
+-

0
1
2
3
4
5
6
7
8
9

260
261
262
263
264
265
266
267
270
271

8-Bit Code

Leader!Trailer
Line-Feed
Carriage-A et urn
Space
Rub-out
Blank
alt-mode
escape

241
242
243
244
245
246
247
250
251
252
253
254
255
256
257
272
273
274
275
276
277
300
333
334
335
336
337
200
212
215
240
377
000
375
233

F-1

Table F-2. Model 33 ASR/KSR Teletype Code (ASCII) in Binary Form
1 = HOLE PUNCHED = MARK
0 =NO HOLE PUNCHED =SPACE

MOST SIGNIFICANT BIT

LEAST SIGNIFICANT BIT )

8 7 6 5 4

r--

.,.....__
A
~

s 3 2

0 0 0

START OF MESSAGE

0 0

END OF ADDRESS

0 0

1 0
1

I---

.._.,!_

END OF MESSAGE

0 0

$
I---

END OF TRANSMISSION

0 0

1 0 0

.,.....__
F
.,...___
G
1---

%
t----

&
I---

(

I---

1--)
1---

N
r----i

1-----1

fo-

i---

w
..x
i---

y
....,.__.,
z
t---

[

.......
t---

..
]

0 0 0

0 0

1 0

VERTICAL TAB

1 1

FORM FEED

1 0 0

r--!--

r-~
0

CARRIAGE RETURN

1 0

SHIFT OUT

1 l

SHIFT IN

DCO

1 0

f----1

1 l

0 0 0

READER ON

TAPE (AUX ON)

1 0

1 0
1 1

0 0

1---

3
t--4
t---

t---

t-7
t--

8
1---

t--

.--....:-

READER OFF

1 0

(AUX OFF)

1 0

1 0 0

ERROR

1 0

SYNCHRONOUS IDLE

1 0

1 1 0

LOGICAL END OF MEDIA

1 0

1 1 1

so
s1

0 0

1 1

1 0
1 1

~
<

1 l

1 1

1 0 0

I--

1 0

1 1 0

1 l

1 1 1

t--

'--r-

u
....,.__.,
v

1 1 1

FORMAT EFFECTOR

f----1
2

0 0

BELL

1-----1
R
r----i
~

1 1 0

1---

1 0

0 0

HORIZONTAL TAB

1---

0 0

LINE FEED

t--K
1---

WHO ARE YOU
ARE YOU

i---

I---

F-2

0 0

NULL/IDLE

1---

D
t--E

SPACE
I--!
I---

1---

RUB OUT

t--

'--v--J '--v---J

~~
·~

1 0 0

SAM~

SAME

...-1

1 0

SAME

--1

1 1

SAME

Table F-3. LT-37 Transmit and Receive Code Table
33 ASRMODE

37 KSRMODE

NOT SHIFT

SHIFT

NOT SHIFT

SHIFT

CHARACTER CODE

101
102
303
104
305
306
107
110
311
312
113

3i4

M
N

115
116
317
120
321
322
123
324
125
126
327
330
131
132

m
n

240
41
42
243
44
245
246
47
250
251

c
D

E
F
G
H
I

0
p

Q
R

s
T

u
v
w

x
y

z
SPACE
!

#
$

%
&

'
(

)

<
=

>
?
@

[

273
74
275
276
77
300
333
134

a
b
c
d

e
f
g
h
i
j
k
1

r
s
t
u

v
w
x
y

2
3
4

5
6
7
8
9

*
+

I
'

{

341
342
143
344
145
146
347
350
151
152
353
154
355
356
157
360
161
162
363
164
3(;)5
366
167
170
371
372

CODE

301
302
303
304
305
306
307
310
311
312
313
314
315
316
317
320
321
322
323
324
325
326
327
330
331
332

c
D
E
F
G

H
I
J
K
L
M
N
0
p

Q
R

s
T

u
v

x
y

60
261
262
63
264
65
66
267
270
71
252
53
254
55

SPACE

257
140
173
374

CHARACTER

!
,,

#
$

%
&

(

)

?
@

[

240
241
242
243
244
245
246
247
250
251
272
273
274
275
276
277
300
333
334

0
1

2
3
4

5
6
7
8
9

*
+

260
261
262
263
264
265
266
267
270
271
252
253
254
255
256
257

F-3

Table F-3. LT-37 Transmit and Receive Code Table (cont)

37KSRMODE

CODE

]

t
~

NULL
SOH
STX
ETX
EOT
ENQ
ACK
BELL
BACK SPACE
~TAB

NEW LINE
vTAB
FORM
RETURN
So
Si

SHIFT

NOT SHIFT

SHIFT
CHARACTER

33ASRMODE

335
336
137
000
201
202
3
204
5
6
207
210
11
12
213
14
215
216
217

CHARACTER

CODE

}

175
176
377
220
21
22
223
24
225
226
27
30
231
232
33
234
35
36
237

,....,

DEL
DLE
DCl
DC2
DC3
DC4
NAK
SYNC
ETB
CANCEL
EM
SUB
ESCAPE
FS
GS
RS
QS

CHARACTER

]

t
~

NULL
SOH
STX
EXT
EOT
ENQ
ACK
BELL
BACK SPACE
~TAB

NEW LINE
vTAB
FORM
RETURN
So
Si

NOT SHIFT
CODE

CHARACTER

CODE

335
336
337
200
201
202
203
204
205
206
207
210
211
212
213
214
215
216
217

ALT
OR MODE
DEL
DLE
DCl
DC2
DC3
DC4
NAK
SYNC
ETB
CANCEL
EM

375

SUB
ESCAPE
FS
GS
RS
QS

NOTE
Letter codes transmitted from the 37 KSR keyboard in 33 mode will be upper case
regardless of the position of the shift key; however, letter codes received by the KSR
37 in 33 mode will be printed in upper or lower case, as received.

F-4

377
220
221
222
223
224
225
226
227
230
231
232
233
234
233
236
237

Table F-4. Card Reader Codes
The following table gives the octal representation of the internal (binary) codes for the listed punch combinations.
These internal codes are generated by the card reader and are transmitted to the PDP-12 upon execution of the
appropriate IOT instruction. Any combination of punches which is not shown in the table is invalid, and the card
reader can not detect invalid combinations.

Card Code
Num.
Zone
-

12
12
12
12
12
12
12
11
11
11
11
11
11
11
0
0
0
0
0
0
0
-

12
12
12
12
12
12

8·2
8·3
8·4
8·5
8·6
8·7
8·2
8·3
8·4
8·5
8·6
8·7
1
8·2
8·3
8·4
8·5
8·6
8·7
8·3
8·4
8·5
8·6
8·7
1
2
3
4

5
6

Internal
Code

Character

Card Code
Zone Num.

Internal
Code

Character

00 0000
11 1010
11 1011
11 1100
11 1101
11 1110
11 1111
11 0000
10 1010
10 1011
10 1100
10 1101
10 1110
10 1111
10 0000
01 0001
01 1010
01 1011
01 1100
01 1101
01 1110
01 1111
00 1011
00 1100
00 1101
00 1110
00 1111
11 0001
11 0010
11 0011
11 0100
11 0101
11 0110

Space

11 0111
11 1000
11 1001
10 0001
10 0010
10 0011
10 0100
10 0101
10 0110
10 0111
10 1000
10 1001
01 0010
01 0011
01 0100
01 0101
01 0110
01 0111
01 1000
01 1001
00 1010
00 0001
00 0010
00 0011
00 0100
00 0101
00 0110
00 0111
00 1000
00 1001

G
H
I
J
K
L
M
N
0
p

12
12
12
11
11
11
11
11
11
11
11
11
0
0
0
0
0
0
0
0

[

<
(

+
t
&
!
$

*
)

'
\
-

I
]

'
%

8
9

1
2
3
4
5
6
7
8
9

2
3
4
5
6
7
8
9

0
1
2
3
4
5
6
7
8
9

Q
R

s
T

w
x
y

z
0
1
2
3
4
5
6
7
8
9

E
F
..----:

F-5

Table F-5. LP08 Line Printer Code

64-Character Printer

AC 5
AC 6

AC 7

AC 9

AC10 AC11

0
0
0
0
0
0
0
0
I
I
I
I
I
I
I
1

0
0
0
0
I
I
I
I
0
0
0
0
1
1
1
1

0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1

Space
!
"

0
I
0
I
0
I
0

'
a
b
c

u
v

v
w

[

<
=
>

K
L
M
N

w
x

g
h
i

p
q

r
s

x
y

j
k

{

()

]

}

96-Character Printer

F-6

A
B

(
)

5
6
7

1
0

FF
CR

2
3
4

D
E
F
G
H

0
I
0
I
0
I
0
1

0
I

1
0

AC 8

Table F-6. LPI 2 Automatic Line Printer Code

Character
(ASCII)

6-Bit Code
(in octal)

(cL

A
B

D
E
F
G
H
I
J

K
L
M
N

0
p
Q

s
T

v
w
x
y

z
[

\
J

2
3
4
5
6
7
10
11
12
13
14
15
16
17
20
21
22
23
24
25
26
27
30
31
32
33
34
35
36
37

Character
(ASCII)

6-Bit Code
(in octal)

40
41
42
43

O/o

2
3

47
50
51
52
53
54
55
56
57
60
61
62
63

5
6
7

65
66
67
70
71

0
l

8
9

<
>
?

73
74
75
76
77

F-7/F-8

APPENDIX G
CABLE CONNECTIONS TO PDP-12 FRONT PANEL

Access to analog channels 10-17 and the extension scope socket is by means of the relay and analog input panel
(see Figure 2-3). The addition of 16 channels of analog input with the AG 12 option, 16 additional preamplifiers,
connects channels 20 8 to 37 8 to the analog extension panel supplied with the option.
Analog knobs 0 8 to 7 8 , analog channels 10 8 to 37 8 , console scope display, and extension scope display utilize the
following connectors and connect to the following module slots in the EMl 2 memory wing:
Device

Front Panel Connector

Module Slot

Analog Knobs 0 8 - 7 8
Analog Chan 10 8 -17 8
Analog Chan 20 8 -27 8
Analog Chan 30 8 -37 8
Extension Scope Display
Console Display

SK, 10-turn Potentiometers
Switchcraft JAX # 13 B
Amphenol 26-4401-32P
Amphenol 26-4401-32P
Amphenol 26-4401-24P
Amphenol 57-30240

F33
F32
F31
F30
F39
F38

Table G-1 lists cable connections and signal names from each front panel termination to its corresponding slot in
the EMI 2 memory wing.

G-1

Table G-1. Cable Connections for PDP-12 Front Panel
FRONT
DEVICE

SIGNAL NAME

Analog
Knobs
0-7

+7 volts
- 7 volts
Analog Chan 7
Analog Chan 6
Analog Chan 5
Analog Chan 4
Analog Chan 3
Analog Chan 2
Analog Chan 1
Analog Chan 0

Analog
Channels
10-17

Analog
Channels
20-37

Console
Display
and
Extension
Scope
Display

Type 503 Scope
Connections

G-2

PANEL PIN

All Knobs
All Knobs
Knob 7
Knob 6
Knob 5
Knob4
Knob 3
Knob 2
Knob 1
Knob 0

- Analog Chan 20
+Analog Chan 20
DRAIN
- Analog Chan 21
+Analog Chan 21
DRAIN
- Analog Chan 22
+ Analog Chan 22
DRAIN
- Analog Chan 23
+ Analog Chan 23
DRAIN
- Analog Chan 24
+ Analog Chan 24
DRAIN
- Analog Chan 25
+ Analog Chan 25
DRAIN
- Analog Chan 26
+ Analog Chan 26
DRAIN
- Analog Chan 27
+ Analog Chan 27
DRAIN

I
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25

DSX Chan Sel. (1) H
SystemGND
DRAIN
DSC Intensity L
System GND
DRAIN
XHQGND
DSXXDefl.
DRAIN
YHQGND
DSY Y Deft.
DRAIN

1
2
3
4
5
6
7
8
9
10
11
12

503 Intensify
System GND
DRAIN

19
20
21

MODULE
SIGNAL NAME

FRONT PANEL PIN

SLOT PIN

- Analog Chan 10
+ Analog Chan 10
- Analog Chan 11
+ Analog Chan 11
- Analog Chan 12
+ Analog Chan 12
- Analog Chan 13
+ Analog Chan 13
- Analog Chan 14
+ Analog Chan 14
- Analog Chan 15
+ Analog Chan 15
- Analog Chan 16
+ Analog Chan 16
- Analog Chan 17
+ Analog Chan I 7

Analog Phone Jack 10
Analog Phone Jack 10
Analog Phone Jack 11
Analog Phone Jack 11
Analog Phone Jack 12
Analog Phone Jack 12
Analog Phone Jack 13
Analog Phone Jack 13
Analog Phone Jack 14
Analog Phone Jack 14
Analog Phone Jack 15
Analog Phone Jack 15
Analog Phone Jack 16
Analog Phone Jack 16
Analog Phone Jack 1 7
Analog Phone Jack 17

Al
Bl
Cl
Dl
El
H1
Jl
Kl
L1
Ml
NI
Pl
Sl

- Analog Chan 30
+ Analog Chan 30
DRAIN
- Analog Chan 31
+ Analog Chan 31
DRAIN
- Analog Chan 32
+ Analog Chan 32
DRAIN
- Analog Chan 33+Analog Chan 33
DRAIN
- Analog Chan 34
+ Analog Chan 34
DRAIN
- Analog Chan 35
+ Analog Chan 35
DRAIN
- Analog Chan 36
+ Analog Chan 36
DRAIN
- Analog Chan 37
+ Analog Chan 3 7
DRAIN

1
2
3
4
5
6
7
8
9

10
11
12
13
14
15
16
32
31
30
29
28
27
26
25

Tl
U1
VI

Bl
GND
Cl
Dl
GND
El
H1
GND
JI
Kl
GND
L1
Ml
GND
Nl
Pl
GND
Sl

Tl
GND
U1
Vl
GND
Al
Bl
GND
Cl
Dl
GND
El
H1
GND

J1
Kl
GND

Tl
GND

APPENDIX H
MATHEMATICAL DATA

Scales of Notation
2x IN Decimal
2'
0.001
0.002
0.003
0.004
0005
0.006
0.007
0.008
0.009

O.Ql

l.00069 33874 62581
1.00138 72557 11335
I.00208 16050 79633
l.00277 64359 01078
1.00347 17485 09503
l.00416 75432 38973
1.00486 38204 23785
1.00556 05803 98468
1.00625 78234 97782

0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09

1.00695 55500 56719
1.01395 94797 90029
1.02101 21257 07193
1.02811 38266 56067
1.03526 49238 41377
1.04246 57608 41121
1.04971 66836 23067
1.05701 80405 61380
1.06437 01824 53360

0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9

1.07177 34625 36293
1.14869 83549 97035
1.23114 44133 44916
1.31950 79107 72894
1.41421 35623 73095
1.51571 65665 10398
1.62450 47927 12471
1.74110 11265 92248
1.86606 59830 73615

1o+n IN Octal
10"
1
12
144
1 750
23 420

10-·

0
1
2
3
4

1.000 000 000 000 000 000 00
0.063 146 314 631 463 146 31
0.005 075 341 217 270 243 66
0.000 406 111 564 570 651 77
0.000 032 155 613 530 704 15
0.000 002 476 132 610 706 64
0 000 000 206 157 364 055 37
0.000 000 015 327 745 152 75
0.000 000 001 257 143 561 06
0.000 000 000 104 560 276 41

303 240
3 641 100
46 113 200
575 360 400
346 545 000

10-·

0.000 000 000 006 676 337 66
0.000 000 000 000 537 657 77
0.000 000 000 000 043 136 32
0.000 000 000 000 003 411 35
0.000 000 000 000 000 264 11

10"
112 402 762 000
1 351 035 564 000
16 432 451 210 000
221 411 634 520 000
657 142 036 440 000

n log

34
434
5 432
67 405

12
13
14

327 724 461 500 000
157 115 760 200 000
127 413 542 400 000
553 164 731 000 000

15
16

0.000 000 000 000 000 022 01
0.000 000 000 000 000 001 63
0.000 000 000 uoo 000 000 14
0.000 000 000 000 000 000 01

2, n log 2 10 IN Decimal

n log10 2

n log2 10

n los10 2

n log2 10

1
2
3
4

0.30102 99957
0.60205 99913
0.90308 99870
1.20411 99827
1.50514 99783

3.32192 80949
6.64385 61898
9.96578 42847
13.28771 23795
16.60964 04744

6
7
8
9
10

l.80617 99740
2.10720 99696
2.40823 99653
2.70926 99610
3.01029 99566

19.93156 85693
23.25349 66642
26.57542 47591
29.89735 ~8540
33.21928 09489

Addition and Multiplication Tables
Addition

Multiplication
Binary Scale

O+l=lo to=
O= ol
1
I= 10

0 x

0 x 0 =0
l=lXO=O
l x 1 = 1

Octal Scale
01

rr =

Mathematical Constants in Octal Scale
e = 2.55760 5213051
I =

3.11037

5524211

= 0.24276

301556,

e-1

0.27426

5306611

Vrr = 1.61337

6110671

Ve= 1.51411

2307041

log11 -, - .0.62573 0306451

In rr = 1.11206

4044351

logioe = 0.33626

754251'

v2=

1.32404

746320,

logi rr = 1.51544

163223,

logi e = 1.34252

1662451

In 2 =

0.54271

027760,

vTci = 3.12305

407267,

logi 10 = 3.24464

7411361

In IO=

2.23273

067355,

,,.-1

In 1

0.44 742 147707,
0.43127 2336021

H-1

Powers of Two
2

1
2
4
8
16
32
64
128
256
512
1 024
2 048
4 096
8 192
16 384
32 768
65 536
131 072
262 144
524 288
1 048 576
2 097 152
4 194 304
8 388 608
16 777 216
33 554 432
67 108 864
134 217 728
268 435 456
536 870 912
1 073 741 824
2 147 483 648
4 294 967 296
8 589 934 592
17 179 869 184
34 359 738 368
68 719 476 736
137 438 953 472
274 877 906 944
549 755 813 888
l 099 511 627 776
2 199 023 255 552
4 398 046 511 104
8 796 093 022 208
17 592 186 044 416
35 184 372 088 832
70 368 744 177 664
140 737 488 355 328
281 474 976 710 656
562 949 953 421 312
1 125 899 906 842 624
2 251 799 813 685 248
4 503 599 627 370 496
9 007 199 254 740 992
18 014 398 509 481 984
36 028 797 018 963 968
72 057 594 037 927 936
144 115 188 075 855 872
288 230 376 151 711 744
576 460 752 303 423 488
1 152 921 504 606 846 976
2 305 843 009 213 693 952
4 611 686 018 427 387 904
9 223 372 036 854 775 808
18 446 744 073 709 551 616
36 893 488 147 419 103 232
73 786 976 294 838 206 464
147 573 952 589 676 412 928
295 147 905 179 352 825 856
590 295 810 358 705 651 712
1 180 591 620 717 411 303 424
2 361 183 241 434 822 606 848
4 722 366 482 869 645 213 696

H-2

-n

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72

1.0
0.5
0.25
0.125
0.062
0.031 25
0.015 625
0.007 812 5
0.003 906 25
0.001 953 125
0.000 976 562 5
0.000 488 281 25
0.000 244 140 625
0.000 122 070 312 5
0.000 061 035 156 25
0.000 030 517 578 125
0.000 015 258 789 062 5
0.000 007 629 394 531 25
0.000 003 814 697 265 625
0.000 001 907 348 632 812 5
0.000 000 953 674 316 406 25
0.000 000 476 837 158 203 125
0.000 000 238 418. 579 101 562 5
0.000 000 119 209 289 550 781 25
0.000 000 059 604 644 775 390 625
0.000 000 029 802 322 387 695 312 5
0.000 000 014 901 161 193 847 656 25
0.000 000 007 450 580 596 923 828 125
0.000 000 003 725 290 298 461 914 062 5
0.000 000 001 862 645 149 230 957 031 25
0.000 000 000 931 322 574 615 478 515 625
0.000 000 000 465 661 287 307 739 257 812 5
0.000 000 000 232 830 643 653 869 628 906 25
0.000 000 000 116 415 321 826 934 814 453 125
0.000 000 000 058 207 660 913 467 407 226 562 5
0.000 000 000 029 103 830 456 733 703 613 281 25
0.000 000 000 014 551 915 228 366 851 806 640 625
0.000 000 000 007 275 957 614 183 425 903 320 312 5
0.000 000 000 003 637 978 807 091 712 951 660 156 25
0.000 000 000 001 818 989 403 545 856 475 830 078 125
0.000 000 000 000 909 494 701 772 928 237 915 039 062 5
0.000 000 000 000 454 747 350 886 464 118 957 519 531 25
0.000 000 000 000 227 ~73 675 443 232 059 478 759 765 625
0.000 000 000 000 113 686 837 721 616 029 739 379 882 812 5
0.000 000 000 000 056 843 418 860 808 014 869 689 941 406 25
0.000 000 000 000 028 421 709 430 404 007 434 844 970 703 125
0.000 000 000 000 014 210 854 715 202 003 717 422 485 351 562 5
0.000 000 000 000 007 105 427 357 601 001 858 711 242 675 781 25
0.000 000 000 000 003 552 713 678 800 500 929 355 621 337 890 625
0.000 000 000 000 001 776 356 839 400 250 464 677 810 668 945 312 5
0.000 000 000 000 000 888 178 419 700 125 232 338 905 334 472 656 25
0.000 000 000 000 000 444 089 209 850 062 616 169 452 667 236 328 125
0.000 000 000 000 000 222 044 604 925 031 308 084 726 333 618 164 062 5
0.000 000 000 000 000 111 022 302 462 515 654 042 363 166 809 082 031 25
o.ooo ooo ooo ooo poo 055 511 151 231 257 827 021 181 583 404 541 015 625
0.000 000 000 000 000 027 755 575 615 628 913 510 590 791 702 270 5v7 812 5
0.000 000 000 000 000 013 877 787 807 814 456 755 295 395 851 135 253 906 25
0.000 000 000 000 000 006 938 893 903 907 228 377 647 697 925 567 626 953 125
0.000 000 000 000 000 003 469 446 951 953 614 188 823 848 962 783 813 476 562 5
0.000 000 000 000 000 001 734 723 475 976 807 094 411 924 481 391 906 738 281 25
0.000 000 000 000 000 000 867 361 737 988 403 547 205 962 240 695 953 369 140 625
0.000 000 000 000 000 000 433 680 868 994 201 773 602 981 120 347 976 684 570 312 5
0.000 000 000 000 000 000 216 840 434 497 100 886 801 490 560 173 988 342 285 156 25
0.000 000 000 000 000 000 JOB 420 217 248 550 443 400 745 280 086 994 171 142 578 125
0.000 000 000 000 000 000 054 210 108 624 275 221 700 372 640 043 497 085 571 289 062 5
0.000 000 000 000 000 000 027 105 054 312 137 610 850 186 320 021 748 542 785 644 531 25
0.000 000 000 000 000 000 013 552 527 156 C68 805 425 093 160 010 874 271 392 822 265 625
0.000 000 000 000 000 000 006 776 263 578 034 402 712 546 580 005 437 135 696 411 132 812 5
0.000 000 000 000 000 000 003 388 131 789 017 201 356 273 290 002 718 567 848 205 566 406 25
0.000 000 000 000 000 000 001 694 065 894 508 600 678 136 645 001 359 283 924 102 783 203 125
0.000 000 000 000 000 000 000 847 032 947 254 300 339 068 322 500 679 641 962 051 391 601 562 5
0.000 000 000 000 000 000 000 423 5.16 473 627 150 169 534 161 250 339 820 981 025 695 800 781 25
0.000 000 000 000 000 000 000 211 758 236 813 575 084 767 080 625 169 910 490 512 847 900 390 625

Octal-Decimal Integer Conversion Table

to
0000
0177
IOctol)

to
0000

0511

(Deciftlol)

Octal Decimal
10000- 4096
20000- 8192
30000 - 12288
40000-1638'
50000 - 20480
60000 - 24576
70000 - 28672

.ooo
to

0000
0010
0020
0030
0040
0050
0060
0070

0000
0008
0016
0024
0032
0040
0048
0056

0001
0009
0017
0025
0033
0041
0049
0057

0002
0010
0018
0026
0034
0042
0050
0058

1777

1023

(Octol)

10.cilftol)

0005
0013
0021
0029
0037
0045
0053
0061

0006
0014
0022
0030
0038
0046
0054
0062

0007
0015
0023
0031
0039
0047
0055
0063

0400 0256 0257
0410 0264 0265
0420 0272 0273
0430 0280 0281
0440 0288 0289
0450 0296 0297
0460 0304 0305
0470 0312 0313

0258 0259
0266 0267
0274 0275
0282 0283
0290 0291
0298 0299
0306 0307
0314 0315

0260
0268
0276
0284
0292
0300
0308
0316

0261
0269
0277
0285
0293
0301
0309
0317

0262 0283
0270 0271
0278 0279
0286 0287
0294 0295
0302 0303
0310 0311
0318 0319

0100 0064 0065
0110 0072 0073
0120 0080 0081
0130 0088 0089
0140 0096 0097
0150 0104 0105
0160 0112 0113
0170 0120 0121

0066 0067
0074 0075
0082 0083
0090 0091
0098 0099
0106 0107
0114 0115
0122 0123

0068
0076
0084
0092
0100
0108
0116
0124

0069
0077
0085
0093
0101
0109
0117
0125

0070
0078
0086
0094
0102
0110
0118
0126

0071
0079
0087
0095
0103
0111
0119
0127

0500 0320 0321
0510 0328 0329
05~0 0336 0337
0530 0344 0345
0540 0352 0353
0550 0360 0361
0560 0368 0369
0570 0376 0377

0322
0330
0338
0346
0354
0362
0370
0378

0323
0331
0339
0347
0355
0363
0371
0379

0324
0332
0340
0348
0356
0364
0372
0380

0325
0333
0341
0349
0357
0365
0373
0381

0326
0334
0342
0350
0358
0366
0374
0382

0327
0335
0343
0351
0359
0367
0375
0383

0200 0128
0210 0136
0220 0144
0230 0152
0240 0160
0250 0168
0260 0176
0270 0184

0129
0137
0145
0153
0161
0169
0177
0185

0130
0138
0146
0154
0162
0170
0178
0186

0131
0139
0147
0155
0163
0171
0179
0187

0132
0140
0148
0156
0164
0172
0180
0188

0133
0141
0149
0157
0165
0173
0181
0189

0134
0142
0150
0158
0166
0174
0182
0190

0135
0143
0151
0167
0175
0183
0191

0600 0384
0610 0392
0620 0400
0630 0408
0640 0416
0650 0424
0660 0432
0610 0440

0385
0393
0401
0409
0417
0425
0433
0441

0386
0394
0402
0410
0418
0426
0434
0442

0387
0395
0403
0411
0419
0427
0435
0443

0388
0396
0404
0412
0420
0428
0436
0444

0389
0397
0405
0413
0421
0429
0437
0445

0390
0398
0406
0414
0422
0430
0438
0446

0391
0399
0407
0415
0423
0431
0439
0447

0300 0192
0310 0200
0320 0208
0330 0216
0340 0224
0350 0232
0360 0240
0370 0248

0193
0201
0209
0217
0225
0233
0241
0249

0194
0202
0210
0218
0226
0234
0242
0250

0195
0203
0211
0219
0227
0235
0243
0251

0196
0204
0212
0220
0228
0236
0244
0252

01~7

0205
0213
0221
0229
0237
0245
0253

0198
0206
0214
0222
0230
0238
0246
0254

0199
0207
0215
0223
0231
0239
0247
0255

0700
0710
0720
0730
0740
0750
0760
0770

0448
0456
0464
0472
0480
0488
0496
0504

0449
0457
0465
0473
0481
0489
0497
0505

0450
0458
0466
0474
0482
0490
0498
0506

0451
0459
0467
0475
0483
0491
0499
0507

0452
0460
0468
0476
0484
0492
0500
0508

0453
0461
0469
0477
0485
0493
0501
0509

0454
0462
0470
0478
0486
0494
0502
0510

0455
0463
0471
0479
0487
0495
0503
OSI 1

1000 0512 0513
1010 0520 0521
1020 0528 0529
1030 0536 0537
1040 0544 0545
1050 0552 0553
1060 0560 0561
1070 0568 0569

051<&
0522
0530
0538
0546
0554
0562
0570

0515
0523
0531
0539
0547
0555
0563
0571

0516
0524
0532
0540
0548
0556
0584
0572

0517
0525
0533
0541
0549
0557
0565
0573

0518
0526
0534
(1542
0550
0558
0566
0574

0519
0527
0535
0543
0551
0559
0567
0575

1400
1410
1420
1430
1440
1450
1460
1470

0768
0776
0784
0792
0800
0808
0816
0824

0769
0777
0785
0793
0801
080!1
0817
0825

077Q
0778
0786
0794
0802
0810
0818
0826

0771
0779
0787
0795
0803
0811
0819
0827

0772
0780
0788
0796
0804
0812
0820
0828

0773
0781
0789
0797
0805
0813
0821
0829

0774
0782
0790
0798
0808
0814
0822
0830

0775
0783
0791
0799
0807
0815
0823
0831

1100 0576
1110 0584
1120 0592
1130 0600
1140 0608
1150 0616
1160 0624
1170 0632

0577
0585
0593
0601
0609
0617
0625
0633

0578
0586
0594
0602
0610
0618
0626
0634

0579
0587
0595
0603
0611
0619
0627
0635

0580
0588
0596
0604
0612
0620
0628
0636

0581
0589
059'7
0605
0813
0621
0629
0637

0582
0590
0598
De06
IMl14
0622
0630
0638

0583
0591
0599
0607
0615
0623
0631
0639

1500
1510
1520
1530
1540
1550
1560
1570

0832 0833
0840 0841
0848 0849
0856 0857
0864 0865
0872 0873
0880 0881
0888 0889

0834
0842
0850
0858
0866
0874
0882
0890

0835
0843
0851
0859
0867
0875
0883
0891

0836
0844
0852
0860
0868
0876
0884
0892

0837
0845
0853
0861
0869
0877
0885
0893

0838
0846
0854
0862
0870
0878
0886

0839
0847
0855
0883
0871
0878
0887
0895

1200 0640
1210 0648
1220 0656
1230 0664
IZ40 0672
1250 0680
1260 0688
1270 0696

0641
0649
0657
0665
0673
0681
0689
0697

0642
0650
0658
0666
0674
0682
0690
0698

0643
0651
0659
0667
0675
0683
0691
0699

0644
0652
0660
0668
0676
0684
0692
0700

0645
0653
0661
0669
0677
0685
0693
0701

0646
0654
0662
0670
0678
0686
0694
0702

0647
0655
0663
0671
0679
0687
0695
0703

1600 0896
1610 0904
1620 0912
1630 0920
1640 0928
1650 0936
1660 0944
1670 0952

0897
0905
0913
0921
0929
0937
0945
0953

0898
09b6
0914
0922
0930
0938
0946
0954

0899
0907
0915
0923
0931
0939
0947
0955

0900
0908
0916
0924
0932
0940
0948
0956

090 I 0902 0903
0909 0910 0911
0917 0918 0919
0925 0926 0927
0933 0934 0935
0941 0942 0943
0949 0950 0951
0957 0958 0959

1300 0704 0705
1310 0712 071!
1320 0720 0721
1330 0728 0729
1340 0736 0737
1350 0744 0745
1360 0752 0753
1370 0760 0761

0706
0714
0722
0730
0738
0746
0754
0762

0707
0715
0723
0731
0739
0747
0755
0763

0708
0716
0724
0732
0740
0748
0756
0764

0709
0717
0725
0733
0741
0749
0157
0765

0710
0718
0726
0734
0742
0750
0758
0766

0711
0719
0727
0735
0743
0751
0759
0767

1700
1710
1720
1730
1740
1750
1750
1770

0961
0969
0977
0985
0993
1001
1009
1017

0962
0970
0978
0986
0994
1002
1010
1018

0963 0964
0971 0972
0979 0980
0987 0988
0995 0996
1003 1004
lOll 1012
IOU 1020

0512

000;5 0004
0011 0012
0019 0020
0027 0028
0035 0036
0043 0044
0051 0052
0059 0060

01~9

0960
0968
0976
0984
0992
1000
1008
1016

0965
0973
0981
0989
0997
1005
1013
1021

089~

0966
0974
0982
0990
0998
1008
1014
1022

0967
0975
0983
0991
0999
1007
1015
1023

H-3

Octal-Decimal Integer Conversion Table (Cont)
0

I 024
I 032
1040
1048
1056
1064
1072
1080

1025
1033
1041
1049
1057
1065
1073
1081

1026
1034
1042
1050
1058
1066
1074
1082

1089
1097
1105
1113
1121
1129
2160 1136 II 37
2170 1144 114!'1

1090
1098
1106
1114
1122
1130
1138
114G

2200111S2 1153
2210 1160 1161
2220 1168 1169
2231J 1176 1177
2240 1'184 1185
2250 1192 1193
2260 1200 1201
2270 1208 ·1209

2000
2010
2020
2030
2040
2050
2060
2070
2100
2110
2120
2130
2140

1088
1096
1104
1112
1120

"'T"'

1027 1028
1035 1036
1043 1044
1051 1052
1059 1060
1067 1068
1075 1076
1083 1084

1029
1037
1045
1053
1061
1069
1077
1085

1030 1031
1038 1039
1046 1047
1054 1055
1062 1063
1070 10'11
1078 1079
1086 1087

1091
1099
1107
1115
1123
1131
1139
1147

1092
1100
1108
1116
1124
1132
1140
1148

1093
1101
1109
1117
1125
1133
1141
1149

1094
1102
1110
1118
1126
1134
1142
1150

1154 1155 1156
1162 1163 1164
1170 1171 1172
1178 1179 1180
1186 1187 1188
1194 1195 1196
1202 1203 1204
1210 1211 1212

1157
1165
1173
1181
1189
1197
1205
1213

1219 1220
1227 1228
1235 1236
1243 1244
1251 1252
1259 1260
1267 1268
1275 1276

2400
2410
2420
2430
2440
2450
2460
2470

1280
1288
1296
1304
1312
1320
1328
1336

1281
1289
1297
1305
1313
1321
1329
1337

1282
i290
1298
1306
1314
1322
1330
1338

1283
1291
1299
1307
1315
1323
1331
1339

1284
1292
1300
1308
1316
1324
1332
1340

1285
1293
1301
1309
1317
1325
1323
1341

1286
1294
1302
1310
1318
1326
1334
1342

1287
1295
1303
1311
1319
1327
1335
1343

1095
1103
1111
1119
1127
1135
1143
1!51

2500
2510
2520
2530
2540
2550
2560
2570

1344 1345
1352 1353
1360 1361
1368 1369
1376 1377
1384 1385
1392 1393
1400 1401

1346
1354
1362
1370
1378
1386
1394
1402

1347
1355
1363
1371
1379
1387
1395
1403

1348
1356
1364
1372
1380
1388
1396
1404

1349
1357
1365
1373
1381
1389
1397
1405

1350
1358
1366
1374
1382
1390
1398
1406

1351
1359
1367
1375
1383
1391
1399
1407

1158
1166
1174
1182
1190
1198
1206
1214

1159
1167
1175
1183
1191
1199
1207
1215

2600
2610
2620
2630
2640
2650
2660
2670

1408
1416
1424
1432
1440
1448
1456
1464

1409
1417
1425
1433
1441
1449
1457
1465

1410 1411
1418 1419
1426 1427
1434 1435
1442 1443
1450 1451
1458 1459
1466 1467

1412 1413
1420 1421
1428 1429
1436 1437
1444 1445
1452 1453
1460 1461
1468 1469

1414 1415
1422 1423
1430 1431
1438 1439
1446 1447
1454 1455
1462 1463
1470 1471

1221
1229
1237
1245
1253
1261
1269
1277

1222
1230
1238
1246
1254
1262
1270
1278

1223
1231
1239
1247
1255
1263
1271
1279

2700
2710
2720
2730
2740
2750
2760
2770

1472
1480
1488
1496
1504
1512
1520
1528

1473
1481
1489
1497
1505
1513
1521
1529

1474
1482
1490
1498
1506
1514
1522
1530

1475
1483
1491
1499
1507
1515
1523
1531

1476 1477
1484 1485
1492 1493
1500 1501
1508 1509
1516 1517
1524 1525
1532 1533

1478 1479
1486 1487
149~ 1495
1502 1503
1510 1511
1518 1519
1526 1527
1534 1535

1795
1803
1811
1819
1827
1835
1843
1851

1796
1804
1812
1820
1828
1836
1844
1852

1797
1805
1813
1821
1829
1837
1845
1853

1798
1806
1814
1822
1830
1838
1846
1854

1799
1807,
1815
1823
1831
1839
1847
1855

1216
1224
1232
1240
1248
1256
1264
1272

1217
1225
1233
1241
1249
1257
1265
1173

1218
1226
1234
1242
12SO
1258
1266
1274

3000 1536
3010 I 544
3020 1552
3030 1560
3040 1568
3050 1576
3060 1584
3070 1592

1537
1545
1553
1561
1569
1577
1585
1593

1538
I 546
1554
1562
1570
1578
1586
1594

1539
1547
1555
1563
1571
1579
1587
1595

1540
1548
1556
1564
1572
1580
1588
1596

1541
1549
1557
1565
1573
1581
1589
1597

1542
1550
1558
1566
1574
1582
1590
1598

1543
1551
1559
1567
1575
1583
1591
1599

3400 1792 1793 1794
3410 1800 1801 1802
3420 1808 1809 1810
3430 1816 1817 1818
3440 1824 1825 1826
3450 1832 1833 1834
3460 1840 1841 1842
3470 1848 1849 1850

3100 1600
3110 1608
3120 1616
3130 11124
3140 1632
3150 1640
3160 1648
3170 1656

1601
1609
1617
1625
1633
1641
1649
1657

1602
1610
1618
1626
1634
1642
1650
1658

1603
1611
1619
1627
1635
1643
1651
1659

1604
1612
1620
1628
1636
1644
1652
1660

1605
1613
1621
1629
1637
1645
1653
1661

1606
1614
1622
1630
1638
1646
16.>4
1662

1607
1615
1623
1631
1639
1647
1655
1663

3500 1856 1857
3510 1864 1865
3520 1872 1873
3530 1880 1881
3540 1888 1889
3550 1896 1897
3560 1904 1905
3570 1912 1913

1859
1867
1875
1883
1891
1899
1!~06 1907
1914 1915

1860
1868
1876
1884
1892
1900
1908
1916

1861
1869
1877
1885
1893
1901
1909
1917

1862 lBU
1870 1871
1878 1879
1886 1887
1894 1895
1902 1903
1910 1911
1918 1919

3200 1664
3210 1672
3220 1680
3230 1688
3240 1696
3250 1704
3260 1712
3270 11720

1665
1673
1681
1689
1697
1705
1713
1721

1666
1674
1682
1690
1698
1706
1714
1722

1667
1675
1683
1691
1699
1707
1715
1723

1668
1676
1684
1692
1700
1708
1716
1724

1669
1677
1685
1693
1701
1709
1717
1725

1670
1678
1686
1694
1702
1710
1718
1726

1671
1679
1687
1695
1703
1711
1719
1727

3600
3610
3620
3630
3640
3650
3660
3670

1922
1930
1938
1946
1954
1962
1970
1978

1923
1931
1939
1947
19:i5
1963
1971
1979

1924
1932
1940
1948
1956
1964
1972
1980

1925
1933
1941
1949
1957
1965
1973
1981

1926
1934
1942
1950
1958
1966
1974
1982

3300 1728
3310J11J6
3320 1744
3330 1752
3340 1760
3350 1768
3360 1776
3370 1784

1729
1737
1745
1753
1761
1769
1777
1785

1730
1738
1746
1754
1762
1770
1778
1786

1731
1739
1747
1755
1763
1771
1779
1787

1732
1740
1748
1756
1764
1772
1780
1788

1733
1741
1749
1757
1765
1773
1781
1789

1734
1742
1750
1758
1766
1774
1782
1790

1735
1743
1751
1759
1767
1775
1783
1791

3700 1984 1985 1986
3710 1992 1993 1994
3720 2000 2001 2002
3730 2008 2009 2010
3740 2016 2017 2018
3!50 2024 2025 2026
3760 2032 2033 2034
3770 2040 2041 2042

1987
199S
2003
2011
2019
2027
2035
2043

1988 1989
1996 1997
2004 2005
2012 2013
2020 2021
2028 2029
2036 2037
2044 2045

2300
2310
2320
2330
2340
2350
2360
2370

H-4

1920
1928
1936
1944
1952
1960
1968
1976

1921
1929
1937
1945
1953
1961
1969
1977

1858
1866
1874
1882
1890
1898

2000

102•

2777
(Octol)

1535
(Decimal)

Octal Decimal

10000. 4096
20000. 8192
30000- 12288
.coooo - 1638.C
50000 - 20.CSO
60000 • 24576

70000 • 28672

1927
1935
1943
1951
1959
1967
1975
1983

1990 1991
1998 1999
2006 2007
2014 2015
2022 20Z3
2030 2031
2038 2039
2046 2047

3000
to

1536
to

3777

20•7

COctol)

(Deci111of)

Octal-Decimal Integer Conversion Table (Cont)
0

.ooo
to

2048

to
255~

•777
IOctall

IDf'c;mal'

Octal

Decimal

10000· .. 096
20000. 8192
30000. 12288
.cooon • 1638..
50000 • 20480
60000 • 24576
70000 . 28672

4000
4010
4020
4030
4040

2048
2056
2064
2072
2080
40~0 2088
4060 2Q96
4070 2104

2049
2057
2065
2073
2081
2089
2097
2105

2050
2058
2066
2074
2082
2090
2098
2106

4400 2304 2305
4410 2312 2313
4420 2320 2321
4430 2328 2329
4440 2336 2337
4450, 2344 2345
4460 2352 2353
4470 2360 2361

2051 2052 2053 2054 2055
2059 2060 2061 2062 2063
2067 2068 2069 2070 2071
207~ 2076 2077 2078 2079
2083 2084 20a5 2086 2087
2091 2092 2093 2094 2095
2099 2100 2101 2102 2103
2107 2108 2109 2110 2111

2306
2314
2322
2330
2338
2346
2354
2362

2307
2315
2323
2331
2339
2347
2355
2363

2308
2316
2324
2332
2340
2348
2356
2364

2309
2317
2325
2333
2341
2349
2357
2365

2310 2311
2318 2319
2326 2327
2334 2335
2342 2343
2350 2351
2358 2359
2366 2361
2374 2375
2382 2383
2390 2391
2398 2399
2406 2407
2414 2415
2422 2423
2430 2431

2116
2124
2132
2140
2148
2156
2164
2172

2117 2118
2125 2126
2133 2134
2141 2142
2149 2150
2157 2158
2165 2166
2173 2174

2119
2127
2135
2143
2151
2159
2167
2175

4500
4510
4520
4i30
4540
4550
4560
4570

2368
2376
2384
2392
2400
2408
2416
2424

2369
2377
2385
2393
2401
2409
2417
2425

2370 2371
2378 2379
2386 2387
2394 2395
2402 2403
2410 2411
2418 2419
2426 2427

2372
2380
2388
2396
2404
2412
2420
2428

2373
2381
2389
2397
2405
2413
2421
2429

2179 2180
2187 2188
2195 2196
2203 2204
2211 2212
2219 2220
2227 2228
2235 2236

2181 2182
2189 2190
219':' 2198
2205 2206
2213 2214
2221 2222
2229 2230
2237 2238

2183
2191
2199
2207
2215
2223
2231
2239

4600
4610
4620
4630
4640
4650
4660
4670

2432 2433
2440 2441
2448 2449
2456 2457
2464 2465
2472 2473
2480 2481
2488 2489

2434 2435
2442 2443
2450 2451
2458 2459
2466 2467
2474 2475
2482 2483
2490 2491

2436
2444
2452
2460
2468
2476
2184
2492

2437 2438 2439
2445 2446 2447
2453 2454 2455
2461 2462 24~3
2469 2470 2471
2477 2478 2479
2485 2486 2487
2493 2494 2495

4700 2.496 2497 2498 2499
4710 2504 2505 2506 2507
4720 2512 2513 2514 2515
4730 2520 2521 2522 2523
474012528 2529 2530 2531
4750 2536 2537 2538 2539
4760, 25H 2545 2546 2547
4770 ! 2552 2553 2554 2555

2500
2508
2516
2524
2532
2540
2548
2556

2501
2509
2517
2525
2533
2541
2549
2557

4100 2112 2113
4110 2120 2121
4120 2128 2129
4130 2136 2137
4140 2144 2145
4150 2152 2153
4160 2160 2161
4170 2168 2169

2114 2115
2122 2123
2130 2131
2138 2139
2146 2147
2154 2155
2162 2163
2170 2171

4200 2176 2177
4210 2184 2185
4220 2192 2193
4230 2200 2201
4240 2208 2209
4250 2216 2217
4260 2224 2225
4270 2232 2233

2178
2186
2194
2202
2210
2218
2226
2234

4300 2240 2241 2242 2243 2244 2245 2246 2247
4310 2248 2249 2250 2251 2252 2253 2254 2255
4320 2256 2257 2258 2259 2260 2261 2262 2263
4330 2264 2265 2266 2267 2268 2269 2270 2271
4340 2272 2273 2274 2275 2276 2277 2278 2279
4350 2280 2281 2282 2283 2284 2285. 2286 2287
4360 2288 2289 2290 2291 2292 2293 2294 2295
4370 2296 2297 2298 2299 2300 2301 ~302 2303,

2502 2503
2510 2511
2518 2519
2526 2527
2534 2535
2542 2543
2550 2551
2558 2559

-~,

- I ,,..
lo

5777

3071

(Octal)

(Oec;mol)

5000
5010
5020
5030
5040
5050
5060
5070

2560
2568
2576
2584
2592
2600
2608
2616

25831
2591
2599
2607
2615
2623

54oo12s16
541012824
5420 2832
5430 2840
5440. 2848
5450 2856
5460 2864
5470 2872

2817
2825
2833
2841
2849
2851
2865
2873

2818
2826
2834
28-12
2850
2858
2866
2874

2819
2827
2835
2843
2851
2859
2867
2875

2820 28:!1
2828 2829
2836 2837
2844 2845
2852 2853
2860 286l
2868 2869
2876 2877

2822
2830
2838
2846
2854
2862
2870
2878

2123
2131
2131

2631
2639
2647
2655
2663
2671
2679
2687

5500
5510
5520
5530
5540
5550
5560
5570

2880
2688
2896
2904
2912
2920
2928
2936

2881
2889
2897
2905
2913
2921
2929
2937

2882
2890
2898
2906
2914
2922
2930
2938

2883
2891
2899
2907
2915
2923
2931
2939

2884
2892
2900
2908
2916
2924
2932
2940

2886 2887
2894 2895
2902 2903
2910 2911
2918 2919
2928 2927
2934 2935
2942 2943

0
2561
2569
2577
2585
2593
2601
2609
2617

2562 2563 2564 2565 2566
2570 2571 2572 2573 2574
2578 ·2579 2580 2581 ~5ll2
2586 2587 2588 258\J 2590
2594 2595 2596 2597 2598
2602 2603 2504 2605 2606
2610 2611 2612 2613 2614
2618 2619 2620 2621 2622

5100 2624 2625 2626
5110 2632 2633 2634
5120 2640 2641 2642
5130 2648 2649 2650
5140 2656 2657 2658
5150 2664 2665 2666
5160 2672 2673 2674
5170 2680 2681 2682

2627
2635
2643
2651
2659
2667
2675
2683

2628
2636
2644
2652
2660
2668
2676
2684

2629 2630
2637 2638
2645 2646
2653 2654
2661 2662
2669 2670
2677 2678
2685 2686

2691
2699
2707
2715
2723
2731
2739
2747

2692
2700
2708
2716
2724
2732
2740
2748

2693 2694 2695
2701 2702 2703
2709 2710 2711
2717 2718 2719
2725 2726 2727
2733 2734 2735
2741 2i42 2743
2749 2750 2751

5200 2688
5210 2696
522012704
5230 2712
5240 '2720
5250 ! 2728
5260 2736
5270 2744

2689
2697
2705
2713
2721
2729
2737
2745

5300 2·; -2
5310 2760
5320 2768
5330 2776
5340 2784
5350 2792
5360 2800
5370 2808

2753 2754 2755 2756 2757 2758 2759
2761 2762 2763 2764 2765 2766 2767
2769 2770 2771 2772 2773 2774 2775
2777 2778 2779 2780 2781 2782 2783
2785 2786 2787 2788 2789 2790 2791
2793 2794 2795 2796 2797 2798 2799
2801 2802 2803 2804 2805 2806 2807
2809 2810 2811 2812 2813 2814 2815

2690
2698
2706
2714
2722
2730
2738
2746

2567
2575

5600 2944 2945
561012952 2953
562012960 2961
5630 2968 ~9!i9
564012976 2977
5650 298-1 2985
5660 2992 2993
5670 3000 3001
:>700 3008
5710 3016
5720 3024
5730 3032
5740 3040
5750 3048
5760 3056
5770 3064

2885
2893
2901
2909
2917
2925
2933
2941

:u1
2155
2HJ
2871
287V

2946 2947 2948 2949 2950 2951
2954 2955 2956 2957 2958 2959
2962 2963 2964 2965 2966 2961
2970 2971 2972 2973 2974 2975
2978 2979 2980 2981 2982 2983
2986 2987 2988 2989 2990 2991
2994 2995 2996 2997 2998 2999
3002 3003 3004 3005 3006 3007

3009 3010 3011 3012
3017 3018 3019 3020
3025 3026 3027 3028
3033 3034 3035 3036
3041 3042 3043 3044
3049 3050 3051 3052
3057 3058 3059 3060
3065 3066 306'.7 3068

30l 3 3014 3015
3021 3022 3023
3029 3030 3031
3037 3038 3039
3045 3046 3047
3053 3054 3055
3061 3062 3<Je3
3069 3070 3071

H-5

Octal-Decimal Integer Conversion Table (Cont)
0
8000
8010
8020
8030
8040
8050
6060
6070

3072 3073
3080 3081
3088 3089
3096 3097
3104 3105
3112 3113
3120 3121
3128 3129

3074
3082
3090
3098
3106
3114
3122
3130

3075
3083
3091
3099
3107
31 lS
3123
3131

3076
3084
3092
3100
3108
3116
3124
3132

3077
3085
3093
3101
3109
3117
3125
3133

3078
3086
3094
3102
3110
3118
3126
3134

3079
3087
3095
3103
3111
3119
3127
3135

6400
6410
6420
6430
6440
6450
6460
6470

3328
3336
3344
3352
3360
3368
3376
3384

3329
3337
3345
3353
3361
3369
3377
3385

3330
3338
3346
3354
3362
3370
3378
3386

3331
3339
3347
3355
3363
3371
3379
3387

3332
3340
3348
3356
3364
3372
3380
3388

3333
3341
3349
3357
3365
3373
3381
3389

3334
3342
3350
3358
3366
3374
3382
3390

3335
3343
3351
3359
3367
3375
3383
3391
3399
3407
3415
3423
3431
3439
3447
3455

1100 3136
8110 I 3144
1120 3152
8130 3160
1140 3168
1150 3116
8160 3184
1170 3192

3137
3145
3153
3161
3169
317T
JIBS
3193

3138 3139
3146 3147
3154 3155
3162 3163
3170 3171
3178 3179
3186 3187
3194 3195

3140 3141
3148 3149
3156 3157
3164 3165
3172 3173
3180 3181
3188 3189
3196 3197

3142 ~143
3150 3151
3158 3159
3166 3167
3174 3175
3182 3183
3190 3191
3198 3199

6500
6510
8520
6530
6540
6550
6560
6570

3392
3400
3408
3416
3424
3432
3440
3448

3393
3401
3409
3417
3425
3433
3441
3449

3394
3402
3410
3418
3426
3434
3442
3450

3395
3403
3411
3419
3427
3435
3443
3451

3396
3404
3412
3420
3428
3436
3444
3452

3397
3405
3413
3421
3429
3437
3445
3453

3398
3406
3414
3422
3430
3438
3446
3454

8200
f1210
1220
1230
1240
1250

3200
3208
3211
3224
3232
3240
IHO 3248
1270 3251

3201
3209
3117
3225
3238
3241
3249
3257

3202
3210
3218
3226
3234
3242
3250
3258

3204 3205
3212 3213
3220 3221
3228 3229
3236 3237
3244 3245
3252 3253
3260 3261

3206
3214
3222
3230
3238
3246
3254
3262

3207
3215
3223
3231
3239
3247
3255
3263

6600
6610
6620
6630
6640
6650
6660
6670

3456
3464
3472
3480
3488
3498
3504
3512

3457
3465
3473
3481
3489
3497
3505
3513

3458
3466
3474
3482
3490
3498
3508
3514

3459
3467
3475
3483
3491
3499
3507
3515

3460
3468
3476
3484
3492
3500
3508
3518

3461
3469
3477
3485
3493
3501
3509
3517

3462 3463
3470 3471
3478 3479
3486 3487
3494 3495
3502 3503
3510 3511
3518 3519

8300
8310
6320
1330
1340
1350
8310
1370

3264 3265
3272 3273
3280 3Z81
3288 3289
3296 3'297
3304 3305
3312 3313
3320 3321

6700
8710
6720
6730
6740
15750
8760
6770

3520
3528
3528
3544
3552
3560
3568
3576

3521
3529
3537
3545
3553
3561
3569
3577

3522
3530
3538
3548
3554
3562
3570
3578

3523
3531
3539
3547
3555
3583
3571
3579

3524
3532
3540
3548
3558
35154
3572
3580

3525 3526
3533 3534
3541 3542
3549 3550
3557 3558
3565 3586
3573 3574
3581 3582

3203
3211
3219
3227
3235
3243
3251
3259

3266 3267
3274 3275
3282 3283
3290 3291
3298 3299
3306 3307
3314 3315
3322 3323

3268
3276
3284
3292
3300
3308
3316
3324

3269
3277
3285
3293
3301
3309
3317
3325

3270 3271
3278 3279
3288 3287
3294 3295
3302 3303
3310 3311
3318 3319
3326 3327

7000 3584 3585 3586 3587 3588 3589 3590 3591
7010 3592 3593 3594 3595 3596 3597 3598 3599
7020 3100 3601 3602 3603 3604 3605 3606 3607
7030 3108 3609 3610 3811 3612 3813 3114 3615
7040 3816 3817 3618 3619 3620 3621 3122 3123
'1050 3824 3825 3828 3821 3628 3829 3130 3631
7080 3832 3633 3834 3835 3636 3837 3638 3639
7070 3840 3141 3&42 3643 3144 3645 3841 3647

7400 3840 3841
7410 3848 3,849
7420 3858 3857
7430 3864 3865
7440 3872 3873
7450 3880 3881
7480 3888 3889
7470 3896 3897

3842 3843 3844 3845
3850 3851 3852 3853
3858 3859 3860 3881
3888 388'1 3888 3889
3874 3875 38'16 3817
3882 3883 3884 3885
3890 3891 3892 3893
3898 3899 3900 3901

3848 384?.
3854 3855
3862 3883
3170 3871
38'18 38'rll
3888 3881
3894 3895
3902 3903

3906 3907 3908
3914 3915 3918
3922 3923 3924
3930 3931 3932
3938 3939 3940
3946 394'1 3948
3954 3955 3956
3952 3963 3964

3909
3917
3925
3933
3941
3949
3957
3965

3910 3911
3918 3919
3926 3927
3934 3935
3942 3943
3950 3951
3958 3959
3988 3987

3904 3905
3912 3913
3920 3921
3928 3929
3938 3937
3944 3945
3952 3953
3960 3961

3714 3'115 3718 3717 3'18 3719
3122 3723 3'124 3725 3121 3727
3130 3731 3732 3'133 3'734 3735
3738 3139 3740 3741 3742 3743
3748 374T 3748 3149 3750 3751
3754 3755 37H 3757 3758 3759
3782 3783 3784 3'185 3'718 3787
37'70 3771 3772 3773 37'74 3'175

'1800
7810
7820
'1630
'1640
7650
7860
7870

3988
3976
3984
3992
4000
4008
4016
4024

3969
3977
3985
3993
4001
4009
4017
4025

3970
3978
3988
3994
4002
4010
4018
4028

3971
3979
3987
3995
4003
4011
4019
4027

3972
3980
3988
3998
4004
4012
4020
4028

3973
3981
3989
3997
4005
4013
4021
4029

3974 3915
3982 3983
3990 3991
3998 3999
4008 4007
4014 4015
1022 4023
4030 4031

37'78 3'777 3771 3779 3780 3781 3'782 3783
3'114 3715 3716 3717 3711 3'189 3790 3791
3792 3793 3794 3'795 3798 3797 3798 3799
3100 3801 3802 3103 3804 3805 3808 3807
310I 3109 3810 3811 3812 3813 3814 3815
'135~ 3111 3817 3818 3819 3820 3821 3822 3123
'1HO 3124 3125 3828 3827 3821 3829 3'30 3831
U'TO 3132 3133 3'134 3835 3838 3837 3131 3839

7700
'7710
7720
7730
7740
7750
7760
7770

4032 4033
4040 4041
4048 4049
4058 4057
40154 4085
4072 4073
4080 4081
4088 4089

4034
4042
4050
4058
4088
4074
4082
4090

4035 4038
4043 4044
4051 4052
4059 4080
40157 4088
4075 4078
4083 4084
4091 4092

4037
4045
4053
4081
4019
4077
4085
4093

4038 4039
4048 4047
4054 4055
4082 4083
40'10 4071
40'18 4079
4088 4087
4094 4095

'1100
'1310
n20
'1330
'7>40

(Octol)

3072
to
3513

(Decimal)

Octal Decimal
10000- ..096
20000- 8192
30000 - 12288
"0000 - 1638..
50000 - 20..80
60000 - 2 ..576
70000 • 28672

7500
7510
'1520
7530
7540
7550
7580
7570

'1200 3112 3713
'1210 3120 3721
7220 3721 3'29
'1230 3731 3737
'1240 3744 3745
'12$0 3752 3753
'7HO 2110 3711
'12'70 3Vll 3'789

6000
to
6777

3527
3535
3543
3551
3559
358'1
3575
3583

3654 3655
3662 3663
3870 3671
3878 3879
36H 3887
31594 3695
3702 3703
3710 3711

7100 3648 3649 3850 3851 3852 3653
7ll0 3656 3857 3658 3659 3660 3681
7120 3814 3685 3868 3667 3868 3819
7130 3172 3173 36'14 36'15 3878 31577
7140 3110 3111 3882 3883 3684 3885
'1150 31518 3189 31590 3691 3192 3813
7110 3698 38t'T 3698 3699 3700 3'101
7110 3704 3705 370& 3707 3108 3709

H-6

7000

I 3,.,

7777

"4095

COctal)

(DHimal)

Octal-Decimal Fraction Conversion Table
OCTAL

DEC.

OCTAL

Dl::C.

OCTAL

m:c.

OCTAL

m:c .

.000
.001
.002
.003
• 004
. 005
. 006
.007
.010
. Oll
.OlZ
.013
.014
.015
.016
• 017
.020
.021
.022
.023
• 024
.025
.02&
.027
. 030
.031
.032
.033
.034
.035
.036
• 037
.040
. 041
.042
.043
.044
.045
. 046
.047

• 000000
• 001953
• (Jo3905
. 005859
• 007812
. 009765
• 011718
• 013671
• 015625
.017578
• 019531
• 021484
• 023437
• 025390
• 027343
• 029296
.031250
• 033203
• 035156
• 037109
• 039062
.041015
• 042968
• 044921
. 046875
• 048828
• 050781
• 052734
• 054687
• 056640
• 058593
• 060546
• 062500
• 064453
• 066406
• 068359
• 070312
• 072265
• 074218
• 076171
• 078125
• 080078
• 082031
• 083984
• 085937
• 087890
• 089843
• 091796
• 093750
• 095703
• 097656
• 099609
• 101562
.103515
• 105468
• 107421
.109375
• 111328
• 113281
• 115234
• 117187
• 119140
.121093
.123046

.100
.101
.102
.103
• 104
• 105
.106
.107
.110
• 111
.112
.113
.114
.115
.116
.117
.120
.121
.122
, 123
• 124
• 125
.126
.127
.130
• 131
.132
.133
• 134
.135
.136
• 137
.140
.141
.142
• 143
.144
.145
.146
.147
.150
.151
.152
.153
.lM
• 155
• 156
.157
• 160
.161
• 162
.163
• 164
.165
.166
. 167
. 170
• 171
.172
. 173
. 174
. 175
• 176
• 177

• 125000
• 126953
. 128906
• 130859
.13:?812
• 134765
• 136718
• 138671
• 140625
• 142578
• 144531
• 146484
.148437
• 150390
.152343
• 154296
• 156250
• 158203
.160156
• 162109
• 164062
.166015
.167968
• 169921
• 171875
• 173828
.175781
• 1'17734
• 179687
• 181640
• 183593
. 185546
• 187500
. 189453
. 191406
• 193359
.195312
.197265
.199218
• 201171
• 203125
• 205078
• 207031
• 208984
• 210937
• 212890
• 214843
• 216796
• 218750
• 220703
• 222656
• 224609
• 226562
• 228515
• 230468
• 232421
• 234375
• 236328
• 238281
• 240234
• 242187
• 244140
• 246093
• 248046

. 200
• 201
• 202
.203
. 204
.205
. 206
. 207
• 210
. 211
• 212
.213
.214
.215
.216
.217
. 220
• 221
.222
.223
.224
.225
• 226
.227
.230
.231
.232
.233
.234
• 235
.236
• 237
• 240
• 241
• 242
.243
.244
.245
.246
.247
.250
• 251
• 252
.253
• 254
• 255
.256
.257
.260
• 261
.262
.263
.264
.265
.266
• 267
• 270
• 271
.272
.273
.274
.275
.276
.277

• 250000
. 251953
• 253906
• 255859
• 257812
. 259765
.261718
• 263671
. 265625
. 267578
• 269531
• 271484
• 273437
• 275390
• 277343
• 279296
• 281250
• 283203
• 285156
• 287109
• 289062
• 291015
• 292968
.294921
• 296875
• 298828
• 300781
• 302734
• 304687
• 306640
.308593
.310546
• 312500
• 314453
• 316406
• 318359
.320312
• 322265
• 324218
• 326171
• 328125
• 330078
• 332031
• 333984
• 335937
• 337890
• 339843
• 341796
• 343750
• 345703
• 347656
. 349609
• 351562
.353515
• 355468
.• 357421
• 359375
,361328
• 363281
• 365234
• 367187
,369140
• 371093
,373046

. 300
. 301
. 302
. 303
. 304
. 305
. 306
. 307
. 310
. 311
. 312
• 313
. 314
.315
.316
.317
• 320
• 321
. 322
. 323
.324
. 325
. 326
.327
.330
. 331
.332
,333
.334
.335
.336
.337
.340
. 341
.342
,343
.344
.345
.346
.347
.350
• 351
.352
.353
,354
,355
.356
.357
.360
.361
.362
• 363
.364
• 365
.366
. 367
.370
• 371
.372
.373
,374
.375
.376
.377

.375000
• 37G953
.37890(,
.380859
. 382812
.3847fi5
• 386718
.388671
.390625
. 3!12578
. 394531
.396484
.398437
,400390
• 402343
.404296
.406250
.408203
.410156
.412109
.414062
.416015
• 417968
.419921
• 421875
.423828
• 426781
.427734
.429687
.431640
.433593
,435M6
• 437500
.439453
.441406
,443359
,445312
.447265
,449218
,451171
.453125
,455078
• 457031
,458984
• 460937
.462890
,464843
• 466796
,468750
• 470703
• 472656
• 474609
• 476562
• 478515
,460468
.482421
• 484375
,486328
,488211
,490234
,492187
• 494140
.496093
.4990415

.oso
. 051
.052
.053
.054
.055
• 056
. 057
. 060
• 061
• 062
. 063
. 064
. 0&5
.066
. 067
. 070
• 071
,072
. 073
. 074
• 075
. 076
• 077

H-7

Octal-Decimal Fraction Conversion Table (Cont)
OCTAL

DEC.

OCTAL

DEC.

OCTAL

DEC.

OCTAL

DEC •

.000000
.000001
.000002
.000003
.000004
• 000005
.000006
.000007
• 000010
• 000011
• 000012

• 000000
.000003
.000007
.000011
.000015
.000019
.000022
.000026
.000030
.000034
.000038
,000041
,000045
.000049
.000053
• 000057
.000061
,000064
,000088
.000072
• 00007'
.000080
,000083
.000087
.000091
.000095
.000099
.000102
.000106
.000110
,000114
.000118
.000122
.000125
.000121
.000133
.000137
,000141
• 000144
.000148
• 000152
.000158
.000180
• 000164
.000167
.000171
.000175
.000179
.000183
.000188
.000190
.000114
.000198
,000202
.000205
,000209
.000213
.000217
.000221
.000225
.000221
.000232
,000238
.000140

.000100
. 000101
• 000102
• 000103
• 000104
• 000105
.000106
• 000107
,000110
.000111
• 000112
.000113
,000114
,000115
.000116
.000117
.000120
,000121
.000122
,000123
.000124
,000125
.000128
.000127
.000130
.000131
,000132
.000133
,000134
,000135
,000138
.000137
.000140
,000141
.000142
.000143
.000144
,000145
,000148
.000147
.000150
,000151
.000152
.000153
,000154
,000155
.000158
.000157
.000180
.000181
.000182
.000113
• 000184
.000165
• 000166
.000167
• 000170
,000171
.000172
• 000173
• 000174
• 000175
,000176
,000171

.000244
.000247
.000251
.000255
.000259
.000213
.001)267
.000270
.000274
.000278
.000282
.000288
.000289
.0002u
.000297
,000301
.000305
.000308
.000312
.000318
.000320
.000324
.000329
.000331
.000335
,000339
.000343
.000347
,000350
.000354
,000358
.000312
.000318
,000370
.000373
.00037'
.000311
.000315
.000389
.000392
.000396
,000400
.000404
.000408
,000411
,000415
.000411
.000413
.000427
.000431
.000434
.OOH38
.000442
.000448
.000450
.000453
.000457

.000200
.000201
.000202
.000203
.000204
.000205
.000206
.000207
.000210
.000211
.000212
.000213
.000214
,000215
,000218
,000217

• 000488
• 000492
• 000495
• 000499
• 000503
• 000507
• 000511
• 000514
• 000518
• 000522
• 000526
• 000530
• 000534
• 000537
• 000541
• 000545
• 000549
• 000553
.000551
• 000580
• 000564
. 000588
• 000572
• 000576
• 000579
• 000583
• 0005•1
.000591
• 000595
,000598
.000802
.000808
• 000610
• 000614
• 000817
.000621
.000825
• 000629
• 000833
.000637
,000640
.000844
.000648
.000852
,00065'
.000859
.000813
• 000187
,000671
,000875
.000679
• 000682
• 000686
• 000690
.00069<
.000698
.000701
.000705
.000709
.000713
.000117
.000720
,000724
• 000121

.000300
.000301
.000302
.000303
• 000304
.000305
.000306
.000307
• 000310
.000311
.000312
.000313
.000314
.000315
,000316
,000317
• 000320
• 000321
• 000322
• 000323
• 00032'4
.000325
• 000326
• 000327
• 000330
• 000331
• 000332
.000333
.000334
.000335
.000338
.000337
.000340
,000341
.000342
.000343
.000344
,000345
.OOOHt;
.000347
,000350
• 000351
.000351
,000353
.000354
.000355
.000356
,0003 ...
.000380
.000361
.000362
.000313
.000364
.000365
.000316
.000367
.000370
.000371
• 000372
.000373
.000374
,000375
.000376
.000377

• 000732
.000736
• 000740
• 000743
.000747
• 000751
.000755
.000759
.000762
.000766
.000710
.000714
.000718
.000782
,000715
.000799
• 00079'3
.000797
• 000801
.000805
.000808
.000812
• 000818
• ooo8zo
.000823
.000821
• 000831
.000835
.000139
.000843
.000846
.000850
.000854
.000858
.000182
.000185
.000869
,000813
.000877
.000881
,000885
,000818
.Oto892
.000898
,000900
.000904
.000907
.000911
.000915
• 000919
.000923
.000926
• 000930
• 000934
• 000938
• 0009"2
• 000946
.000949
.000953
.000957
,000961
.000965
.000968
,000912

.000013
.000014
,000015
.000018
,000017
.000020
.000021
,000022
.000023
,000024
.000025
,000026
,000027
.000030
.000031
• 000032
.000033
,000034
.OU0035
.000038
.000037
,000040
.000041
.000042
• 000043
.000044
.000045
.000046
.l'00047
.000050
,000051
.000052
,000053
,000054
.000055
,000058
,000051
.000080
• 000081
.000062
.000063
.000064
.000065
.000066
,000067
,000070
,000071
.000072
.000073
.000014
.000075
.000071
.000011

H-8

.000481

.000485
.000469
.000413
.000476
.000480
,000484

.oooazo
.000221
,000222
,000223
,000224
.0002Z5
.000226
.000227
,000230
.000231
.000232
.000233
,000234
.000235
,000238
,000237
,000240
.000241
.000242
.000243
.000244
,000245
,000248
.000241

.ooouo
.000251
.000252
.000253
,000254
.000255
.000258
.000257
.000260
.000261
.000262
.000263
.000264
.000265
.000266
.000267
.000270
.000271
,000212
.000273
.000274
,000275
,000276
.000277

Octal-Decimal Fraction Conversion Table (Cont)
OCTAL

DEC.

OCTAL

DEC.

OCTAL

DEC.

OCTAL

DEC,

.000400
• 000401
.000402
.000403
.000404
.000405
.000406
,000407
.000410
.000411
.000412
,000413
.000414
.000415
.000416
.000417

.000976
• 000980
.000984
• 000988
• 000991
• 000995
.000999
• 001003
.001007
• 001010
• 001014
• 001018
• 001022
• 001026
• 001029
.001033

• 000500
• 000501
.000502
. 000503
• 000504
• 000505
• 000506
• 000507
• 000510
• 000511
.000512
,000513
.000514
• 000515
.000516
• 000517

• 001220
• 001224
• 001228
• 001232
• 001235
• 001239
• 001243
• 001247
. 001251
• 001255
• 001258
• 001262
• 001266
• 001270
• 001274
• 001277

• 000600
• 000601
.000602
.000603
.000604
• 000605
.000606
.000607
.000610
• 000611
• 000612
,000613
• 000614
• 000615
• 000616
• 000617

• 001464
• 001468
• 001472
• 001476
• 001480
• 001483
• 001487
• 001491
• 001495
• 001499
• 001502
• 001506
• 001510
• 001514
,001518
• 001522

• 000700
• 000701
• 000702
• 000703
• 000704
• 000705
• 000706
• 000707
• 000710
• 000711
• 000712
• 000713
• 000714
• 000715
• 000716
• 000717

• 001708
• 001712
• 001716
• 001720
• 001724
• 001728
.001731
• 001735
• 001739
• 001743
.0017·47
• 001750
• 001754
• 001758
• 001762
• 001766

.000420
.000421
,000422
.000413
.000424
.000425
.000426
,000427
.000430
.000431
.000432
,000433
.000434
,000435
,0004311
.000437
.000440
.000441
.000442
.000443
.000444
.000446
.000448
.000447
.000450
.000451
.000452
.000453
.000454
.000455
.000458
.000457
.000410
.000411
.000411
.000483
.0004M
.000465
• 000466
.000467
.000470
.000471
.000472
.000473
.000474
.000475
.000476
.000477

• 001037
• 001041
• 001045
• 001049
• 001052
.001056
.001060
• 001064
.001068
,001071
.001075
• 001079
• 001083
.001087
• 001091
.001094

.000520
.000521
.000522
.000523
• 000524
.000525
.000526
.000527
.000530
.000531
.000532
,000533
.000534
.OOOS35
.000536
.000537
.000540
.000541
.000542
.000543
.00054-4
.000545
.000546
.000541
,000550
,000551
.000552
.000553
.000554
,000555
.000556
.000557
,000560
.000561
.000562
,000563
.000564
.000565
.000566
.000567
.000570
.000571
.000572
.000573
.000574
.000575
• 000576
• 000577

• 001281
• 001285
• 001289
• 001293
• 001296
• 001300
• 001304
• 001308
• 001312
• 001316
• 001319
• 001323
• 001327
• 001331
• 001335
• 001338
• 001342
• 001346
.001350
• 001354
• 001358
• 001361
.001365
.001369
• 001373
.001377
• 001380
.001384
• 001388
• 001392
• 001396
.001399
.001403
• 001407
• 001411
.001415
.001419
.001422
• 001426
• 001430
.001434
• 001438
• 001441
• 001445
• 001449
• 001453
• 001457
• 001461

.000620
.000621
.000622
• 000623
.000624
.000625
.000626
,000627
.000630
• 000631
• 000632
.000633
.000634
,000635
• 000636
.000637
• 000640
• 000641
.000642
,000643
.000644
.000645
.000646
.000647
.000650
• 000651
.000652
.000653
.000654
.000655
.000656
,000657
,000660
• 000661
.000662
,000663
000664
.000665
.000666
000667
.Ci>0670
• 000671
.000672
,000673
.000674
.000675
.000676
• 000677

,001525
. 001529
• 001533
• 001537
• 001541
• 001544
• 001548
• 001552
. 001556
• 001560
• 001564
• 001567
.001571
. 001575
.001579
• 001583
• 001586
. 001590
• 001594
• 001598
.001602
• 001605
• 001609
• 001613
,001617
• 001621
• 001625
• 001628
• 001632
• 001636
• 001640
• 001644
,001647
• 001651
• 001655
• 001659
• 001663
• 001667
• 001670
• 001674
• 001678
• 001682
• 001686
• 001689
. 001693
• 001697
. 0017.Dl
• 001105

• 000720
• 000721
• 000722
. 000723
• 000724
• 000725
• 000726
• 000727
• 000730
• 000731
• 000732
• 00()733
• 000734
• 000735
• 000736
• 000737
• 000740
• 000741
• 000742
• 000743
• 000744
• 000745
• 000746
• 000747
• 000750
• 000751
• 000752
• 000753
• 000754
.000755
.000756
• 000757
• 000760
• 000761
• 000762
.000763
• 000764
.000785
• 000766
• 000767
• 000770
.000771
.000772
• 000773
• 000774
• 000775
.000776
• 000777

• 001770
• 001773
• 001777
.001781
• 001785
• 00171:19
• 001792
• 001796
• 001800
• 001804
• 001808
,001811
.001815
• 001819
• 001823
• 001827
• 001831
.001834
• 001838
• 001842
,001846
• 001850
.001853
• 001857
.001861
• 001865
.001869
.001873
.001876
• 001880
• 001884
.001881
.00189%
.001895
.001899
.001903
• 001907
• 001911
,001914
,001918
,00lt22
• 001926
,001930
• 001934
• 001937
• 001941
,001945
• 001949

• 001098
• 001102
• 001106
• 001110
• 001113
.001117
• 001121
• 001125
• 001129
• 001132
.001136
• 001140
• 001144
• 001148
• 00115%
• 001155
• 001159

.oonu
• 001167
• 001171
• 001174
.001178
• 001182
• 001186
• 001190
,001194
• 001197
.0012
• 00120:)
• 001209
• 001213
• 001216

H-9

Index

A
AAOl-A Digital-To-Analog
Accumulator (AC), Description
Accumulator, I/O Transfers
A-D Converter Controls
A-D Converter Instructions
AD 12 Analog-Digital Converter and Multiplexer
Addressing: a-Class
Addressing, Combination of
Extended Memory Programming
Addressing Methods, 8 Mode
Addressing Methods, Memory
Addressing: a-Class
{3-Register
{3-Register Indexing
Direct Addressing, LINC mode
Indirect Addressing: ~-Class
AFOl-A A-D Converter Specifications
AFOl-A Analog-To-Digital Converter
AFOl-A Sample and Hold Options
a-Class, Addressing
a-Class and Non-Memory Reference Format
a-Class and Others
a-Class Operations
Analog-To-Digital Converter AFOl-A
Analog Inputs
Analog Inputs, Equipment
Analog Knobs and Power Switch Panel
Analog-To-Digital
A-D Converter Controls
Analog-To-Digital Converter AFOl-A
Instructions, A-D Converter
Sample and Hold Options, AFOl-A
Specifications, AFOl-A A-D Converter
ASR-33 Character Set Display Pattern
Autoindexing, Extended Memory Programming
Autoindexing, 8 Mode
Auxiliary Scope Connector

6-82
1-3
5-9
6-78
6-78
3-35
3-6
4-21
4-2
3-3
3-6
3-4
3-5
3-3
3-3
6-76
6-76
6-81
3-6
3-6
3-6
3-14
6-76
1-5,3-35
1-1
2-8
6-76
6-78
6-76
6-78
6-81
6-76
3-34
4-21
4-4
1-5

BA 12 Peripheral Expander
{3-Class Format
{3-Class Instruction Format
{3-Register
{3-Register Indexing
Block, (LINC tape)
Block Number (BM)
Break Field Register, Extended Memory

1-6
3-6
3-4
3-4
3-5
3-39
3-39
4-19

c
Cable Connections, Front Panel
Cable Connections to I/O Bus
Cable Selection
Card Readers
Card Reader and Control CR12
CM12 Optical Mark Card Reader
CM12 Optical Mark Card Reader Instructions
Controls and Indicators CMl 2
Control or Indicator, CR12
Instructions, CM12 Optical Mark
Card Reader
Instructions, CRl 2 Card Reader
Optical Mark Card Reader, CMl 2
Card Reader and Control CRl 2
Central Processor, Logic Description
Accumulator (AC), Description
Instruction Field Register (IF), 5-Bits
Instruction Register (IR), 12 Bits
Link (L) I Bit
Memory Address Register (MA) 12 Bits
Memory Buffer (MB), 12 Bits
Mode Status Register 1 Bit
Program Counter (PC) 12 Bits
Central Processor, Major State Indicators
Central Processor, Miscellaneous Indicators
Central Processor, Register Indicators

G-1
5-45
5-40
6-63
6-63
6-66
6-66
6-67
6-65
6-66
6-63
6-66
6-63
1-1
1-3
1-4
1-3
1-3
1-3
1-3
1-3
1-3
2-3
2-4
2-3

1-1

Character Displays
Character Set
Character Size
Checksum (CM)
Check Words (CW)
Classic LINC
CM12 Optical Mark Card Reader
Controls and Indicators CM 12
Codes, Table of
Combining Group 1 Operations
Combined Operations: Group 1
Combined Skips In Group II
Command Register, Contents, Magnetic Tape
Configuration of, PDP-12
Connections, Front Panel Cable
Connections, Interface
Connections, I/O Bus Cable
Connector Selection
Console Controls and Indicators
Console Key Functions
Console Switches
Console Toggle Switches
Console Teletype Control
Controls and Indicators
Control Registers
Continued Operations, Magnetic Tape
Construction of Interfaces
Converting ASCII Code to PDP-12 Teletype
Conventions, Logic
CRT Display Character Size
CRT Display, Equipment
CRT Display, Remote
CRT Display, VR12
ASR-33 Character, See Display Pattern
Character Displays
Character Set
DIS Display (a-Class)
DSC Display Character ('3-Class)
DSC Display Pattern for
Half-Size Characters
Point Displays
CR12 Card Reader and Control
CR12 Card Reader, Control or Indicator
CRl 2 Card Reader Instructions
Counter Register, KWl 2-A
Current Address, Three Cycle Data Break

3-32
3-33
1-5,3-29
3-39
3-39

1-4
6-66
6-67
F-1
4-9
4-8
4-11
6-51
1-1
G-1
5-44
5-45
5-41
2-1
2-6
3-22
3-7
6-5
2-1
3-40
6-49
5-39
6-3,F-3
5-3
1-45
1-1
3-31
2-1,3-31
3-34
3-32
3-33
3-32
3-32
3-33
3-33
3-32
6-63
6-65
6-63
6-62
5-29

D
Dataphone Control, Type DP12-B
Dataphone Interface DP 12-B
Data Break, Input Data Transfers
Input Interface Logic
Memory Increment
Output Data Transfers
Output Interface Logic
Output Transfer Timing
Request for
Single Cycle
Single Cycle Timing
Three Cycle
Three Cycle Timing

1-2

6-9
1-6
5-22
5-24
5-27
5-23
5-26
5-25
5-22
5-21
5-23
5-21,5-29
5-29

5-2,5-21
Data Break Transfers
5-24
Data Break Input Interface Logic
Data Break Output Interface Logic
5-26
5-25
Data Break Output Transfer Timing
5-23
Data Break Single Cycle Timing
5-21
Data Break Transfer Interface
5-30
Increment CA Inhibit, Three Cycle Data Break
5-22
Input Data Transfers, Data Break
5-27
Memory Increment, Data Break
5-28
Memory Increment, Data Break Timing
Output Data Transfers, Data Break
5-23
5-29
Three Cycle Data Break
Three Cycle Data Break Timing
5-29
Word Count Overflow, Three Cycle Data Break
5-30
Data Break Transfer Interface
5-21
Data Break, Types of
5-21
Data Buffer DB 12-P, N
3-1
Data Field
1-4
Data Field in Memory
4-19
Data Field Register, Extended Memory
3-2
Data Field Reserved Locations
H-1
Data, Mathematical Table
3-39
Data Path
1-5,3-35
Data Terminal
2-1
Analog Extension Panel
3-37
ATR AC to Relays
2-1
Clock Input Panel
3-36
Fast Sample
2-1
Power Switch Panel
2-7
Relay and Analog Input Panel
3-36
Relay Terminals and Corresponding AC Bits
3-37
RTA Relays to AC
3-36
SAM Sample
5-2
Data Transfers, see Programmed Data Transfers
5-10
Data Transfers, Input
5-11
Data Transfers, Output
5-6
Data Transfer Timing
Data Words (DM, FM)
3-39
6-73
DB12-P, N Data Buffer
6-15
DC02-D Instructions
6-14
DC02-E Control Instructions
DC02-E Multiple Teletype Control
6-13
6-16
DC02-F Multiple Teletype Control
6-17
DC02-F Instructions
54
Decoding, Instruction JOT
5-7
Device Selector
DF/DS32, -D Random Access Disk File,
Instructions
6-27
Digital-To-Analog
6-82
Digital-To-Analog AAOl-A
6-82
Digital-To-Analog AAOl-A
6-82
Direct Address
3-6
Direct Addressing
4-2
Direct Address Format of
3-3
DIS Display (a-Class)
3-32
Disable Teletype Interrupt
3-29
6-38
Disk Cartridge Memory, RK8/RK01
6-30
Disk Memory System, RF/RS08
643
Disk, RK.8-P, RK8-N, RK.01, RKOl-K
Disk Storage
6-27
bF/DS32, -D Instructions
6-27
6-38
Disk Cartridge Memory, RK8/RK01

Disk Memory System, RF/RS08
Instructions, RF 3 2 to RF /RS08 Comparison
Instructions, RK08/RKO1
Programming, Disk Software
Programming, RK08/RK01 1/0 Subroutine
Random Access Disk File,
DF/DS32 and DF/DS32-D
RF /RS08 Instructions
RF /RS08 Programming, Example
Specifications, RF /RS08
Specifications, RK9/RK01
Display
Display Scope Controls
Division
Division of 24-bit numbers
EAE Programming
DM12
DSC Display Character ({3-Class)
DSC Display Pattern for,
DW08A I/O and Bus Converter

6-30
6-35
6-38
6-44
6-42
6-27
6-30
6-34
6-37
6-43
1-5
2-11
4-18
4-17
5-20
3-32
3-33
1-6

RIB Read Interrupt Buffer
RIF Read Instruction Field
RMF Restore Memory Field
Program Interrupt, Extended Memory
Programming, Extended Memory
Register, Extended Memory
Save Field Register, Extended Memory
Extended Memory, 8 Mode see also
LINC mode control
Extended Operations
Extended Operations Buffer
Extended Operations, LINCtape
Extended Tape Addressing
Hold-motion
No-Pause
Program Interrupt
Tape Interrupt
with Core
Extended Units
External Level Lines
External Skips

4-20
4-20
4-20
4-22
4-21
4-19
4-19
3-22
3-45
3-41
3-40
1-4
14
1-4
14
1-4
1-4
3-47
3-20
3-20

E
4-13
EAE Instruction Format
4-13
EAE Instructions
4-16
ASR Arithmetic Shift Right
4-16
ASR, Shift Path for
4-14
CLA Clear AC
4-15
DVI Divide
4-16
LSR Logical Shift Right
4-16
LSR, Shift Path for
4-14
MQA Place MQ in AC
4-14
MQL Load MQ from AC
4-15
MUL Multiply
4-15
NMI Normalize
4-15
NMI, SHL Shift Path for,
4-14
SCA Step Counter to AC
4-14
SCL Load Step Counter
4-15
SHL Shift Left
4-4
Effective Address, 8 Mode
3-3
Effective Addressing
B-1
8 Mode Instructions
D-1
8 Mode Perforated Tape Loader
3-8
End-around carry
3-46
Extended Address Format
Extended Arithmetic Element,
4-16
Programming for
1-6,4-13
Extended Arithmetic Element (EAE), KEl 2
4-13
Extended Arithmetic Element, KE12
4-2,4-19
Extended Memory
Addressing Combination of Extended
4-21
Memory Prograir·ming
4-21
Autoindexing, Extended Memory Programming
4-19
Break Field Register, Extended Memory
4-19
Data Field Register, Extended Memory
Extended Memory, Calling A Subroutine
4-21
Across Fields
Instruction Field Buffer, Extended Memory
4-19
4-19
Instruction Field Register, Extended Memory
Instructions, Extended Memory
4-19
4-20
CDF Change Data Field
CIF Change Instruction Field
4-20
RDF Read Data Field
4-20

F
Fast Sample
Field Address, Use of
First Word
Fixed Interval Clocks
Format Routines
Frequency Range, KWl 2-B,C
Front Panel Cable Connections
Full-Word Arithmetic
Full-Word Comparison
Full-Word Data Transfers
Full-Word Instructions
Full-Word Logic
Functional Description, Magnetic
Tape Control

3-29
3-2
3-42
6-25
6-7
6-26
G-1
3-8
3-12
3-7
3-7
3-11
6-45

G
General Description, System PDP-12
Group I, Operate Class Instruction Format
Group II, Combined Skips
Group II, Operate Class
Guard Word (GM)

1-1
4-7
4-11
4-9
3-39

H
Half-Size Characters
Half-Word Addressing, defined
Hold-Motion, Extended Tape Addressing
Hold Unit Motion

3-33
3-13,3-14
14
3-48

I
I-Bit
I-Bit, Octal Value
I-Bit, 8 Mode Addressing
Increment CA Inhibit, Three Cycle
Data Break
Incremental Plotter XYl 2

34
3-7
44
5-30
1-6

1-3

Incremental Plotter and Control
Type XY12
Indexing, {3-Register
Indicators & Controls
Analog Knobs and Power Switch Panel
Central Processor Major State Indicators
Central Processor Miscellaneous Indicators
Central Processor Register Indicators
Console Key Functions
Display Scope Controls
Individual Console Toggle Switches
Tape Processor Major State Indicators
Teletype Model 33ASR Controls
Toggle Switch Registers
TU55 Tape Transport Controls and Indicators
Indirect Address, /3-Class
Indirect Addressing
Input Data Transfers
Input Data Transfers, Data Break
Input/Output Bus Description
Input/Output Facilities and Display,
LINC mode, 1/0 Bus
Analog Inputs
Auxiliary Scope Connector
Dataphone Interface DPl 2-B
Data Terminal
Display
Extended Arithmetic Element (EAE) KEl 2
Incremental Plotter XYl 2
Input/Output 1/0 Bus
Keyboard/Printer
LINCtape
Programmable Real-Time Interface KWl 2A
Relay Buffer
Sense Lines
TTY Interface, DPl 2-A
Input/Output Skip
Input/Output Transfer Class
Interaction between Modes Switching
Interface Connections
Interface Construction
Interface Design and Construction
Cable Connections to I/O Bus
Cable Selection
Connector Selection
Construction of Interfaces
Interface Connections
Interface Modules
IOT Allocations, Octal
Module Cooling
Module Layout
Module Selection for Interface Circuit of
Peripheral Equipment
M-Series Flip Chip Modules
M-Series Module Summary
MlOl Bus Data Interface
Ml 03 Device Selector
Ml 11 /M906 Positive Input Circuit
MS 16 Positive Bus Receiver Input Circuit
M623/M906 Positive Output Circuit
M660 Bus Driver Output Circuit
Wiring Hints

1-4

6-68
3-5
2-3
2-8
2-3
2-4
2-3
2-6
2-11
3-7
2-4
2-14
2-6
2-12
3-6
3-3,4-3
5-10
5-16
3-22,5-1
1-5
1-5
1-5
1-6
1-5
1-5
1-6
1-6
1-6
1-6
1-5
1-6
1-5
1-5
1-6
5-8
4-12
1-5
5-44
5-39
5-30
5-45
5-40
5-41
5-39
5-44
5-30
5-43
5-43
5-40
5-32
5-34
5-35
5-33
5-33
5-30
5-31
5-31
5-32
5-32

Interface Modules
5-30
Interrupt, LINC mode,
data path during
3-27
Interrupt, LINC Mode Service Routine
3-29
Interrupt OFF, IOF
4-13
Interrupt ON, ION
4-12
Interrupts, LINC Mode M
3-26
Instruction Decoding, IOT
54
Instruction Descriptions, see Instructions
3-7
Instruction Field
3-1
Instruction Field Buffer (IB)
3-24
Instruction Field and Data Field Registers
3-2
Instruction Field Register (IF), 5-Bits
1-4
Instruction Field Register,
Extended Memory
4-19
Instruction Field Reserved Locations
3-2
Instruction Format
3-7,3-41
Instruction Format, Group II Operate Class
4-10
Instruction Formats, Direct Address,
Indirect Address {3-Class, a-Class and others
3-6
Instruction Register (IR), 12 Bits
1-3
Instruction Set, 8 Mode
3-1,4-5,B-1
4-6
AND Logical And to AC
CIA Complement and Increment AC
4-9
CLA Clear Accumulator
4-10
CLL Clear Link
4-7
CMA Complement Accumulator
4-7
CML Complement Link
4-8
DCA Deposit and Clear Accumulator
4-5
GLK Set Link
4-9
HLT Halt
4-11
IAC Increment Accumulator
4-8
ISZ Increment and Skip if Zero
4-6
JMP Jump
4-6
JMS Jump to Subroutine
4-6
LAS Load Accumulator from Switches
4-10
LINC Switch to LINC mode
4-12
NOP No Operation
4-7
OSR OR Switch Register with AC
4-11
4-8
RAL Rotate Accumulator Left
4-8
RAR Rotate Accumulator Right
RTL Rotate Two Places Left
4-8
RTR Rotate Two Places Right
4-8
SKP Skip Unconditionally
4-10
SMA Skip on Minus AC
4-10
SNA Skip on Non-Zero AC
4-10
SNL Skip on Non-Zero Link
4-10
SPA Skip on Plus AC
4-11
STA Set Accumulator
4-9
STL Set Link
4-9
4-10
SZA Skip on Zero AC
4-10
SZL Skip on Zero Link
TAD Two's Complement Add to AC
4-5
Instruction Trap
3-29 ,3-30 ,3-49
Instructions,
A-D Converter
6-78
6-66
CMl 2 Optical Mark Card Reader
6-63
CRl 2 Card Reader
6-5
Console Teletype Control
DC02-D
6-15
DC02-E
6-14
3-7
Descriptions

DF/DS32, -D
EAE
Extended Memory
Format Explanation of
I/O Bus
IOT
LINC
KP12
KW12-A
KW12-B,C
LP08 Line Printer
LPl 2 Line Printer
Magnetic Tape Control
PC12, PP12 Paper Tape
Readers and Punch
PR12 Reader
PT08
RF32 to RF /RS08 Comparison
RF/RS08
RK08/RK01
Tape Maintenance
Two-word
XYl 2 Plotter
IOB 1/0 Bus Enable
IOB/IOT
1/0 Bus Access
I/O Bus Cable Connections
1/0 Bus External Level Lines
1/0 Bus Instructions
1/0 Control
1/0 Handler, LINC-8 Simulator
Trap Processor
IOP Generation
IOP Generation and Timing
I/O Preset Pulse
I/O Program Interrupt
IOS, Multiple Inputs
IOS and Program Interrupts,
Mul.tiple Inputs
IOT Allocations, Octal
IOT Command Pulse Generation
IOT Instruction
IOT Instruction Decoding

6-27
4-13
4-19
3-7
C-1
14
3-1,3-6,A-1
6-74
6-22
6-26
6-60
6-59
645
6-71
6-72
6-11
6-35
6-30
6-38
E-1
1-4
6-68
3-23
3-25
1-4
5-45
3-20
C-1
5-4
1-4
5-5
5-6
3-29
5-11
5-13
5-13
5-43
5-7
1-4
14

J-K
Keyboard Reader
Keyboard/Printer
KF12B
KPl 2 Instructions
KPl 2 Power Failure Option
KPl 2 Power Fail/Restart
KW12-A Input Panel
KW 12-A Instructions
KW12-A Real-Time Interface
KW12-A with A-D
KW12-B, KW12-C
KW12-B, C Instructions

6-5
1-6
5-15
6-74
6-74
6-74
6-22
6-22
6-18
6-22
6-25
6-26

L
LAP6-DIAL-MS
LINC Instruction Trap
LINC Mode Direct Access Devices

6-44
3-24
14

3-2,A-l
LINC Mode Instructions
Character Size
3-29
3-22
Console Switches
3-29
Disable Teletype Interrupt
Fast Sample
3-29
Full-Word Arithmetic
3-8
Full-Word Comparison
3-12
Full-Word Data Transfers
3-7
Full-Word Instructions
3-7
ADA Add to Accumulator (.6-Class)
3-9
ADD Add to Accumulator
3-8
ADM Add to Memory (.6-Class)
3-9
APO Accumulator Positive
3-19
AZE Accumulator Zero
3-19
BCL Bit Clear {/3-Class)
3-11
BCO Bit Complement (.6-Class)
3-12
BSE Bit Set (.6-Class)
3-11
CLR Clear
3-21
COM Complement AC
3-21
DJR Disable JUMP Return
3-28
ESF Enable Special Functions
3-30
FLO Overflow
3-20
HLT Halt
3-21
IBZ LINCtape Inter-Block Zone
3-20
IOB-IOF Interrupt Off
3-26
3-26
IOB-ION Interrupt On
IOB-RIB Read Interrupt Buffer
3-27
IOB-RDF Read Data Fielr:l
3-26
IOB-RIF Read Instruction Field
3-25
IOB-RMF Restore Memory Fields
3-27
JMP Jump
3-15
KST Key Stuck
3-21
LAM Link Add to Memory (.6-0ass)
3-9
3-8
LDA Load Accumulator (.6-0ass)
3-25
LDF Load LINC Data Field Register
LDH Load Half
3-14
LIP Load LINC Instruction Field Buffer
3-24
LINC Switch to the LINC Mode (see PDP)
3-22
LSW Left Switches
3-22
3-19
LZE Link Zero
MUL Multiply (.6-Class)
3-10
NOP No Operation
3-21
PDP Switch to the 8 Mode
3-22
QAC Place MQ in AC
3-21
QLZ MQ Low-Order Bit Zero
3-19
ROL Rotate Left
3-16
ROR Rotate Right
3-17
RSW Right Switches
3-22
SAE Skip if Accumulator Equal to
Operand (.6-Class)
3-12
SCR Scale Right
3-18
SET Set a-Register
3-14
SPA Place Special Function Flip-Flops in AC 3-30
SHD Skip if Half Differs
3-14
SKP Skip Unconditionally
3-20
SNS Sense Switch
3-20
SRO Skip and Rotate (ft-Class)
3-13
STA Store Accumulator (.6-Class)
3-8
STC Store and Clear (Direct Address)
3-7
STH Store Half
3-14
SXL Skip on External Level
3-20
XSK Index and Skip
3-15

1-5

Full-Word Logic
Half-Word Addressing, defined
LINC Mode I/O Bus Access
LINC Mode IOT Instructions
LINC Mode, Memory Modules
LINC Mode Programming
LINC Mode Program Interrupt
LINC Mode Provisions of
LINC Switch to LINC Mode
LINCtape, Equipment Required
LINCtape Formats
LINCtape Instructions
LINCtape Option, TC12-F
LINCtape Processor Information Paths
LINCtape Programming
LINCtape Registers
LINCtape Transport, Type TU55
LINCtape TCl 2
Block (LINCtape)
Block Number (BM)
Check Words (CM)
Checksum
Control Registers
Data Path
Data Words (DM, FM)
Extended Address Format
Extended Operations
Extended Operations Buffer
Extended Units
First Word
Guard Word (GM)
Hold Unit Motion
Instruction Format
LINCtape Instructions
AXOAC to XOB
CHK Check One Tape Block
IOB-LMR Load Maintenance Register
MTB Move Toward Block
RDC Read and Check
RDE Read Tape
RDG Read and Check Group
STD Skip if Tape Done
TAC Tape Accumulator to AC
TMA Load TMA Setup Register
TWC Skip on Tape Word Complete
XOAXOBto AC
WCG Write and Check Group
WRC Write and Check
WRI Write Tape
LINCtape Processor Information Paths
LINCtape Programming
Maintenance Mode
Mark Condition
No Pause Condition
Organization of Data
Organization of LINCtape Data, Schematic
Read/Write Buffer (RWB)
Reverse Block Number (RBM)
Second Word
Subprocessor, LINCtape
Tape Accumulator (TAC)
Tape Block Number (TBN)

1-6

3-11
3-13,3-14
14
3-25
14
3-1
3-26
1-4
4-12
1-1,1-5
3-37
3-43
6-57
3-40
3-41
3-39
2-1
3-37
3-39
3-39
3-39
3-39
3-40
3-39
3-39
346
3-45
3-41
3-47
3-42
3-39
348
341
3-43
3-46
3-45
3-48
3-45
3-43
3-43
343
3-48
3-45
3-46
349
346
3-44
3-44
344
340
3-41
3-49
3-48
3-48
3-37
3-38
3-39
3-39
3-42
3-39
340
341

Tape Buffer (TB)
Tape Interrupt Enable
Tape Memory Address (TMA)
Tape Motion
Tape Trap
Tape Word Skip
LINC-8, Comparison with PDP-12
LINC-8 Programs
LIN C-8 Program Changes
Line Printers
Instructions, LP08 Line Printer
Instructions, LPI 2 Line Printer
Line Printer and Control LP08
Line Printer and Control, LPI 2
LP08 Line Printer Specifications
Line Printer and Control LP08
Line Printer and Control, LPI 2
Link
Link (L) I Bit
Logic Conventions
Logic Symbols, Figure 5-1
LP08 Line Printer and Control
LP08 Line Printer Instructions
LP08 Line Printer Specifications
LP12 Line Printer and Control
LPl 2 Line Printer Instructions
LT37-AD Option, Teletype

340
3-47
341
342
349
3-49
1-1
3-31,349
14
6-59
6-60
6-59
6-60
6-59
6-62
6-60
6-59
3-8,3-9
1-3
5-3
5-3
6-60
6-60
6-62
6-59
6-59
6-4,F-3

M
Magnetic Tape
Command Register Contents, Magnetic Tape
Continued Operations, Magnetic Tape
Functional Description, Magnetic Tape Control
General Description, TU20C
Instructions, Magnetic Tape Control
LINCtape Option, TC12-F
Magnetic Tape Control, TC58
Magnetic Tape Functions
Magnetic Tape Transports
Magnetic Tape Transports, TU20
(7 Channel, 9-Track)
Magnetic Tape Transport, TU20C
Magnetic Tape Control, TC58
Magnetic Tape Control Instructions
Magnetic Tape Functions
Magnetic Tape Transports
Magnetic Tape Transports, TU20
(7 Channel, 9-Track)
Magnetic Tape Transport, TU20C
Maintenance Mode
Mark Condition
MARK 12 Program
Mathematical Tables
Maximum Data Rates PT08
Memory Address Control
Memory Addressing Methods
Autoindexing, 8 Mode
Direct Addressing
Indirect Addressing
Memory Reference Instruction Format
Summary Addressing Methods,
8 Mode, Table of

6-45
6-51
6-49
6-45
6-56
6-45
6-57
6-45
6-47
6-54
6-54
6-56
6-45
6-45
6-47
6-54
6-54
6-56
3-49
3-48
3-48
H-1
6-13
3-24
4-2
4-4
4-2
4-3
4-3
4-4

Memory Address Register (MA) 12 Bits
Memory Buffer (MB), 12 Bits
Memory Control Programming
Memory, Description, Organization of,
Segments of, Pages of
Memory Extension Control
Memory Increment, Data Break
Memory Increment Data Break Timing
Memory, Organization of
Memory Reference Instructions
Memory Size, PDP-12
Microprograrnma ble
Microprograrnmable EAE Instructions
Microprogramming Operate Class Group II
Mode Control
Mode Control, from 8 to LINC
Mode Programming,
Extended Memory
Organization of Memory, 8 Mode
Page 0
Mode Status Register 1 Bit
Model 33ASR, Teletype
Model 33KSR, Teletype
Model 35KSR, Teletype
Model 37KSR, Teletype
Modes of Operation, LINC and 8
Module Cooling
Module Layout
Module Selection for Interface
Circuits of Peripheral Equipment
M-Series Module Summary
Multiplication of 12-bit Numbers
EAE Programming
M-Series Flip-Chip Modules
M101 Bus Data Interface
MI 03 Device Selector
Ml 11/M906 Positive Input Circuit
M516 Positive Bus Receiver Input Circuit
M623/M906 Positive Output Circuit
M660 Bus Driver Output Circuit
M706 Receiver, Teletype Control
M707 Transmitter, Teletype Control
Multi-Level Automatic Priority Interrupt
Multiple Teletype Control DC02-E
Multiple Teletype Control, DC02-F
Multiple Use of IOS and Program Interrupt
Multiplication

1-3
1-3
3-24
1-4
4-19
5-27
5-28
3-1
4-1,4-3,4-5
1-1
4-7
4-13
4-9
3-22
4-12
4-1
4-2
4-2
4-1
1-3
6-3
6-3
6-4
6-4
1-1
5-43
5-40

4-17
5-34
5-33
5-33
5-30
5-31
5-31
5-32
6-5
6-5
5-15
6-13
6-16
5-14
4-16

1-5
3-48
1-4

0
Operands
Operate Class: Group I
Operate Class: Group II
Operate Class Instructions
Operation of EAE
Operating Modes
Character Size, CRT Display

1-5

1-4
1-4
1-5
1-4
1-4
1-5
1-4
4-12
6-66
6-1
3-37
3-38
4-2
3-1
3-2
3-2
3-2
3-2
3-2
3-2
5-11
5-23
3-8

p
5-32
5-35

N
Non-Bus I/O Devices
No Pause Condition
No Pause, Extended Tape Addressing

CRT Display, Character Size
Extended Tape Addressing with Core,
Tape Interrupt, Program Interrupt,
No-Pause, Hold-motion
Hold-Motion, Extended Tape Addressing
Interaction between Mode Switching
I/O Bus Access
No-Pause, Extended Tape Addressing
Special Functions, LINC Programming
Tape Interrupt, Extended Tape Addressing
Operation, Program Interrupt
Optical Mark Card Reader, CM 12
Option Groupings, Peripheral Devices
Organization of Data
Organization of LINCtape Data, Schematic
Organization of Memory, 8 Mode
Organization of Memory, General
Data Field Reserved Locations
Field Address, Use of
Instruction Field and Data Field Registers
Instruction Field Reserved Locations
Program Counter, LINC mode
Reserved Field Address, 8 and LINC mode
Output, Data Transfers
Output, Data Transfers, Data Break
Overflow, defined

3-3
4-7
4-9
4-6
4-13
1-4
1-5

Page 0
Pages, Memory
Paper Tape Punch and Reader PC12
Paper Tape
Instructions, PCl 2, PPl 2 Paper Tape
Readers and Punch
Paper Tape Punch and Reader PC12
PCl 2 Paper Tape Punch and Reader
PC12, PP12 Instructions
PDP-8 Options used with PDP-12
Perforated Tape Loader
Peripheral Devices
Peripheral Equipment requirements of
Peripheral Expander, BA 12
Peripheral Status Testing
Point Displays
PPl 2 Paper Tape Punch
Prewired, Optional Groupings
Power Fail/Restart
Instructions, KP 12
KP 12 Power Fail/Restart
KP12 Power Failure Option
Program Control
Program Counter, LINC mode
Program Counter (PC) 12 Bits
Program Interrupt
Program Interrupt, see LINC
Mode and 8 Mode Programming
Programmed Data Transfers
Conventions, Logic
Data Break Transfers
Logic Symbols

4-1
4-1
6-71
6-71
6-71
6-71
6-71
6-71
6-1
D-1
6-1
5-4
6-1
5-9
3-32
6-71
6-1
6-74
6-74
6-74
6-74
3-15
3-2
1-3

4-12,5-12
5-2
5-3
5-2
5-3

1-7

Program Interrupt
5-2
Signal Names
5-2
5.4
Programmed Data Transfers and I/O Control
5.9
Accumulator, 1/0 Transfers
Data Transfer Timing
5-6
5-10
Data Transfers, Input
5.7
Device Selector
Input Data Transfers
5-10
5-8
Input/Output Skip
IOS and Program Interrupt
5.13
Multiple Inputs
5.7
IOT Command Pulse Generation
IOT Instruction Decoding
Multiple Use of IOS and Program Interrupt
5-14
Output Data Transfers
5-11
5.9
Peripheral Status Testing
5.5
Programmed Data Transfer Interface Diagram
Programmed Data Transfer Timing
5-6
5-11
Programmed Interrupt, 1/0
5-6
Timing and IOP Generator
4-12
Program Interrupt
4-13
IOF Interrupt Off
4-12
ION Interrupt On
Program Interrupt, Using the
4-13
4-22
Program Interrupt, Extended Memory Programming
Program Interrupt, Extended Tape Addressing
1-4
3-26,4-13
Program Interrupt LINC mode
5.13
Program Interrupt, Multiple Inputs
5-12
Program Interrupt Request
4-13
Program Interrupt, Using the
1-6
Programmable Real-Time Interface KW12A
Programmed Data Transfers description of
5-1
5.5
Programmed Data Transfer Interface Diagram
Programmed Data Transfer Timing
5-6
5-11
Programmed Interrupt, 1/0
Programmed Interrupt and Instruction Trap
3-31
Programming
6-44
Disk Software
4-16
EAE
4-21
Extended Memory
6-7
Format Routine, Teletype
3-1
LINC Mode
6-10
PT08
6-42
RK8/RK01 1/0 Subroutine
6-7
Teletype
4-1
8Mode
6-72
PR12 Paper Tape Reader
6-72
PR12 Paper Tape Reader Instructions
PT08 Equipment Configuration
6-11
PT08 Instructions
6-11
PT08 Programming
6-10
PT08 Specifications
6-10

Q-R
Random Access Disk File,
Types DF/DS32 and DF/DS32-D
Read/Write Buffer (RWB)
Real Time Clocks
Counter Register, KW12-A
Frequency Range, KW12-B, C
Input Synchronizers, KW12-A

I-8

6-27
3.39
6-18
6-22
6-26
6-19

KW12-A Input Panel
KWl 2-A Instructions
KW12-A with A-D
KW12-B, KW12-C
KW12-B, C Instructions
Real Time Interface, KW12-A
Register, Extended Memory
Relays
Relay Buffer Equipment Description
Relay Terminals and Corresponding AC Bits
Reserved Field Address, 8 and LINC Mode
Reverse Block Number (RBM)
RF /RS08 Disk Memory System
RF /RS08 Instructions
RF /RS08 Programming, Example
RF /RS08 Specifications
RK08/RK01 Disk Cartridge Memory
RK08/RKO1 Instructions
RK08/RK011/0 Subroutine Programming Example
RK08/RKO1 Specifications

6-22
6-22
6-22
6-25
6-26
6-18
4-19
3-36
1-1, 1-5
3-36
3-2
3.39
6-30
6-30
6-34
6-37
6-38
6-38
6-43
6-43

s
Sample and Hold Options AFOlA
Save Field Register, Extended Memory
Save Field Register, purpose
Scaling, defined, see Shift and Rotate Operations
Second Word
Sense Lines
Shift and Rotate Operations
SHL, NMI Shift Path for
Signal Names
Sign-bit
Single and Dual TTY Control,
Type PT08 Teletype Control
Single Teletype Control Type DP12-A
Skip, defined
Skip Instructions
Skip loop programming example
Skips external
Skips, Miscellaneous
Special Functions, LINC mode
Special Functions, LINC programming
Specifications, AFOl-A A-D Converter
Specifications, DC02-E
Specifications, RF /RS08
Specifications, RK08/RK01
Stand Alone Peripherals, list of
Standard Mode Addressing, LINCtape
Standard Mode, LINCtape
Status or Error Conditions,
Magnetic Tape
Subprocessor, LINCtape
Summary Addressing Methods, 8 Mode
Table of
Symbols and Abbreviations
System Configuration
Analog Inputs, Equipment
CRT Display, Equipment
LINCtape, Equipment Required
Relay Buffer, Equipment Description

6-81
4-19
3-24
3-16
3-42
1-5
3-16
4-15
5-2
3-8
6-10
6-9
3-19
3-19
3-23
3-20
3-21
3-29
1-5
6-76
6-14
6-37
6-43
6-2
3-42
3-40
6-49
3.39
4-4
1-6
1-1
1-1
1-1
1-1
1-1

T
Table of Codes
Tape Accumulator (TAC)
Tape Block Number (TBN)
Tape Buffer (TB)
Tape Interrupt Enable
Tape Interrupt, Extended Tape Addressing
Tape Maintenance Instructions
Tape Motion
Tape Memory (TMA)
Tape Processor Major State Indicators
Tape Trap
Tape Word Skip
TC12-F LINCtape Option
TC58 Instructions
TC58, Magnetic Tape Control
Teleprinter/Punch
Teletype Code, discussion
Teletype
C-onsole Teletype Control
Dataphone Control, DPl 2-B
DC02-D Instructions
DC02-E Control Instructions
Format Routines
Instructions, Console Teletype Control
Instructions, PT08
Keyboard Reader
LT37-AD Option, Teletype
Maximum Data Rates, PT08
Model 33ASR, Teletype
Model 33KSR, Teletype
Model 35KSR, Teletype
Model 37KSR, Teletype
Multiple Teletype Control, DC02-E
Multiple Teletype Control, DC02-F
Option Groupings, Peripheral Devices
Prewired, Optional Groupings
Programming the PT08

F-1
3-40
341
340
3-47
1-4
E-1
3-42
341
2-4
3-21,3-31,3-49
3-49
6-57
645
6-45
6-7
6-3
6-3
6-5
6-9
6-15
6-14
6-7
6-5
6-11
6-5
6-4
6-13
6-3
6-3
6-4
64
6-13
6-16
6-1
6-1
6-10

PT08 Equipment Configuration
PT08 Specifications
Single Teletype Control, DP12-A
Specifications, DC02-E
Stand Alone Peripherals, List of
Teleprinter/Punch
Teletype Controls
Teletype Interface, DP12-A
Teletype Model 33ASR Controls
Teletype, Subroutine
Ten Bit indexing, Program Counter
Three Cycle Data Break
Three Cycle Data Break Timing
Timing and IOP Generator
Toggle Switch Registers
Transfer Class, Input/Output
Transfers, Data Break
Transports, Magnetic Tape
Turnaround State, Tape
TU20 Magnetic Tape Transport,
General Description
TU20C Magnetic Tape Transport
TUSS Tape Transport Controls and Indicators
TUSS/56 Tape Transports
Two-Word EAE Instructions
Two-Word Instruction

6-11
6-10
6-9
6-14
6-2
6-7
64
1-6
2-1,2-14
6-7
3-2
5-29
5-29
5-6
2-6
4-12
5-15
6-54
3-42
6-54,6-56
6-56
2-12
1-5
4-14
1-4

U-V-W
Wiring Hints
Word Count Overflow, Three Cycle Data Break

5-42
5-30

X-Y-Z
XY Plotters
Incremental Plotter and Control,
XY12
Instructions XY 12 Plotter

6-68
6-68
6-68

1-9

PDP-12 COMPUTER
SYSTEM REFERENCE MANUAL
D EC-12-SRZB-D

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