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DEC-14-GGZA-D

November 1969

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Document:	DEC-14-GGZA-D PDP14UM Nov69
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DEC-14-GGZA-D

PDP-14
USER'S

MANUAL

The PDP-14 system and its unique approach to machine control, including its physical parts,

its

circuitry, and

its expressed

or implied

methods of programming, is patent-pending. All rights are claimed
by Digital Equipment Corporation. The information presented herein

proprietary in nature, and is intended solely to inform our cus-

tomers in the use of our products.

DIGITAL

EQUIPMENT

CORPORATION

•

MAYNARD, MASSACHUSETTS

1st

The following are registered trademarks of Digital
Equipment Corporation, Maynard, Massachusetts:

DEC

PDP

FLIP CHIP

FOCAL
COMPUTER LAB

DIGITAL

Printing

November 1969

CONTENTS
Page

CHAPTER

GENERAL CONCEPTS OF INDUSTRIAL CONTROL SYSTEMS

General Control Systems

1-1

Catagories of Control Systems

1-2

Numeric Control

1-2

Binary Control

1-2

Efficiency

1-5

Versatility

1-5

Maintainability

1-6

Monitoring of Performance

1-6

CHAPTER 2

PDP-14 SYSTEM INTRODUCTION

Purpose

2-1

History

2-1

Training for the PDP-14

2-1

The PDP-14 System

2-2

General PDP-14 System

2-2

Box Function

2-6

Box Mechanical

2-6

Control Unit

2-7

Read-Only Memory

2-7

Control Unit Mechanical

2-9

O Box Mechanical

2-11

Auxiliary Boxes (A and S)

2-12

Auxiliary Box Mechanical

2-13

Computer Monitoring

2-13

Summary of PDP-14 System Control Circuits (One System)

2-14

CHAPTER 3

PDP-14 SYSTEM PARTS AND FUNCTION

Input Box Operation

3-1

Control Unit Operation

3-2

Boolean Logic

3-4

Read-Only Memory (ROM) Operation

3-5

Changing Instruction Codes

3-8

O Box Operation

3-8

CONTENTS (Cont)
Page
3-11

Auxiliary Box Operation

AddiHonai Module Information

3-16

Control

3-16

Monitoring

3-16

Control and Monitoring

3-17

Shared Control

3-17

Adding the Computer

3-18

CHAPTER 4

INTRODUCTION TO PDP-14 PROGRAMMING

Programming the PDP-14

4-1

Input and Output Organization

4-2

PDP-14 Inputs

4-2

PDP-14 Outputs

4-4

Boolean Representations of Machine Control
Equations Containing

"NOT"

4-4
4-6

Evaluating Equations

4-7

Equations with Variable Groups

4-8

Equation Simplifications

4-9

PDP-14 Program Description

4-10

Introduction to the PDP-14 Software

4-11

Paper Tape Formats

System Documentation

CHAPTER 5

4-12
4-13

PDP-14 BASIC INSTRUCTIONS

Basic Instruction Classes

5-1

PDP-14 Test Flag

5_]

PDP-14 Test Instructions

5-2

PDP-14 Set Output Instructions

5-3

Addressing Locations in the PDP-14

5-4

PDP-14 Memory Organization

5-5

Absolute Addresses and Page Addresses

5-6

PDP-14 Jump Instructions

5-6

Conditional Jump Instructions

5-6

Unconditional Jump Instructions

5-10

CONTENTS (Cont)
Page
Subroutine Jump Instructions

5-11

Sample PDP-14 Program and Analysis

5-13

Program Examples

5-15

Control Function (Example

5-16

Boolean Equivalent

5-16

PDP-14 Program

5-17

Control Function (Example 2)

5-17

Boolean Equivalent

5-18

PDP-14 Program

5-18

Control Function (Example 3)

5-19

Boolean Equivalent

5-20

PDP-14 Program

5-20

Control Function (Example 4)

5-21

Boolean Equivalent

5-21

PDP-14 Program

5-22

Control Function (Example 5)

5-22

Boolean Equivalent

5-23

PDP-14 Program

5-23

Example 5, Simplified

5-24

Control Function

5-24

Boolean Equivalent

5-24

PDP-14 Program

5-24

Timing Considerations in a PDP-14 Program

5-25

Conclusion

5-27

CHAPTER 6

BOOL-14 CONTROL EQUATION TRANSLATOR

BOOL-14 Statement

6-1

Input and Output Specification

6-3

Operators

6-4

Variable Groups

6-4

Statement Continuation

6-5

Comments

6-5

Subroutines and Storage Outputs

6-6

Intermediate Results

6-6

Z-Functions

6-7

CONTENTS (Cont)
Page
R-functions

°~°

Storage Outputs

6-10
6-11

Control Statements

End of Program -

.END or .ENDN

6-11

END and ENDN Examples

6-11

End of Tape -. EOT

6-11

Memory Allocation

6-12

LOC

6-14

Spacing Between Equations - .FIXSor .VARS

6-14

Spacing Examples

6-15

Start of Program -

Monitoring Provisions in BOOL-14

6-15

ON - .MN

6-15

Monitor Transitions to OFF - .MF

6-16

Monitor Transitions to

Monitor All Transitions -

.MFN

Monitoring Input Transitions

6-16

6-17

BOOL-14 Options

6-18

Binary Output

6-18

Compiler Listing

6-19

Program Source

6-21

Editing

6-21

Error Messages

6-22

Optimum Form for BOOL-14 Equations

6-25

Sample BOOL-14 Program

6-26

CHAPTER 7

PAL-14

PDP-14 Symbolic Program Assembler

7-1

PAL-14 General Features

7-1

Location Assignment

7-2

Symbolic Addresses

7-4

Assignment Statements

7-5

PAL-14 Program Conventions

7-6

Comments

"^'^

Two-Location Instructions

'^'J

Permanent Symbol Table

7-8

CONTENTS (Cont)
Page
Special Characters and Operators

PAL-14 Output

7-10
^

7_^^

Binary Output

7-16

Assembly Listing

7-16

Symbol Table

7-17

Error Messages

l-U

Error Listing

7-20

Sample Output

CHAPTERS

7-21

SIM-14

PDP-14 Program Debugging Aid

8-1

Modes of Operation

8-1

Local Mode

8-1

On-Line Mode

8-1

Restrictions

8-2

Conventions

8-2

PDP-14 Instructions Recognized by SIM-14

3_2

SIM-14 Command Description

o.o

PDP-14 General Commands

8-4

LM Command

8-4

OM Command

8-4

RUBOUT

8-5

Local Mode Program Debugging

g.c

MB Command

g_c

Program Manipulation and Modification Commands

3_7

R Command

8-7

RH Command

8-8

Open Location Commands

o_g

LS Command

8-10

LN Command

8-12

P Command

8-13

PH Command

8-14

Verification of a Paper Tape Program Record

Q-\A

Equation Verification Commands (Local Mode)

8-15

Continue Verification

8-16

VII

CONTENTS (Cont)
Page
Verifying an Equation which Contains Subroutines
Truth Table Generation Commands (Local

Mode)

°"22
°"25

Generating a Truth Table without Subroutines

8-26

Generating Truth Tables for Equations Containing Subroutines

8-28

Simulated Program Execution in Local Mode

LM Execution Commands

o'^^^

p on

Switch Register Options in Simulated Execution

8-31

Types of Simulated Execution

o-oZ

Simulated Timer Execution

o-oo

On-Line Mode Debugging

O/L
p
o-oo

On-Line Mode Commands

o-o/

On-Line Mode Switch Options

8-38

Program Stops

8-38

Stop Equations

o-oV

On-Line Mode Execution

o-oV

SIM- 14 Summary

Commands Common to Local and On-Line Modes
Local

Mode Commands

On-Line Mode Commands
Local

Mode Switch Options

8-40
8-42
8-43

8-45
8-45

On-Line Mode Switch Options

8-46

Error Messages

o-46

CHAPTER 9

MONITORING THE PDP-14

PDP-14 Internal Registers

9-2

PDP-14 Extended Instructions

9-3

External Mode Instructions

""3

Memory Transfer Instructions

9-4

Conditional Skip Instructions

9-4

Test and Display Instructions

9-5

9-6

PDP-8 Interface Instructions

9-7

Skip Instructions

9-7

Input and Output Register Instructions

9-8

Load PDP-14 Instructions

9-8

CONTENTS (Cont)
Page
Using PDP-8 Program Interrupt to Monitor

9-11

Monitor Descriptions
Transition

9-11

Checking With BOOL-14

9-12

Supervisory System

9-13

Decision Making

9-14

Input Interrogating

9-14

CHAPTER 10

PDP-14 SYSTEM SOFTWARE OPERATION

PDP-8 Switch and Switch Register Operations

10-1

PDP-8 Loader Program

10-4

Loading the HELP Loader

10-4

Loading a Binary Tape into the PDP-8

10-6

PDP-8 Editor

10-7

Composing Source Programs

10-7

Updating Source Programs

10-7

Text Buffer

]0-7

Modes of Operation

10-7

Transition Between Modes

]0-8

Adding Text to the Buffer

10-8

Editing Keys

10-8

Reading a Paper Tape

10-9

Listing a

Program

Inserting a

10-10

New Line of Text

10-10

Deleting Lines from the Text Buffer

10-1

Changing Lines of Text

10-11

Moving Lines of Program Text

10-12

Search Feature

10-12

Special Characters

10-13

Punching a Source Tape

10-13

Editor Summary Tables

10-14

Loading the Editor

10-16

Starting the Editor

10-16

BOOL-14 Operation

10-17

Loading BOOL-M

10-17

Starting BOOL-14

10-17

CONTENTS (Cont)
Page

PAL-14 Operation

10-18

Loading PAL-14

10-18

Starting PAL-14

10-19

Assembly Passes

10-20

Error Halt

10-21

SIM- 14 Operation

10-21

Loading SIM-14

10-21

Starting SIM-14

10-22

Switch Register Key

10-22

CHAPTER n

INSTALLATION

Basic Factors Affecting System Installation

11-1

The PDP-14 AND Electrical Noise

11-1

Heat Dissipation

11-2

Cabling and Maintenance Clearance

11-3

Environmental Specifications

11-3

Typical Installation

11-4

Enclosure

11-4

Electrical

Grounds

System Power and Other Devices

11-6
1

1-6

Control Unit Mounting

11-6

CD Mounting Dimensions

11-8

CU Mounting Sequence

11-8

Auxiliary Box Mounting

11-10

and O Box Mounting

11-12

O, A and S Box Mounting Dimensions

11-12

O, A, and S Box Mounting Sequence

11-12

Wiring and Cable Installation

11-13

AC Wiring

11-14

Control Cable Installation

11-18

Box Cable Connections

1-22

CU Cable Connectors

11-22

CU Power Supply, Computer Interface, and ROM Installation

11-26

CU Power Supply Installation

11-26

CONTENTS (Cont)
Page

ROM Installation

11-32

Computer Interface Installation

11-35

Initial

Checkout

11-35

11-37

Initial Startup

MAINTENANCE CONCEPT

CHAPTER 12
Approach

12-1

Checking the CU and ROM

12-3

Checking the Input and Output Boxes

12-3

ROM Modifications

12-4

Programming for ROM Changes

12-4

ROM Wire Additions
Preparing the ROM Braid Board

12-9

12-10

Removing the Old Braid Wire

12-1

Replacing ROM Braid Board

12-11

ILLUSTRATIONS
Figure

Page

1-1

General Control Systems

1-1

1-2

Binary Control Systems (Electric)

1-3

2-1

General PDP-14 Control Arrangement

2-3

2-2

Input Box Pictorial

2-5

2-3

Input Box Dimensions

2-6

2-4

Control Unit-Pictorial

2-8

2-5

Control Unit Dimensions

2-9

2-6

Output Box -Pictorial

2-10

2-7

Output Box Dimensions

2-11

2-8

Auxiliary Boxes - Pictorial

2-12

2-9

Auxiliary Box Dimensions

2-13

3-1

Box Input Circuit - Simplified

3-1

3-2

3-3

ROM Board Group-Pictorial

3-7

3-4

O Box Selection System

3-9

3-5

Box Output Circuit - Simplified

3-10

3-6

A or S Box

3-12

Box Selection System

3-3

ILLUSTRATIONS (Cont)
Page

Figure

K302

3-13

3-7

Timer Module

3-8

A Box Socket Functions and Allocations

3-14

3-9

Retentive Memory Module K272

3-15

4-1

Input Assignment Sheet

4-2

Output Assignment Sheet

4-3

Ladder Diagram

4-4

Ladder Diagram

4-5

Ladder Diagram

4-6

Program Description

4-3

4-5
4-6
4-6
4-7
4-10
5-7

5-1

5-2

Ladder Diagram

5-16

5-3

PDP-14 Wiring

5-17

5-4

Ladder Diagram

5-18

5-5

PDP-14 Wiring

5-18

5-6

Ladder Diagram

5-19

5-7

PDP-14 Wiring

5-20

5-8

Ladder Diagram

5-21

5-9

PDP-14 Wiring

5-21

5-10

Ladder Diagram

5-22

5-n

PDP-14 Wiring

5-23

5-12

PDP-14 Wiring

5-24

6-1

6-2

7-1

7-3

8-1

Local Mode Debugging Procedure

8-6

8-2

Switch Register Functions in SIM- 14

8-32

8-3

On-Line Mode Debugging Procedure

8-41

10-1

10-2

10-3

10-3 (Part

10-3

10-3 (Part 2)

10-4

10-6

10-5

10-8

10-6

10-22

11-1

PDP-14 System Layout Example

11-5

11-2

Control Unit Housing Components

11-7

ILLUSTRATIONS (Cont)
Figure

Page

11-3

Control Unit Mounting Dimensions

11-9

11-4

Control Unit Mainframe Mounting

11-11

11-5

11-6

Mainframe Back Panel

11-15

11-7

Input Box Terminal Connections

11-17

11-8

Output Box Terminal Connections

11-19

11-9

PDP-14 System Control Cable Arrangement

11-20

11-10

DEC BC-14A Control Cable Assembly

11-21

11-11

Box Control Cable Insertion (O Box Shown)

11-23

11-12

Installing Box Protective Cover

11-24

11-13

CU Cable Socket Allocations

11-25

11-14

CU Control Cable Insertion

11-27

11-15

CU Control Cable Clamp Use

11-28

11-16

CU Control Cables Installed

11-29

11-17

CU Mainframe Allocations

11-30

11-18

Installing

G922/G923 ROM Modules Assembly

11-33

11-19

Installing

G924/ROM Module

11-34

11-20

Computer Interface Installations

11-36

11-21

CU Control Panel

11_38

11-22

Special Startup Procedure

11-39

12-1

General Testing Sequence

12-2

Ladder Diagram Showing Output Controlled and Inputs and Output Tested

12-5

12-3

Wire Placement in ROM Transformer Rows

12-6

12-4
12-5

ROM Change Sheet - Example
ROM Wire Placement Example For One Transformer ROW

12-9

12-6

Pin Location Example - Pin 62

12-11

12-7

ROM Board Assembly

12-12

O Box Mounting Dimensions

11-13

G922-G923 (Edge View)

12-8

TABLES
TabI e

Page

5-1

PDP-14 Test Instructions

5_2

5-2

PDP-14 Set Output Instructions

5_3

5-3

PDP-14 Conditional Jump Instructions

5-8

5-4

PDP-14 Unconditional Jump Instructions

5-10

5-5

PDP-14 Subroutine Jump Instructions

5-12

TABLES (Cont)
Page

Table

5-6

Sample PDP-14 Program

5-13

5-7

Program Execution Times

5-26

6-1

BOOL-14 Equation Characters

6-3

6-2

Summary of Control Statements

6-17

7-1

PAL-14 Symbol Rules

7-5

7-1

PAL-14 Permanent Symbol Table

7-9

7-3

PAL-14 Special Characters

7-10

8-1

PDP-14 Instructions Recognized by SIM-14

8-3

9-1

PDP-14 Internal Registers

9-2

10-1

Special Editor Keys

10-15

10-2

Summary of Editor Commands

10-15

11-1

PDP-14 Environmental Specifications

11-4

PURPOSE OF THE USER'S MANUAL

This User's Manual describes the

PDP-14 Industrial Control System in three general categories:

Chapters 1 through 3 define the applications of the PDP-14, and explain the function of the
system,

its

major components, and monitoring additions.

Chapters 4 through 10 provide complete instructions for designing control operations using
simplified computer programming techniques, and describes programming for computer monitor.

Chapters 11 and 12 contain installation and maintenance concepts for the control engineer

and electrician.

A glossary is also included to define unusual or special terms.
The User's Manual is intended for readers who are familiar with industrial control techniques and basic
electrical terms.

Using this manual, special training in electronics or computer operation is not re-

quired to operate the system.

(The chapters in the manual which discuss monitoring are written for com-

puter programmers.)

OTHER PDP-14 TECHNICAL INFORMATION

A complete PDP-14 Maintenance Manual for use by the electronic technician is available.
Manual describes the operation and servicing of all electronic circuits in the system.
some modules of the PDP-14 is provided in the DEC Control Handbook.

This

Information on

PREFACE

GENERAL

This User's Manual describes the

PDP-14 Industrial Control System (Frontispiece),

designed and manufactured by Digital Equipment Corporation (DEC).

The

PDP-14 is of a new solid-state design which provides remarkable advantages
over previously available systems.

APPLICATIONS

The PDP-14 can control any operation or process which can be broken into a

number of discrete steps or logical expressions, each with just two states.
is, status

That

inputs are either on or off, and the control operation selects outputs

and turns them on or off.

This type of control sequence

production equipment and materials handling systems.

used

most mass-

also used in such

diverse industries as automotive, steel, food processing, petrochemical, ap-

pliances, and others.

CONTROL

The PDP-14 system uses an easily replaceable memory to direct specific control

FLEXIBILITY

operations.

Convenient computer programming techniques allow each user to

design a memory to suit his unique control needs.

can bo redefined by changing the memory.

The entire control process

The memory operation is reliable,

and cannot be accidentally altered by electrical means.

COMPUTER

MONITORING

The PDP-14 system is designed to operate independently or with computer monitoring or control.

Since the PDP-14 can access all control inputs and outputs,

the added monitoring components are simply a general -purpose computer and a

simple interface device (available from DEC).

A group of PDP-14 systems can

be monitored by a single computer using a multiplexer, to provide status and malfunction reports for a large control complex.

OTHER
FEATURES

The PDP-14 system is extremely reliable, using no moving parts for control operations.' All components are modular, and are fully inspected and tested before

and after assembly.

Diagnosis of system faults is highly automated, and can be

accomplished by oF>erators with only limited training in electronic systems.

The PDP-14 system is extremely compact, and requires very little operating
power.

Installation

quick and simple, and requires no special training.

PDP-1 4 Industrial Control System

CHAPTER

GENERAL CONCEPTS OF INDUSTRIAL

CONTROL SYSTEMS

The chapter first discusses the general concepts of industrial control systems of all types.

Binary and numeric

control systems are described as they are ordinarily encountered in mass production or materials handling.

Secondly, the chapter focuses on binary control systems and develops criteria for judging their relative value
as production equipment.

Strengths and weaknesses of conventional systems are discussed, and some desirable

improvements are indicated.

GENERAL CONTROL SYSTEMS
Control Systems are organized in general as shown in the following illustration.

EXTERNAL DATA

PDP-14

CONTROL SYSTEM

POWER

INPUTS

CONTROLLED
DEVICE

Figure 1-1

OUTPUTS

General Control Systems

The control unit senses the status (or position) of the controlled device through its inputs.

Specific input con-

ditions cause the control unit to send signals to the controlled device to effect its operation.
results in changes in the device status,

The operation

and thus changes in the input signals to the control unit.

unit then reacts to this new status by changing outputs, etc.

The control

This cyclic process is termed a control loop.

The

process of transforming a small input signal into a higher energy control operation is called control gain, and

1-1

(as in any amplification process) requires energy which,

The external data are

by itself, does no useful work.

operator controls
status information which do not result from changes in device condition (for example, from

and prepared instruction commands).

CATEGORIES OF CONTROL SYSTEMS
signals:
Industrial control systems are often divided into two general categories according to the type of control

numeric control and binary control.

(Although the PDP-14 system is a binary controller, we will briefly define

numeric control .)

Numeric Control

Numeric control (NC) devices use control signals (inputs and outputs) which range over many voltage values,
each defined by a number.
magnitude.

The variation of input magnitude causes a fixed, proportional change in output

Equipment which responds precisely to varying signals is then required to transform control com-

mands into action.

NC is a flexible method of controlling a small number of relatively intricate operations.

For example, a multi-

purpose, NC-controlled machine can be given a series of instructions (usually on punched or magnetic tape),

and then proceed through dozens of automatic steps to transform raw blanks into complex finished pieces.

The

memory of required operations consists of the instructions on tape, which can be changed at any time.
control implies:

a single multi-purpose machine
a small production lot

moderate production rates
relatively high cost, and
programmed operation

For small lots,

NC techniques reduce set-up time enormously, and therefore justify the high cost.

Binary Control
Binary control systems use control signals having only two values -

ON or OFF. Binary controllers are

commonly used in mass production, where operations are divided into a number of simple functions, each defined by only two conditions.
is

on or off.

For example, a drill head is up or down, a moving bed

left or right,

a motor

Binary control signals can be hydraulic, electric, pneumatic, fluidic, or even mechanical.

monly, the input signals are all electric and the outputs are combinations of electrical, and electricallyactivated hydraulic and pneumatic systems.

Electric binary controls commonly are In the form shown in

Figure 1-2.

1-2

Com-

440 VAC

115 VAC

A C INPUT

CONTROL

COUNTERS

MOTOR
STARTERS
CONTACTORS

*-- "^

POWER
WIRES

TIMERS

COUNTERS
AIR OIL

CONTROL

WIRES

CONTROLLED

HYDRAULIC
PNEUMATIC
ACTIVATORS

DEVICE

TIIJ LIMIT SWITCHES
OPERATORS
PANEL

O
O

fi
PUCH

o
o
O o
o
o

MOTORS
HEATERS

LAMPS HIGH ENERGY
BELLS ELECTRICAL

DEVICES

SELECTOR

BUTTON

Figure 1-2

Binary Control Systems (Electric)

The control unit has three types of inputs:

those responding to the status or position of various sections of the controllecl device

others established by the operator (initial conditions, manual operations, and emergency controls)

pre-set status signals (from timers and counters).

Because the operation is a number of simple steps, status inputs can be generated by simple devices such as limit
sensors and proximity detectors.

Operator commands are sensed by pushbuttons and selector switches.

put is controlled by some variety of switch which turns power on or off.

Each unique combination of inputs stipulates which outputs will be activated or deactivated.

The control function has three general steps:

TEST inputs for state (on or off)

DECIDE what control function is required (which outputs must be controlled)
SET outputs on or off (execute control decision).

1-3

Each in-

In electrical binary controls, decision making

accomplished by relays and the wires which connect them.

The

wires actually represent the control memory, for they route the input control signals to the proper sets of inter-

mediate relays for processing to the proper outputs.

The control system must be rewired whenever a change in

operation is needed.

Control system outputs are ordinarily low-power, and must be boosted to higher energy to operate most equipment
(Exceptions are indicating devices and small solenoids and motors.)

The control signals drive contactors, to

switch high energy electrical loads, and solenoid valves, to activate hydraulic and pneumatic power.

Control

outputs also activate timers and counters, which are later sensed as inputs.

The controlled device responds to changing control signals by producing directed work.

Input sensors determine

when this operation proceeds to a new condition which requires a change in actions. The sensors deliver new
electrical signals to the control unit and the control loop continues.

The "ladder diagram" is commonly used to present an electrical schematic of system operation.

machine function is represented by one rung of the ladder.

Each unique

All inputs which determine a single required equip-

ment action are on one side of the ladder and the output is on the other.

To initiate a machine operation, the

unique combination of variables (control inputs) which allow that operation must be supplied.

Binary control applied to production equipment implies:

many relatively simple machines - single purpose
often repeated cycles

low cost for control

These criteria represent the general requirements of industrial mass-production equipment, but do not necessarily
establish the limits of binary control systems.

The PDP-14 control system is an example of an electrical binary control system.
of its type to appear in several decades.

It is

the first really new system

would appear that most industrial users are satisfied with their

present systems but this is often only because satisfaction has been created by familiarity.

Therefore, the

PDP-14 merits its own evaluation in terms of something new in control equipment.
The following discussion provides some guidelines for evaluating binary control systems in terms of something
better than the status quo in control equipment.

The performance of a control system can be defined in terms of

efficiency (including economic), versatility, maintainability, and performance monitoring.

1-4

EFFICIENCY
The overall efficiency of a control system can be measured in terms of:

Cost - the amount of control provided for the money (dollars per input or output)
Service

life of the entire system

Life of irdividual

components (MTBF)

Cost of repair, including length of downtime

Speed of the system (efficient use of control time)
Efficient use of space (physical size of the system)

Electrical efficiency (use of energy to provide control)

Present relay control systems are reasonably reliable.

have performed millions of correct actions.

low-power signal switching for railroad use, relays

The cost of relays is also considered reasonable by many users.

However, today's industry often demands that moderate control currents be switched at high repetition rates
and,

in this case

the practical use of relays become limited.

One operation per second is more than 30 million

a year, which only special -purpose relays can withstand for any long period of time.
limit of relay response time.

There is also an upper

Relays are somewhat bulky devices; and a complete relay control system may re-

quire a significant percentage of available manufacturing space.

Any attempt to miniaturize a relay system

makes servicing more difficult.

Diagnosis of faults is the most perplexing problem of conventional control systems.

When one unit of a highly-

interconnected system deteriorates, the real problems may appear to be at any one of several places or at several
places at once.

Troubleshooting often begins with an educated guess and continues through several time-

consuming circuit checks.
if

A complete monitoring system is a fine diagnostic aid, but can be quite expensive

not designed as part of the original control system.

Monitoring ordinarily requires considerable additional

equipment.

VERSATILITY
The versatility factor can be discussed in terms of:

Ability of a pre-packed control system to be adapted to a specific need

Ease of system design and construction (if a user must design and build his own
system from supplied building blocks)
Ease of control revision or retrofit, when modif/ing present functions or

changing entire control requirements.

System changes and adaptations must remain reasonably permanent.
operator error should alter proper control operation.

Neither the environment nor accidental

Although it seems a contradiction in purpose, the ideal

1-5

control system should be immune to arbitrary change but easily modified in case control requirements vary.
Present relay-type control signals are quite immune to accidental change except that, in corrosive environments,

contacts and electrical connections may deteriorate.

Since each relay systems is custom-designed,

can do its

However, this specialized kind of system does not easily adapt itself to desired updating, since com-

job well.

ponent layouts and wiring changes must be overlaid on the existing control structure.
system modifications can be a major effort.)

(Just documentating

When complete control requirements change, it is often more

economical to discard the old system and design an entirely new one.

Digital computer technology seems to offer a handy combination of easy system design and simple system modifi-

cation.

A designer could provide his instructions as a program list, which the computer would learn and then

provide control through an all-purpose system.

new tricks, which is quick and convenient.
thus provide incorrect control).

Control changes would be equivalent to teaching the computer

Unfortunately, ordinary computers can accidentally forget (and

They can be also susceptible to electrical noise often found in industrial

environments.

MAINTAINABILITY
To be easily maintained in operation, a control system must have:

A low failure rate of individual components (high MTBF).

Faults which can be quickly traced to specific components.

Easily and quickly replaceable parts and readily available spares.

One producer of heavy automotive manufacturing equipment estimated that 80% of control repair time is spent
finding system faults and only 20% repairing them.
is

Here is a major area for improvement.

Diagnosis of faults

often the greatest single non-machinery factor contributing to downtime.

Once the difficulty is isolated, nearly every control system allows for modular parts replacement. To replace
coils and contacts in relays is a relatively easy process.

Even though replacement parts are industry standardized

and easy to obtain, a large parts stock may sometimes be required for the many varieties of relays available.

MONITORING OF PERFORMANCE
A very useful feature of modern control systems is their ability to monitor and report equipment operations.
the equipment operating properly or are slowdowns occurring?

a need for preventive maintenance before failure can occur?

Has degraded machine performance indicated
Is

the production schedule being met?

questions can be answered continually by computer-assisted control equipment.

1-6

These

Unfortunately, computer monitoring is often added as a retrofit operation.
is

This means that an interface apparatus

added piggyback fashion to an ordinary control system to provide monitoring points for the computer.

Adding

this monitor requires a complete re-evaluation of the old system

and a number of new parts.

control are limited to the test points selected by the designer.

Monitoring can be easily more trouble than it's

worth when these limitations are imposed.

Monitoring and

The solution is an integral control/monitor package which can be

augmented as production operations change.

1-7

CHAPTER 2
PDP-14 SYSTEM INTRODUCTION

PURPOSE
This chapter explains the major features of the

PDP-14 control system and its function.

The major units of the

system are presented here and are discussed in detail in Chapter 3.

HISTORY
For several years. Digital Equipment Corporation (DEC) has been developing a large reserve of
computer tech-

nology.

Our industrial interest has centered around numeric control computer programs and the popular K-series

control modules.

We had created custom control systems of many sorts, but no genera -purpose industrial
I

equipment.

In the fall of 1968,

one of our industrial customers approached us with a request for an all-purpose, solid-state

industrial controller.

We found that much of the technology to meet his requirements was right "on our shelf",

and needed only to be combined into a useful system.
From our experience with small computers, we borrowed digital logic circuits and a modular concept.
adapted the rugged K-series industrial control modules.
trated on developing a reliable, low-cost system.

And finally, DEC mass production skill was concen-

When we finished development, we found that we could suppi)

most industrial users with a product greatly improved over previous control systems.

This

the PDP-14.

TRAINING FOR THE PDP-14
The PDP-14 is functionally equivalent to nearly all binary control systems in industrial use.
should understand

This means that one

general how such systems operate, and how desired control operations may be translated

into electrical circuitry.

Machine sequence charts and electrical ladder diagrams are two of the common design

aids you should be familiar with.

The PDP-14 system is easy and straightforward to install and use since it simplifies, rather than complicates,
electrical design of the control operation.

This manual provides the new information required about programming

2-1

computer monitoring operations.
the system for specific control needs, and about installation and
offers intensive training courses on various

PDP-14 topics to supplement this manual

DEC also

Check with your local

sales office for information on present offerings.

THE PDP-14 SYSTEM
The PDP-14 is a related group of modular units.
to provide a control function.

becomes a system when these units are properly combined

You buy only what you need to perform a specific control purpose.

Features

Here are some of the features of the PDP-14 control system:

It is

a truly general -purpose device, adaptable to nearly every binary control

requirement.

Control operations are defined through a series of flexible computer-assisted programming

steps.

without
Control modifications and retrofit can be made at any time with minimum downtime and
rebuilding the control system.

The control system is modular, has easily replaceable parts, and can be serviced quickly and
accurately, using computer based diagnostics.
Cost is comparable to systems it can replace.

The system takes less space than equivalent systems, and uses much less electric power.
The anticipated service life of the system is well over 10 years.
Reliability is very high, and all active components are solid-state (there are no active

moving parts)

General PDP-14 System

The PDP-14 control system is designed to replace conventional systems directly, with a minimum of special considerations.

The equipment uses standard 115 Vac input and output signals.

Each of the units is divided into

plug-in modules containing solid-state devices and other components, to allow for easy repair or replacement
of parts.

The PDP-14 is a direct replacement for the typical binary control system shown in Figure 1-2.
shows a general system layout.

2-2

Figure 2-1

~ 115 VAC"
440 VAC

BOX

A>
y/////A

PDP-I4
I

CONTROL
UNIT

//y»>»>yy^>y>y^///^^

BOX

"ZZZZZL

STARTERS
CONTACTORS

KXJ
BOX

^f10T0R

BOX
s

BOX

TIMERS
AIR

OIL

CONTROLLED DEVICE

f=U

HYDRAULIC a
PNEUMATIC

LIMIT

ACTUATORS

TIL^ SWITCHES
OPERATORS
PANEL

Figure 2-1

The Input (I) boxes and Output (O) boxes
trol signals from the controlled
device

°
O
o

MOTORS
LAMPS
BELLS

HEATERS
ETC.

General PDP-14 Control Arrangement

provide on "interfoce" or electrical buffer

and the electronic circuits of the Control

Unit.

between the 115 Vac conIn the conventional

control system we have:

115 VAC POWER

"-r

VAC
INPUT
SIGNALS
115

INTERMEDIATE
CONTROL
RELAYS

INPUT-

ACTIVATED
RELAYS

TIMERS
COUNTERS
-.

CONTROL SYSTEM

2-3

OUTPUT

-J
1

SWITCHING
RELAYS

115 VAC

SWITCHED
OUTPUTS

And in the PDP-14 system, the equivalent parts are:

115 VAC

POWER

^
I

BOX

BOX
115 VAC

V///////M

INPUT

POP- 14

7ZZZZ17ZZZ

CONTROL UNIT

SIGNALS
I

MEMORY

'//////////.

115 VAC

SWITCHED
OUTPUTS

y////////A

BOX

t LOW-VOLTAGE
CONTROL CABLES
saA
ELECTRONIC
BOXES
TIMERS AND
RETENTIVE

MEMORIES

The low-voltage, solid-state circuits of the Control Unit (CU) test and direct the 115 Vac circuits of the controlled device through control cables.

The I and O boxes provide effective isolation of the control circuits

from the AC power supply, giving added safety when handling PDP-14 equipment.
small number of AC circuits and has its own control cable to the CU.

Each I or

O box handles a

This means that by selecting the proper

number of I and O boxes, only the input and output circuits actually needed for the specific control operation,
need be purchased.

The PDP-14 system is a unified assembly of five basic units consisting of a Control Unit, with its Memory, Input
(I)

Boxes, Output (O) Boxes, Auxilary Boxes, (timers, retentive memories, etc.)/ Storage Boxes.

This system does exactly what ordinary systems do;

accepts low-power AC signals at its inputs, determines

which signals are necessary for a given machine function, and then turns on and off the required outputs.
it

does it in a different way.

The following paragraphs describe each of the PDP-14 systems separately.

2-4

But

115 VAC
NPUT SIGNALS

BOX
^

'///////////y

'///////

PDP-14

CONTROL UNIT
x
/

\
\

v////y\////

k
^

BOX

'////A

1
f

115

VAC

"HOT"

NEON
INDICATOR LAMPS

NPUTS

1.5

VA LOAD EACH

115

VAC COMMON

CONTROL MODULES
14-0031

Figure 2-2

Input Box Pictorial

2-5

Box Function (See Figure 2-3)

The I boxes are signal-conditioning devices which accept 115 Vac inputs from two-state sensing devices such
as limit switches, pushbuttons, proximity switches, pressure switches, and photocells.

These inputs are con-

verted into signals which are proper for the solid-state circuits, and then pass the signals along control cables
to the

PDP-14 Control Unit.

Each I box contains 32 independent input circuits.

control cables from a maximum of eight I-boxes (256 inputs per system).

The Control Unit will accept

A lamp on each input circuit shows

when ac power is being supplied to the box terminals.

Box Mechanical

J.
7~
6^/4

O
s
10 7,
16

V
Figure 2-3

4V4

Input Box Dimensions

The I box is a strong, "U "-shaped steel channel with three mounting tabs.
its

back wall that accepts plug-in solid-state modules.

strips mounted on the front of the

The box contains a wired socket on

Wire connections are made to screw-type terminal

box, which accept number 14

minals and modules.

2-6

AWG leads. A plastic shield covers the ter-

Control Unit (Figure 2-4)
Tiie circuits of tiie Control

Unit and the memory perform the three basic operations of any control system.

They:

TEST inputs for state (ON or OFF);

DECIDE what control function is required; and

SET outputs

ON or OFF (execute the control decision).

Read -Only Memory

The memory used in the PDP-14 system is called a Read-Only Memory, or ROM.
cause it canrrot be altered electrically (that is written on).

woven together.

This pattern

It is

termed "read-only" be-

The ROM contains a pattern or a "braid" of wires

actually a list of permanently wired electrical instructions which are read by

the CU to determine system operation.

The function of memory in a conventional control system is provided by the wires which interconnect relays and
inputs and outputs.

They route the input control signals to the proper sets of intermediate relays for processing

to the proper outputs.

To modify this sort of memory, leads must be rewired and relays added or removed, an

inconvenient process at best.

The ROM braid is the functional equivalent of all the wiring in a conventional system.

A control designer

specifies the instructions (to suit his control task) to be placed in the braid for each PDP-14 system.

He first

determines the control operations he requires, by referring to equipment sequence charts, and deciding conditions to be sensed (inputs) and energy to be switched (outputs).

Then,

in a series of computer-assisted steps,

described in Chapters 4 through 10, the operations are converted into a list of coded instructions termed a pro-

gram.

This program is then punched into a paper tape and sent to DEC, where it is used to control an automatic

weaving machine which makes a wire braid.

When the braid is mounted in the ROM, and the system started, the

CU will test inputs and set outputs according to the program instructions.
design effort is either on paper or in a computer.

Note that the entire control system

This process is equivalent to designing a relay control network,

including layout of all the terminals, relays, wires, and other hardware.

2-7

V///////////////////A

y/////////////////////A

PDP-14

CONTROL UNIT

CONTROL
CABLES

Figure 2-4

Control Unii— Pictorial

2-8

The ROM program can be changed at any time by repeating the program design steps, preparing a new braid,

and installing it.

This is equivalent to rewiring a complete control system panel .

Minor changes to the program

can also be made manually, if desired, by changing braid wires.

Control Unit Mechanical (Figure 2-5)

Figure 2-5

Control Unit Dimensions

The CU consists of a heavy steel mainframe containing low-voltage power supplies and module sockets, hinged
to a base frame for mounting.

Plug-in modules containing all control circuits,

ROM assemblies and control

cables, are inserted in this mainframe, and a sheet metal shield cover is fastened over the entire assembly.

2-9

115 VAC

115

VAC

SWITCHED OUTPUTS

BOX
77777
.

PDP-14

CONTROL UNIT

CONTROL CABLE

NEON
INDICATOR LAMPS

AC COMMON

OUTPUTS 500 VA MAX EACH
(SEE TEXT)

TERMINAL STRIP

CONTR OL MODULES

Figure 2-6

Output Box-Pictorial

2-10

O Box Function (Figure 2-6)
The O box contains isolated 1 15 Vac switches directed by the CU.
state sensed by the

CU (as though they were inputs).

AC power can be turned on or off, and the

These switches drive such output devices as indicators,

motor starters, contactors, and any other 115 Vac load which does not exceed 500 VA (volt-amperes) per circuit,
(See Chapter 3 for further specifications on output loads.)

A lamp on each output switch shows when ac power

O box contains 16 independent output circuits. Command
signals pass from the CU along control cables to each O box. The CU will accept as many as 16 O box cables
is

actually being supplied to a terminal strip.

for a total

Each

256 outputs per system (actually, the last output is special-purpose, and is not normally used.)

O Box Mechanical (Figure 2-7)

J_
B'^/z

o
10 7,
16

^4V4

Figure 2-7

The O box shell is identical to the I box.
used.

Output Box Dimensions

differs in the wiring of the rear

module sockets, and in the modules

The fronts of both I and O boxes are covered with a plastic safety shield.

2-11

Auxiliary Boxes (A and S) (Figure 2-8)

Figure 2-8

Auxiliary Boxes - Pictorial

A control system may sometimes require a group of pre-set status signals which cannot be generated by direct
machine operation.

For example, timers can provide duration and sequencing control for a controlled device.

These functions are provided in the PDP-14 system by:

Accessory (A) boxes, containing electronic timers with a range of 0.01 to 30 seconds (and
special modifications to 4 minutes), retentive memories, which store results of selected
control operations.

Storage (S) boxes, providing "dummy outputs" which temporarily store the interim results
of selected control operations for status indications. The S box is a temporary memory.

Each of these boxes appears to the CU electrically as an O-box, and requires some of their control cable slots.

An A box contains up to 16 electronic timers, one for each output circuit, or up to four retentive memories.
Using program techniques, any standard type of timer operation may be produced.
half-size or full-size versions.
electrically a double

The S box is available in

The half-size box is equivalent to one O box (16 circuits).

The full-size is

O box (32 circuits), although it is physically no larger than a standard box.

2-12

Auxiliary Box Mechanical (Figure 2-9)

6^/4

o
5
10 7,
16

4V4

Hgure 2-9

Auxiliary Box Dimensi ons

Both the A and S box shells are mechanically identical to the I or

O box, and are mounted in the same way.

Each has a complement of modules which allow it to function in its special way.

more modules than the half box.
is

The full S box has several

Neither S nor A boxes has modules which contain terminal strips, since neither

intended to be connected to input or output circuits directly, but only through operation of the ROM

program.

COMPUTER MONITORING
The PDP-14 system design allows for optional computer monitoring to be added at any time.

A small

general-

purpose computer is connected through control cables to the CD, and certain monitoring modules are also installed.

The computer can then monitor any control operation of the PDP-14 system, or the status of any input

or output and transfer this information into a printed record if desired.
of any control functions, either on a standard or emergency basis.

2-13

The computer can also assume command

Some of the best suited computers for monitoring with the PDP-14 are the DEC PDP-8/l, or PDP-8/L.
are convenient to use and install, and inexpensive.

The monitoring modules to adapt these computers are avail

able for the PDP-14.

SUMMARY OF PDP-14 SYSTEM CONTROL CIRCUITS (One System)
INPUTS

Eight I-boxes of 32 inputs each, total of 256 inputs.
All inputs 115 Vac, 1.5

OUTPUTS

16 O-boxes with 16 outputs each, total of 255 outputs
(one output unusable).
All outputs

15 Vac, 500

load of 250 VA each.

CONTROL UNIT

They

VA max.

or total distributed

(See Chapter 3 for details.)

Accepts memory containing over 4000 separate instructions,
Requires 115 Vac, less than 160 VA.

2-14

CHAPTER 3
PDP-14 SYSTEM PARTS AND FUNCTION

INPUT BOX OPERATION
The I box has two general functions:

signal conditioning and isolating, and

input selection for testing

As a signal conditioner, the I box reduces each 115 Vac input signal to a low, controlled voltage, and also
isolates and filters it.

The following is a simplified presentation of one input circuit (Figure 3-1):

STEPDOWN
TRANSFORMER

AC HOT

Qt
I

vw-

115 VAC

INPUT SIGNAL
1.5

L_T

RECTIFIER
AND
FILTER

VDC

Xr±_A

AC NEUT

LAMP
COMMON

Figure 3-1

Box Input Circuit - Simplified

Each input circuit loads its 115 Vac signal to 1.5 VA, with a slight inductive surge to cause mild arcing at
sensor contacts.

This provides a self-cleaning function without excessive contact wear.

some cases, the

switch could wear out mechanically before its contacts become unreliable.

A small neon lamp on each input line lights to show that the circuit is energized.

The stepdown transformer

(which provides the inductive surge) is effective isolation between input signals and the PDP-14 electronic circuits.

The reduced voltage is rectified and filtered to remove electrical noise and a 5 Vdc signal is available

for testing whenever an input is

energized.

3-1

Eight input circuits are provided on each

Four of these plug-in modules (with

K578 input converter module.

circuits per box.
their screw terminal strips) are inserted in the left and right sides of an I box, for a total of 32

The remaining I box modules provide for the selection of one input

from the 32 available.

Rgure 3-2 shows

the general selection system for one I box.

A SELECTION CODE is sent from the Control Unit to the

box along the control cable.

The PACKAGE SELECT

used by the Control Unit to select one I box for testing from the eight possible boxes in a complete sys-

signal

tem.

The K135 GATE module extends PACKAGE SELECT to allow two K161 DECODERS to respond to the

SELECTION CODE.

Part of this code selects one of the

K161 modules to operate for this particular input test.

The rest of the code is used by the active K161 to select one of the eight inputs on two K578 INPUT CONVERTERS.

This means, that for each test,

two inputs have been selected by the K16], one on each of two K578

Each tested input provides a SAMPLE RETURN signal.

modules.

In the last step of input selection, the Control

Unit checks one of the two SAMPLE RETURN lines for a signal, effectively selecting one of the 32 box inputs.

An active AC input provides a 5 Vdc signal on the SAMPLE RETURN, and the absence of an input provides zero
voltage.

All control cable voltages are 5 Vdc with limited current for complete safety.

A summary of the selection operation (Figure 3-2).

PACKAGE SELECT

selects one box from eight

SELECTION CODE

selects one of two K161

DECODERS and (through K161)

selects one of eight inputs on each of two

The Control Unit selects one of two SAMPLE RETURN signals for testing.

K578 modules.

This results in a selection of one

input from a total of 256.

CONTROL UNIT OPERATION
The Control Unit (CU) is the most complex part of the PDP-14 system.
conventional small computer.
"electronic catch."

Even so, it is much less complex than a

The CU and the Read Only Memory (ROM) interact in what might be called

CU begins the ball game by demanding that the ROM "pitch" one instruction.

responds, and the instruction is "caught" by the CU, which must now "run the play."

The ROM

This instruction deter-

mines the operation of the CU and also in some cases, the next "pitch" the CU will demand from the ROM.

The CU controls the ROM and the ROM controls the function of the CU.
call

an arbitrary "time-out.

However, in this case, no referee can

The CU functions to:

ROM for an operating instruction

Interrogate the

Generate signals that address or select specific inputs or outputs

3-2

CONTROL CABLE
SELECTION CODE
(3 LINES)

PKG
SELECT,

K161

K135

DECODER

NEON LAMPS
INPUTS

^^/////////////////////////y//////////////////y/////////////^^^^

NEON LAMPS

INPUTS

^//////////////////////////////////////////^^^/////////^^^y/y'^^^^

INPUTS

NEON LAMPS

* ISOLATED
115 VAC INPUT

CONVERTER

#2(INPUTS 17-32)

SAMPLE RETURN
*1(INPUTS 1-16)

Figure 3-2

Box Selection System

whether it is on or off

c .

Test a selected input or output to determine

Combine the results of one or more test steps

Turn an output on or off depending on the combined

Interrogate the

In these operations, the

results of the testing operations

ROM for a new operating instruction.

ROM

functionally an electronic list of:

Inputs and outputs to be tested

Alternate commands to be followed depending on the results

Outputs to be turned on or off; and

Sometimes a special group of monitoring commands.

The ROM thus directs the CU circuits to perform the three basic

of the testing

operations of a control system:

Test (of inputs and outputs)

Decision

Execution (of decision)

When a computer is connected to the CU for monitoring, it can functionally replace
can request the condition of an input or the result of testing, or it can
outputs.

In another monitoring approach, the

information to a waiting computer.

the ROM.

The computer

actually control the operation of selected

ROM can include instructions which force the CU to send status

The computer doesn't need to make a request.

temporarily stores the results of several test operations and allows

The active element which

alternate output control instructions to be per-

formed is called the TEST FLAG.

Boolean Logic

The PDP-14 control system operates by a formal binary logic termed

Boolean.

This logic

a simple way of

expressing binary equipment operation, as in this example:

IF a pushbutton

pressed OR the drill head

turning,

THEN move the drill head

The operator of the machine wants to be able to move the drill head
In any case, the
left at any point in its automatic cycle by pressing a button.

to the left.

drill

head should automatically move left whenever it is turning.

corresponding to the operation of any control system:
This simple Boolean statement has three functional parts;

IF pushbutton

TEST

pressed

OR
drill head is turning (the motor is on)

DECISION

THEN
EXECUTION

move drill head to the left

3-4

We will arbitrarily assign address numbers to the input and outputs involved.
The pushbutton is input 36
The drill head motor contactor is output 7 , and the hydraulic solenoid which causes
a ram to force the drill head slide to the left is output 142.

The Boolean statement is now:
IF input

36 is

OR
output 7 is

THEN
turn output 142 ON.

The statement is one of the control sequences stored in the ROM.

Let's follow this step-by-step sequence

through the PDP- 14 system.

The CU requests its first instruction from the ROM.

receives the electronic command; TEST

INPUT 36.
The CU addresses input 36 by sending the proper address code along the control cables to I box A.
The proper SAMPLE RETURN is sent to the TEST flag circuit.
The TEST flag begins the sequence in the off condition and turns on if the input tested is on.

(Input 36 is input number 31 in I box A.)

The CU requests an instruction from the ROM to TEST OUTPUT 7.

The CU requests a SAMPLE RETURN from output 7 (in O box A) just as it did for input 36 in step 2.
no output command signals are sent. The TEST flag is turned on if output 7 is on (it may
have already been turned on by input 36). If output 7 is off, the TEST flag is left unchanged.

(In this case,

The CU requests more instructions from the ROM.
the results of the testing operation (to the TEST flag).
5.

These instructions will tell it how to respond to
There are two basic ROM instruction, one for

each possible state of the TEST flag.

At this point, if input 36 OR output 7 is on, the TEST flag would be on also, and the ROM would
direct the CU to SET OUTPUT 142 ON. (The ROM would probably also contain the alternate instruction
SET OUTPUT 142 OFF, so that when neither proper condition existed, the output is to be turned off.)
6.

The CU now selects output 142 through the control cable for O box G. (Output 142 is output numO box G.) It also sends the ENABLE SET signal , which will turn on output 142 when it is ad-

ber 3 in
dressed
7.

The CU now requests an instruction from the ROM for the next control sequence.

This control sequence example may seem at first to be overly complicated but these are the same logical steps

you would perform if you were to control the equipment manually.

This sequence can be completed in less than

100 millionths of a second.

Read -Only Memory (ROM) Operation

The Read-Only Memory (ROM) contains all PDP-14 system instructions in its pattern of wires.

These wires are

formed into a compact, replaceable package called a "braid", and then encapsulated to make them immune to
accidental change.

By replacing wires manually, all instructions can be altered to make revisions in control

3-5

operation.

The manual procedure is ordinarily used only to make minor changes involving a few wires.

The operation of the ROM depends on the same principle as

the familiar current transformer used to monitor AC

power leads.

LINE

IRON CORE

MAGNETIC

-'SENSE"WINDING

FIELD

AC "AMMETER"

Fluctuations in the AC current flow produce a varying magnetic field around the wire.

an iron core around the wire, producing a small voltage in a sense winding.
to give an indirect measurement of the current in the

AC lead.

This field

This voltage is measured by a metei

The lead is equivalent to a one-half turn trans-

former primary, and the sense winding to the secondary.

The following illustration shows three of the 12 transformers in a group

FERRITE CORES

POWER

POWER RETURN

PULSE

-^TRANSFORMER CORE

SENSE WINDING

VOLTMETER

3-6

induced in

ROM circuit operation

similar to the current transformer, except that:

Many wires (128) are used

The current is checked only to be present or absent on a wire, not for actual value

Groups of twelve transformers are used, rather than just one (a total of 96 transformers)

Circuits are added to select the proper wire and to boost the sensed voltage to operate CU circuits.

To "read" the instruction wire, a pulse of current is applied to it.

a quick-<3cting voltmeter were applied,

the left and right transformers would show voltage present at the sense winding and the middle

show none.

Remember that all signals used are binary, i.e.

transformer would

they have only two possible conditions (on or off).

The presence of a voltage is defined as a data "1" and its absence as a "0" in the PDP-14 system; thus, the
transformer outputs can be given as a code (in this case, "101 ").

Since a group of 12 transformers form a single

instruction, a typical instruction code might be:

101

111

001

Each number of the code is termed a "bit".
for easier reading.

sections).

The 12-bit instruction is divided into four groups of three bits each,

Each of these four groups can be expressed as an octal number (discussed in the programming

(For example, the binary instruction code shown above has an octal equivalent of 5716.)

The ROM is a self-contained package, consisting of three circuit boards (Figure 3-3):

ONE PLUG-IN ASSEMBLY

G923

SENSE

SELECTION
BOARD

BOARD-

WIRE CHANGE SIDE

KEEPER PLATE
BRAID (ENCAPSULATED)

BRAID BOARD
14-0013

Figure 3-3

ROM Board Group- Pictorial
3-7

The boards correspond to the three general operating steps of the ROM:

SELECTION - The PDP-14 Control Unit provides the ROM an address code, telling the ROM which

wire to select (and which group of 12 transformers).
b.

READ - the Control Unit now signals the ROM to begin, and the ROM responds by placing a current

pulse on the selected wire in the braid.
c.

SENSE - The ROM circuits sense the 12 transformer voltage outputs, boost them to proper values,

and transfer them to the Control Unit for use as operating instructions.

The Control Unit alone interprets and responds to instruction codes provided from the ROM.

In this sense, the

ROM does not know its own contents, and has no way of reacting to its own output codes.

Changing Instruction Codes
The position of the wires in the braid determines the instruction code which is generated in ROM operation.
a wire is placed inside a core,

produces a 1 , if outside, a 0.

Therefore, wires can be threaded by hand

around and through the ROM transformers to produce any instruction code desired.

This feature is useful to im-

plement minor changes in control operation.

The process of modifying instructions is equivalent to rewiring the

control system, and is much easier and faster.

The technique of ROM wire additions is discussed in Chapter 12.

The group of three circuit boards is termed a memory bank.

Up to four of these banks may be added to a CU,

as options, to increase the memory locations available for a control program.

Each bank will contain its own

braid and independent selection and sensing circuits for over 1000 locations.

Thus, each memory bank is said

to contain

IK units of memory.

erating, the individual

The CU can accept four memory banks, or 4K of memory.

When the CU is op-

memory banks are all used as one large memory in sequential program operation.

O BOX OPERATION (Rgure 3-4)
The O box functions much like an I box, but with these general operations:

output selection (and testing),

output function command, and

isolated ac output switching.

The output selection system is nearly identical to input selection already discussed, except that only one of
sixteen circuits must be selected instead of one of 32.

Figure 3-4 indicates the selection sequence.

PKG

SELECT and part of the SELECTION CODE cause the K135 to activate the particular O box and select one of
the two K161 DECODERS.

These DECODERS then accept the remainder of the SELECTION CODE to select one

output control circuit from eight contained on two K207 STORAGE REGISTERS.

Each K207 contains four

output control circuits, one for each ac output on a K614 ISOLATED AC SWITCH.
trol

Unit sends its SELECTION CODE,

At the same time the Con-

can also issue one of three function commands,

RESET and CLEAR.
3-8

ENABLE SET, ENABLE

CONTROL
CABLE
SELECTION CODE
3 LINES

PKG

SELECT
K135

K161

DECODER

STORAGE

—
CLEAR ALL —

ENABLE SET
ENABLE RESET—
AC NEUT

AC HOT
1

OUTPUTS

NEON
C>0

LAMP

K207

(4)

O
-o

o 0«

—

K614

<^7ZZZZZZZZZZZZZZZA

ksw

OUTPUTS

y/////////////////.V/////////////}^ K614

OUTPUTS

^Tzzzzzzzzzzzi:^

° 04

—
o
—
O
—

0-"

OUTPUTS

K614

g^/'yyyyy/yy//yy/y//y//y//y//yvy////^

° 04
* ISOLATED

—

120 VAC

SWITCH

SAMPLE RETURN
(OUTPUTS

Figure 3-4

O Box Selection System

1-16)

ENABLE RESET will turn

ENABLE SET will turn on a K207 control circuit corresponding to the selected output.
the circuit off.

The CLEAR signal will turn every output circuit off regardless of selection.

The K207 output control circuits receive the CD commands which establish the condition of each output, and
then maintain that condition until the CU changes it.

In other words, the

K207 functions as a memory device.

When the PDP-14 system is stopped and then restarted, all K207 output circuits are turned OFF and wait further

CU action, just as if the CLEAR command had been issued.
Whenever the SELECTION CODE has selected an output, a SAMPLE RETURN indicates the condition of the
selected K207 output circuit to the Control Unit.

This would occur even

a K614 ISOLATED SWITCH module

were removed from the O box, because the SAMPLE RETURN indicates the status of the K207 holding circuits
and not ac power conditions.

an output circuit is to be tested for status only and not changed, no command

signals are sent and the selection sequence produces only a SAMPLE RETURN.
issued, the SAMPLE

If a

function command was also

RETURN shows the condition after the command has been executed.

The K207 output circuits directly control the action of the K614 115 Vac ISOLATED SWITCH modules.

The four

circuits in one K207 serve the four switch outputs of one K614 module.

TRIGGER PULSE
GENERATOR

FUSE

115

PULSE
TRANSFORMER

VAC

OUTPUT

TRIAC

TO 500 VA

K207
CONTROL

TRIGGER PULSE

CIRCUIT
ON OR OFF

CIRCUIT

^^—

AC NEUT

SWITCHING

LOAD
FERRITE CORE

Figure 3-5

Box Output Circuit - Simplified

The active switching element is a triac, a solid-state AC control device.
thyristors, discussed in most modern circuit handbooks.)

(The triac belongs to the family of

The triac requires a series of low-voltage pulses to

turn the ac power on; otherwise it acts as a very high resistance.

In other words,

a high-voltage switch

operated by a low-voltage control signal.

The K207 control circuit is first directed
condition indefinitely.

ON or OFF by the selection and control sequence.

now holds either

When it is ON, it allows pulses from a trigger oscillator on the K614 module to enter

the primary of a small pulse transformer formed of two isolated lengths of wire looped through ferrite cores.
pulses from the transformer secondary activate the triac, switching on the 115 Vac current.

provides effective isolation of the low-voltage control circuits from the ac power supply.

3-10

The transformer

The

A 5-ampere replaceable pigtail fuse is provided directly on the K614 module to protect the trice from damaging
overcurrents

A neon lamp indicates when the triac is energized and ac power is being provided.

This allows

easy checking for actual power switching operation.

Each of the four triacs on a K614 module is mounted on its own heat sink to dissipate the slight resistance heating

which is typically less than 2% of the total ac circuit load.

An individual triac circuit is rated at 500 VA when

operated alone, and will withstand moderate inductive surges for brief periods.

However, the temperature rise

caused by the collective operation of the triacs on the K614 limits the total power rating of the module to
1000 VA.

Thus, the total rating per

O box is 4000 VA.

Output

Example

500 VA
500 VA

250 VA
250 VA
250 VA
250 VA

400 VA
200 VA
400 VA
no load

300 VA

no load
no load

Four examples of maximum loading for one K614 are as follows:

100 VA

300 VA
300 VA

No particular distribution must be followed, as long as no single ac circuit is loaded more than 500 VA and no
single
is

K614 module is loaded more than 1000 VA. The maximum evenly distributed load of 250 VA per circuit

more than adequate for most industrial control switching.

If higher

loads are required, distribute them be-

tween several K614 modules, or use a power contactor.

Each ac circuit is completely independent from every other, even on the same K614 module, and can be supplied
from separate ac power sources,

if necessary.

terminals, as shown in Chapter 11
ratings.

It is

Ordinarily, a common source of ac is strapped to all circuit hot

not recommended that outputs be paralleled to form higher current

For 230 Vac operation, two triac circuits can be connected in series.

This special arrangement and

other specifications are contained in the DEC publication, "The Control Handbook", Catalog CllO.

Copies

are available on request.

AUXILIARY BOX OPERATION
The A and S box shells ore physically identical to those of the I and O boxes.

Since these boxes require no ac

circuits or terminal strips, the entire space may be used for electronic modules.

This makes possible an S box

which contains double the usual quantity of output-type circuits.

The auxiliary box modules are protected by a

metal cover which fastens in place of the four absent K614 ac switch modules (Figure 3-6).

3-11

Rgure 3-6

A or S Box

3-12

Each auxiliary box functions in SET, RESET, and TEST operations exactly as an O box, and thus contains
groups of:

K135 GATES
K161 DECODERS
K207 STORAGE REGISTERS
The meaning of the SET and RESET commands is similar to the O box; they activate or deactivate the selected
output circuit.

The TEST command produces a SAMPLE RETURN which indicates the operation of the special

auxiliary device in the selected circuit.

The A box may contain either timer or retentive memory modules, up to a total of 16 circuits.

The K302 timer

modules each contain two timer circuits, and can be inserted into any of the eight sockets along the left or
right edge of the box (Figure 3-7)

Rgure 3-7

Timer Module K302

Each K302 circuit is separately adjusted for the desired timeout in two steps.
selected by cutting two components from the module, providing either:

0.01 to 0.3 seconds
0. 1 to 3.0 seconds
1 .0 to 3.0 seconds
Up to 4 minutes by special modification (see Chapter 11).

3-13

The proper range is permanently

Timing within each range is adjusted by a potentiometer,
the module

change.

installed.

which can be turned with a small screwdriver when

Timing error due to temperature variations is typically less

than ± 1% for a 5°C (9°F)

time of 0.3% of the maximum
Repeatability is better than 95%, allowing a minimum recovery

time

available in the range.

The K272 retentive memory modules use a magnetically-latching

mercury relay, which must be mounted in one

the sealed unit.
position to keep the mercury where it belongs inside

Therefore,

of the A box.
output circuit each, are mounted only along the right side

may contain:

K272 modules, containing one

Thus the 16 output circuits of this box

- 16 timers, or four K302 timer modules (2 circuits) = 8 timers,
Eight K302 timer modules (2 circuits)

memories.
and four K272 retentive memory modules (1 circuit) = 4 retentive
K272 modules per
They may also contain reduced amounts of K302 or K272 modules, but never more than four

box (Figure 3-8)

TOP

K302
(2TIMERS)

K302

OR
K272
(1 MEMORY)

(2 TIMERST^

BOX

K302
(2TIMERS)

K 302
(2

OR
K27

TIMERS)

MEMORY)

K302
(2TIMERS)

K302

OR
K27
(1MEM0RY)

(2 TIMERS)

(ALWAYS MOUNT

BOX VERTICALLY)

K302
K302

(2TIMERS)
OR
K27
(1MEM0RY)

(2 TIMERS)

Figure 3-8

A Box Socket Functions and Allocations

3-14

As In all oufput circuits, a timer is normally off.

A timing cycle is begun by a SET command from the CU.

the end of the timeout, the timer output turns on (indicated by an active SAMPLE RETURN).

remains on until a RESET command turns it off.

In other words, the timer

The output then

a delayed-on type, although all

types of timing cycles can be simulated by program variations.

Unlike a timer, a retentive memory circuit is not turned off by the initial startup of the PDP-14 system.

The

memory (relay) can be turned on or off only by a direct SET or RESET command addressed to that circuit. The
state of the memory is available as a SAMPLE

RETURN, just as an ordinary output circuit. The individual mem-

ory circuit may also be manually reset by a toggle switch on the module (Figure 3-9).

Rgure 3-9

Retentive Memory Module K272

The S box, or "storage" box, contains groups of K207 output holding circuit,

O box, but withThe half S box contains the same number of circuits as a regular O box (six-

out the K614 ac switch modules.
teen), and uses one control cable.
circuits, the equivalent of two

exactly as an

The full S box actually contains two entirely independent groups of sixteen

O box output circuits in one box shell

The 32 output circuits are addressed

through two control cables, one at the top, the other at the bottom of the box

shell

The S box functions as a "dummy" O box - its addressing and control commands
out actual ac power switching.

are exactly the same, but with-

The S box stores the outputs of intermediate testing operations which must be

recalled for use later in the control operation; a sort of temporary function.

3-15

Additional Module Information
For further information about modules used in I and

O boxes, consult the DEC publication, "The Control

Handbook", Catalog C-llO, available on request.

The Handbook provides complete specifications for the

K578 and K614 modules, and explains some special applications.

Computer Operations With the PDP-14 System
The PDP-14 system may operate in one of four general ways:

Control

Monitoring
Control and Monitoring

Shared Control

CONTROL
The control operation has been described without any monitoring function.

has been shown how the CU re-

quests input and output samples and uses them to make a proper control decision.

This same information may

in many ways.
also be sent to a genera -purpose computer for interpretation and processing

For example, the

computer can prepare a complete status report of equipment operation, and signal slowdowns

and other un-

desirable situations before they become major catastrophes.

This points out the importance of preventive main'

tenance
EXTERNAL DATA

PDP-14

CONTROL SYSTEM
POWER

INPUTS

OUTPUTS

_L_
CONTROLLED
DEVICE

MONITORING
The PDP-14 can be used for monitoring only,

if desired,

with no control operations.

contains instructions for inputs end outputs to test, and the proper
puter.

In this mode, the

ROM

format to send the information to the com-

The system can also be run without an ROM; the computer controls

all testing operations.

PDP-14 functions as a giant "interface," providing ac coupling and addressing circuits for the

That is, the

computer.

For ex-

send data through long lines to a single
tended monitoring, special options allow several PDP-14 systems to
entire network of equipment.
waiting computer, where the data are assembled into a report for an

3-16

COMPUTER

<^22^

PDP-14

CONTROL
SYSTEM
INPUTS

DEVICE
(MANUAL OR INTERNAL
CONTROL)

CONTROL AND MONITORING
When bofh monitoring and control are mixed in one installation, the PDP-14 system shows its most complete
versatility.

In this mode, the

ROM contains the usual control instructions, including TEST and SET commands,

as v/ell as a group of special monitoring instructions.
results for transfer to the
(to signal the

computer.

Part of the

These instructions allow the CU to select specific TEST

ROM program may be designed for emergency conditions only

computer operator that the controlled device needs special attention).

In this situation, the

com-

puter may assume command of control functions until the emergency passes.

COMPUTER
PDP- 14

CONTROL
SYSTEM

OUTPUTS
'iJi/Zu.

INPUTS

i
I

^^
CONTROLLED DEVICE

Shared Control
This approach, like control and monitoring,

a union of PDP-14 and computer.

In this case, control or moni-

toring of analog processes or other difficult functions is handled directly by the computer.

small computer can provide numeric control and also monitor a PDP-14 system supplying

same (or another) device.

For example, our

binary control to the

A computer could also provide (analog) quality-control measurements to an industrial

operation being controlled by the PDP-14 system.

Shared control, although requiring additional equipment,

makes the most efficient use of both the PDP-14 and the computer.

3-17

COMPUTER
PDP-14
CONTROL
SYSTEM
INTERFACE

NC OrI

CONTROLLED DEVICE

ANALOG >
signals]

Adding the Computer
The most convenient computer to use with the PDP-14 system is either the PDP-8/l or PDP-8/L.

All the equip-

ment to connect these computers is available, and additional programs and equipment for numberic control and
analog operations can be quickly supplied.

you already have a general-purpose digital computer, a simple

interface device may allow it to operate with the PDP-14.

Contact an Applications Engineer, who can explain

when it is feasible to design the proper interface.
To add any computer operations to the PDP-14 system, a small group of special modules is added to the CU,

and three cables are inserted.

These cables carry the data signals from the PDP-14 to the computer, and return

computer control and interrogation signals.
either the computer or

ROM program.

The modules allow these signals to be transmitted on command from

The type of control or monitor operation performed, depends mostly on

the program used, although some specialized applications could require a few additional modules in the CU.

About 15 minutes is needed to convert a PDP-14 system used only for control to one for complete computer
monitoring.

3-18

CHAPTER 4

INTRODUCTION TO PDP-14 PROGRAMMING

Anyone who has designed machine controls has actually been a programmer. Although he has used relays as his
medium, he has still specified a series of actions (in a given sequence) which control machine operations.
specification of actions and their sequence is programming in a general sense.

The

The basic difference between

what is usually called programming and other forms of machine control is that the programmer uses instructions
or a programming language in place of specifying the relays which control the various pneumatic, hydraulic,

and electric devices.

PROGRAMMING THE PDP-14
The PDP-14 was designed specifically to control machines.
tion to be performed in a particular application.

the wiring of a relay panel.

The programmer need only specify the control func-

This is analogous to drafting a relay ladder diagram to specify

The difference is that the control designer is designing a PDP-14 memory instead

of directing the actions of an electrician.

Once the control function is specified, the PDP-14 will control a

machine (or series of machines) just as relays would in the same application.

There are distinct advantages to programming machine control with a PDP-14 over programming with relays.
Logic errors are easier to find and, once detected, easier to correct.

Programming in the PDP-14 system is simply the procedure used to generate the Read Only Memory (ROM) to
control a process or machine.

PDP-14 programming does not require previous computer experience although it

does require experience in machine control

PDP-14 programs provide relationships between inputs (limit switches, pushbuttons, selector switches, etc.) and
outputs (solenoids, motor contactors, indicator lights, etc.).

These relationships, or control functions, may be

expressed as Boolean equations which, when solved for particular input values, specify the state (ON or OFF)
of an output

The following definitions are for the reader who has not been exposed to computer terminology.

Memory

the unit of the PDP-14 which contains (stores) the program.

Location

the smallest part of the memory, in which instructions are stored.

4-1

Instruction

specific
the smallest part of a program. An instruction causes the PDP-14 to perform one
onebe
may
instruction
An
operation, such as testing an input or setting an output.
location (requires one memory location for storage) or two-location (requires two loca-

The actual instructions executed by the PDP-14 are binary numbers,
but they are usually given symbolic names.
tions for storage).

operated upon by an instruction.
struction is the specific input to be tested for
that which

Operand

instruction

the specific output which is

a plan for solving a problem.

Program

For example, the operand of a test in-

ON or OFF. The operand of a set output
set ON or OFF.

A PDP-14 program is basically a series of instructions

or OFF dependent upon the result of the tests.
which tests inputs and sets outputs
PDP-14 programs have three basic forms:

Machine Code Program - a program which contains instructions to be executed

(1)

by the PDP-14.

PAL-14 Source Program - a program containing symbolic representations for

(2)

instruction operands which must be translated into machine code before it can be

executed by PDP-14.

BOOL-14 Source Program - a program containing equations which must be

(3)

translated into machine code before

can be executed by the PDP-14.

INPUT AND OUTPUT ORGANIZATION
Machine inputs and outputs must be assigned to the PDP-14 input ( I ) and output (O) boxes before a PDP-14
control program can be written.

These assignments permit the PDP-14 instructions to test the state of specific

inputs and outputs.

The technical descriptions of the I and O boxes are contained in Chapter 3.
boxes, lettered A through H.

gram inputs.

There are eight possible input

Each I box contains 32 inputs, thereby allowing a maximum of 256 PDP-14 pro-

There are sixteen possible output boxes which are designated A through S (excluding I,

to prevent possible confusion).

Each O box contains 16 output drivers.

possible; the 256th output (the 16th output of O-box S)

O, and Q

A total of 255 separate outputs are

reserved for other purposes and should not be used as

a normal output.

PDP-14 Inputs
The inputs of the PDP-14 system are limit switches, selector switches, pushbuttons, etc.
of either
if

Each input has a value

ON or OFF at any one time. These machine inputs are wired to an I-box terminal

there is 115 Vac present at the specific input terminal.

For programming purposes, all

An input is ON

The input is OFF to show the absence of 115 Vac.

PDP-14 inputs are denoted by an "X" followed by an octal (base 8) number.

convention of identifying inputs with the letter "X" is used throughout the PDP-14 system.
termined by the selection of the I box and terminal to which the machine input is wired.

PDP-14 input 15.

Specifically X15

the

This

The number Is deFor example,

X15 is

PDP-14 representation of a machine input (e.g., a limit switch) which

4-2

PDP-14

ASSIGNMENT SHEET -PI

INPUT
INPUT

ROy

INPUT
NUMBER

(A THROUGH H)

ASSIGNMENT

LS201

- Activated

when slide 2 at full return position

NORM
COND

PROGRAM
NUMBER

n/c

X40

n/c

X41

]

LS202 - Activated when slide 2 at full depth.
2

PDP-14

INPUT ASSIGNMENT SHEET -P2
INPUT

<A THROUGH H)

B0X_1_

INPUT

NORM
COND

PROGRAM
NUMBER

PBS - Cycle start pushbutton.

n/c

X60

PB12 - Start motors pushbutton.

n/c

X61

ASSIGNMENT

NUMBER

INPUT NUMBERS
Box
'

Box Terminal Number
1

/|5

100

101

102

103

104

105

106

107

117

120

121

122

123

124

125

126

127

140

141

142

143

144

145

146

147

157

160

161

162

163

164

165

166

167

Figure 4-1

4-3

Note that program inputs are numbered octally (there are no "8's" or

wired to terminal 14 of I-box A.

used in the number system).

number system.
Input screw terminals are numbered in the familiar decimal

The normal procedure to be followed when assigning input numbers is
as shown in Figure 4-1.

This sheet is completed for each

to complete an Input Assignment Sheet,

machine input (e.g. , LS 201 for limit switch 201) which is wired to a

normal condition of the contacts which are wired to the PDP-14 I box

The sheet records the

assignments.

particular terminal and notes the impli-

position").
cation of this input (e.g. , "activated when slide 2 is in full return

A separate column records the

(normally open or normally closed).

the last column of the Input Assignment Sheet all the numbers

The

These input numbers

contains the input numbers used for PDP-14 programming purposes.

are read from the chart in Appendix A (part of which is reproduced

The Input Assign-

box used in the PDP-14 system.

ment Sheet for one I box has two pages, each page containing 16 input

last column of the sheet

"9's"

Figure 4-1) and are obtained by listing in

which are found in the row for that particular

box in the Input Assignment Chart.

PDP-14 Outputs
The outputs of the PDP-14 system are solenoids, motor contactors, timers,
devices, etc.
outputs.
is

These outputs are set

ON or OFF by the PDP-14, dependent upon the current state of inputs or

PDP-14 outputs are denoted by a "Y" followed by a number.

PDP-14 output 301; etc.

small motors, indicators, signal

Thus, YT23 is PDP-14 output 123; Y301

The convention of identifying an output with the letter

Y" is used throughout the

PDP-14 system in the same way that inputs are identified by the letter "X".
The procedure followed to assign output numbers is similar to assigning
ment Sheet is shown in Figure 4-2.

input numbers.

This sheet should be completed for each

O box in the PDP-14 system.

machine output (solenoid, motor contactor, etc.) which is wired to each O-box
function in the machine being controlled (e.g. ,

A sample Output Assign-

terminal

The

recorded with its

"SOL A - clamps part at beginning of cycle. ") The final

column is the output numbers for programming purposes.

These output numbers are read from the chart in Appen-

dix A (reproduced In part in Figure 4-2).

PDP-14 Timers and retentive memories which are in A boxes are assigned to output box
procedure.

positions using the same

Retentive memories may only be assigned to the addresses shaded in the chart

of Appendix A.

BOOLEAN REPRESENTATIONS OF MACHINE CONTROL
Programming a PDP-14 requires familiarity with simple Boolean representations of
sentatlons are comprised of operators and variables.

and outputs (Y's).
*

These repre

The variables of PDP-14 control equations are Inputs (X's)

The variables have two states; namely,

(AND), + (OR) and / (NOT).

control functions.

ON and OFF. The operators In these equations are

Parentheses may be used within equations to group variables.

4-4

PDP-14 OUTPUT ASSIGNMENT SHEET
(A THROUGH S

OUTPUT BOX__L_
OUTPUT

EXCLUDING 1,0 SQ)
PROGRAM
NUMBER

ASSIGNMENT

NUMBER

SOL A - Clamps part at beginning of cycle.

Y120

SOL B - Returns head; activated by LS12.

Y121

SOL F - Unclamps part when LS4 is tripped.

Y122

Y123

OUTPUT NUMBERS
Box

Box Terminal Number

Box

-ml

16
17

^1 77

100

101

102

103

104 105

106

107

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

154 155

156

157

160

161

162

163

164 165

166

167 170

171

172

173

174 175

176

177

Figure 4-2

4-5

For example, the equation:

Y10=X23 + X21 * Y7
is

read "output 10 is set

instructs the

input 21

ON when input 23

ON, or when both output 7 and input 21 are ON. "

PDP-14 to test input 23 and if it is ON, set output 10 ON.

If they

are both

ON, set output 10 ON.

This equation

input 23 is OFF, test output 7 and

neither set of conditions is satisfied, set output 10 OFF.

The above equation could be represented by the following ladder diagram (Figure 4-3):

SOL F=2LS + 3LS»7CR
2LS

SOL F

7CR

3LS

Figure 4-3

where SOL F corresponds to YIO; 2LS corresponds to X23; 7CR corresponds to Y7; and 3LS corresponds to X21.
It

important to remember that input and output numbers are determined when the inputs and outputs are as-

signed to PDP-14 I and

Equations Containing

O boxes, respectively.

"NOT"

The equation operator/ (NOT) is often used in control functions.

For example, the equation:

Y27 = X5 * /X30
could represent the control function "solenoid A is energized if limit switch 5 is tripped and pushbutton 12 is not
activated. "

This function could be solved with the following ladder diagram (Figure 4-4).

5LS

12PB

SOL A

v°

V
14

-0034

Figure 4--4

where SOL A corresponds to Y27; 5LS corresponds to X5; and X30 corresponds to 12PB.
closed set of contacts for 12PB is shown in the ladder diagram.
or not pushed;

a physical description.

4-6

Note that a normally

The NOT sign in the equation means not tripped

The NOT sign in the PDP-14 system relates to the absence of 115 Vac at the input or output.
to physical switch positions.
it,

does not relate

The PDP-14 may have either normally open or normally closed contacts wired to

depending upon the user's choice.

or the OFF state.

This is possible because the

PDP-14 can test an input for the ON state

Thus, only one set of contacts need be wired to the PDP-14.

The choice of normal condition for input contacts must be made before writing the control equations for the

PDP-14.

The normal condition of the contacts should be noted on the Input Assignment Sheet.

open contacts are used, the equation "Y5 = X15" means that output 5 will be set
is

When normally

ON when machine input 15

activated (e.g. , a limit switch is tripped) and 115 Vac is applied, and that output 5 will be set OFF when

input 15 is not activated.

Using normally closed contacts reverses the sense of the logic.

When normally

closed contacts are wired to the PDP-14, the equation Y5 = X15 means that output 5 will be set OFF when
input 15 is activated, and will be set

ON when input 15

not activated.

Because normally closed contacts result in equations which seem contrary to common sense,
all

normally open contacts be used in the PDP-14 system.

suggested that

This allows standardization of programming and spare

parts inventory.

Evaluating Equations

When an equation contains more than one variable, it is very important to note the manner in which the output
state

determined.

For example, consider the following equation:

Yl = XI * X2 + X3
Does the above equation represent Yl = (XI * X2) + X3 or Yl = XI

(X2 + X3)?

By drawing two ladder dia-

grams it is obvious that the two interpretations are not equivalent (Figure 4-5).

<s>
X3

Figure 4-5

To remove possible ambiquities when evaluating equations, the variables grouped by the AND (*) operator are
always combined before the variables grouped by the OR ( + ) operator whenever the order of combination is not
clearly spelled out by parentheses.

In the

preceding example, therefore, (XI * X2) + X3 (the second ladder

diagram) is the correct interpretation of the expression XI

Yl = XI * X2 + X3 Is equivalent to Yl = X3 + XI * X2.

4-7

X2 + X3.

should also be observed that

Examples:

X27 +/X17 * X20 = X27 + (/X17 * X20)

Xn * X23 + X31 * X14= (Xn * X23)+ (X31 * X14)
(X12+X15) VX21 + X22= [(X12+ X15) VX21] + X22
X21 + X22 * X23 + X24 * X25 = X21 + (X22 * X23) + (X24 * X25)
Parentheses may be added wherever necessary to define an expression more clearly.

When the NOT operator (/) precedes a single variable, the equation checks for the absence of the input (or
output) at the I box or

O box.

Equations with Variable Groups

Many control equations contain groups of variables which are separated from the rest of the equation by parentheses.
This grouping simply means that the content of the parentheses is to be evaluated (for
sult is to be treated as a single variable of the whole equation.

ON or OFF) and the re-

For example, consider the following equation:

Y21=/(X121 * X26)
The states of inputs 121 and 26 are tested and the resultant state of the quantity in the parentheses is inverted
by the "NOT" to achieve the value of output 21

Notice that output Y21

The following truth table summarizes the function:

X121

X26

X121*X26

Y21=/(X121*X26)

ON
ON

OFF

ON
ON
ON

either X121 or Y26 is OFF, or if both inputs are OFF.

expresses this relationship:

Y21 =/X121 +/X26
Thus, the following replacement may always be made in control equations:

/(A*B) is equivalent to /A+/B

A similar reduction is possible for the following equation:
Y22 = /(X107+ X12)

4-8

The following equation

The truth table to determine the state of output Y22 for all states of inputs follows.

X107

X12

(X107+X12)

Y22=/(X107+X12)

ON
ON

OFF

ON
ON
ON

OFF

The reduction is possible when output Y22 is ON, only if input X107 and input X12 are both OFF.

Thus, the

equation may be rewritten as:

Y22 = /X107*/X12
and the following replacement is always possible:

/(A + B) may be replaced by /A * /B

Equation Simplifications

There are several ways in which equations may be simplified before they are programmed for the PDP-14. While
equations need not be in their simplest form, in many cases these simplifications conserve memory locations and
lessen the time required to execute the program.

Consider the following equation:

Y5 = XI + (XI * X2) + (X3 * X5)
Note that the expression XI * X2 adds no meaning to the equation.
regardless of the state of X2.

XT is ON, output Y5 will be set

XI is OFF, again the state of X2 cannot affect Y5.

simplified to:

Y5 = XI + (X3 * X5)
and the following rule is established:

A + (A * B) = A
The following equation may also be simplified:

Y6 = (XI * X2 + X3) * X4 */X3

4-9

Thus, the equation may be

Note that because of the last element of the equation (/X3), output Y6 will never be turned on when X3 is ON.
Thus, the last element within the parentheses (+X3) is meaningless since X3 may not be

same time.

ON and OFF at the

The simplified equation is

Y6= XI * X2 * X4*/X3
Thus the following rules are established:

A */A can never be true, and A -I-/A is always true

PDP-14 PROGRAM DESCRIPTION
After recording the input and output assignments and their functions, the programmer codes the program for the

given control function.

general, a PDP-14 control program is made up of disjoint instruction groups.

PDP-14 inputs and outputs and, at its conclusion, sets an

instruction group solves a Boolean equation by testing

output either

ON or OFF. The final instruction group in the program ends with an unconditional jump to the

start of the first instruction group.

For example,
trol

program.

Each

if a

Thus the PDP-14 Program is a closed loop.

machine control requires twenty outputs, there must be twenty instruction groups in the con-

The following diagram illustrates the construction of the program (Figure 4-6).

SOLVE
FOR

OFF

OUTPUT

SET Y1

ON
1

SOLVE
FOR
OUTPUT

OFF

SET Y2

ON
1

SOLVE
FOR
OFF

OUTPUT

SET Y20

ON
\

GO TO

Figure 4-6

4-10

The disjoint instruction groups are often separated by several NOP's.

The PDP-14 NOP instruction specifies

No operation*. The NOP instruction is simply a space filler which leaves room for future program modifications or corrections.

The jump to the start of the program is very important.

there were no instruction to return control to the be-

ginning of the program, the PDP-14 would stop executing instructions when it reached the end of its memory

and the program would not start again.

should be emphasized that each instruction group is independent.

For example,

some of the instruction groups

could be controlling one device while other instruction groups control a second device.

The sharing of a PDP-14

among many devices may be extended until the limits for inputs (256), outputs (255) or memory locations (4000)
are exceeded.

INTRODUCTION TO THE PDP-14 SOFTWARE
"Software" describes the programs and systems which are used to operate a computer.

There are three system

programs in the PDP-14 Software Package.

These three programs operate on PDP-8 family computers and are

used to develop programs for the PDP-14.

The three programs are:

BOOL-14

BOOL-14 is a compiler which translates special Boolean equations into PDP-14
A compiler translates expressions into machine code. How-

machine instructions.

ever, there is no direct machine code counterpart of an element in the Boolean

equation.

The Boolean equation is translated into PDP-14 machine code but the

translation process is not a one-for-one replacement.

PAL-14

PAL-14 is the assembler for the Program Assembly Language of the PDP-14. An
assembly language is a set of instructions which are in mnemonic or symbolic form
(letters) but which

have a direct counterpart in the machine code of the PDP-14.

PAL-14 assembler translates the symbolic representations of the
PDP-14 into the PDP-14 machine code.

In other words, the

instructions of the

SIM-14

SIM- 14 is a program which simulates PDP-14 operation in two modes of operation.
The user may operate in an off-line or local mode to debug and modify his program
completely within the PDP-8. When relatively certain that the program (or a particular part of the program)

correct, the user may switch to on-line mode and

control the machine's operation by executing the program.

Chapters 6, 7 and 8 of this manual discuss the three foregoing software items.

Before the system software may

be understood, the reader must gain an understanding of the PDP-14 instruction set and its operation.

The in-

structions used to solve control equations are described in Chapter 5.

PDP-8

family computer to monitor a PDP-14 are described in Chapter 9.
for the

Instructions used by an external

Chapter 10 describes operating procedures

PDP-14 Software, and introduces a text Editor program which is useful for PDP-14 programming.

*NOP is the first PDP-14 instruction introduced in this manual.

4-n

Others are presented in Chapters 5 and 9,

A few observations about use of the software items are helpful.

The control engineer who is a computer novice

wishing to use the PDP-14 will find BOOL-14 to be a practical approach to PDP-14 programming.

He may write

PDP-14 programs in equation form and have BOOL-14 generate the machine code instructions for him. The generated instructions are then tested or debugged with SIM-14.

BOOL-14 will also allow the user to do transition

checking, (one form of computer monitoring the PDP-14).

If greater flexibility in

programming the PDP-14 is needed, PAL-14 may be the answer.

which translates symbolically written PDP-14 instructions into machine code instructions.

PAL-14 is an assembler
Use of PAL-14 allows

the user greater flexibility in the approach to monitoring, and more efficient use of memory.

SIM-14 is also

used to debug this translated program.

In general,

BOOL-14 and PAL-14 are mutually exclusive; the user chooses one or the other, although this is

not absolutely necessary.

If the

needed PDP-14 program is a combination of straightforward equations and more

complicated instruction sequences, the user may compile part of the program with BOOL-14 and assemble the

remainder with PAL-14.

The two partial programs are merged by SIM-14.

Care must be taken that the same

memory locations are not used by both the BOOL-14 compiled program and the PAL-14 assembled program.
SIM-14 is a very powerful tool for exercising and testing PDP-14 machine language programs.

Practically all

PDP-14 users will find SIM-14 helpful regardless of whether BOOL-14 or PAL-14 is chosen to translate the
program

Chapter 10 outlines the operating procedures for PDP-14 software.

Detailed descriptions of the use of BOOL-14

PAL-14 and SIM-14 are also included, as well as the operation of the PDP-8 family computer.

Chapter 10 also

describes the Editor, a fourth system program which will be indispensable when writing programs for BOOL-14
or PAL-14.

Paper Tape Formats

Programming a PDP-14 involves the use of several paper tapes.
information in a similar manner to the familiar punched card.
to established codes or formats.

A paper tape uses punched holes to represent
The holes in the paper tape are punched according

The three types of PDP-14 paper tapes are as follows.

System Software Tapes - Punched in PDP-8 binary fonmat.

These tapes contain the SIM-14, PAL-14,

BOOL-14 and Editor programs. They are loaded directly into a PDP-8 family computer.
Symbolic or Source Tapes - Punched in ASCII* format. These tapes have no meaning to the PDP-14
They are prepared by the Editor and are the input or source program representation for
BOOL-14 or PAL-14. They may be listed on a Teletype to generate a readable copy of the program.

or to SIM-14.

Binary or Machine Language Tapes - The translated form of PDP-14 programs and are punched in
binary format. These tapes are punched by BOOL-14, PAL-14 or SIM-14 and may be read by SIM-14
c.

or may be used to generate an

ROM (Read-Only-Memory).

*ASCII is an abbreviation for U.S.A. Standard Code for Information Interchange.

4-12

SYSTEM DOCUMENTATION
While programming tiie PDP-14, many handwritten sheets of paper. Teletype listings and paper tapes will be

Some of these documents may be discarded but some should be saved and continuously updated.

generated.
It is

very important that each document be marked as it is generated.

being programmed, the type of tape (e.g. ,

Note the date, your name, the system

"BOOL- 14 source tape," "SIM- 14 binar/ tape"), and other per-

tinent data.

The following is a partial list of forms with comments concerning their use and importance.
fully understood at the present.

These may not be

However, when programming the PDP-14, bear this list in mind.

can save

hours of time.

Forms Used During Programming of PDP-14

Form
Input Assignment and

Output Assignment Sheets

List of Equations

Description

These sheets note which machine input or output (e.g. , LSI) is wired to
each PDP-14 terminal (e.g. , X15). It should be constantly updated with
any changes.

The handwritten list of equations (e.g. , SOLA = LSI * LS2) should be
saved until they become part of a program listing in the form of comments.
At that time, the handwritten sheets may be discarded.

Program Coding Sheets

These sheets constitute the handwritten PDP-14 program in the form of
equations (e.g., Y17= X15*X16) or instructions to be typed into the
Editor.

Source Program Listing

Once a source listing is generated from the Editor, it is discarded.

This is a Teletype printout of the program in the input format to BOOL-14

or PAL-14.

(e.g.,

should always reflect the latest program changes. The
contain "comments" to reflect the equations in symbolic form

listing should

SOLA= LS1*LS2).

Source Program Paper Tape

This

BOOL-14 Compiler

This is a Teletype printout of the translated program. It contains the symbolic and numeric contents of memory locations used by the PDP-14 pro-

PAL- 14 Assembler Listing

is a paper tape record which may be used as input to BOOL-14 or
PAL-14. It corresponds to the above source listing and should also reflect
latest program changes.

gram. The numeric listing may be used when wiring changes are made by
hand to the ROM. It must be kept updated.

BOOL-14 or PAL-14

This tape is input to

Binary Tape

or assembly listing.

SIM- 14 Listing

This is a Teletype listing of any changes or "patches" made to the PDP-14

SIM-14 and should correspond to the above compiler

program with SIM-14.

These listings should be kept until the changes are
incorporated in the source program and a new source listing and tape is

generated and recompiled or re-assembled to generate a new BOOL-14 or

PAL-14 listing and tape.

4-13

Forms Used During Programming of PDP-14 (Cont)
Description

Pqp^

SlM-14 Binary Tape

This binary tape is punched in IK segments and is the form required to
generate an ROM. It is punched from SIM-14 when no errors have been

detected in the BOOL-14 or PAL-14 program.

4-14

It is

then sent to DEC.

CHAPTER 5
PDP-14 BASIC INSTRUCTIONS

This chapter introduces the

PDP-14 basic instructions which determine the state (ON or OFF) of outputs

according to the changing state of inputs and outputs.

They are the primary operating instructions of the

PDP-14 system, and are recognized and simulated by SIM- 14.

A PDP-14 program may be written either as equations for BOOL-14 or as instructions for PAL-14, but its final
form always uses the basic instructions.

(AdditiorKil

PDP-14 instructions used for computer monitoring are in-

troduced in Chapter 9.)

BASIC INSTRUCTION CLASSES
The three classes of basic instructions used in PDP-14 programs are listed below:

Test Instructions - used to sample the current state (ON or OFF) of an input or output.

Set Instructions - used to set outputs

ON or OFF. (The state of inputs

changed by the controlled

equipment, not by the PDP-14 itself.)
c.

Jump Instructions - used to execute instructions out of sequence. That is, to "branch" the PDP-14

program.

Instructions are always executed in sequence unless a jump occurs.

PDP-14 TEST FLAG
The TEST flag is the element of the PDP-14 system which records the results of input and output testing.
TEST flag has two values (ON and OFF).
test.

raised (set ON) by a true test and left unchanged by a false

(True tests and false tests are defined below.)

tions to determine set output operations.

The

The condition of the TEST flag is sampled by jump instruc-

In this way, the basic instructions are used with the TEST flag to

control the operations of a machine.

The TEST flag is sometimes referred to as the test flip-flop or simply the test flop.

This terminology is most

often used when describing the PDP-14 processor hardware, in which the TEST flag

state flip-flop.

5-1

represented by a solid-

PDP-14 TEST INSTRUCTIONS
The PDP-14 test instructions are:

Test an input for the

ON state.

Test an input for the

OFF state.

Test an output for the

Test an output for the OFF state.

ON state.

The symbolic and numeric forms of these instructions and their precise definitions are given in Table 5-1

Table 5-1

PDP-14 Test Instructions
Instruction

Symbolic

Numeric

TXN XXX

2400 + XXX

Definition

Test input

XXX for the ON state.

input XXX is

ON and the TEST flag

currently OFF, the TEST flag is set ON.

Otherwise the flag remains unchanged.

2000 + XXX

TXF XXX

Test input

XXX for the OFF state.

input XXX is OFF and the TEST flag is

currently OFF, the TEST flag is set ON.

Otherwise the flag remains unchanged.
1400 + YYY

TYN YYY

Test output

YYY for the ON state.

output YYY is

ON and the TEST flag

currently OFF, the TEST flag is set ON.

Otherwise the flag remains unchanged.
1000 + YYY

TYFYYY

Test output

YYY for the OFF state.

output YYY is OFF and the TEST flag is
currently OFF, the TEST flag is set ON.

Otherwise the flag remains unchanged.

NOTE: The expressions XXX and YYY represent numeric values of inputs (XXX)
and outputs (YYY) as assigned using the Appendix A Charts. Legal values are
0-377.
The definitions may be explained by defining the terms "true test" and

"false test" as given in the following

table.

State of Input or Output

Test for

OFF

True test

False test

True test

(TXN or TYN)
Test for OFF

(TXF or TYF)

5-2

The action of the test instructions may be summarized making use of the above definitions: Test instructions
which result in a true test set the TEST flag ON; those which result in a false test leave the TEST flag unchanged

NOTE
The TEST flag is NOT cleared by a false test, as
summarized below.

Original State of TEST Flag

True test
False test

OFF

ON
ON

-N
\

OFF

Resultant
State of

TEST Flag

PDP-14 SET OUTPUT INSTRUCTIONS
Set instructions turn an output

ON or OFF at the end of a sequence of test instructions.

meric forms of these instructions and their definitions are given in Table 5-2.
reference output numbers (YYY) from

The symbolic and nu-

The SYN and SYF instructions

through 377 (octal), and are determined by the selection of

and the assignment of outputs within the O box.

Table 5-2

PDP-14 Set Output Instructions
Instruction

Symbolic

Numeric

SYN YYY

3400-YYY

Definition
Set output YYY to the

ON state.

Output YYY remains ON until it
is set OFF by a SYF or CLR instruction.

SYF YYY

300CM-YYY

Set output

YYY to the OFF state.

Output YYY remains OFF until
it

CLR

3377

set

tion

ON by a SYN instruc-

Set all

PDP-14 outputs to the OFF

state.

This instruction sets every

output OFF unconditionally (with
the exception of the retentive

memories) and it should not be used
In normal conditions.

NOTE:

The expression YYY represents the numeric value of an output
as assigned from the Appendix A chart.

5-3

O box sockets

The instruction CLR is equivalent to SYF 377 and causes ail timers, storage outputs and regular outputs
set OFF.

Retentive memories are only set OFF when addressed individually.

to be

Thus, output 377 should not be

used as a "real" output since it cannot be set OFF without setting all outputs OFF.

ADDRESSING LOCATIONS IN THE PDP-14
Jump instructions cause the transfer of program control to another section of the program. The jump instruction
must specify the section of the program to which it is transferring control .

That is, in PDP-14 terminology,

jump instructions must be able to address or reference memory locations.
Every instruction must be stored in the PDP-14 memory.
the discussion.

The storage process is not of concern at this point in

What is important here is that the instructions are stored in certain locations in the memory and

that these locations have a numeric order (i.e., there

the last memory location).

a first location, a second, a third, etc. , through to

Each of these PDP-14 memory locations has an assigned number, or address.

Thus,

a PDP-14 program consists of instructions which are stored in memory locations each of which has an address.
This permits Jump instructions to direct the

PDP-14 to "jump to location 305" (begin execution of the instructions

starting in location 305).

The PDP-14 memory locations are not numbered in an ordinary way, however.
a numbering system which does not use the digits

"8" or "9".

They are numbered in "octal",

Counting in octal is the same as counting in the

familiar decimal number system except that any number which contains an

"8" or "9" is excluded.

Thus the

number which follows 7 in octal is 10, and the number which follows 77 is TOO.
Octal numbers are usually given a subscript (8) to avoid confusion with decimal numbers.

same as the decimal number "10".

5-4

Thus "lOg" 's not the

The following sequence of numbers illustrates the octal counting technique.

Since the octal number system contains no
eights or nines, after counting to the
digit 1 , simply place a zero in the ones

column and carry 1

The carry out of the ones' place produces
a second carry out of the next place.

Hence, 77 + 1 = 100 in the octal number
system

PDP-14 Memory Organization
The locations of a PDP-14 memory are numbered in octal as previously described.

A IK PDP-14 memory con-

tains 1024 locations in which program instructions may be stored.

1777q.
o

These locations are numbered O- through
8
The locations of a 2K PDP-14 memory (2048 locations) are numbered
through Z711
3K memory
•

locations (3072 locations) are numbered 0„ through 5777

•,

and 4K memory locations (4096 locations) are num-

bered 0_ through 7777^.
o
o

A PDP-14 memory is constructed of blocks of 256 locations. A IK PDP-14 memory contains four of these blocks,
called "pages".

The 256 locations of each page are numbered from 0- through 377

5-5

Figure 5-1 shows the

relationship between the numbering of locations through all memory ("absolute" addresses) and the numbering

of location within each page of memory ("relative" or "page" addresses).

The maximum possible PDP-14 mem-

ory (4K) is diagrammed.

Absolute Addresses and Page Addresses

Each location in the PDP-14 memory has an absolute address and a relative, or page, address.
Figure 5-1 shows that the location with absolute address 4377 has page address 377.
locations with the same relative or page address, but each PDP-14 location has

its

For example^

Note that there are many

own unique absolute address.

The page address of a location can easily be determined from its absolute address by means of the following
procedure:

absolute address is 1000 or greater, cross off the first (most significant) digit.

If the

the number resulting from step

less than 400,

the number resulting from step

400 or greater, the page address is found by subtracting 400

from the step

the page address.

result.

The examples below illustrate the procedure.
Absolute address

a. result

Page address

3347
2652

234
347
652

234
347
252

7521

521

121

7400
5000

400

1234

PDP-14 JUMP INSTRUCTIONS

Once program execution is started, the PDP-14 normally proceeds by executing the instructions in memory in
their natural sequence.

For example,

if execution

of the

PDP-14 program begins at location 200, the instruc-

tion in that location will be executed, then the instruction in location 201, followed by the instruction in lo-

cation 202, etc. , throughout the entire program.

Jump instructions cause departures from this sequential ex-

ecution of instructions.

Conditional Jump Instructions

The PDP-14 has two conditional jump instructions.
whether the jump will occur.

The state of the TEST flag is the condition which determines

The symbolic and numeric forms of the conditional jump instructions and their

definitions are given in Table 5-3.

5-6

BANK
Absolute
Address

BANK 2
Relative

Address

(Page)

Address

0000
1

Relative

Absolute
Address

(Page)

2000

Page =
256

locations

0377
0400

377

2377
2400

377

2777
3000

377

"lK"of PDP-14
^Memory = 1024

256
'

0777

377

locations = 4

memory pages

1000

256
1377
1400

377

3377
3400

377

1777

377

3777

377

256

BANK 3
Absolute

Address

BANK 4

Relative

Absolute
Address

(Page)

Address

Relative

(Page)

Address

4000

4377
4400

377

6377
6400

4777
5000

377

6777
7000

5377
5400

377

7377
7400

5177

377
Figure

5-7

5-1

Conditional jump instructions ore used to
the TEST flag and an SYF (set output

cause an SYN (set output ON)

instruction to occur for one state of

OFF) for the other TEST flag state.

NOTE
the TEST flag OFF.
The JFF and JFN instructions always set
the TEST flag
instruction,
JFN
After execution of a JFF or
jump was
the
not
or
whether
of
is always OFF, regardless
executed.

Table 5-3

PDP-14 Conditional Jump Instructions
Instruction

Definition

Symbol

Numeric

Jump to location NNN if the TEST flag
instructions
is now ON and execute the

5400+ NNN

JFN NNN

beginning with the instruction in location

NNN.

(If the

flag

structions following the

OFF, the in-

JFN continue to

be executed in sequence.) The TEST
flag is set OFF, regardless of its original
state

JFF

Jump to location NNN if the TEST flag
instructions
is now OFF and execute the

5000 + NNN

NNN

beginning with the instruction in location NNN. (If the TEST flag is ON,
the instructions following the JFF continue to be executed in sequence.) The

TEST flag is set OFF, regardless of its
original state.

page address
NOTE: The expression NNN represents the relative or
control

Legal values are

may be transferred.

Conditional jump instructions are limited.
377) on their own page (often called the

to 377 (octal).

They can only reference the 256 locations (page

addresses

through

current page).

Because of internal restrictions, a JFF or JFN

page (e.g., locations 377, 111

to which

location of a
instruction must never be stored in the last memory

\^11 , 1777, etc.).

The instruction JFN 300 illustrates the use of a

conditional jump instruction.

TEST flag is ON, jump to relative location 300 on
have the same relative or page address.

the current page.

This instruction means that if the

Recall that several absolute addresses

meanings when it is
Thus, a conditional jump instruction has different

stored on different pages of PDP-14 memory.

Observe the examples given in the following paragraphs in

to properly understand location to be addressed.

5-8

order

Follow these steps to find the relative address to be used to jump to a specific absolute address:

Make certain that the location which contains the jump instruction is on the same page as the

location to be addressed by the jump instruction.
b.

Cross off the first (most significant) digit of the address if it is 1000 or greater.

the result of step b

the result of step b is 400 or greater, subtract 400 to obtain the relative (page) address.

less than

400, the relative (page) address is that number.

Examples:

Location of Instruction:

500

Location to be Addressed:

750

Correct Instruction:

JFN 350

Location of Instruction:

Location to be Addressed:

372

Correct Instruction:

JFF 372

Location of Instruction:

2005

Location to be Addressed:

2345

Correct Instruction:

JFN 345

Location of Instruction:

5500

Location to be Addressed:

5675

Correct Instruction:

JFF 275

Location of Instruction:

2311

Location to be Addressed:

2450

Correct Instruction:

Cannot be done

Location of Instruction:

4251

Location to be Addressed:

5300

Correct Instruction:

Cannot be done. (Off -page reference)

Location of Instruction:

5631

Location to be Addressed:

5237

Correct Instruction:

Cannot be dor>e

Location of Instruction:

435

Location to be Addressed:

776

Correct Instruction:

JFN 376

5-9

(Off -page reference)

(Off-page reference)

Location of Instruction:

2722

Location to be Addressed:

3010

Correct Instruction:

Cannot be done

(Off -page reference)

NOTE
The foregoing examples which cannot be done with conditional jump instructions require modifications in the
program. The program may be changed to use unconditional jumps to pass from memory page to memory page.
Unconditional jump instructions are described on the
following pages.

Unconditional Jump Instructions

The PDP-14 has two unconditional jump instructions.

The symbolic form, numeric form and definition of each

instruction is given in Table 5-4.

Table 5-4
PDP-14 Unconditional Jump Instructions
Instruction

Definition

Symbolic

JMP NNNN

Numeric
4224

NNNN

Jump to location NNNN unconditionally.
Execution of the PDP-14 program proceeds
sequentially beginning with the instruction
in location

NNNN. JMP

a two-

location instruction; the absolute address of
the "jump-to" location is stored in the lo-

cation following that which contains the

JMP instruction.
SKP

Skip the following memory location unconThis instruction causes the

0344

ditionally.

PDP-14 to not execute the instruction which
is

stored in the next sequential location.

Sequential execution continues with the instruction stored in the second location fol-

lowing the SKP instruction.

NOTE: The expression NNNN represents an absolute address for the PDP-14 memory,
There is no page restriction for the JMP instruction.

As stated in Table 5-4, the JMP is a two-location instruction.
to

The first part of the instruction tells the PDP-14

jump to the address given in the second part of the instruction.

will

be the one stored in the location with that address.

5-10

The first instruction executed after the jump

The JMP instruction may reference any PDP-14 memory location using an absolute address.

Thus, whenever

the program must pass between memory pages, the unconditional jump is used.

For example, to transfer control to location 1523 from location 1375, use the instruction:

Location

Content

1375
1376

JMP
1523

1523

(Contains next instruction
to be executed.)

The SKP instruction is an unconditional skip of one PDP-14 memory location and is very convenient to use because the address of the location to which control

need to reference memory.

passed need not be specified.

The SKP instruction has no

Note that the SKP instruction skips one PDP-14 location only.

may therefore

be used to skip any one-location PDP-14 instruction only, but may not be used to skip a two-location instructic
(such as in JMP).

Subroutine Jump Instructions

Included in the PDP-14 basic instructions are jump instructions that allow programs to contain subroutines.

subroutine is simply a set of instructions to be executed more than once on each pass through PDP-14 memory.
Instead of including them in more than one place in the program, these instructions are written in the form of a

subroutine.

Repeated execution of the same instructions is permitted via an instruction to jump to the start of

the set of subroutine instructions and another instruction that jumps to return after executing the set of instructions contained in the subroutine.

The jump instructions which are used for subroutines are given in Table 5-5.

The JMS instruction is similar to

the JMP instruction; both are two-location instructions which may address any PDP-14 memory location.

The

JMS differs from the JMP in that it allows subroutines to return to the next sequential location following the
second part of the JMS instruction by saving the address of the next sequential instruction.

5-11

Table 5-5

PDP-14 Subroutine Jump Instructions
Instruction

Definition

Symbol

JMS NNNN

Numeric

NNNN

4645

Jump to the subroutine beginning in location
NNNN. The PDP-14 executes in sequence
the instructions beginning with the Instrucand termition stored in location

NNNN,

nated by a JMR instruction.

The JMS instruc-

tion is a two-location instruction which may

PDP-14 memory.

directly address all

JMR

Jump return to the location following the

0354

second part of the JMS instruction. The JMR
must always be paired with a JMS instruction.

NOTE: The expression NNNN represents the absolute address of the start of a subroutine. There is no page restriction for the JMS instruction.

The PDP-14 permits only one level of subroutines because only one return address may be stored
If

one time,

be lost, and return to the
a subroutine were to jump to a second subroutine, the first return address would

original program would be impossible.

PDP-14 subroutines are written in the following manner:
Subroutine

Main Program

1200 TXN 27
1201

TXN 30

TXN 5
TXF7
JMR

JFF 250

JMS
1200

JFN 250

TXN 12

The JMS in the above example causes transfer to the subroutine which starts at location 1200.
of the subroutine are then executed in sequence until the JMR instruction

encountered.

Control

turned to the instruction which follows the second part of the two-location JMS instruction.

5-12

The instructions
is

then re-

SAMPLE PDP-14 PROGRAM AND ANALYSIS
The following equation represents a typical control requirement to be programmed:

Yl = X123 + X54 * Y3
This equation could represent the control function "Solenoid A (Yl)

energized when pushbutton 43 (X123) is

ON, or when both limit switch 12 (X54) is activated and Solenoid C (Y3) is energized."
The equation may be solved by the PDP-14 with the instructions in Figure 5-6.

Notice that the user must write

down the location of each instruction and he must refer to each input (X) and output (Y) by its program number
as determined from the tables in Appendix A.

Table 5-6
Sample PDP-14 Program
Location

Symbolic
Content

300

TXN 123

301

JFN 307

the flag is ON, jump to 307 and set Yl

302
303
304
305
306
307
310

TXF 54
TYF 3

output 3 is OFF, the flag is set ON.

flag is OFF, jump to 307 and set Yl

ON.

311

300

JFF

SYF
SKP

SYN

307
1

Comment
input 123 is

JMP

ON.

Otherwise, if either input 54 is OFF, or if
the

Otherwise set output 1 OFF and skip the set
output

ON, the flag is set ON.

ON instruction. This instruction sets

Yl ON. After determining the state for
output

return to the start of the program.

To demonstrate that the instructions in Figure 5-2 actually solve the equation properly for all possible values
of the variables, three cases are analyzed below.
result of a previously executed

In each case, the TEST flag

assumed to be OFF as the

JFF or JFN instruction.

Case 1 - Input 123 OFF, input 54 OFF, and output 3 OFF; Result: Yl OFF
Location

Content

Program Execution

300

TXN 123

Input 123 is tested for the
state. Since it is OFF, the TEST flag
remains OFF, and program execution proceeds to the instruction contained

301

JFN 307

location 301

TEST flag is
at this point, the program will proceed to location
The flag is OFF, however, and program execution proceeds to the
instruction contained in location 302.

If the

307.

302

TXF 54

The program tests input 54 for the OFF state. Since input 54 is OFF, the
TEST flag is now set ON. Program execution proceeds to the instruction
contained in location 303.

5-13

Case 1 (Cont)
Location

303

Program Execution

Content

The program tests output 3 for the OFF state. Since output 3 is OFF, the
already by the previous
had it not been set
TEST flag would be set
contained in
instruction
to
the
execution
proceeds
Program
instruction.
location 304.

TYF 3

304

JFF 307

TEST flag is OFF at this point, the program will proceed to location
307 to set output 1 ON. The TEST flag is ON, however. Thus program
execution proceeds to the instruction contained in location 305. (The TEST
flag is set OFF by the JFF before proceeding.)

305

SYF 1

Output 1

If the

set

OFF (as it should be).

Program execution proceeds to the

instruction contained in location 306.

306

This instruction causes program execution to skip location 307 and proceed

SKP

to the instruction contained in location 310.

310

JMP

311

300

The instruction in location 310 is recognized as the first part of a twolocation unconditional jump instruction. The JMP causes program execution
to proceed to location 300, which will start testing the equation again.

NOTE
The instruction in location 307 is not executed.

Case 2 - Input 123 ON, input 54 ON, and output 3 OFF; Result: Yl
Location

Content

300

TXN 123

Program Execution

ON state. Since input 123 ON, the TEST flag
ON and program execution proceeds to the instruction contained in

Input 123 is tested for the
is

set

location 301

301

JFN 307

Since the TEST flag is

ON at this point, program execution proceeds to the

instruction contained in location 307.

(The TEST flag is set OFF by the

JFN before proceeding.)
307

SYN

Output 1 is set

ON (as

should be).

Program execution proceeds to the

instruction contained in location 310.

310

JMP

311

300

NOTE
The instructions in locations 302, 303, 304, 305, and
306 are not executed

5-14

Case 3 - Input 123 OFF, input 54 ON, and output 3 ON; Result: Yl
Location

Content

300

TXN 123

Program Execution
Input 123

state and since It is OFF, the TEST flag
Program execution proceeds to location 301.

tested for the

remains OFF.
301

JFN 307

Since the TEST flag is OFF at this point, program execution does not proceed to location 307, but rather proceeds to the instruction contained in
location 302.

302

TXF 54

Input 54 is tested for the OFF state. Since input 54 is ON, the TEST flag
remains OFF and program execution proceeds to the instruction in location

303.

TYF 3

303

Output 3 is tested for the OFF state.

Since output 3

ON, the TEST flag

again remains OFF and program execution proceeds to the Instruction contained

304

JFF 307

location 304.

Since the TEST flag is OFF at this point, program execution proceeds to the
instruction contained in location 307.

SYN

307

Output

set

ON (as

the instruction contained

310

JMP

311

300

should be).
in

Program execution then proceeds to

location 310.

The instruction in location 310 is recognized as the first part of a two-

The JMP causes program execution
which will start testing the equation again.

location unconditional jump instruction.
to proceed to location 300,

NOTE
The instructions in locations 305 and 306 are not executed.

PDP-14 programs may be written as the sample described above, but they may be written in formats which are
easier to work with.

and 7.

These easier techniques for writing PDP-14 programs are fully described in Chapters 6

However, an understanding of the material described in this chapter is necessary to perform the debug-

ging procedure required for all PDP-14 programs regardless of their format.

PROGRAM EXAMPLES
The following examples show the relationship between the circuit diagram, the Boolean representation and

PDP-14 programs.

Each example contains five parts.

A verbal explanation of the control function.

The ladder diagram which would be used to perform this function.

A Boolean representation of the control function.

5-15

A wiring diagram for the PDP-14 input and output boxes.

The PDP-14 program for the control function.

each of the examples, it is assumed that the TEST flag is OFF initially.

Boolean "OR" Control Function - A simple control circuit in which a solenoid is energized by either one of

two limit switches is presented in Example
state.

To solve this problem with a PDP-14, test for either input's

Since a positive test from either input will set the TEST flag to

1, the output should

be turned on when

the TEST flag is ON, and OFF when the TEST flag is OFF.

Notice that normally open contacts of each switch are wired to the PDP-14.
for an activated switch.

EXAMPLE

Thus, testing for

ON means testing

Testing for OFF means testing for a not activated switch.

Control Function

either limit switch

or limit switch 2 is

ON, energize Solenoid D (otherwise. Solenoid D should be OFF).

Ladder Diagram (Figure 5-2)

SOL D
1

2 LS

Figure 5-2

Boolean Equivalent
Outputs:

Inputs:

lLS(n/o)

2LS(n/o)

X12

Equation:

SOL D Y7

Y7 = XI + X12
1

5-16

EXAMPLE

(Cont)

PDP-14 Wiring (Figure 5-3)

LS(n/o

SOL D
)

""^^

XII

X12

PDP

2 LS (n/o)

Figure 5-3

PDP-14 Program
Location

Content

TXN 11
TXN 12

JFN

SYF
SKP

SYN 7

Comments
Test input 11 and 12;

if either is

ON, set

output ON; if not, set output OFF.

Boolean

"AND "Control Function - Example 2 illustrates a control where two inputs are in series to drive an

output.

other words, both limit switch 3 and pushbutton

must be activated for Solenoid A to be energized.

Normally open contacts are wired to the PDP-14 input box.
The PDP-14 program checks for the condition which is not wanted.

be energized.
if

either input is OFF, Solenoid A should not

Thus, the program tests both inputs, setting the TEST flag

the TEST flag

for Solenoid

ON, to the set output OFF instruction.

If the

if either is

OFF.

The program jumps,

flag remains OFF during the testing, the output

A is turned ON, and the solenoid is energized.

EXAMPLE 2

Control Function
If

pushbutton

and limit switch 3 are ON, energize Solenoid A (otherwise Solenoid A should be de-energized).

5-17

EXAMPLE 2 (Cont)
Ladder Diagram (Figure 5-4)

SOL A

6PB

3 LS

Figure 5-4

Boolean Equivalent
Output:

Inputs:

SOL A

lPB(n/o)
3LS (n/o)

X13

Equation:

Y4 = XI * X13

PDP-14 Wiring (Figure 5-5)

-o
I

SOL A

PB (n/o)

PDF

3 LS (n/o)

X13

Figure 5-5

PDP-14 Program
Location

TXF
TXF

JFF

SYF
SKP

SYN 4

Comment

Content

and

13; if either

Test inputs

output will not be set.

5-18

OFF, the

Control Functions with Normally Open and Closed Contacts - Example 3 is a control function which (in ladder

diagram form) has both normally open and normally closed contacts.
contacts for such control functions.

The PDP-14 does not require two types of

All normally open contacts may be used, as illustrated in

Normally open contacts for both pushbutton 7 and limit switch 5 are wired to the PDP-14.

Example 3.

Thus, an

ON input

An OFF input means that the button or switch is not activated.

means that the button or switch is activated.

The example also illustrates the combination of AND and OR functions.

Each leg is an AND function and the

output results from the OR of the legs.

The PDP-14 program could also be written to test normally closed contacts.
the opposite state

(ON or OFF) of the input.

Thus,

normally closed contacts are used in the wiring, all TXF's

become TXN's for the input and all TXN's become TXF's.
that the switch

The program would merely test for

An ON input from normally closed contacts means

not activated while an OFF input means it is activated.

EXAMPLE 3

Control Function

pushbutton 6 and limit switch 4 are on, or if pushbutton 7 and limit switch 5 are both OFF, then Solenoid C

energized (otherwise Solenoid C is de-energized).

Ladder Diagram (Figure 5-6)

SOL C
6 PB

-Q

7 PB

4 LS

o...^ o-

o5 LS

Figure 5-6

5-19

EXAMPLE 3 (Cont)
Boolean Equivalent
Output:

Inputs:

6PB (n/o)
7PB (n/o)
4LS (n/o)
5LS (n/o)

SOLC Y6

X6
X7
X14
XI5

Equation:

Y6 = (X6 * X14) + (X7 * X15)

PDP-14 Wiring (Figure 5-7)

6PB (n/o)

o
7PB(n/o)

L
o

4LS(n/o)

SOL C
X7

PDP
X14

^*«'==;^

5LS (n/o)
^^-^^

X15

Figure 5-7

PDP-14 Program
Location

Content

14
15

TXF 6
TXF 14

JFF

Comment
If either

X6 or X14 is OFF, other leg must be

tested.

If both

X7 or X15 is ON and other leg

ON, output should be ON.

TXN7

If either

TXN 15

failed, set output OFF.

JFF

22
23

SYF 6
SKP

Set output OFF if both legs fail

SYN6

Set output

if either

leg solves.

Latching Control Function - Example 4 is a motor contactor latching function.

and pushbutton 3 is the stop button for energizing a motor contactor.
sumed for all inputs.

Pushbutton 2 is the start button,

Again, normally open contacts are as-

However, the normally closed contact for 3 PB could be used by replacing the TXN 3 by

TXF 3 in the PDP-14 program.

5-20

The program uses a test output instruction, TXF 10, to latch the motor contactor on.
as long as it is currently on and pushbutton 3

The output will remain on

A PDP-14 input for the motor contacts is not re-

not pressed.

quired because outputs may be tested as inputs.

EXAMPLE 4

Control Function

Motor 1 is started if pushbutton 2 is pressed, and continues to operate until pushbutton 3 is pressed.

Ladder Diagram (Figure 5-8)

^Y^^^Y-

^Zr^

1M
O

II
1

°_l_°

3 PB

Figure 5-8

Boolean Equivalent
Output:

Inputs:

YIO

2PB (n/o)
3PB (n/o)

X2
X3

Equation:

YIO = X2 + (X3 * YIO)

PDP-14 Wiring (Figure 5-9)

2PB (n/o)_ L_
-o

POP
3 PB (n/o)

Figure 5-9

5-21

Y10 /

2>-

PDP-14 Program
Comments

Content

Location

X2 is ON, jump to set output ON; other-

TXN

26
27

JFN 34

wise, if X3 is OFF and YIO is already ON,

TXN 3

leave it ON; otfierwise, set the output OFF.

TYF

JFF

32
33
34

SYF
SKP

SYN

Relay Controlled Function - Example 5 uses a control relay to energize a solenoid.

All normally open contacts

(As explained in the two preceding examples, normally closed contacts could

are used as inputs to the PDP-14.

be used by reversing the sense of the test instructions.) Control relay 2 is energized by inputs, and latches itself
in the engaged position.

The output for control relay 2 is then tested to energize solenoid B.

EXAMPLE 5
Control Function
If pushbutton

4 is not

ON and limit switch 2

ON already, then control relay 2

set

ON.

Q-

actuated, and either pushbutton 5 is
If

control relay 2 is

ON, solenoid B is energized.

Ladder Diagram (Figure 5-10)

5 PB
-o

2 LS
o
°Vss^

•

4 PB
2 CR

SOL B

2CR

Figure 5-10

5-22

ON or control relay 2

EXAMPLE 5 (Cont)
Boolean Equivalent
Outputs:

Inputs:

4PB (n/o) X4
5PB (n/o) X5
2LS (n/o) X12
Equations:

2CR

SOL B Y5

Yl = X4 * (X5 + Yl) * X12

Y5 = Yl

PDP-14 Wiring (Figure 5-11)

4 PB (n/o)
o

—

5 PB (n/o)

o
2

LS (n/o)

^^^^

^^^-/T^

POP
SOL B

X12

Figure 5-11

PDP-14 Program
Location

35
36
37
40

Content

ON or X12

TXN

TXF

put should be OFF.

either X4 is

OFF, the out-

JFN 43

TXN 5
TYN

JFN

SYF
SKP

44
45
46
47
50

Comments

SYN
TYN

X4 is OFF, and X12 is ON, then either
X5 or Yl must be ON for the output to be ON,
If

45
1

JFN 52
5

SYF
SKP

SYN

is ON, jump to set output 5 ON.
1
Otherwise, set output 5 OFF.

If output

The Example 5 illustrates an important PDP-14 concept.

Note that although the original equation was

Yl = X4 * (X5 + Yl) * X12, the program was written for the equation Yl = X4 * X12 * (X5 + Yl).
is

Programming

more efficient when single variables connected with the same operator (AND or OR) are grouped together.

5-23

5 could be greatly simplified
Simplifications - The control program for Example
relay 2 is an unnecessary output.

by the observation that control

The control relay is needed in the ladder diagram to

the PDP-14 however, the output to energize the

solenoid may itself be tested as an input.

Example 5 Simplified (following), output Yl may be
of output Y5 is equivalent to testing output Yl

latch the circuit on.

Thus, as shown in

eliminated and the control relay may be removed.

The test

in this case.

EXAMPLES, SIMPLIFIED

Control Function

pushbutton 4 is not

ON and limit switch

actuated, and either pushbutton 5 is

ON or solenoid B

ready, then solenoid B is engated.

Boolean Equivalent

Output:

Inputs:

SOL B

4PB (n/o) "xT
5PB (n/o) X5
2LS (n/o) X12
Equation:

Y5 = X4 * (Y5 + Yl) * X12

PDP_14 Wiring (Figure 5-12)

4 PB (n/o)

SOL B
5 PB (n/o)
.

2 LS(n/o)

POP

X12

""^-^

14-0012

Figure 5-12

PDP-14 Program
Comments

Location

Content

35
36

TXN 4

If either

TXF

should be OFF.

JFN

5-24

X4 is ON or X12 is OFF, the output

ON al-

Location

Content

Comments

TXN 5
TYN 5

JFF

SYF
SKP

SYN

44
45

Either X5 or Y5 itself must be

ON for Y5 to

be set ON.

Simply set output 5

ON or OFF directly,

without using intermediate control realy.

TIMING CONSIDERATIONS IN A PDP-14 PROGRAM
For most

PDP-14 applications, timing is of little or no consequence.

must be considered.

For example, the maximum amount of time should be determined which could elapse before

a momentary contact closure is checked.

put is missed.

For other applications; however, timing

Otherwise, in lengthy PDP-14 programs, it could happen that the in-

By considering timing, this condition will be prevented.

should be noted that a PDP-14 program is a collection of instruction sequences, where each sequence controls

An average time of 20 microseconds is required to execute one PDP-14 instruction. Using this

a single output.

average time, the following program execution times are determined:

K program

20 ms
40 ms
60 ms
80 ms

2K program
3K program
4K program

However, in the case of a normal PDP-14 program (e.g., as translated by BOOL-14) it is impossible to execute
all instructions.

For example,

the SYN instruction is executed, the SYF instruction could not be executed.

A second example is that if an output equation is of the form:
Y5 = YO * (XI + X2+ X3),
and it is compiled by BOOL-14, the inputs XI , X2 and X3 are never tested whenever YO is OFF.

A third example of instructions which could not be executed is if an output equation is of the form:
Y6 = X3 * X52 + X4 * X12 + X7 * X53,
The last four inputs will not be tested when the first two are both ON.

and the third and fourth inputs are ON, the last two will not be checked.

when Y6 is set to be OFF, or when Y6 is set ON by the last two inputs.

5-25

either of the first two inputs ore OFF,

Thus, all inputs will be tested only

The conclusion of the previous argument is that on the average no more than 75% (and often only 50%) of the
instructions are executed.

Better estimates of program execution time are given in Table 5-7

Table 5-7

Program Execution Times

Assumption

K program

75%

50%

5 ms
30 ms
45 ms
60 ms

20 ms
30 ms
40 ms

2K program
3K program
4K program

Table 5-7 indicates, for example, that if a 3K program is being used, assuming that 50% of the instructions are
being executed, each input must be present for 30 ms in order to guarantee that the input will be acknowledged.
If 30

ms is not fast enough for some inputs in

this particular application, the

than once, thereby decreasing the time between input samplings.

equation could be checked more

To determine the choice of execution assump-

tion (50% or 75%), consider the following analysis:

How much memory is not used (i.e.

filled with

NOP's) and is jumped around?

Are there many subroutines in the program? These effectively increase the memory size when they
are executed
b.

Are there any sizable routines (e.g.

start-up, shut-down, or manual) which are not executed

under normal conditions?
d.

Are the majority of equations short (1-5 elements) or long (6 or greater)? The longer the equation

the less probability that all instructions will be executed.

Very detailed analyses of program execution time require the nominal execution times for each PDP-14 instruction.

Although some of the following instructions are not actually introduced until Chapter 9 of this manual

they are included here for conciseness.

The times given are nominal and are subject to a ±30% variation.
Time

Operation Code

Instructions
(ms)

SKP, JMR, EEM, LEM
TYF, TYN
TXF, TXN
SYF, SYN

JMP, JMS, TRM

JFF,

6
7

JFN
SKE, SKZ
TXD, TYD

5-26

4.0
19.5
19.5
19.5

4.5
4.0
4.0
19.5

CONCLUSION
The instructions introduced in this chapter are the instructions used by the PDP-14 to solve control functions.
Although programs may be written in equation form and compiled with BOOL-14 (as described in Chapter 6),

BOOL-14 actually translates the equations into the instructions introduced in this chapter.
user debugs his program with

Thus,

when the

SIM-14, he must be familiar with these instructions.

The user may choose to write his program in instruction format, using the symbolic features of PAL-14 to make
addressing, input and output assignment, and other programming tasks easier.

Again, however, the program

which actually operates in the PDP-14 has absolute location and input/output assignments, as described herein.
Thus, the user must be familiar with the instruction format given in this chapter.

Instead of using BOOL-14 or PAL-14, programs which are in the format of this chapter (as illustrated by the

preceding examples) may be typed into SIM-14, the PDP-14 simulator and debugging aid.
directly typing programs is presented in Chapter 8.

The procedure for

However, the user who chooses to directly compose programs

with SIM-14 sacrifices many features of BOOL-14 or PAL-14 which greatly ease the programming task.

5-27

CHAPTER 6

BOOL-14 CONTROL EQUATION TRANSLATOR

BOOL-14 translates control equations, which are written with symbols similar to Boolean notation, into the
PDP-14 machine code instructions given in Chapter 5.

A series of these equations constitute a PDP-14 program.

The program of control equations is prepared using the Editor and a "source program paper tape" is generated.
Use of the Editor allows the source program to be corrected and revised easily during the stages of program development.

BOOL-14 reads the source program paper tape and translates (compiles) the equations into a

PDP-14 machine code program containing the instructions introduced in Chapter 5.

BOOL-14 will also permit equations to be typed on the keyboard and compiled.
quickly checking an equation.

However, complete programs should be prepared in paper tape form.

The programming procedure used with BOOL-14 is diagrammed in Figure 6-1
errors in the source program with the Editor cannot be overemphasized.

The importance of correcting

The user should maintain a current and

correct version of the program in equation form throughout the life of the system.
in lost hours when

This feature is useful for

Failure to do so may result

changes must be made to the system and an accurate representation of the program is not

available.

BOOL-14 STATEMENT
The body of BOOL-14 source programs is a series of control equations, such as the following:

Y10=(X1 + X2) *X3^
Each character in the control equation has special meaning to BOOL-14.
riage return character (

)

the signal to BOOL-14 that it has read the complete source statement.

acceptable equation characters and their use is given in Table 6-1.
characters.

For example, the non-printing car-

This table includes all legal

The

BOOL-14

Functional descriptions of some characters are given later in this chapter.

The characters SPACE, TAB, LINE FEED, and FORM FEED may be included in BOOL-14 programs to format the
source program.

They are ignored during processing by BOOL-14.

ignored by BOOL-14.

Blank leader/trailer (null) tape is also

All characters other than these formatting characters and the characters given in

6-1

Assign inputs and

Read source tape back

outputs to PDP-14
I- and

into EDITOR.

O -boxes.

Correct the program

Express the machine

errors.

sequence in equation
form.

I
Type the equations
in program form with
EDITOR.

I
Generate the source
tape for BOOL- 14.

Errors may be corrected

I
Compile the PDP-14
program with BOOL-14.
Compiler errors found?

Yes

with the BOOL-14 Edit
option and compilation
will continue.

tape

Load the compiled
program paper tape
into

SIM-14.

TZZ
Check for program
errors.

I
No errors fou

These

errors should also be
corrected in the source

Operational
Errors found

I
Generate paper tape
and send to DEC for

ROM.
Figure 6-1

6-2

Table 6-1 are illegal and cause errors if they are included in the statement portion of the BOOL-14 source
program.

All illegal non-printing characters are replaced by a

"?" in the BOOL-14 listing.

Table 6-1

BOOL-14 Equation Characters
X

Input indicator

Output indicator

0-7

Identify specific inputs and outputs

Equation indicator

Boolean OR operator

Boolean AND operator

Boolean NOT (negates a single variable or a variable group)

(,[

Start of a variable group

),]

End of a variable group

Repetitive equation indicator

Repetitive variable indicator

0-9

Identify specific repetitive equations or variables

Indicates start of repetitive equation

Comment indicator

Line break indicator

Control statement indicator

(return)

End of statement (often represented by " )

ctab:)

Formatter, converted to 8 spaces or less

CTRL/D

Search for error character in Editing Option

CTRL/U

Delete complete statement line, when typed from keyboard

(rubout)

Delete one character to left, when typed from keyboard.

Input and Output Specification

The numbers which follow the "X" or "Y" are input and output numbers respectively, as obtained from Appendix A charts.

Particular input and output numbers are determined by the selection of the input (or output) box

and are octal numbers between
puts.

and 377.

The state of an output is determined by the state of inputs and out-

That is, a single output number (e.g., Y17) is the left hand member of an equation, while the right hand

member of the equation is a combination of inputs and outputs.
ables of an equation using the following operators.

6-3

These inputs and outputs are combined as vari-

Operators

The BOOL-14 operators are * (Boolean AND), + (Boolean OR, inclusive), and / (Boolean NOT).
operators combine input and output values to determine the value of an output.

These

Thus the equation:

Y17 = Y17 */X4+ X23
means that output 17 is set ON if (a) Y17 is already
is

set

ON and X4

not ON, or (b) X23 is ON; otherwise, Y1I7

OFF.

Note that the equation specifies the ON and OFF conditions for an output.
the conditions are met (true) and

Namely, the output is set ON if

set OFF otherwise (the conditions are false).

set OFF when the conditions are not met is not always expressed explicitly, but

it is

The fact that an output is
always implied in a

BOOL-14 equation.
The NOT operator (/) may negate the sense of single variables or variable groups.

may also negate the left

member of an equation, in which case the equation specifies the set OFF conditions rather than the set ON
conditions.

For example:

/Y21 = X12 + /X31
means that output Y21 is set OFF if (a) XI 2 is ON, or (b) X31 is OFF; otherwise output Y21 is set ON.

Variable Groups
Input and output variables may be grouped with either parentheses or square brackets.
is

(The square bracket "["

SHIFT/K and "] " is SHIFT/M on the Teletype keyboard.) For example:

Y12 = (X12 + X13) * [X27 + Y15]
There is no difference in the treatment of square brackets and parentheses by BOOL-14.
the user's convenience in distinguishing between variable groups.
these symbols must be used in pairs.

They are available for

The only requirement by BOOL-14 is that

Any grouping which is opened with a square bracket must also be closed

with a square bracket.

For example:

Y12 = (X12 + X13] * [X27 + Y15)
will generate an error because both groupings are closed with the wrong bracket type.

6-4

However, the equations:

Y12- (X12+ X13) * [X27 + Y15]
Y]3 = (X22 + Y17 * [X42+ X3]) * X15

and

are in proper form

Statement Continuation

Extremely long equations which will not fit on one line in the source program may be broken
parts using "$" as the statement continuation character.
If

Each incomplete line is terminated with a dollar sign.

the equation is being typed directly to BOOL-14 from the keyboard,

carriage return after the "$".

the equation

BOOL-14 will automatically provide a

part of a source program paper tape generated with the Editor,

the user has typed a carriage return after the "$ " on the source tape.
riage return,

into two or more

Whenever a dollar sign precedes a car-

BOOL-14 will not treat the carriage return as an end of statement Indicator.

a new input line and accepts the additional characters until

simply provides

encounters a carriage return which is not preceded

by a dollar sign.

Example:

Y21=/(X1 + X2+ X3) * ((X4+ [X5 * X6]) * /X7$
)

+ Y12 * (X27+ X5+/X2])

The dollar sign/carriage return combination may be anywhere within the statement line; otherwise,

all

other

statement rules are followed.

Comments
Program comments are text lines included in the BOOL-14 source program to clarify the function
or to document the program in general.

program.

of an equation

Comments are merely typed by BOOL-14 as they appear in the source

The comments have no effect upon the machine code which is generated for an equation.

BOOL-14 comments must be preceded by a semicolon (;). When BOOL-14 encounters a semicolon, it treats
all

characters to the right as a comment.

sign ($).

Any Teletype character may be included in the comment except dollar

This character may be used to write comments on more than one line.

Any characters to the right of

the $ will be ignored by BOOL-14.

The following are comment examples:

Y15 = XI + X2 * (X3 + /X4)
;SOLA = PBl + PB2 * (LS13$
+ /LS14)
;LS14 TRIPPED WHEN SLIDE IS FULL FORWARD.

6-5

Notice that the first comment is broken into two lines using the dollar sign.

NOTE
BOOL- 14 may handle approximately 160 input characters
(i.e., equation and comment) in one statement.

If this

maximum is exceeded, BOOL- 14 will type the message:
BUFFER OVERFLOW
The remaining characters in the statement will be typed
but are not part of the statement compilation. If the buffer overflow occurs within a comment it should be ignored.
If it occurs within an equation, the equation must be di-

vided using a Z-function as described later in this chapter,

and recompiled.

SUBROUTINES AND STORAGE OUTPUTS
Subroutines serve two functions in BOOL-14 equations:

put

Z-functions solve for an intermediate value or result. A Z-function does not directly turn an outit is part of a larger equation which does.

ON or OFF; rather,

R-functlons solve for an output state. R-functions are the same as the normal output equation except that provision is made to solve for the output more than once on each pass through the program.
2.

A BOOL-14 program may contain a maximum of 64 subroutines (viz.

R- and Z-functions).

Intermediate Results

There are many cases in PDP-14 programs which require the "storage"of an intermediate result. For example, one
set of inputs energizes or de-energizes control relay 1; a second set of inputs energizes or de-energizes control

relay 2; and a third set of inputs energizes or de-energizes control relay 3.
in various combinations with other inputs and

These control relays are then used

outputs to control solenoids A, B, and C.

There are three possible

approaches to such control functions:

Complete coding

Control equations are written which substitute the variables which determine the state of the control relay for the control relay itself. Thus, the

equation for each solenoid will separately test the control relay inputs to
determine the state of the solenoid. The actual control relays are eliminated from the system
Z-functions

A Z-function is written to solve for the state previously represented by a
control relay.

(No PDP-14 output is set by the Z-function.) The solenoid

equations may then contain Z-functions as variables. Only one set of
PDP-14 instructions is needed to solve for each Z-function. These same
instructions are used to solve for every output which contains the Z as an

equation variable.

6-6

A normal output equation is written which sets an output in an S-box ON

Storage outputs

OFF.

These outputs may then be used as variables in other equations.

NOTE
Before proceeding, the reader should review the section
on Subroutine Jump Instructions, pages 5-11 and 5-12.

Z-functions
Z-functions are repetitive variables which are solved whenever they are needed in a normal output equation.

They do not set an output to record the result of the testing; instead the result is recorded by setting the PDP-14
TEST flag

ON or OFF.

Z-functions usually represent values which must be solved

For example, suppose the following equations were compiled by

Yl = XI

many different equations.

BOOL-14:

(X21 + X13 * /X42 + Y17 * Xll)

Y2= X2 * (X21 + X13 */X42 + Y17 * Xll)
Y3 = X3 * (X21 + X13 * /X42 + Y17 * XI 1)

Y4 = X4 * (X21 + X13 * /X42 + Y17 * XI 1)
If

given this set of equations,

equation.

BOOL-14 would generate PDP-14 machine code to test each variable for each

Notice that many of the instructions will be the same for all four outputs, namely those instructions

which test the state of the variables within parentheses.

The same machine control function could be represented by the following group of equations with a considerable
saving in the number of memory locations required for the program.

Zl = X21 + X13 * /X42 + Y17 * XI
Yl = XI * Zl
Y2= X2 * Zl
Y3= X3 * Zl
Y4= X4 * Zl

The new form is analogous to a control relay in a ladder network which represents the combined state of a group
of inputs (Zl).

The contacts from the relay are then included in the circuits for solenoids, motor starters, etc.

The number following Z is arbitrary and may be any decimal number between
only be defined once.

and 2047.

The Z function must

may be referenced as many times as necessary.

If given this group of equations,

BOOL-14 will generate the series of instructions to establish Zl as a subroutine.

The Zl instruction will test the inputs Just as a normal output equation would; however, no actual output will be
set.

The subroutine will set the TEST flag

if the

equation is true; otherwise it will set the TEST flag OFF.

BOOL-14 then tests the state of the TEST flag to determine the result of the subroutine.
6-7

The subroutine instructions for a Z-function are terminated in the following way (compared to the termination
of a normal equation).

Normal

Z-function

Equ(

Test and

Conditional
>

jump
instructions

TYN377

If the

TYF 377

SYF output
SKP

JMR

SYN output

result of the Z-function

not true,

BOOL-14 generates a JFF or JFN instruction that jumps past the

TYN 377 and TYF 377 to the JMR, thereby returning with the TEST flag OFF.
is

true, the

states,

If the

result of the

Z-function

Since output 377 must be in one of the two

TYN 377 and TYF 377 instructions will be executed.

one of the tests must be true and the TEST flag will thus be set before the JMR is executed.

The instructions to solve the equations which contain Z-functions differ greatly from the original equations.
place of the instructions to test the variables in the Z-function,

BOOL-14 will generate a JMS (jump to sub-

routine) to the beginning location of the subroutine that solves the Z-function.

the main program with the result reflected in the TEST flag.
or JFN instruction.

The subroutine will return to

The main program will test the result with a JFF

Thus the JMS instruction serves a purpose similar to a test instruction.

Instead of testing a single variable, the logical combination of a group of variables is tested and the result is
reflected in the TEST flag.

The PDP-14 will only accommodate one level of subroutines.

JMS instruction.

In terms of

variable of its equation.

If a

This

means that a subroutine may not contain a

BOOL-14, this means that a Z-function may not contain another Z-function as a
second level

needed, it must be written as a storage output and tested with a

TYN or TYF instruction in the subroutine, as described later in this chapter.

R-functions

R- functions (repetitive equations) are subroutines which do set an output

which set the TEST flag).

ON or OFF (as opposed to Z-functions

Characteristically, R-functions are outputs which must be checked very often and

cannot wait for a complete memory cycle.

The state of these outputs could be determined simply by compiling

the complete instruction sequence to solve the equation in several places in the source program.
is

inefficient if the same equation is solved more than once, however.

to generate the equation as a subroutine.

This technique

Defining an R-function causes BOOL-14

Whenever the output state is to be determined, BOOL-14 generates a

JMS (jump to subroutine) instruction to the R-function to set the output ON or OFF.

Thus the instructions to

solve the equation are stored in only one place in memory, but they are executed as many times as necessary.

6-8

An R-function is defined in the following form:
Rn:

Ym - XI *

...

where n is any decimal number between

and 2047.

Ym specifies a specific output to set by the subroutine

The reference to the subroutine is made by writing the R-function designation.

For example, the follov/ing

statement defines an R-function to set output Y53.

R81:

Y53 = X32 * (X41 + X12 * Y13) + X2]

BOOL-14 generates the machine code instructions to solve the equation for Y53 in the same form as a normc
output equation.

After the set output instructions,

BOOL-14 compiles a JMR instruction:

SYF 053
SKP

SYN053
JMR
Whenever the R-function should be solved in the main program, the user writes the following statement in the
source program:

R81 )

BOOL-14 will compile a JMS instruction to the subroutine which solves for Y53.
As seen in the following examples, all R- and Z-functions must be defined at the beginning of the source pro-

gram and not following an output equation.
tion (e.g. ,

Yl = X4) will generate an error.

Any R- or Z-function which is defined following an output equaEach R- or Z-function must have a unique decimal identifying

number.

Subroutine Examples

R13:

R13^

Y6=X2+X4

;

DEFINES THE SUBROUTINE

REFERENCES THE SUBROUTINE, EQUIVALENT

TO WRITING Y6 = X2 + X4

6-9

Z8 = X2 + X4 * Y7
Z9 = X31 + X4+X12
Z8 = X21 * Y7

Z8 function has already been defined.

Error because R-functions cannot be variables in equations.
(Only Z-functions may.)

Yl = X21 + R8

R21:

Error because the

YIO =Z1 * X17

Error because an R-function may not contain a

Zl = XI + X31 * Y21
Z2 = X3 * (X21 + X31) + Zl

Z-function as

(A subroutine may not jump to another subroutine.)

a variable.

Error because the equation for a

another Z-function.

Z-function may not contain

(A subroutine may not jump to another

subroutine.)

Y12= X12* (X13+ X15)
R13:

Y12 = X15 + Y13

Error because definition of all R- and Z-functions must

precede

any output equations.

Storage Outputs

They are programmed exactly like other Y-functions.

Storage outputs are outputs in an S-box of the PDP-14.

The only difference is that the output does not drive a solenoid, motor starter, or such.
is

set,

Once a storage out|xjt

however, it may be tested with the TYN and TYF instructions of the PDP-14.

The advantage of storage outputs is that the instructions to solve for the result as represented by a storage output
The storage output itself may then be tested when-

are executed only once for each pass through the program.

ever it is needed.

However, subroutines must be executed every time the result is needed in an output equation.

Storage outputs may also be tested by a subroutine.

Thus if one intermediate result is a function of another, a

storage output could be used to record the second result.

As previously stated, a subroutine may not jump to a

second subroutine.

A storage output must be used in place of a subroutine whenever the control function has itself as an element of
the equation, i.e.,

if it is

a latched function.

The equation to establish a storage output is of the form:

Y33= X23 * X21 +Y17
where output Y33 is contained in an S-box which is connected to O-box socket "B".

The result is tested by

including the output as a variable in an equation.

Y16 = Y33 + (X3 + X5+ X7)

BOOL-14 will generate a TYN 033 instruction as required to solve the equation for Y16.
6-10

CONTROL STATEMENTS
Control sfatements are directions to BOOL-14 which affect the machine code instructions generated during

compilation.

Specifically, control statements affect the allocation of memory locations to the

instructions generated by

End of Program -

Each

BOOL-14 and mark the end of source program tapes.

.END or .ENDN

BOOL-14 source program must be terminated with an .END or .ENDN statement to indicate the end of

compilation.
dress of the

The .END statement completes the BOOL-14 program by compiling a JMP instruction.

JMP is specified by the user such that the program is a "closed loop".

written following the

.END.

Any octal number between

statement, or a default value of

The
is

PDP-14 program

assumed.

The ad-

The address of the JMP is

and 7777 may be specified as the value of the .END

The value is often the same as the value of the

LOC statement.

.ENDN (end-no jump) statement may be used to terminate an incomplete program where no JMP instruction

needed.

This statement marks the end of the source program but generates no

machine code instruction.

.END and .ENDN Examples
Statement

Instruction

.END 50

Generated

JMP
50

.END 2000

JMP
2000

.END

•

End of Tape -

END 2008

JMP
error--octal

numbers only

.ENDN

non generated

.ENDN 50

error -no value allowed

EOT

The BOOL-14 source tape may be physically segmented using the .EOT (end of tape) statement to terminate all
but the last paper tape in a series.

The last segment must be terminated with an

.END or .ENDN statement.

When BOOL-14 encounters an .EOT statement it will type "EOT" and halt the PDP-8 system allowing the user
to load the paper tape reader with the next tape.

Pressing the

proceed

6-11

PDP-8 CONT switch permits the compilation to

For example,

if the

program is on three tapes, the end of the tapes will be

Tape

terminated by an .EOT statement

EOT^
Tape 2 is also terminated by an

EOT statement,

EOT^
"ZL

Tape 3 is terminated by an .END, .END with value, or an

ENDN statement.
END^

Memory Allocation

BOOL-14 compiles all subroutines (R- and Z-functions) as the first elements of the program.

This is necessary

to allow BOOL-14 to generate JMS instructions to these subroutine locations from the main program.

BOOL-14

will place immediately before the subroutines a JMP to the start of the main program which follows the subroutines.

An example of memory assignment is:
Location assigned

by BOOL-14

Content

JMP
1

231

The JMP instruction goes to the first instruction of
the first output equation (in this case Y12).

Z15
15

The Z- and R-function definitions may be in any order
and may be assigned any identifying number less than
or equal to 2047.

R29
31

Z5
57

6-12

Example (Cont)
Location assigned

by BOOL-14

Content

215

R84
230
231

Once the first Y equation is encountered,
further R- or Z-function definitions cause

Y12

errors.

247
250

Y23
263
264

Y16
275

1720

1723

The program was terminated by an

1735
1736

".END" statement causing a JMPO.

BOOL-14 will assign generated machine code instructions to consecutive memory locations beginning with
location 0.

The first instruction of a new equation is assigned to the next sequential memory location after the

previous equation.

This sequential assignment does not provide room for changes with

SIM- 14.

The .LOC,

.FIXS and .VARS control statements, described later, permit the user to start the program at a location other
than

and to leave space after each instruction sequence.

When compiling an equation, BOOL-14 will check the number of remaining locations on the current page.
there are not enough
will compile

PDP-14 memory locations for the machine code instructions to solve the equation, BOOL-14

NOP's in the remaining locations of the current memory page, and start the equation in the first

location of the next page.

The NOP's thus generated are not typed as part of the listing.

The user should remember that PDP-14 program execution starts in location 0.
ginning with

The content of the locations be-

must control "start up", either with instructions to initialize the system, or with a JMP to an in-

itialize or start up routine.

6-13

Start of Program -

LOC

The initial location of a program is specified by the .LOC (location) statement.

BOOL-14 will generate

machine code instructions for the locations beginning with the value specified by

LOC.

For example:

LOC 50

Yl = XI + X2
yields the compiled instructions:

0050
0051
0052
0053
0054
0055

Only one

2401

2402
5455
3001
0344
3401

JFN 055
SYF
SKP

001

SYN

001

Note that the instructions begin in location 50. If no .LOC
LOC would be assumed and the
first instruction would be placed in location 0.
statement were given, a

LOC statement is permitted in a BOOL-14 program.

must precede the first subroutine or equation

The value of .LOC may be any octal number between

of the program.
units are:

TXN 001
TXN 002

MBl ,

to 1777; MB2,

and 7777

(Remember that the memory

2000 to 3777; MB3, 4000 to ^777) MB4, 6000 to 7777 .)

Spacing Between Equations - .FIXS or .VARS

BOOL-14 is directed to compile a specified number of NOP (no operation) instructions after equations by the
.FIXS (fix spacing) and .VARS (vary spacing) control statements.

changes in SIM-14 during debugging.

The

NOP instructions allow for program

For example, the statement:

.FIXS 5

will result in five

NOP instructions at the end of all subsequent instruction sequences.

statement may be any decimal number between

and 2047.

The value of the .FIXS

As many .FIXS statements as needed may be placed

in a program.

The .VARS (vary spacing) control statement only affects the equation which immediately follows it and overrides
for the one equation any

.FIXS statement currently in effect.

The .FIXS statement is reinstated after each .VAR

statement and remains in effect until overridden by another .VARS statement or replaced by a new .FIXS state-

ment.

The value of .VARS is a decimal number between

and 2047.

The .VARS statement may be used to suppress the

output of NOP instructions after an equation by specifying a value of 0:

•

VARSO

6-14

Spacing Examples
Equation and Control

Number of NOP's after

Statements

The Equation

Zl = (X27 * YO) * X13 + X4

none

.FIXS5
R12: Yl = X23 * X14 + XO
.VARS 2
Y1 = X23*Z1

R12
.FIXS 10
Y2 = X27 * X3 + X30 * X2

5
10

The NOP instructions are not part of the compiler listing, although they are punched on the binary output tape

when binary is requested.

MONITORING PROVISIONS IN BOOL-14
Using control statements,
eration of the

BOOL-14 can be directed to automatically supply monitoring instructions if the op-

PDP-14 system is to be monitored by an external computer.

niques involved are fully described in Chapter 9.

The instructions used and the tech-

The procedure involved in BOOL-14 to generate these in-

structions is described below.

BOOL-14 may be directed to add instructions to monitor the transition in the state of an output.
instructions may be added to monitor transitions to

Specifically,

ON (make), transitions to OFF (break), or both, for any

PDP-14 output, storage output or R-function.
The choice of the TYD or TRM instruction for monitoring is left to the user.
cific 12-bit word to the monitoring computer; the word
Is

The TYD instruction outputs a spe-

determined by the PDP-14 (see Chapter 9).

The TRM

a two location instruction which outputs a 12-bit word specified by the user.

Monitor Transitions to

ON - .MN

The .MN control statement will cause BOOL-14 to add instructions to the first output equation which follows
it

to monitor transitions from

OFF to ON.

These instructions will load a 12-blt word into the PDP-14 output

transition, or when the transition

from

ON.

The output register is not loaded as long as there is no

ON to OFF.

Example:

.MN
Y5 = /X2 * (X3 + Y5)
(the instructions generated will include a TYD 005)

6-15

Only the immediately following equation will contain the sequence of monitoring instructions.

The instructions

generated are described in Chapter 9.

the output is to be monitored with a TRM instruction, the user must supply an octal number (four digits or less)

after the

".MN".

Example:

.MN4123
Y5 = /X2 * (X3 + Y5)
(the instructions generated will include a TRM 4123)

the user supplies less then four digits after the control statement,

BOOL-14 will assume leading zeros.

Monitor Transitions to OFF - .MF

ON to OFF. Instructions
changed from ON to
output register whenever the output

The .MF control statement allows the user to monitor the transition in an output from
are added which will load a 12-bit word into ifie

OFF. The output register is not loaded as long as there is no transition or if the transition is from OFF to ON.
Example:

.MF

Y6 = X3 * (X4 * X5 + /XIO * XI 1)
(the instructions generated will include a TYD 006)

The .MF control statement above only has effect for the first equation which follows it (i.e. , Y6).

the output is to be monitored using a TRM instruction, the user must supply an octal number (four digits or less)

after the

".MF".

Example:

.MF 103

Y6 = X3 * (X4 * X5 + /XIO * XI 1)
(the instructions generated will include a TRM 0103)

Monitor All Transitions - .MFN

The .MFN control statement is used to monitor all transitions in output state (viz. , both the

OFF to ON).

Instructions will be added which will load a 12-bit word into the

transitions in the state of the output.

ON to OFF and

PDP-14 output register on all

The output register is not loaded as long as the output remains

6-16

ON or OFF.

Example;

.MFN

YN = X21 + X15 * Y5
(the instructions generated will include two TYD 007's)

the output is to be monitored with TRM instructions, the user must
supply two octal numbers after the

".MFN"

Example:

•

MFN 2007, 1007

(the instructions generated will include:

TRM 2007 - executed on transition to OFF
TRM 1007 - executed on transition to ON)
It is

important to remember that the first number is used in transitions to OFF

used in transitions to

(.MFN) and the second number is

ON (.MFN).

Monitoring Input Transitions

As stated above, BOOL-14 allows monitoring of output states.

If the

user wishes to monitor the transitions in

state of an input, he must assign a storage output to record the
previous state of the input.

the transitions in the state of the storage output to provide monitoring information

He may then monitor

concerning the input.

Example:

MF
Y40= XI
•

(the instructions generated include a TYD 040)

In the above example, the transitions in state of output Y40 are
used to monitor the transitions in state of input

XI.

Table 6-2

Summary of Control Statements

Command
.

LOG 250

Control Operation
Start the program compilation at

PDP-14 location 250.

.FIXS5

Leave 5 (decimal) NOP's after all equations beginning
with the next equation.

.VARS30

Ignore any .FIXS statement currently in effect and leave
30 (decimal) NOP's after the next equation only.

6-17

Table 6-2 (Cont)

Summary of Control Statements
Control Operation

Command

.MN

Monitor the next equation for transitions to the

•

ON state.
OFF state.
Monitor the next equation for all transitions

.MFN

End of tape - interrupt the compilation while a

.EOT

new tape is loaded.

.END

End of program - compile a JMP

.END 50

End of program - compile a JMP 50 instruction.

instruction.

End of program - do not compile any JMP

.ENDN

instruction.

BOOL-14 OPTIONS
The options available to the user are requested through a series of four queries as described below.
queries are typed to start the BOOL-14 compilation process.
a query,

These

the user types other than a legal response to

BOOL-14 will retype the query.

Example:

*SRC-KLH?
*SRC-KLH?

N is not a legal response to the SRC query. BOOL-14
retypes the query.

the user types more than one character in response to a query,

ter typed before the carriage return.

BOOL-14 will recognize only the last charac-

Thus if a wrong response is typed, the user may correct it by typing the

correct character prior to the carriage return.

Binary Output

The binary paper tape output from BOOL-14 which is input to SIM-14 is requested in response to the query:

V2
*BIN-NLH?
Where N, L, and H are the possible user-supplied responses with the following meanings: The V2 is the BOOL-14
version designation which is always typed before the BIN query.

6-18

No binary output is wanted.

The binary paper tape is requested on the low-speed paper tape
punch associated with the Teletype unit.

The binary paper tape is requested on the high-speed paper tape
punch.

The user types one of the possible responses followed by a carriage return.
a binary tape if he expects errors in his program.
listing without wasting

For example, the user may not want

By typing N, he may compile the program and get an error

time generating an incomplete binary tape.

The other two possible responses request the

binary output and specify the device to be used.

the user requests binary output from a 4K

PDP-8 system and the compiled program requires more than IK of

PDP-14 memory, the message "BINARY OVERFLOW" is typed and no binary will be punched.
will continue,

The compilation

however.

Compiler Listing

The compiler listing, which contains error messages and generated machine code instructions for solving the
equations of the source program,

output according to the following query:

*LST - NYW?

where N, Y, and

W have the following meanings:

No listing output is requested. BOOL-14 will only type the
lines which contain errors and the applicable error number.

The complete listing of source statements, compiled machine
code instructions, error messages, and any equation reductions
will be typed on the Teletype.
The complete listing will be typed exclusive of the reduced form
of equations.

The user types one of the above responses followed by a carriage return.
user types

If only

an error listing is wanted, the

BOOL-14 will type only those lines of the source program which contain en-ors.

For example,

BOOL-14 might type:
YIO = X27 (Y3 + X21) * X4

Note that an operator is missing

EOll

after "X27".

The user could then correct this and any other error detected during compilation and generate an updated and
correct source program tape with the Editor.

When all the errors have been corrected, the program is recompiled

with BOOL-14 and a complete compiler listing should be requested.

6-19

The Y response causes BOOL-14 to generate the complete compiler listing.
are typed (followed by an error number if the line contains an error).

All lines of the source program

there is no error, the generated

PDP-14 machine code instructions are listed below the equation.

BOOL-14 converts some equation forms to equivalent equations which it can solve more readily.
BOOL-14 types the converted form to assist the user in debugging his program.
which the NOT (/) operator applies to single variables only.

In these cases

This reduction is to a form in

For example:

Y21=/(X2 + Y31)
CONVERTED TO:
Y21 = (/X2) * (/Y31)

BOOL-14 reduces the equation and types the converted form, followed by the machine code instructions to solve
the equation.

the user does not find the converted equation form useful, he may suppress the converted form output by

responding with the letter

W (listing without converted forms) to the *LST-NYW? query.

The listing will contain the PDP-14 generated machine code instructions following each equation.
structions are typed in three columns.

instruction will be stored.

The first column is the octal absolute address in PDP-memory where the

The second column is the numeric form of the instruction.

symbolic form of the instruction.

001

The third column is the

For example:

Y13=X2*X4+Y13*(/X4+/X5)

Y1=X1+(X32*X3+Y12)
0000
0001
0002
0003
0004
0005
0006
000 7
0010

These in-

00 12 200 2 TXF 00 2
00 13 200 4 TXF 00 4

TXN 001
JFN 01
2032 TXF 032
2003 TXF 003
JFF 01
501
412 TYN 012
JFN 01
541
SYF 00
300
0344 SKP
3401 SYN 001

2401

541 1

0014 5024
001 5 1013
001 6 5422
0017 2004
0020 2005
0021 5424
0022 3013
0023 0344
0024 341

1
1

JFF 024
TYF 01
JFN 022
TXF 004
TXF 005
JFN 024
SYF 013
SKP
SYN 01

At the end of the program listing, BOOL-14 will type the following messages:

ERROR LINES:

The decimal number of lines in the source program which
contained errors.

EDITED LINES:

The decimal number of error lines which were subsequently
edited successfully.

PROGRAM BREAK:

The highest absolute PDP-14 memory address used by the
compiled program.

6-20

Program Source

The source program may be supplied to BOOL-14 from one of three devices:

Teletype keyboard, low-speed

paper tape reader or, if the PDP-8 system is so equipped, the high-speed paper tape reader.

The source is

specified in response to the query:

*SRC-KLH?
where the K, L and H are the possible responses with the following meanings:

The source program will be typed from the Teletype keyboard.

The source program is in paper tape form and will be read with
the low -speed reader of the Teletype unit.

The source program is in paper tape form and will be read with
the high-speed reader.

the keyboard is selected as the source device,

BOOL-14 will type a quotation mark (") when it is waiting

for the user to type an equation.

The user then types his equation terminating it with a carriage (the dollar sign ($) may be used to break a statement line into two or more parts as previously described).

When the keyboard is source device, the RUBOUT, CTRL/U and TAB may be used.
line of the source

program may be erased with the RUBOUT key which will erase one character to the left for

each striking of the key up to the beginning of the equation.

back slash (\).

Characters on the current

The RUBOUT key is recorded by BOOL-14 as a

CTRL/U* may be used to delete a complete statement line from the source program.

key may be used to format the program.

TAB positions are set at 8 character widths.

The TAB

Striking TAB advances

the printer to the next Tab position.

Editing

The user may correct error lines in the program by requesting the editing option.

The query is:

*EDT-NY?
where the possible responses,

If the

N and Y, mean No and Yes respectively.

editing option is requested,

BOOL-14 will type a ">" after each error line and its error number.

allows the user to retype the equation.

"CTRL/U is formed by holding the CTRL key depressed while striking the letter U

6-21

This

For example:

"Yl = XI + X9
E002

>Y1 = XI + XIO

Retyped by the user

TXN
TXN 10
1

Generated machine code

the source program is read from the low-speed reader and the editing option is requested,

after typing the

"> ".

BOOL-14 will halt

The user must turn the low-speed reader to STOP, and press the PDP-8 CONT switch.

When editing is complete, the reader should be set to START, and compilation will continue.
If

the user, having requested the edit option, wishes to ignore the error line and proceed with the compilation,

he types a carriage return after the "> " symbol.

In this case, the source equation containing the error will

completely ignored.

the editing option is requested, the user may type CTRL/D* to direct BOOL-14 to type all characters in the

equation up to the character which caused the error.

The remainder of the equation may then be typed by the

user, thereby correcting the error.

If more

than one error is contained in a single line of the source program, only the first encountered error will

be detected.

Repeatedly use the CTRL/D and the editing option will find and correct all errors,

ERROR MESSAGES
The following is a list of the possible errors which are detected and diagnosed by BOOL-14.

The error numbers

are typed under the equation which caused them in the form "Ennn" where nnn is the error number.
stop compilation of the erroneous equation.

All errors

(BOOL-14 will either proceed to the next equation or, if the

editing option is requested, wait for the user to correct the error.)

No machine code instructions are generated

for erroneous equations, unless they are first corrected.

Error Number

Cause

A required number is missing after an input (X), output (Y), Z-function,
R-function or control statement.

Examples:

Yl = X

Y = X1
Y15=X2 +
* CTRU/D is

formed by holding the CRTL key depressed while striking the letter D

6-22

Error

Number

(Cont)

Cause

Z = X3 + Yl

Y17=X5 *Z
R:

Y12 = X27 * XI

.FIXS
2

A non-octal digit is encountered after an X, Y, .END, or .LOG.

Illegal number error caused by: an input or output number greater than
377; a decimal number greater than 2047 following an R, Z, .VARS,
or FIXS; an octal number greater than 7777 following a .LOG or .END

statement

The first or second character of an equation is not valid.
acter may be a

NOT sign (/), or a "Y".

If the first

The first charcharacter is a "/",

the second character must be a 'Y".

Examples:
B = X1

/G14= X27* Y3
5

The equals sign (=) is either missing or not in the proper place within an
equation, Z-function, or R-function.
Examples:

Yl XI * X2

Y15/=X3
6

A variable grouping is not closed with the character type with which
was opened.
Examples:
[

[

XI + X2)
X3 + (X5 * X6] + Y7)

The character following a negation sign (/) is not valid.
Example:

Y23 = / n * X2
8

The character following a left parenthesis or left bracket is not valid.
Example:

Y10= (R5* X2)
9

The character following an AND (*) or OR (+) sign is not valid.
Examples:

Yll = XI + *
Y12= XIO * Rl
10

The character following an equals sign (=) is not valid.
Example:

Y21 = R1

6-23

_Cayse_

Error Number

The character following a number is not valid.
Example:

] ]

Y32= XT/* X2
The character following a right parenthesis or right
Example:

bracket is not valid

Y7 = X12 * (X5 + X7) / * X2

A Z-function is contained as a variable in an R-function or Z-function.

Examples:

Z29 = X3 + Z50
RIO:

Y73=X1 * Z12

An R-function or Z-function is referenced which has not been defined

previously.

An equation contains more right parentheses and brackets than left paren-

theses and brackets.

Example:

Y37 = XI * (X2 * X24 + X25]

X4)

An equation contains less right parentheses and brackets than left paren-

theses and brackets.

Example:

Y42 = X12 * X2 * (X2 * [23 + X17] * X14

A control statement is not recognized.

Examples:

.MZN
.MNF
.SAZ

A control statement contains an illegal character.

Examples:

.M#N
.M.N
19

There is no control statement after the period (

The .LOG statement must precede all equations, R-functions and Z-functions

Examples:

Z12=X1 * X2
LOG 50
.

A subroutine definition is encountered after at least one equation has been
compiled.
Examples:

Y12=X3 * X15
R12: Y5= X27*/Y51
6-24

Error

Number
22

Cause
The statement defines an R-function or Z-function which has been defined
previously.

Examples:

Z129 = X25+ X3 * X12
Z129 = Y3 * X21 + X5 * X12
23

The source program contains more than 64 R-functions and Z-functions combined, the maximum that BOOL-14 can handle.

The character following a colon (

)

not valid.

Examples:
R15:

Z5- X27* X12

R29:

R5 = X121 + Y13 * X122

OPTIMUM FORM FOR BOOL-14 EQUATIONS
Although equations may be written in many forms, the optimum form for BOOL-14 equations is achieved by
following the following rules.

The first two rules affect the number of memory locations used to solve the

equation.

The other rules affect the amount of time required to execute the program.

rules is not

mandatory for proper PDP-14 operation.

Adherence to these

The rules only serve to increase the efficiency and speed

of program execution in the PDP-14.

Group together all single variables (inputs or outputs) which are combined with the same operator.
Examples:

Yl = XI + X2 + (X3 * X4 * X5) + Y12 + X15
should be rewritten:

Yl = XI + X2 + Y12 + X15 + (X3 * X4 * X5) and,

Y12 = X3 * Y7 * (X4 + X27 + X21) * Y5 * X32
should be rewritten:

Y12 = X3 * Y7 * Y5 * X32 * (X4 + X27 + X21).
2.

BOOL-14 will generate a test instruction for every variable occurrence on the right side of the

equation.

Therefore, factor equations to eliminate repeated variable occurrences.

Examples:

Y15 = X3 * Y5 + X6 * Y5 + X12 * Y5 + Y17 * Y5
should be rewritten:

Y15 = Y5 * (X3 + X6 + X12 + Y17)
3.

Where a single variable is ANDed with an expression, preceed the expression with the single variable,
Example:

Y6 = (X31 + X4 * X52) * X27
should be rewritten:

Y6 = X27 * (X31 + X4 * X52)

6-25

Group variables and expressions in order of their complexity, with single variables at the beginning

of equations and large expressions, and the more complex expressions at the end.

Example:

Y31 + [(X5 * X7 + X3) * X21 + (Y52 * Y12) + X13 * Y17 */Y5)]

X22

should be rewritten:

Y31 = X22 * [(Y52 * Y12) + (X13 * Y17 * / Y5) + (X3 + X5 * X17) * X21]
5.

When expressions of approximately the same complexity are combined using either the OR operator

or the

AND operator, the expression which represents the set of conditions which

more often true

should preceed the other expression.

Example:

Y5 = m2*X4 + / X27)^ + ^X21 * (X 3 +/X51] + (Y7 * / X23)
true 30% of time

true 20% of time

true 50% of time

This equation should be rewritten:

Y5 = (Y7 * / X23) + (/ X27 + X12 * X4) + (X21 * (X3 + / X51)
6.

Try to group subroutines near the end of equations or expressions.

Remember that subroutines take

longer to test than a single variable.

Example:

Yll = (Z3 * / X21) + ((Z7 + X4) * X3 * X5)) + XI * X2
should be rewritten:

Yll = XI * X2+ (/X21 * Z3)+ (X3 * X5 * (X4 + Z7))

The foregoing rules are sometimes contradictory.

However, the guiding rule is to write the equations in the form

which will permit the PDP-14 to determine as quickly as possible if the output is to be set ON or OFF.
rules attempt to limit the amount of testing which the

The

PDP-14 will perform before it is able to make the ON/

OFF decision.

SAMPLE BOOL-14 PROGRAM

A BOOL-14 program representing a simple control circuit is given on the following pages.

The reader should

note the extensive use of comments to indicate the physical input or output which is represented by an X or Y.

The control statements .LOC, .FIXS, .VARS, and .END are illustrated.
cluded with the regular output equations.

Z-functions and R-functions are in-

The output listing from BOOL-14 follows the program.

6-26

;bool-14 sample program
;COMME?JTS TO IDENTIFY THE PROGRAM VJOULD APPEAR HERE.
JCONTOL STATEMENTS WHICH AFFECT THE WHOLE PROGRAM FOLLOW.
.LOC250
.FIXS5
JSUBROUTINES PRCEED THE MAIM PROGRAM.
;2CR=/6PB*/7PB*/ IPS*/ 1FS*/5CR
Z2=/X13*/X14*/X6*/X7*/Y1

JS0LE=3CR=(8PB*CRH+CRA)*7CR*8CR*9CR*/3LS*/4LS*/5LS
Rl :Y4=(X15*Y7+Y6)*Y12*Y13*/Y14+/X2*/X3*/X4

;S0LF=4CR=/7CR*(CRA*5CR+/9CR+9PB*CRH)
R2:Y5=/Y12*(Y6*Y1 +Y14+X1 6*Y7
; NORMAL
EQUATIONS FOLLOW.
;2LT = CRA = RESET*/CRH*( AUTO +CRA)
Y6=X10*Y7*(X1 1+Y6)
JCALL TO REPETITIVE EQUATIONS.
1

.VARS0
Rl

JNORMAL EQUATIONS CONTINUE BELOW.
;3LT=CRH=RESET*(MAN+CRH)
Y7=X10*(X12+Y7)

;S0LA=S0LC=CR1=/6CR*(6PB*7PB*2CR*/1LS*/2LS*5LS*6LS*7CR+1CR)
Y0=/Y3*(X13*X14*Z2*/X0*/X1*X4*X5*Y12+Y0)
Y2 = X0

;4LT = /6PB + .''7PB*( IPS + IFS
Y10=/X13*Xl4*(X6+X7)
J5LT=5CR=3LS*/4LS+5CR*8CR
Yl 1=X2*/X3+Y1 1*Y13
;SOLB=SOLD-6CR=7CR*(CRA*/5LS*/6LS*(6CR+5CR*8CR)+Pni0+CRH)
Y2=Y12*(Y6*/X4*/X5*(Y2+Y1 1*Y13 )+xi7*Y7)
;6LT=7CR=4LS
Y12=X3
;7LT=8CR=1LS*2LS
Y13=X0*X1
;/8LT=9CR=/llPB*(9CR+12PB)*(7CR+8CR)
/Y14=/X20*(Y14+X2 )*(Y12+Y13)
JCALL TO REPETITIVE EQUATIONS.
)

.VARS0
Rl

.END 250

6-27

VI
*F3IXr-\fLH''L
*I.ST-MYW"? Y

*SRC-KLH''L
*KDT-MY''M

ji^OOL-l-^ SAMPLE PROGRAM
;':3mmp:mts to idemtify the

program would appear here.

;co\itol statements which affect the whole program follow^
.LOC2 50

.FIXS5

JSUBROUTIMES PRCEED THE MAIM PROGRAM.
;2CR=/6PB*/7PB*/ IPS*/ 1FS*/5CR
Z2=/X13*/X14*/X6+/X7*/Y1
0252 2413 TXM 013
0253 2414 TXM 014
0254 2406 TXM 006
02 5 5 2407 TXM 00 7
TY-M
0256 141
02 57 5662 JEM 2 62
2 60 1377 TYF 377
0261 1777 TYM 3 77
3 54 JMR
02 62
1

JS0LE=3CR=(RPB*CRH+CRA)*7CR+8CR*9CR*/3LS*/4LS*/5LS
Rl :Y4=(X1 5*Y7+Y6)*Y12*Y13*/Y14*/X2*/X3*/X4

0270 20 15 TXF
02 7
10 7 TYF
02 72 5275 OFF
2 73 140 6 TYN
2 74 53 04 JFF
02 7 5 1012 TYF
02 7 6 1013 TYP
02 7 7 1414 TY^J
0300 2402 TXM
3
2403 TXM
0302 2404 TXM
0303 5306 JFF
0304 3004 SYF
3 44 SKP
03 5
0306 3404 SYM
0307 0354 JMR
1

015
00 7

275
00 6
3 04

012
013
14

002
00 3
4

306
004
004

;S0LF=4CR=/7CR*(CRA*5CR+/9CR+9PB+CRH)
R2:Y5=/Y12*(Y6*Y1 +Y14+X16*Y7)
1

0315
0316
0317
0320
0321
0322
0323

0324
0325
0326
0327
0330
0331

0332

1412 TYM 012
5727 JEM 327
100 6 TYF 006
101
TYF 01
5331 JFF 331
1414 TYM 014
5731 JEM 331
2016 TXF 016
1007 TYF 007
5331 JFF 331
3005 SYF 005
0344 SKP
3405 SYM 005
0354 JMR
1

6-28

NORMAL EQUATIONS FOLLOW.
;2LT=CRA=RESET*/CRH*(AUT0+CRA)
Y6=X10*Y7*(X1 1+Y6)
;

0250 4224 JMP
0251 0340 0340
0340
0341
0342
0343
0344
0345
0346
0347
0350

2010 TXF 010
1007 TYF 007
5746 JFN 346
241 1 TXN 01
1406 TYN 006
5750 JFN 350
3006 SYF 006
0344 SKP
3406 SYN 006

;CALL TO REPETITIVE EQUATIONS
.VARS0
Rl

1356 4645 JMS
)357 0270 0270

0360 4645 JMS
0361 0315 0315

;normal equations continue below.
;3lt=crh=reset*(man+crh)
Y7=X10*(X12+Y7)
367 2010 TXF
370 5774 JFN
371 2412 TXN
372 1407 TYN
0373 5776 JFN
0374 3007 SYF
0375 0344 SKP
0376 3407 SYN

010
374
012
007
376
007

007

;S0LA=S0LC=CR1=/6CR*(6PB*7PB*2CR*/1LS*/2LS*5LS*6LS*7CR+1CR)
Y0=/Y3*(X13*X14*Z2*/X0*/X1*X4*X5*Y12+Y0)
0^04
0405
0406
0407
0410
0411
0412
0413

0414
0415
0416
0417

1403 TYN 003
JFN 024
TXF 013
TXF 014
JFN 022
JMS

5424
2013
2014
5422
4645
0252
5022
2400
2401
2004
2005

0252
JFF 022
TXN 000
TXN 001
TXF 004
TXF 005

6-29

0420
0421
0422
0423
0424
0425
0426

1012
5026
1400
5426
3000
0344
3400

TYF 012
JFF 026
TY^ 000
JF^J 026
SYF 000
SKP
SYM 000

2400
5440
3002
0344
3402

TXM
JFM
SYF
SKP
SYM

Y2 = X0

0434
0435
0436
0437
0440

000
040
002
002

;4LT=/6PB*/7PB*C IPS+IFS
Y10=/X13*X14*(X6+X7)

)

0446 2413 TXM 013
0447 2014 TXF 014
0450 5454 JFM 054
04 51 2406 TXM 006
0452 2407 TXM 007
0453 5456 JFM 056
4 54 3010 SYF 0-10
0455 0344 SKP
0456 34 10 SYM 010

J5LT=5CR=3LS*/4LS+5CR*8CR
Yl 1==:X2*/X3+Y1 1*Y13

2002 TXF 002
2403 TXM 003
0466 5074 JFF 074
0467 1011 TYF 01
47
10 13 TYF 013
0471 50 74 JFF 074
0472 301
SYF 01
0473 0344 SKP
0474 341
SYM 01
1^464
465

;SOLB=SOLD=6CR=7CR*(CRA*/5LS*/6LS*(6CR+5CR*8CR)+PB10*CRH)
Y2=Y12*(Y6*/X4*/X5*(Y2+Y1 1*Y13 )+xi7*Y7)
0502
0503
0504
0505
0506
0507
0510

1012
5520
1006
2404
2405
5515
1402

051 1

5 52 2

0512
0513
0514
0515
0516
0517
0520
0521
0522

101 1

1013
5122
2017
1007
5122
3002
0344
3402

TYF
JFN
TYF
TXM
TXM
JFM
TYM
JFM
TYF
TYF
JFF
TXF
TYF
JFF
SYF
SKP
SYM

012
120

006
004
005
1

002
122
01 1

013
122
017
007
122

002
002

6-30

j6LT=7CR=4LS
Y1S=X3
TXM 003
JFM 13^12
532 30 IP. SYF
0533 034/4 SKP
53/4 3/412 SYM 012

0530

P.403

53 1

5 53 A

J7LT=8CR= 1LS*2LS
Y13=X0*X1
2000
2001
5147
3013
0344
3413

0542
0543
0544
0545
0546
0547

TXF
TXF
JFF
SYF
SKP

000

SY^J

013

001
147
013

j/8LT=9CR=/ 1PB*(9CR+12PB)*(7CR+8CR)
/Y14=/X20*(Y14+X2 )*(Y12+Y13)
1

0555 2420 TXN 020
0556 5565 JFM 165
0557 1414 TYN 014
5 60 2421 TX^ 021
0561 5165 JFF 165
0562 1412 TYiM 012
0563 1413 TYN 013
0564 5567 JF)J 167
0565 3414 SYN 014
0566 0344 SKP
0567 3014 SYF 014
;CALL TO REPETITIVE EQUATIONS
.VARS0
Rl

0575 4645 JMS
0576 0270 0270
R2

0577 4645 JMS
0600 0315 0315
.EMD 250

0606 4224 JMP
0607 0250 0250
ERROR LINES

0000

EDITED LINES

0000

PROGRAM BREAK:
TURN PUNCH

60 7

OXI

>
.2??^
/< +$,/+/+$;,/&/ ($&%8&%
/ >S> , &%*(

B^*^

SPURIOUS chahactfks akf
TYPED WHI1.F HIWAkY IS
PUNCHED

s
)

"( C%

•

$-5) 5

-7I&%8&%

6-31

CHAPTER 7
PAL-14

PDP-14 SYMBOLIC PROGRAM ASSEMBLER
The PAL-14 symbolic assembler translates programs Into the binary machine code which is input to SIM-14, or

which may be used to generate an ROM for the PDP-14.

PDP-14 programs may be written with the Editor and

"assembled" (translated into machine code) by PAL-14, thereby enabling the user to correct program errors with
the Editor and to reassemble with PAL-14.

This capability considerably eases the debugging procedure because

sections of the source program may be moved, or new lines inserted, without retyping the remainder of the pro-

gram

Figure 7-1 outlines the procedure for developing programs using PAL-14.

PAL-14 GENERAL FEATURES
Chapter 5 described the machine code instructions of the PDP-14.

Remember that test instructions referred to

specific input and output numbers and that the jump instructions referenced locations by an address number (viz.,

an absolute address for a JMP or JMS; a relative or page address for a JFF or JFN)

Consider the following

PDP-14 program segment:

227 TXN 15
230 JFN 233
231

SYF 12

232 SKP
233 SYN 12
234 JMP
235 437

NOTES
1

Each instruction is assigned to a numbered location.

The JFN and JMP instructions refer to locations by

specific address numbers.

The TXN, SYF, and SYN instructions refer to input

or outputs by specific number.

7-1

Changing PDP-14 programs written with numeric addresses and references is very cumbersome.

For example,

assume that there should be a "TYN 27" instruction after the "TXN 15" stored in location 227 in the above pro-

gram
it

To correct the program with SIM-14, each instruction is moved to the next sequential location (by typing

into that location) thereby allowing the

"TYN 27" to be inserted at location 230.

However, simply moving each instruction to the next successive location does not properly solve the problem,,
The result of simply moving the instructions is:

227 TXN
230 TYN
231

JFN

27
233

232 SYF
233 SKP

234 SYN
235 JMP
236 437

Note that by relocating the program segment, the sense of the JFN 233 instruction has changed.
jump caused transfer to the SYN 12 instruction; now it causes transfer to the SKP.

changed to a JFN 234 to preserve the original sense of the program.
programs with SIM-14.

Originally the

The JFN instruction must be

Thus, there are dangers in simply relocotin-

These dangers can be removed by using PAL-14 and reassembling, as will be seen.

Location Assignment

Note that PDP-14 programs are stored in consecutive memory locations.
instruction

therefore unnecessary.

sequence of instructions.

The need to specify the address of each

The locations may be assigned by PAL-14 using an origin statement for the

The statement is "LOG NNNN" where

NNNN

an absolute PDP-14 address.

This

statement instructs PAL-14 to assign the instructions which follow to consecutive PDP-14 locations beginning
with location

NNNN.
LOG 227
TXN 15
TYN 27
JFN 234
SYF
SKP

SYN 12
JMP
437

7-2

Assign inputs and
oufputs to PDP-14 I-

and O-boxes

I
Express the machine

sequence in equation
form.

I
Translate the equations

Read source tape back

into instruction form.

into the

EDITOR.

Type the instructions
in program form with

Correct the program
errors.

the EDITOR.

I
Generate the source
tope for PAL-14.

I
Assemble the PDP-14
program with PAL-14.

W Assembly

errors found

Load the assembled
program paper tape
into SIM-14.

I
Check for program

Operational errors found. V

errors

No errors found.

I
Generate paper tape
and send to DEC for

ROM.

Figure 7-1

7-3

PAL-14 recognizes the LOG 227 as an origin statement, and assigns the instructions which follow to sequential
locations, beginning with location 227.

Hence, the TXN 15 is stored in 227; the TYN 27 is stored in 230; the

Thus, the need to write location numbers is eliminated by PAL-14.

JFN 234 is stored in 231; etc.

Symbolic Addresses

The LOG statement by itself does not eliminate the problems arising when PDP-14 programs are altered.

How-

ever, automatic location assignment using the LOG statement permits symbolic addresses which do eliminate

some of the problems.

Symbolic addresses are simply name tags or labels used to identify memory locations.

Instead of writing }ump instructions with numeric addresses, jump instructions are written with symbols for addresses.

These symbols are then identified (defined) elsewhere in the program.

The symbol is assigned a numeric

value during the assembly of the program by PAL-14.

The instruction JFN 234, for example, may be written JFN TAG
address label

The location to be jumped to is assigned the

"TAG", by writing TAG followed by a comma, preceding the referenced instruction.

JFN TAG

TAG, SYN

The JFN instruction above references the symbolic address "TAG", while the statement "TAG, SYN 12" defines
the symbolic address.

PAL-14 will assign address values to each instruction of the program using a "location counter" (LG)
statement sets the LG to a value (e.g

LOG 200 sets the LG to 200)

The LG is incremented for each instruc-

tion, thereby storing the program In sequential locations of PDP-14 memory.

(recognized because it is followed by a comma) is encountered,

The LOG

PAL-14 then assigns each successive

instruction of the source program to the locations specified by the LG

Whenever a symbolic address

assigned the value of the LG

Thus,

if the

LG is equal to 234 when the line "TAG, SYN 12" is encountered in the source program, the SYN 12 is stored
in

PDP-14 memory location 234, and TAG is assigned the value 234. The instruction JFN TAG thus becomes

JFN 234 when assembled by PAL-14.

7-4

Note that programs in this form may readily be changed to eliminate bugs.
located by changing the LOG statement.

The program may be completely re-

Parts of the program may be inserted or deleted without affecting

address references made by jump instructions.

Upon reassembly, PAL-14 will correctly assign all symbolic

addresses and any references to them

Symbolic addressing does not eliminate the need to consider paging for JFF and JFN instructions.
error will result if a

An address

PAL-14 program contains such instructions which reference symbolic addresses that are not

defined within the same PDP-14 memory page.

Only the JMP or JMS instruction may directly cross page bound-

aries.

The selection of the symbol "TAG" is arbitrary and could be any group of letters and numbers subject to the rule:
for symbols which are given in Table 7-1

For example,

SETY10N is a valid PAL-14 symbol

7 characters, however, only the first six are recognized by PAL-14.

Since it contains

Thus if the symbols SETYION and SET! OF

were both used as symbolic addresses in a PAL-14 program, multiple definition error would occur.

PAL-14 only

recognizes the first six characters, and therefore cannot distinguish between two symbols which ore identical

The error results because the same symbol is defined twice in the program.

these first six characters.

Note that

the symbols SOLAON and SOLAOFF are perfectly acceptable, since they differ in the first six characters.

Table 7-1

PAL-14 Symbol Rules

The first character of a symbol must be a letter.
The successive characters in the symbol may be only
letters or numbers.
No special characters (e.g., *, +,
-, /, $) are permitted within symbols.

A symbol must only be defined at only one point in a
program. Symbols may be referenced as many times as
necessary

Only the first six characters of the symbol are meaningful to PAL-14. Although more characters may be
used, they are not meaningful to PAL-14.

No spaces or tabs are allowed within the symbol

Assignment Statements

PAL-14 assignment statements equate a six character symbol with a numeric value. Symbols used in assignment
statements are subject to the rules given in Table 7-1

symbolic address is illegal in PAL-14.

Assigning a value to a symbol which is also used as a

The same symbol may, however, be used in more than one assignment

statement; the last assigned value is used whenever a symbol has been redefined in this way.

7-5

The most common use of assignment statements in PAL-14 programs is to identify
It is

more convenient to remember that "LSI is limit switch

1" as opposed to

PDP-14 programs must refer to inputs and outputs by the numbers which

input and output assignments

"17 is limit switch 1".

Since

are determined by the I- and 0-box

used.
assignments (e.g., 17), the following PAL-14 assignment statement is

LS1=17

Instructions

usually at its
may then test "LSI" in place of testing "17". The PDP-14 program may include,

beginning, a list of such assignments which are used throughout the
written in a completely symbolic form.

program.

This allows the program to be

For example:

LS1=17
LS2=30

SOLA=ll
SOLB=12
PB1=10

PB2=n

LOG

250

Yll,

TXN

LSI

TXF LS2
JFN SOLAN
TXF PBl
TYN SOLB
JFF SOLAF
SOLAN, SYN SOLA

SOLAF,

SKP
SYF SOLA

END
The END statement is necessary to mark the end of the program for PAL-14.

Remember that assignment statements

need only be made at one point in the program and the symbols thus assigned may then be
program.

(The above example only controls one output.)

used throughout the

Also note that LSI = "17", not "X17"

The X and Y

designations are not used in PAL-14.

PAL-14 PROGRAM CONVENTIONS
PAL-14 programs are free-form; spaces and/or tabs may be used to organize and
At least one space (or a TAB) must be used between an instruction (e.g. , TXN
or operand (e.g., LSI or SOLB).

format the program as desired.

or SYF) and the referenced symbol

Tabs and spaces may not be within a symbol or instruction, but only between

symbolic addresses, instructions, operands, and comments.

Otherwise these characters have no effect upon the

machine code generated by PAL-14; they are only used to format the source program.

SOLA

TXF

LSI

7-6

For example:

generates the same machine code as

SOLA,TXF LSI
where the comma is needed to identify "SOLA" as a symbolic address.

Comments
Program comments are lines of text included in the PAL-14 program to clarify the function of an instruction or

group of instructions

Comments do not affect the machine code generated by PAL-14; they only exist as a

reminder for later reference to the program listing.

ceding them with a slash (/)

by themselves.

Comments may be added within the PAL-14 program by pre-

Comments may either conclude lines of a program, or may be on separate lines

PAL-14 instructions or assignment statements may not be included on a line started with a

comment because all information would be treated as part of the comment.
The following are examples of PAL-14 comments.

Ahe following program controls solenoid a
LOC 200
Yl ,

TXF

/LSI
/PBl

LSI

TXN PBl

ACTIVATED WHEN SLIDE 2 IS FULL FORWARD.
IS SHUT DOWN BUTTON.

Two-Location Instructions

The PDP-14 two-location instructions (e.g., JMP, JMS, TRM) are written in PAL-14 source programs with both
parts of the instruction on one line.

These instructions will require two PDP-14 memory locations when they are

translated into machine code instructions.

The following example illustrates the two-location translation proces

The input to PAL-14 appears at left; the translated output in machine code is given at right.

The symbols Y5

and NEXT are symbolic addresses which have been assigned the values 1323 and 1401 respectively by the curren
location counter of PAL-14.

STA1N=2002

200

TRM

LOC 200
TRM STAIN

201

2002

J MS

Y5
J MP NEXT

Y5,

TXN

202 JMS
203 1323
204 J MP
205 1401

LS16

7-7

NEXT,

TYN SO LB

Permanent Symbol Table

PAL-14 must "know" what PDP-14 machine code to generate for each symbol of a source program before it can
translate that program into a complete PDP-14 machine code program which

ROM generator.

acceptable to SIM-14 or to the

Numbers are the only elements of PAL-14 source programs which need no definition; all symbols

must be defined in terms of these numbers.

As we have seen, definitions may be in the form of assignment state-

ments {e.g., LSI =27) and symbolic addresses (whose values are defined by the location counter and LOG statements)

In addition to user defined symbols,

lents.

PAL-14 has a table of permanently defined symbols and their numeric equiva-

The permanent symbol table allows the user to write statements such as "TXN 15" without having previous-

ly defined the symbol

PAL-14.

TXN.

This symbol

and all others given in Table 7-2 are permanently defined within

The list includes the basic PDP-14 instructions introduced in Chapter 5 as well as the extended instruc-

tions introduced in Chapter 9.

Also included are internal register names and pseudo-instructions which are

described later in this chapter.

Each of these symbols may be used in PAL-14 source programs without definition by the user; furthermore,

these

symbols must not be used in PAL-14 source programs as symbolic addresses or in assignment statements.

The PAL-14 symbol table is finite in size. When loaded in a 4K PDP-8, 310 symbols may be accommodated,.

When loaded in an 8K PDP-8 (in field 1), 792 symbols may be accommodated. When its capacity is exceeded
by user defined symbols, the following message is typed:

*SMB OFLW
Recovery is described in the PAL-14 Operation section of Chapter 10

7-8

(pages 10-21).

Table 7-2

PAL-14 Permanent Symbol Table
PDP-14 Instructions

Max Arg
.

Value
in Octal

Symbolic

Octal

Meaning

TXF

2000

Test input for OFF

Input

Number

377

TXN

2400

Test input for

Input

Number

377

TYF

1000

Test output for OFF

Output Number

377

TYN

1400

Test output for

Output Number

377

SYF

3000

Set output OFF

Output Number

376

CLR

3377

Clear all outputs

None

SYN

3400

Set output

JFF

5000

JFN

Argument

Output Number

377

Jump if test flag OFF

Page Address

377

5400

Jump if test flag ON

Page Address

377

4224

Jump unconditional

Absolute Address

7117

SKP

0344

Skip next location

None

J MS

4645

Jump to subroutine

Absolute Address

JMR

0354

Jump return from subroutine

None

NOP

0000

No operation

None

HLT

0007

Halt the PDP-14

None

TXD

7000

Test input and display

Input

TYD

7400

Test output and display

Output Number

EEM

0600

Enter external

mode

None

EES

0645

Enter external

mode, store PCI

None

LEM

0400

Leave external mode

None

LER

0454

Leave external mode, restore PCI

None

—
—
—
—

TRM

4226

Transfer memory to Output

Any data word

///7

TRS

4225

Transfer memory to Storage in PC2

Any data word

7777

TRR

0200

Transfer register to register

Src.R Dest.R*

SKE

6704

Skip if register equal to PC2

SKZ

6304

Skip if register is zero

*R is one of the internal r egisters given below.

7-9

7777

—
—
Number

377
377

PDP-14 Internal Registers
Register Name

Octal Code

DUMMY

0000

PCI

0004

0001

PC2

0005

0002

INPUT

0006

SPARE

0003

OUTPUT

0006

Internal

Code

Pseudo- Instructions

END

End of source program

EOT

End of tape In a segmented program

LOG

Set location counter

PAGE J

Page jump to start of next page

Special Characters and Operators

Several characters of the Teletype keyboard have special meaning to PAL-14.

which signals the start of a comment

An example is the slash (/)

Another example is the carriage return which terminates a statement line

Table 7-3 contains all characters which are legal in the operation portion of a PAL-14 statement (viz., the
statement exclusive of any comment field)

If any other character appears in

the operation part of a PAL-14

statement, the "I" error (Illegal character) will be generated.

Table 7-3

PAL-14 Special Characters
Character

Use in PAL-14

(plus)

combines symbols or values by two complement addition

(minus)

combines symbols or values by two complement subtraction

OR)

(logical

(shift)

shifts a

i—i

(space)

separates Instructions from operands and otherwise formats

combines symbols or values by a logical OR
value one octal digit left

the source program
(tab)

separates Instructions from operands and otherwise formats

the source program
(carriage

terminates a statement

return)

(slash)

terminates the operation part of a statement and starts
a comment

(comma)

identifies symbols used as symbolic addresses

(equals)

assigns values to symbols directly

(period)

A symbol which, when encountered in the program. Is
assigned a value equal to the present value of the

PAL-14 location counter
7-10

The following characters are Ignored in PAL-14 source programs but do not generate an error.
line feed

form feed
rubout
leader/trailer (null)

Addition and Subtraction - The "+" and "-" characters may be used with symbols and octal numbers, usually for
addressing purposes.

The statement "J MP START +2" in the following program segment causes an unconditional

jump to the second location after that labeled "START" (i .e., location 102 and the TNX PB3 instruction).

LOG

100

START,

TXN

PBl

JFN OUT

TXN

PBS

MP START +2

Likewise the minus sign may be used; for example "JFF SOLAN-2" causes a JFF to the second location before
the location labeled SOLAN.
will

The location counter of PAL-14 will assign values to all labels and then PAL-14

compute the values of all symbolic addresses which contain operators and symbols.

Logical

OR - The "!" character may be used in PAL-14 programs to combine values of symbols or octal numbers

The result is the bit-by-bit inclusive OR of the two values.

The following table gives the resultant value when

any two octal digits are combined with the "!" character.
1

7-11

When numbers which contain two or more digits are combined, each digit in the result is obtained by combining
the corresponding digits in the original numbers using the above table.

For example:

1234

2460 =3674

The operator may be used in PAL-14 in the following manner:

TRM 15

TRM

translates into

37
The values of symbols may be combined with the "!" character also.

ON =

SOLA = 1500
TRM SOLA

TRM

translates to

1501

Shift - The

> character changes the value of the octal number or symbol which precedes it by shifting it one

octal digit to the left.
lost.

Zeros are shifted into vacated positions on the right and the most significant digit is

For example:

0231 >

=2310

0010 > =0100

1234> =2340
The shift character will often be used with the PDP-14 instruction TRR and internal register names.
maintains the following register assignments in its permanent symbol table.

PAL-14 Register Name

Octal Equivalent

DUMMY
IR

SPARE

PCI

PC2

INPUT

5
6

OUTPUT

The above register names may be used as operands in PAL-14.

TRR

PC2 >

OUTPUT

7-12

For example:

PAL-14

will

generate the PDP-14 instruction to transfer the contents of PC2 to the output register.

The octal value of

PC2 (5) is shifted one octal digit, then OR'd with the octal value of OUTPUT (6) and the result is OR'd with
the octal equivalent of TRR (0200), thereby generating the octal result 0256 for transfer PC2 to the output
register.

Note that the following two expressions are equivalent.
TRR

PC2>

OUTPUT

TRR!

OUTPUT

PC2 >!

The shift character only affects the symbol or number which immediately precedes it.

STATN3=300

TRM

translates to

TRMl+300>

3001

Period - The period is a special symbolic address used in PAL-14.

JFF to the twelfth octal
(less

operators.

(not 3010)

Its

always equal to the present value of the PAL-14 location counter.
period (often read "dot") and the +, -, and

Thus

value changes for each instruction and is

Jump instruction operands may contain the

For example, JFF

(tenth decimal) location after the JFF instruction.

+ 12 (read, JFF dot plus 12) means

The period is most used with small

than 10) octal numbers; large jumps are best done in PAL-14 with true symbolic addresses.

A variation of this instruction is "JFF
ed for both states of the TEST flag.

+ 1"

Note that this instruction causes the next instruction to be execut-

However, the TEST flag is cleared in both cases; thus the instruction JFF .+

may be used to unconditionally clear the TEST flag.
The period may also be used with two location instructions such as JMP, JMS or TRM.

However, the value of

the period is the value of the location counter when the second location is assigned to its location.

.+2 causes transfer to the third location which follows the JMP.

Assuming there are no two location instructions

following the JMP, the jump is to the second instruction which followed.

LOG
JMP

TXN
TXN

200
.+2

translates to

200

JMP

201

203

202
203

TXN
TXN 2

(201+2)
1

The following instruction could be used to have a TRM instruction output its own address:

LOG
TRM

1400

translates to

.-1

7-13

Thus JMP

1400

TRM

1401

1400

Pseudo-Instructions
Pseudo-instructions are included in PAL-14 program listing
cess

on the source paper tape to direct the assembly pro-

They are not themselves translated into PDP-14 machine

tions into machine code.

code; they affect the translation of other instruc-

There are four pseudo-instructions in PAL-14

including the LOG and END statements

described previously in this chapter.

END - The END pseudo-instruction marks the end of a source program
current assembly pass.

and directs PAL-14 to terminate the

The complete assembly process requires either two or

the assignment of input/output devices) during which

three "passes" (dependent upon

the source tape is read by PAL-14 and the translation

the current pass and causes PAL-14
PDP-14 machine code is made. The END statement terminates

the source tape is reloaded to begin the next assembly

Since the END statement halts the reading of a paper

to halt

while

pass.

tape during the assembly, any information present on the

source tape after the END statement will not be read by PAL-14.
of the source program and may be read with the Editor.

However, the comments are a permanent part

The assembly process will be faster if lengthy comments

and program documentation are written here.

program to be segmented and recorded on

EOT - The pseudo-instruction EOT (end of tape) allows a long PAL-14
which
^^than one source paper tope. The EOT is typed as the last statement on all tapes except the last one
reading EOT at the end of each
with the END pseudo-instruction. PAL-14 will stop upon the
must be concluded

tape during an assembly pass and type "*EOT"
This procedure

The next source tape is then loaded and the assembly continues.

repeated for each source tape in the complete program.

operand value of the LOG.

LOG - The LOG pseudo-instruction directs PAL-14 to set its location counter to the
0000"
if no LOG statement is present, a "LOG
As many LOG statements as desired may be used. However,
statement at the beginning of the program is assumed by PAL-14.

The LOG statement may advance or reset the location counter to any
turns the location counter to an earlier value, any

TXN
TXN

If the

LOG statement re-

previously assembled instruction at that location will be lost.

For example,

LOG

desired value.

LSI

LS2

7-14

LOG

SYN SOLA

results in the assembly of two instructions for the some location.

The first instruction (TXN LSI) is lost from the

assembly; PDP-14 location 50 will contain the assembled instruction for SYN SOLA.

The LOG statement may have an expression or symbolic operand.

All terms of the expression must have been

previously defined to allow PAL-14 to set the location counter to the proper value.

For example:

SOLAF, SYF SOLA
/LEAVE 8 LOGATIONS BEFORE STARTING NEXT PROGRAM SEGMENT
LOG SOLAF+10

The value of SOLAF will be assigned at the time of assembly and the LOG statement will set the location counte
to the value of SOLAF plus 10 (octal).

Thus the value of a LOG statement may be determined at the time of

assembly.

The pseudo-instruction "LOG .1377 + 1" causes PAL-14 to advance the location counter to the first location
of the next PDP-14 memory page.

counter

(.)

The statement is evaluated by PAL-14 as: the current value of the location

OR'd with 377 (octal) plus 1

If the

location counter is 1312 for example, the result of the OR will

be 1377 and the LOG statement will set the location counter to 1400 (1377- + l-).
o

PAGE J - The PAGEJ (page jump) pseudo-instruction causes PAL-14 to include in the assembled program whatever instruction is necessary to transfer control to the first location of the next PDP-14 memory page.

code generated is dependent upon the current value of the location counter.

Instruction Generated

Gurrent Location
First

location in a memory page

none

memory page

NOP

Last location in a

Any other memory location

JMP .1377+1

7-15

The actua

If the

next instruction would not have been assembled as the first or last instruction in the

page, PAL-14 will

location counter value and 377.
supply a JMP instruction, the operand of which is 1 plus the OR of the current
This

JMP always goes to the first location of the next PDP-14 memory page.

was assemblThe PAGEJ pseudo-instruction also acts as a "LOG .1377 +1" in the cases where a JMP instruction
ed.

Thus PAGEJ supplies the necessary PDP-14 instruction to transfer control to

the beginning of the next

memory page, and also sets the PAL-14 location counter to that location.

PAL-14 OUTPUT
The output of PAL-14 consists of an assembly listing with error messages,
tape.

a symbol table and a punched binar^^

The outputs are requested by the user in response to three PAL-14 messages:

*BIN -

Does the user want binary output; if so, on what device?

*LST -

Does the user want an assembly listing; if so, on what device?

*SMB -

Does the user want a symbol table listing; if so, on what device?

The responses to the three messages are:
The output is requested and directed to the low-speed device
(e.g. , Teletype printer - LST or SMB; or paper tape punch

BIN).

The output is requested and directed to the high-speed paper
tape punch

The output is not requested.

(return)

Binary Output

The PAL-14 binary output is a paper tape which could be used to generate an ROM for the PDP-14 controller.
Normally It is used as input to SIM-14 where the program may be simulated and debugged.

The paper tape has

to verify reada punched code at its end (checksum) which is read by SIM-14 when the tape is read into memory

ing accuracy.

Assembly Listing

The assembly listing contains the original source statements, the numeric value of the generated PDP-14 machine
code and error codes
It

PAL-14 formats the assembly listing into pages of 66 lines (approximately 1

types the page number

(in

octal) at the top of each output page.

7-16

inches long)

The assembly listing contains four fields:
Error field

contains letters to indicate all assembly errors included
in the line of the source program.

Location field

contains the four digit octal address of the PDP-14
location which contains the assembled instruction.
assembled instructions have entries in this field.

Code field

Only

contains the numeric value of the code for assembled
instructions, assignment statements or the LOG pseudoinstruction .

Source statement
-

field

contains the line of user program as read from the source tape,
If the source statement is

longer than 54 characters it will

not fit on one output line and PAL-14 will break it into two
or more output lines preceding the second and later lines

with an asterisk.

At the end of the program listing PAL-T4 types:
ERR LINES

the number of lines (in decimal) in the source program
which contain at least one error.

MEM BRK

the actual number of memory locations (in octal) occupied
by the assembled program. (This is not the largest address;
it is a count of the locations used.)

Symbol Table

The PAL-14 symbol table is a list in alphanumerical order of all user defined symbols in the source program (viz.,
all

symbolic addresses and assigned values)

values.
if

Any undefined symbol is typed with the letter U in the column of

Symbols which are defined by equating them with undefined symbols are assigned a value " + 0". Thus,

the statement

to distinguish

"PB1=PB0 + 1" and there is no statement which defines PBO, the symbol table will contain "PBO

+0"

-U" and "PB1

Error

The values of directly assigned symbols are typed as five digit numbers (with leading zeros)

them from symbolic address values which are typed as four digit numbers.

Messages

Error messages are single letters typed as the first entry of the same line as the source statement

the error.

If more

than one error is detected, a

of six error codes is typed for each line.

list

which contains

of all error codes is typed in alphabetical order.

If the same

A maximum

error occurs at more than one place in the source statement,

the error code is only typed once

PAL-14 stops processing the source statement when it encounters an S (syntax) error, as described in the table
below. Thus the source statement may contain undetected errors since they occur after the cause of the syntax
error.
is

These errors will , of course, be detected after the cause of the syntax error is removed and the statement

reassembled.

7-17

The following is a complete table of errors recognized by PAL-14.

The table includes examples of source

statements which cause the particular error and states the action taken by PAL-14 when the error occurs.

Action Taken

Meaning

Error Code

Address Error - the page address of
a JFF or JFN instruction is not on
the same page as the instruction itself.

The machine code is generated for
or JFN 0. The code for the
JFF
example is JFN 0, therefore.

Example:

At location 376

LEAVE, JFN .+3

Double Defined Symbol

Error - an

which
has been defined more than once in
the source program
instruction references a symbol

A,
A,

PAL-14 uses the first definition.
The JMP A in the example would
jump to the TYN SOLA instruction.

TYN SOLA
JFN OUT
JMP A

Illegal Character Error - The state-

PAL-14 ignores the illegal

ment contains a character which is
not acceptable to PAL-14.

character.

Example:

Thus the example is

interpreted:

JMP ABC

JMP A#BC

Label or Assignment Error - the first
character of a symbol used in assignments or labels is not a letter (A-Z)

The label or assignment is ignored
by PAL-14.

or the left hand member of an assign-

ment statement is numeric.
Example:

50=LS1

47,

JMP RESTART

Multiple Definition Error - a label
is defined more than once in the
source program

The first definition is used and all
others are ignored by PAL-14. In
the examples, A is equal to the
location which contains TYN SOLB

Examples:

M
M
O

A,
A,

TYN SOLB
JFN SOLBN
PAL-14 will ignore the illegal and

Operation Error - the source program contains an illegal operation
(e .g , two instructions in the same

all

statement)

ated as if the statement were:

subsequent information.

Example:

START, JMP TEST JMP

7-18

In the

example, the machine code is gener-

START,

JMP

TEST

Action Taken

Meaning

Error Code

The current value of the location

Phase Error - a label has a
different Pass 1

and Pass 2 value.

This error is normally caused by

a symbolic

LOC statement the

used

Example:
P
P

for each pass.

Since CDE is unde-

fined at the start of assembly,

operand of which is defined after
it is

counter is used to define the label

LOC CDE
XYZ,
JMP .+2
CDE=50

LOC

assumed, thus, CDE =0 and
XYZ = 0. During the first pass however,
CDE is given the value 50 and on the
second pass LOC CDE becomes LOC 50
and XYZ = 50, thereby causing the phase
is

errors

Redefinition Error - the source

program attempts to redefine
(using an assignment statement)
a PAL-14 permanent symbol (see
Table 7-2) or a previously defined

The symbols retain their original
values and the assignment statement
is

ignored

label.

Examples:

ABC,

LOC 50
J MP =400
TXN LSI

ABC=70

Syntax Error - the source statement is not meaningful to the

The statement is evaluated from left
to right up to the point where the
error occurred

assembi er

Thus:

ExampI es:

ABC,

JMP

.•

assigns ABC the current value of the

ABC,

LS1+LS2,

LS1 =

location counter and generates the
machine code for "JMP .". The

SOLA, TXN+=3
SOLAN,
JFN

value of LSI plus LS2 will be stored
in the next memory location (with-

S
S

The statement "LS1 = " will not generate any
machine code. The location with label
"SOLA" will contain the machine code
for TXN 0. The "JFN SOLAN," will
be assembled as "JFN SOLAN"

out any symbolic address)

Truncation Error - a single
value exceeds 7117 octal, or

hand digits are ignored.

the maximum argument value

result of A=40543 +C

for the instruction (see Table

If the

7-2) if maximum is less than

operand of an instruction, PAL-14
when the value
substitutes the value
Thus the value of:
is too large.

In assigned

1117

7-19

values, the excess right

Thus the

A =4054 +C

truncated value is used as the

Action Taken

Meaning

Error Code

ABC = 375 + 100
ABC
TYN

Examples:

T
T

C=3
A=40543+C
ABC==375+100
TYN ABC
SKZ 40

the following:

ABC =475

TYN
The instruction SKZ 40 becomes

SKZ
U

Undefined Symbol Error - an

The undefined portion of the

instruction references an un-

statement is set equal to 0.

defined symbol

JMP XZZ +3 becomes

Example:

Thus:

JMP 0+3 or JMP

XYZ=50
JMP XZZ +3

where XZZ is not defined

Illegal

Value Error - A value
given in the source program
cannot be evaluated by PAL- 14

The illegal digit is ignored, and
the remainder of the expression is
evaluated

Example:

Th.

ABC =8402 +5

4LS,

TXN

ABC = 402 + 5 = 407

LS4

However, in the second case, the
whole label is ignored.

Error Listing

The assembly listing as typed during pass 2 of PAL-14 includes error messages for all errored lines.

However,

PAL-14 also types a partial error listing of all lines containing errors which were detected during pass 1
listing in general will not report all errors, as some errors are only detected during pass 2.
listing

This

Furthermore, the

may report undefined symbols which will be properly defined during pass 2, such as the statements:

ABC=CDE
CDE=27
which result in ABC being undefined at the end of pass 1.
defined symbols (with a "value" of +0).

will, therefore, be included in the table of un-

However, since CDE is defined later in pass 1, ABC will be defined

equal to 27 on pass 2 of the assembly and will not generate an error for pass 2.

Although the pass

error listing may be incomplete,

does allow the user to detect errors at an early stage of

the assembly and to correct them without wasting time on pass 2 of the assembly process.

Although pass 1 errors

were generated, if the user wishes he may still proceed to pass 2 without correcting the errors and thereby
generate a complete error listing.

7-20

the assembly listing is to be punched on the high-speed punch, all error lines detected on pass 2 are typed

on the Teletype unit in addition to being punched as part of the complete listing on the high-speed punch.

The error table output is controlled by two characters typed during the query sequence which is described later.
If

N is typed, the separate error tables are not typed.

punch, typing E will cause pass 1

the assembly listing

be output on the high-speed

errors to be recorded there also.

Sample Output
Figure 7-2 is sample assembly output including the assembly listing and symbol table.

Several errors are Included

intentionally to illustrate the error codes in the assembly listing and symbol table.

/THE FOLLOW IMG PROGRAM SOLVES THE EQUATLJM
/S0LA=(LS1*PB'2*/PB3+S0LA>;=/LS2 )>i</PPB5

/
/

S0LA=5
LS1=415
LS2=16
PB2 = 7

PB3=10
PB5-12
LOG 200
SOLA^
TXF LSI
TXF PB2

5CHK^

SOLAF^

SOLAM^
EMD

TXM
JFF
TYF
TXM
JFM
TXM
JFF
SYF
SKP
SYM

Source

Program

P*B3
CK5
SOLA
LS2
SOLAF
PB5
SO LAM
SOLA

/TURM SOLA OFF.

SOLA

TURM SOLA OM.

*BIM--L
*LST--L
*SMB--L
*SRC--L

RT
I

LV
T

\r
Command String
? Con

J
0200
0202
0207
0213

2000
2410
2400
3400

ERR LINES-0004

SOLA,
5CHK,
SOLAM,

TXF
TXM
TXM
SYM

LSI

P*B3
PBS
SOLA

\pass

TURN SOLA OM.

MEM BRK-O^i^

UMDEFIMED SYMBOLS
CK5
ON
PBS
TURM

/Errors

-u
-u
-u
-u

Pass

Symbol Table

7-21

*PAS

PAGE

000

PAL-1^ VI

/THE FOLLOWING PR0 GRAM SOLVES THE EQUATION
/S0LA=(LS1*PB2*/P13;3+50LA*/LS2)+/PPB5
/
/

S0LA=5
04

('5

LSI =4 15

LS2=16

PB2 = 7

7766
0200

(^200
1

2 00
22 7

02n2

2 410

02
02

3
'J

24 1 6

5611

02
02

7
1

52 1 3

'12 1

3 2 00

Pass 2

PR5- 12
LOG 2 00
TXF
SOLA,
TXF
TXO
JVV
TYF
TXM
JFM
TXM
50 HK,

020b

02 12
02 13

P}33=10

0000

LUV

Listing

LSI
P^3 2

P*B3
GK5
SOLA
LS2
SOLAF
PI ^5

S JLAM
SYF SOLA
SKP
SYM SOLA
JFr'

SJLAF;,

3 44
3 40n

SO LAM,

/TURM SOLA OFF.
TURO SOLA OM.
>'

Error

VRR LIMES -0007

SYMBOL TABLE
CK5
LSI

LS2
OM
PB2
PB3
PBS
SOLAF
SO LAM
SOLA
TURM

Codes

MEM HRK-00 15
"\

-u
-0041

-00016
-u

Pass 2

-00007
-00010

Symbol Table

-u

assigned values are 5-digit numbers.)

021

0213
0200

(Addresses are 4-digit numbers;

-u

*PAS
(?''

6B (

Spurious characters are
.*!

typed while binary is punched.

*PAS
Pressing

7-22

CONTwill restart PAL-14,

CHAPTER 8
SIM-14

PDP-14 PROGRAM DEBUGGING AID

SIM-14 is the PDP-8 based simulator for the PDP-14 system.

Its

primary use is to assist the PDP-14 user in debug

ging programs which have been compiled by BOOL-14 or which have been assembled by

PAL-14.

may also

be used to compose programs directly by typing PDP-14 instructions under control of SIM-14.

MODES OF OPERATION
SIM-14 has two basic modes of operation (local and on-line), offering the user several approaches to locating
and correcting program bugs.

SIM-14 also protects the user from making mistakes which could damage valuable

machinery.

Local

Mode

Local

mode allows the user to check his program for errors off-line, entirely within the PDP-8 family computer.

All inputs and outputs are simulated by the

PDP-8 computer. The program may be checked without concern for

damage to equipment, since operations in local mode have no effect on the PDP-14 or the controlled
In fact,

it is

machinery.

unnecessary to have the machinery connected to the PDP-14, or even to have the PDP-14

connectec

to the PDP-8.

On-Line Mode
On-line mode is used to check that a program, which has been fully debugged in local mode, will
actual equipment when placed in a PDP-14 memory.

gram contained within the PDP-8 computer.
specifying the location

(or locations)

operate the

The PDP-14 is used in on-line mode to execute the pro-

The program may be executed in part or in total, with the user

where program execution may be stopped.

The user may also specify a

sequence of operations to be performed before program execution (and therefore control) is terminated.

8-1

RESTRICTIONS
if more than IK of
SIM-14 can be used to simulate PDP-14 programs of IK, 2K, 3K or 4K words. However,
least 8K of core memory,
PDP-14 program is to be simulated, SIM-14 must be loaded in a PDP-8 computer with at

CONVENTIONS
The following conventions are used to describe the dialogue between the user and SIM-14.

All characters typed by SIM-14 will be identified in this manual

by an underline.

Examples:

NOP
TXN
b.

Typed by SIM-14

Typed by user

The non-printing character RETURN will be noted in this manual by a curved down arrow.

No character appears on the teleprinter when this character is typed.
Example:

TXN

User concluded typing with

a carriage return

The non-printing character LINE FEED will be noted in this manual by a straight down
arrow
c

Example:

TXN

User concludes typing with a
line feed

PDP-14 INSTRUCTIONS RECOGNIZED BY SIM-14

SIM-14 local mode recognizes and simulates the PDP-14 instructions given in Table 8-1

Only these instruc-

tions are recognized or simulated; if the user attempts to execute any other instruction in local

mode, the error

message OPER (operation error) and the location of the instruction will be typed.

TXD, TYD and TRM are PDP-14 instructions used for monitoring (see Chapter 9)
during equation verification or truth table generation.

They are treated as NOP's

They are simulated and cause appropriate messages

during local mode simulated execution.

On-line mode of SIM-14 does not check for legal instructions; thus all Chapter 9 instructions will be executed
in this mode.

The SKE and SKZ instructions (octal codes 6000 through 6777) are exceptions which, because of

the internal organization of SIM-14, may not be executed in on-line mode.

(SIM-14 will change any such

instruction to set an output instruction with a program stop assigned at that location for on-line execution.)

8-2

Execufion in on-line mode of instructions which affect the PDP-14 output register (e.g.,

TXD, TYD and TRM)

have no effect upon SIM-14.

Table 8-1

PDP-14 Instructions Recognized by SIM-14
Symbolic Instruction

Octal Equivalent

Symbolic Instruction

Octal Equivalent

TYN

1400-1777

TYF

1000-1377

TXN

2400-2777

TXF

2000-2377

SYN

3400-3777

SYF

3000-3377

JMR

0354

JFN

5400-5777

SKP

0344

JFF

5000-5377

NOP

0000

TXD

7000-7377

CLR

3377

TYD

7400-7777

4224

NNNN
J

4645

NNNN
TRM

4226

NNNN

SIM-14 COMMAND DESCRIPTION
SIM-14 has many commands to control program debugging

Some commands are recognized only in local mode;

others ore recognized only in on-line mode; still others are recognized in both modes.

If the

user types a

command which Is not recognized in the present mode of operation, SIM-14 types the error message M? (mode
error)

The command which caused the error will be ignored and the user may either change modes or type a

new command.

(Commands which are not recognized by the truth table mode or the equation verification mode,

will also generate an

All

M? error message when used In the wrong mode.)

commands in SIM-14 are terminated by a carriage return. When the carriage return is typed, SIM-14 will

act upon the command.

Any spaces typed by the user are ignored.

There are three types of commands in SIM-14.
S ? (syntax error) will

be typed

If a

command is not typed in its proper form the error message

The forms of the three SIM-14 command types are:

One or two letters which stand alone
One or two letters followed by a single number.

One or two letters followed by two numbers separated by a minus sign (-).
number must be less than the second number.

8-3

The first

Any command which is of the lost form may also be typed in form b.
will

be covered in the following pages.

It is

Specific examples of these command forms

important that the reader understand that there are three forms

and that a command must be typed in the form expected by SlM-14.

Commands in this manual are presented as specific examples without giving the general form.
mands which have limits (e.g., form c above) may be typed in form b if only

Note that com-

one entity is affected by the

command
The user may substitute any PDP-14 program address, PDP-14 input or output program
for those given for illustration purposes in this manual

number, or other parametei

PDP-14 GENERAL COMMANDS

Once SIM-14 has been loaded into the PDP-8 computer and started (see Chapter 10 for
cedures), the user may type commands to SIM-14 and begin program

debugging

these operating pro-

SIM-14 is initially in local

mode when loaded, and it signals readiness to accept commands by typing its version

number (e.g., V2 is ver-

sion 2) and then a period at the left margin of the Teletype paper.

LM Command
If

SIM-14 is in on-line mode, or if the user is in doubt as to the current mode of

operation, local mode can be

entered by typing the command LM, followed by a carriage return.

^LM^
SIM-14 is now awaiting a local mode command.

OM Command
When the user has completely debugged his program in local mode and
ery to be controlled, he may enter on-line mode by typing the

wants to test the program with the machin

command OM, followed by a carriage return

_.OMj
SIM-14 Is now awaiting on on-line mode command.

On-line mode execution Is possible only when the PDP-14 has been completely
puts and outputs wired to the I and

O boxes of the PDP-14.

Installed, with the machine In-

The ROM for the PDP-14 Is not in place, however,

and the PDP-8 interface modules and cable must be installed.

If any

of these steps has not been taken, or if

enter on-line mode.
the PDP-14 is not running, SIM-14 will type NR?and will not

8-4

RUBOUT
If the

user types a command incorrectly or wishes to

strike the teletype

have SIM-14 disregard a command for any reason, he may

RUBOUT key, if he has not already typed a carriage return to terminate the command.

SIM-14 will record the RUBOUT as the character®.

RUBOUT
The user meant to type MB3 and therefore struck the RUBOUT key at
this point. SIM-14 ignored the command and typed the (o^, the
carriage return and period to signal readiness to accept a further
command. The user then typed MBS, followed by a carriage return.

.MB2@ )

TMB3^

Note that the RUBOUT key can be used only to ignore commands which have not been acted upon by SIM-14
(viz. , those

which have not yet been followed by a carriage return)

LOCAL MODE PROGRAM DEBUGGING
Figure 8-1 illustrates the suggested sequence for using the local

mode features to debug programs.

It is

strongly

suggested that the user pass through all stages of the debugging procedure to insure a methodical approach to

program testing

MB Command
The user should specify the maximum size of the PDP-14 program to be debugged so that SIM-14 may check for
jumps which transfer control out of the simulated program, as well as attempt to store instructions in nonexistent

memory.

The command used in local mode of SIM-14 to specify program size is MB (memory banks) followed by

a 1, 2, 3, or 4, to specify the size of the PDP-14 program (IK,

2K, 3K or 4K)

.MB3^ SIM-14 will allow up to a maximum 3K program (i.e., addresses
through 5777)

Unless otherwise specified,

SIM-14 will assume four memory banks if an 8K PDP-8 is used for simulation, and

one memory bank if a 4K PDP-8 is used.

Furthermore, if SIM-14 is loaded in a PDP-8 computer with 4K of core

memory, only the MB! command is legal (viz,, only IK PDP-8 programs may be simulated).
The memory addresses which may be used in PDP-14 programs of any number of memory banks are summarized
in the following

Memory Addresses

of Memory Banks

0000-1777

0000 - 3777
0000 - S177
0000 - 7777

2
3

8-5

Load the program into simulated PDP-14 memory

I
List

the program with SIM-14. Yes

Any errors found?
Correct the error within SIM-14.

When

the correction has been checked out,

Verify each equation with
varying input. Any errors

the bug should be corrected in the program source to BOOL-14 or PAL-14.
Do not make changes to PDP-14 programs

Yes

gram as it was input to BOOL-14 or
PAL-14.

found ?

with SIM-14 without correcting the pro-

Generate a truth table for
each equation. Any errors

Yes

found ?

Execute in local mode with
varying input. Any errors
found ?

Yes

I
Begin

OM Debugging

Figure 8-1

Local

Mode Debugging Procedure

i-6

PROGRAM MANIPULATION AND MODIFICATION COMMANDS
The following set of SIM-14 commands enables the user to read paper tape programs, make changes to these
programs, list these changed programs, and punch new paper-tape records of the changed program.

These

commands are most often used in local mode, but may also be used in on-line mode.
Since changes may readily be made to PDP-14 programs with SIM-14, the user must keep an accurate record of
the current state of his program.

This may be in the form of SIM-14 generated listings; however,

it is

strongly

recommended that the user maintain a correct and current version of his program in its original "source" form
(i

.e., BOOL-14 or PAL-14 input).

will

If program

changes of large magnitude are needed at a later date, the user

want a correct and debugged version of his original program in the format of the BOOL-14 compiler, or the

PAL-14 assembler, so that he may make changes with the PDP-8 Editor (see Chapter 10)

A correct and current

program listing and paper tape record of each PDP-14 program in BOOL-14 or PAL-14 source form is essential if
changes are to be made in the future.

R Command

The user types R followed by a carriage return to direct SIM-14 to read a paper tape from the low-speed reader
unit of the Teletype console.

The paper tape must be in binary form as output from the BOOL-14 compiler, the

PAL-14 assembler, or SIM-14 itself.
The loading procedure for paper tapes with the low-speed reader in SIM-14 is:
a

Type R fol lowed by RETURN key

Place paper tape in the low-speed reader of the Teletype unit.
the tape must be positioned over the reading head.
c .

Switch the reader to START

The tape is read by SIM-14.

When the tape stops, switch the reader to STOP

Remove the paper tape from the reader.

The leader section of

Press the

^R ^
j_

CONT switch on the PDP-8 computer console.
The user types R followed by a carriage return, then places a binary
program tape in the low-speed reader, and switches the reader to
START. After the tape is read, the user switches the reader to OFF,
removes the tape, and presses the PDP-8 console switch marked CONT.

SIM-14 then types the period (.) to signal readiness to accept further
commands.

8-7

RH Command
The RH command is used to read paper tapes with the high-speed reader, if the PDP-8

computer used for simula-

The binary paper tope (output from SIM-14, BOOL-14, or PAL-14) is first

tion is equipped with this device.

SIM-14 will read the paper tape

placed in the reader unit; the user then types RH followed by a carriage return.

record Into memory, and type the period at the left margin to signal readiness for a

new command.

(The user

does not need to press the CONT switch of the PDP-8 console as in the R command .)

After placing the paper tape in the high-speed reader, the user types
RH followed by a carriage return. The tape is read and SIM-14 types

.RH ^

a period when it is ready for a new command

The leader section of the paper tape must be positioned over the reader head before the RH command is

typed.

When the R or RH command is used to read a SIM-14 generated paper tape for a PDP-14 program requiring more
than one memory bank, the command must be retyped for each successive memory bank after the first

whole tape is read.

(For a full

until the

4K program punched by SIM-14, the R or RH command must be typed four times.)

When either the R or the RH command reads a paper tape for a program which requires more PDP-14 memory than
was reserved by the user with the MB command, SIM-14 types the error message MOV (memory overflow)
user must either reorganize his program to

fit

The

within the allotted number of memory banks or he must add more

memory banks to the simulated memory with the MB command.
SIM-14 types the error message RDER (reader error) when a checksum error occurs while reading a paper tape
with the R or the RH

reread.

command.

This error message Indicates that the tape was Incorrectly read and should be

the same tape generates this error consistently, the paper tape

bad and should be repunched from

BOOL-14 or PAL-14.

Open Location Commands
Open g Location Symbolically - A colon (:) typed following a legal PDP-14 address will cause the content of
that location to be typed symbolically (i.e., with its instruction mnemonic).

of that location by typing a legal
line with a carriage return

If he

The user may then alter the content

PDP-14 instruction next to the content typed by SIM-14, and terminating the
does not wish to change the content of the location, he simply types a carriage

return after the instruction typed by SIM-14.

.10:NOP TXN 7 J

The user changed the content of location 10 from NOP to
TXN 7; modification was terminated by a carriage return

and SIM-14 awaits a new command.

Alternatively, the user may terminate a line which is typed by SIM-14 (and which he may or may not have
modified) by a line feed.

ed for modification.

Lines so terminated will cause the next sequential location to be automatically open-

If a line

also be opened symbolically.

which was opened symbolically is closed with a line feed, the next location will
This feature may be used to scan a series of PDP-14 instructions by continually

typing line feed.

TXN 007 \
nmi MOP TyMin ^l

The user opened location 10 but did not modify the content,
Termination by a line feed caused the next sequential location to be opened for modification. The user terminated
this second line with a carriage return and SIM-14 respond-

ed by typing a period to request a new command.

10:

Each line is ter-

The following example shows the way in which a PDP-14 program could be completely typed.
minated by the line feed key to automatically open the next sequential location

If a

line is terminated by a

carriage return, the line feed may be typed at any time to open the next location, as illustrated in the example

below.

.60: MOP TXM2

JFN65
TXM3
TYF10
JFN67
0065:NOP SYN10
0066:NOP SKP
0067:NOP SYF10

0061 :!NJOP
0062 :!NrOP
0063: NOP
0064: MOP

..r

The user typed a carnage return after modifying location oU;
SIM-14 responded with a period. Since the user really
wanted to enter a group of instructions, he typed a line feed
and the next location (61) was opened. The user continued
f.^ j-y-g program instructions, terminating each line with a
,

linefeed.

Open a Location Numerically - A slash (/) typed following a legal PDP-14 address will cause the content of
that location to be typed numerically.

The user may alter the content, close the location unaltered, or close

the location (altered or unaltered) and open the next sequential location.

This function

may also be used with

the colon (:) previously described to open locations in both symbolic and numeric form.

.65/3410
0066/4224 \
0067/0100 j

The user opens three sequential locations numerically by
following each but the last line with a line feed. No
modifications were performed although the user does have
this option

The following example illustrates both the symbolical and numerical opening of registers.

The same register

may be opened in both forms on the same line. No modifications were performed although they could have beer
made at any time.

8-9

07)66/4224

The user opened location 63 symbolically, after it
had been opened numerically, by simply typing the
colon (:). By following the line with a line feed,
the next location is opened in the same form. Thus^
locations 64 and 65 are opened symbolically. At
location 65, the user reverts to opening locations
numerically. Line 71 is terminated by a carriage

0'^67/0 100

return

•60/2402
0061 /5465
00 62/240 3
0063/1010 :TYF 010
0064:JFN 070
0065: SYN
10 /3410
0'r70/3010
0071 /4224

LS Command

Once a program is loaded into memory, the LS command is used to list the program symbolically. The program
is

listed with instruction

instructions (viz. , JMS,

mnemonics for all locations within the specified limits.

The second part of two word

JMP and TRM) are typed numerically. Any location within the limits which contains

number other than those given in Table 8-1 is also typed numerically. The user specifies the limits of the

listing by following the LS with

two numbers.

For illustration purposes, the listing is shown in two columns.

.L.S2 n-23(^

20
20
20 2
20 3
20 4

•

')',VV:^

20 6
20 7
2. 1

^121

TXN
JFF
TXN
TXN
JFF
SYN
SKP
SYF

The user requests SIM- 14 to list the locations

00
00 2
20 7

altered the content of

21 5

021 2 NOP
No:^

220 :JMS
:

user has not

The user lists the complete set of instructions
by not altering the initial values of M and
(namely M=0000 and W=NOP)

(i223

021 b JiMS
2 6 100
021 7 •JFF 227
22 1

If the

M and W, all locations

within these limits are typed.

0222 JFF

NOP

21 3
')21 4

from 200 to 230 inclusive.

,JFF
NQi^

'')

20 7

1 ^ r;

0224 JFF
022 5 SYN
022 6 SKP
022 7 SYF
0230 JFF
:

2;. 7

227
00 5

005
234

The user may modify the function of this command to list only certain program instructions, or he may list all
program instructions within the limits by not exercising the option.

changing the contents of two special registers,

The user controls the locations listed by

W (word) and M (mask).

When these locations are modified, the LS command will type only certain locations within the limits specified,
thereby searching for particular instructions.

The following examples illustrate the use and power of this feature,

8-10

He changes W to:

He changes M to:

The user wishes to list:

all

SYF or SYN instructions

7000

SYF

or 3000

all

SYF instructions

7400

SYF

or 3000

all

SYN instructions

7400

SYN

or 3400

all

JMP instructions

1177

JMP

or 4224

all

JMS instructions

1111

JMS

or 4645

all

JMR instructions

1177

JMR

or 0354

all

JFF or JFN instructions

7000

JFF

or 5000

all

JFF instructions

7400

JFF

or 5000

all

JFN instructions

7400

JFN

or 5400

all

TXN or TXF instructions

7000

TXF

or 2000

all

TXF instructions

7400

TXF

or 2000

all

TXN instructions

7400

TXN

or 2400

any particular instruction

11T7

the instruction

locations within limits

0000

NOP

0377

the operand

all

a particular operand

The user alters the locations M and

or 0000

W in the same way that he alters PDP-14 program locations. He uses the

colon or slash to open the location and then changes the content and closes the location with a carriage return

.M/000 7000 J

The user changes the mask to 7000,

.W:NOP SYF J

The user changes the word to SYF

The following examples list different instructions within the same limits by changing the M and

.M/,7)r7)0r^

7f;)f7!i/5

.U:NOP SYF
.LS2 10-267
r:^;^-4 5:SYN
020 7: SYF 00
022 5: SYN 00 5
PI

The user changes

M and W to

list all

set output

instructions within the limits of the command.

0227:SYF 005
0244: SYN 00 6

0246:SYF 006
0264:SYN 007
0266: SYF 00 7

8-11

W locations

.M/7000 7 40
.W:SYF 000 SYN

The user changes M and

W so that only the SYN

instructions are listed

.LSg00-267
0205:SYN 001
0225:SYN 005
0244:SYN 006
0264:SYN 007

.M/7400 7777
• WrSYN
000 JMP
.LS200-267
0267: JMP

-M/7777
W: JM^ JFFP6 4
,13200 -26 7

,.>„
The user changes la and ^A, to i.
hst only the JMP
^-i

instructions within the limits of the command.

^^®'" <="'^"9®s

r....w,
M and W to have

the content of

SIM-14 type all the JFF 264 instructions within
There are no such instructions, however, and SIM- 14 types the period to request a
new command
the limits.

.M/77 77
.W:JFF 264 JFN264

.LS200-26 7
0256:JFN 264

The user changes the content of

W to

list

the

JFN 264 instructions and SIM-14 types the
single such instruction within the specified
\;^-^^^

LN Command
If the

user wishes to

list

a section of his PDP-14 program in numeric form, he uses the LN command.

tions within the specified limits will be typed.

The LN command is subject to the M and

W locations described

in the LS command.

.LN200-2v3 5

0200/2411
020 /520 7
1

0202/2401
020 3/2402
020 4/520 7
\
^^^^'^^^^
020 6/0 3 44

207/300
0210/521
021 1/0000
021 2/0000
0213/0000
0214/0000
021 5/4645
021 6/1000
021 7/5227

^^® "^®'' requests SIM-14 to list the locations
from 200 to 235, inclusive. All locations will
^^ typed (in numeric form) if the user has not
altered the content of
and W. Otherwise,
each instruction within the limits will be taken
from memory, masked with the content of
and
then compared with W. The original content of
all matches are then typed numerically on the

Teletype.

8-12

All loca-

0220/4645
0221 /1012

0222/5227
0223/1 401

0224/5227
0225/34':i5

0226/0344
0227/300 5
0230/5234
0231 /0000
0232/000''^

0233/0000
0234/4645
0235/1000

.M/0000 7 77 7
.W:NOP JMS
.LN200-235
021 5/4645

The user requests SIM-14 to type numerically all

JMS instructions within the limits.

0220/4645
0234/4645

.M/7777
[MS

.'•]'
..v.uiio
•

The user requests SIM-14 to type all SKP instructions
SK!^
o\.

II
numerically.
•

LN20 0-2:V)

02'^ 6/0 3 44

i)226/0344

The LN command is useful to obtain the necessary octal values needed to modify a wired ROM braid,

P Command

The user may generate a paper tape record of his PDP-14 program on the low-speed punch by using the following

SIM-14 procedure.

Type P followed by the limits of the program section to be punched.

Turn the paper-tape punch unit of the teletype ON.

Press the

After the tape is punched, turn the punch unit OFF and remove the punched tape.

Press the

CO NT switch of the PDP-8 computer console.
PDP-8 CO NT switch

8-13

The user requests SIM- 14 to punch a paper tape record
through 200,
of the program instructions in locations
(by followpunched
been
has
tape
inclusive. When the

.PO-200 }

ing the procedure above),

SIM-14 types the period (

to request a new command

PH Command
To punch a paper tape record on the high-speed punch, type PH (punch high) followed by the limits of the
program section to be recorded.

SIM-14 punches the paper tape without further operation by the user (viz. , he

need not follow the procedure above).

.PH300-1500 J

The user types PH followed by the limits to be punched.
The command is terminated by a carriage return, SIM-14
punches the tape, and types a period ( ) when it is ready
.

for a

new command

The high-speed punch button must be activated to punch the paper tape.

may be shut off after the tape is

punched
The tape will be punched by the P or PH command in IK segments.

The leader for the first IK segment (addresses

0000 to 1777) will have a single row of punched holes on the right edge of the paper tape; the second IK (20003777) will have two punched rows; the third IK (4000-5777) will have three punched rows; and the leader for
the fourth IK (6000-7777) will have four punched rows.

VERIFICATION OF A PAPER TAPE PROGRAM RECORD

Once the user has punched a paper tope record of his program, he may use the following commands to check
that no punching errors have occurred.

Verify the paper tape in the low-speed reader by
comparing it with PDP-14 simulated memory and
noting any discrepancies.

.VH ^

Verify the paper tape in the high-speed reader by
comparing it with PDP-14 simulated memory and
noting any discrepancies.

The first command above uses the low-speed reader unit of the teletype console. The following procedure
should be followed.

a .

Type the command V, followed by a carriage return

Place the paper tape in the low-speed reader,

Switch the low-speed reader to START.

8-14

When the tape stops reading, switch the low-speed reader to FREE, and remove

the paper tape.
e .

Press the

PDP-8 CONT switch

When using the VH command it is not necessary to follow the above procedure. Simply place the paper tape in
the reader and then type VH, followed by a carriage return.

The tape will be read and return to SIM-14 will

occur without pressing the CONT switch.

The V or VH command must be used for each IK segment in the paper tape to be verified.
The tape verify commands compare the tape being read with the simulated memory within SIM-14.
of the tape does not represent the content of memory ,

If the

content

SIM-14 types the following message:

1234 3774 2774

where the first number typed is the address of the discrepancy, the second number is the numeric representation
of the content of the location

the simulated memory, and the last number is the numeric representation of the

content of the location on the paper tape.

Thus, the above message means simulated memory location 1234

contains the PDP-14 instruction 3774, while the tape being verified has contents 2774 for location 1234.

A new

paper tape should be punched and the old tape should be destroyed whenever there is a tape verification error.

If the

error message

RDER (read error) is typed, the paper tape has a bad checksum punched at its end, and a

new tape should' be punched.
Before sending a program paper tape to DEC to have an
certain that a punching error did not occur.

It is

ROM generated, the user must verify the tape to be

also good practice to verify the paper tapes generated during

the debugging stage to be certain that they are accurate.

Punching errors which cause verify errors do not occur

often, but such errors could change the user's program with dangerous results.

EQUATION VERIFICATION COMMANDS (LOCAL MODE)
Once the PDP-14 instructions for solving a particular output have been stored in the SIM-14 memory, the user
begins debugging the program, using the equation verification feature.

The user supplies the identity of the

variables of the equation, their state (ON or OFF), and the starting address of the equation to be verified.

SIM-14 responds by typing the value of the output, based on the supplied inputs.

SIM-14 also notes any supplied

variables which were not actually part of the solved equation for the output (listed, not encountered), and any

unsupplied variables which were part of the solved equation (encountered, not listed).

8-15

The commands for verifying an equation are:
Verify the equation for output 20. SIM-14 will now await user specification of the variables used in the equation.

VY20

User specifies that inputs 5 through 7 are in the equation, and that

XN5-7

their state

ON.

User specifies that inputs 10 through 13 are in the equation, and that

XF 10-13

their state is OFF

YN 5-6

User specifies that outputs 5 and 6 are in the equation, and that their
state

YF 11

User specifies that output 11

in the

equation and that its state is

OFF.
User instructs SIM-14 to begin execution of the program at location
This should be the starting address for the equation to be verified.

S200

200.

All of the assignment commands above
(e .g . ,

(XN, XF, YN, or YF) can be typed in either the multiple variable form

XN 5-7) or the single variable form (e .g

YF 11).

The messages that may be typed by SIM-14 are:

Y020

ON by the user-supplied variables.

Output 20 is turned OFF by the user-supplied variables.

Y020
X005

Output 20 is turned

Input 5 was encountered by SIM-14 when solving the equation, but it

was not listed by the user.

YOl

Output

]

was listed by the user but it was not encountered by SIM-14

when solving the equation.

YlOO

1023 ?

A set output command for YlOO was encountered at location 1023 when
SIM-14 was verifying a different output.

Indicates that the user supplied

the wrong starting address.

A maximum of 63 variables may be included in one verification.
message TOV (table overflow)

If this

number is exceeded, SIM-14 types the

This limit should be of little consequence because few user programs contain

equations which have as many as 63 variables.

Continue Verification

The user may repeatedly verify the same equation with varying states of variables by using the CV (continue
verification) command.

YN or YF commands.

After one verification, the user may change the states of variables with the XN, XF,

The last entered state of a variable is the state used by SIM-14 for verification; thus,

the user may change variable states at will
is

Those variables which are not re-entered after the CV command

typed, retain their previous state.

8-16

If an E error (a variable encountered but not listed)

occurred on the previous verification, the user may enter

new variables after the CV command has been typed. When a bug is encountered in a program which necessitates changing the PDP-14 instructions, the user should restart verification with the

VY command.

(The CV

command should not be used to continue verification after a change is made to the program being debugged.)
To illustrate the use of the program verification feature, consider the following equation to be solved by the

PDP-14.

Y1 = (X1 * X2 +X3)*/X4* X5
As an example, the user generates the following PDP-14 instructions to solve the equation (errors are included

by intent).

.LS35P)-364

0350:TXF 01
0351 :TXF 002
0352:JFF 355
0353 :TXN 00 3
0354:JFN 362
0355:TXN 004
0356:TXN 005
0357:JFN 362
0360:SYN 001
0361 :SKP

0362:SYN 002
0363: JMP

0364:0400

From analyzing the equation, the user knows that there are two sets of conditions which will cause the output
to be set

ON; namely, when
XI is ON and
X2 is ON and
X4 is OFF and

X3 is ON and
X4 is OFF and
X5 is ON

X5 is ON
The user then checks the program with the equation verification feature to determine whether the program will
correctly solve for the output with varying input.

•VYl
• XNl -3

.XF4
.XN5
.S350

The user begins the verification by typing
j.|^e

and the starting address.
initial input
^

8-17

Y002 0362 ?
.362:SYN 002 SYNl

SIM-14 encounfered a SYN2 instruction at location
The user changes the
362 when verifying output 1
.

.VYl
.XNl -3

instruction to a

SYNl

and restarts verification.

.XF4
.XN5
.S3 50

Y00
X00

SIM-14 reports that with the supplied input, Yl
is now ON; however, XI was listed by the user
1

X0 1 1

.350: TXF
VYl

TXFl

•

.XNl

TXFl. He then restarts verification.

.XN2-3
.XF4
.XN5
.S3 5
Y00
.cv
.XNA
.S3 5^
Y00

To delete any
variables, the verification must be restarted.)
it

was previously encountered.

SIM-14 reports that the output is ON with the
given input. The user continues verification,
The user finds
changing the value of X4 to
when it should be OFF. He
that Yl remains
decides that there must be an extra SYNl instruction in the program and changes the mask (M) and
word (W) to type all such instructions. The SYNl
instruction at location 362 should be an SYFl

)

(He does

not continue the verification because variable 11
was entered in the input table by SIM-14 when

and not encountered in the program. XI 1 was
encountered in the program, but was not listed
by the user. The user thus discovers that the
TXFll instruction at location 350 should be a

777
.M/0000
.W:NOP SYNl
.LS3 50-36 5
(13 60 :SYN
M362 :SYN 00
SYFl
.3 62 :SYN
7

The user then restarts verification. (Assigning
input 4 ON and then OFF is the same as assigning it OFF since only the last value is used by

.VYl
.XN3-:j

SIM-14.)

.XFA
.S3::5'l

X00

X002

The user did not list inputs 1 or 2 and the output
The program
is OFF with the supplied input.
still contains at least one bug since the output
should have been ON when inputs 3 and 5 are
and 4 is OFF.

E
E

The user decides that he should have a listing of
his program with its changes at this point. Since
and W, he must
he has changed the values of
now return them to the original values of 0000
(or NOP). The listing continues below.

M : 7777

NOP
.W:SYN 00
.LS350-362
3 50: TXF 001
0351 :TXF 00 2
352 :JFF 35 5
0353 :TXN 00 3
0354 :JFN 362
0355 :TXN 00 4
0356:TXN 005
1

3 57:,JFN 362
1360 :SYN 00
1

"1361 :SKP
fi3

8-18

62:SYF 00

.354: JFN 362 JFF362
.VYl
-2
• XFl

After scanning the program, the user sees the bug

which caused the output to be set OFF instead
during the last verify case. He changes
the JFN to a JFF at location 354, since the outputs should be OFF only if the flop is OFF (not
ON). He then restarts the verification and finds
that the output remains OFF. Confused at this
point, he tries to solve the equation with the
original set of input, and discovers that again
of

.XN3
.XF4
.XN5
.S35f^

Y001
.cv
.XNl - 2

.XF3
.XF4
.XN5

the output is OFF.

.53 5^^

Y00

.356:TXN 005 TXF5

Examining the program again, the user notices

.VYl
.XNl -2

that the instruction in location 356 should be

TXF5 and not TXN5, since the JFN instruction
jumps to the set output OFF. With this final bug

.XF3
.XF^
.XN5

removed, the program solves all input supplied

.S3 50

to it.

Y00

.CV
.XFl -2

.XN3
.S3 50

Y001
.CV
.XFA

The user continues to supply varying input to
test the program until he is satisfied that all
bugs are removed

.S3 50

Y00
• CV
.XN4
1

.S3 50

Y00

.CV

.XF4
.XN5
.S3 50

Y00
.CV
.XF5
1

.S3 50

Y00

8-19

The user should realize that most of the bugs detected in the preceding example could have been removed by
carefully reading the program.

The user can save valuable debugging time by carefully proofing his program

before entering the debugging stage.

The important point to realize, however, is that SIM-14 allows the user

to completely check and find bugs in his program using the equation verification feature without endangering

the valuable equipment to be controlled.

Equation Verification for Subroutines (Z -Functions)

When the user program contains subroutines, the equation verification process of SIM-14 may also be used to
debug the program

Repetitive equations (subroutines which actually set an output

PDP-14 output verification.

(This type of subroutine

ON or OFF) may be debugged as a regular

called an R-function in BOOL-14.)

Repetitive variables or Z-functions (subroutines which do not set an output) may be debugged with the equation
verification feature of SIM-14 using the VZ command, in the same way that regular outputs are verified with

the VY command.

The VZ command is typed, followed by the input states of the variables (using the XN, XF,

YN or YF commands)

The starting address of the subroutine is specified with the S command and SIM-14 types

out the resultant state of the subroutine as recorded in the TEST flag when the JMR instruction is executed.
subroutine (Z function) is specified by its starting address.

The

Thus, to verify the subroutine starting at location

1000, the user types VZIOOO.

It is

important to remember that the numbers used to identify R- and Z-functions in SIM-14 are not the same as

used in BOOL-14.

R28:

BOOL-14, for example, an R-function would be written as:

Y15=X12 +Y23*/X13

To verify this function in SIM-14, simply verif/ output Y15 (i .e

VY15).

BOOL-14 a Z-function would be written as:

Z19=X123*(Y5 +X2*X3)
When the Z-function is compiled by BOOL-14 it is assigned to memory locations. Assuming that the first
address of the instruction sequence generated by BOOL-14 is 35, the above Z-functlon would be verified

with the command VZ35 (not VZ19).

Suppose the user has a subroutine to solve the repetitive variable (Z-function)

Z1000=X4*X12* (X5 +Y1)

8-20

The subroufine is listed with the LS command below,

LSI' U-V'l- 1'^ 10

•

TXF
TXF
\WA2. JFN
TXN
1004 TYN
1005 JFF

10^

f-1 f;^

00 P
10

00 5
00
1

010

100 6 ;TXF
100 7 ;TXN

10
10

1010 JMR
;

.VZ1000
.XN4-5

The user begins verificotion specifying states for the
XI
X12, X5 and Yl)

inputs to the equation (X4,

.YFl
is

.XN12

used as a dummy variable and is not listed.

Z1000
X012 L
X002 E
X0

SIM-14 computes the state of ZIOOO and notes that

.1 00 1

:TXF
.VZ1000

TXFr:?

variable used to set the test flop.

.XN/i-5
•

'irip

input 12 was listed, not encountered, and input 2
was encountered, not listed. The program was in
error and the instruction is changed. The X010 E
error was ignored since input 10 is the dummy

YFl

.XNl 9,
.

'A ")
1

.\/Z1000
.XiM4

.XF5
.YNl

.XN12
.S1000
Z1000
X0 1

Continued verifications indicate that the subroutine
The encountered XI error
is now fully debugged.
continues to be typed, but is ignored since it does
not indicate an error in the program.

.VZ1000
.XF4-5
.XNl 2
.YNl
SI 000
Z1000
•

X0 10 E
.\/Z1000

.XN4-5
.YNl

.XF12
.S1000
Z1000
X0 10

8-21

The continue verification command (CV) can be used to verify a subroutine in

the same way that it is used to

verify an output

Verifying on Equation which Contains Subroutines

may be verified in two
The user program which contains subroutines (Z -functions) as elements of an equation
ways.
all

The user may arbitrarily assign the result of the subroutine

the variables which determine the state of the subroutine

SIM-14; It is arbitrarily considered ON

(or

ON or OFF, or he may enter the states of

In the first case, the subroutine

OFF) to determine the verification result.

not solved by

In the second case, the

subroutine will be solved with the user supplied input to determine the verification result.

The commands used to include subroutines In an equation verification are:

A subroutine (Z -function) which begins at location 1400 is part of the

Z1400

equation being verified. (SIM-14 types any variables in the subroutine
which have not been previously listed by the user. All variables listed
by this command are considered OFF unless they are later assigned

by either the XN, or the YN Instruction.)

ZN1450

A subroutine (Z -function) which begins at location 1450 is part of the
equation being verified and is considered ON. (The actual subroutine
Is not solved; the result of the subroutine Is arbitrarily considered

for equation verification purposes.)

ZF1500

A subroutine (Z-functlon) which begins at location 1500 is part of the
equation being verified and Is considered OFF. (The actual subroutine
is not solved; the result of the subroutine is arbitrarily considered OFF
for equation verification purposes.)

The following debugging example corrects the PDP-14 program to solve the equation:

Y6=Z1012 + (/Yl *Z1000)
where the subroutines are defined as:

ZIOOO =X4*X12*(X5 +Y1)
Z1012 =X15*(X3+X4)
The user types the program and the subroutines with the LS command (shown In two columns below)

8-22

1002::JFN
1003::TXN
1004::TYN
1005: JFF
1006::TXF
1007::TXN
1010: JMR

.LS254-P70
0254: JMS
0255: 1012
0256:JFN 264
0257:TYN 00
0260:JFF 266
0261 JMS
0262: 1000
0263:JFF 266
026 4: SYN 00 7

001

010
010
010

.LS1012-11021
1012;:TXN 01 5
101 3; JFF 021
1014;:TXN 003
101 5;:TXN 004
1016;:JFF 021
101 7;:TXF 010
1020::TXN 010
1021 JMR
:

0265:SKP
0266:SYF 007
0267: JMP
0270 :0000
LSI 00^-1 -10 10

•

010
005

1000:TXF 004

1001 :TXF 01

.VY6
.ZN10 12

arbitrary values to the subroutines.

.ZF1000

ZN1012 tells SIM-14 that the equation being veri-

At the first stage of debugging, the user assigns
The command

.YNl

fied includes a subroutine beginning at location

.S254
Y00 7

.264: SYN 00 7 SYN6

1012 which should be considered
when determining the state of output 6. SIM-14 responds by

0265:SKP

saying that output 7 was discovered at location

2 64

026 6: SYF 00 7 SYF6

264.

The user finds that the program should be

setting output 6 not 7 and therefore changes it.

.VY6

Since the program was changed, the user restarts

.ZN1 12
.ZF100'i
.YFl

the verification.

.S254
Y00 6

by verification

.cv
.ZF10 12

.ZN1000
.S254
Y00 6
.257:TYN 00
.VY6
.ZN1000
•ZFI
•

Y6 is ON when Z1012 is ON

The user continues verification and finds that
the output is OFF when Z 1000 is ON, and Yl
is OFF (it should be ON)
Examination of the
program shows that output 1 is tested for
when it should be tested for OFF. The program
is changed and the user restarts verification.
.

TYFl

YFl

.S254

8-23

Y^^^

The output is now ON as it should be.
Continued verification indicates that all
bugs have been removed.

CO 5 4

Y006

.CV
.YFl
.ZF 10(^^-1

.S254
Y00 6

.ZN10 2

The user forgot to type the CV command before

he supplied input to the verification. Since
SIM-14 does not recognize the ZN command

•7M1M

,3254
Y00 6

outside of the verification mode, a mode error
(M ?) was typed The user then supplied the

necessary CV and proceeded with the verification

Note that assigning arbitrary values to the subroutines could cause erroneous solutions for Y6.
arbitrarily assign ZIOOO

ON, representing X4 ON, X12 ON, X5 OFF, and Y1 ON.

The user could

The user could now verif>

ON Notice
required to be ON and OFF
an impossible state, since Yl
misleading. The state assigned
that this result
to have X4 ON, X12 ON, X5 ON
OFF, the only way Y6 may be ON
at the same time. Thus, if Z1012

Y6by assigning Yl OFF and Z1012 OFF.

Using these assignments SIM-14 concludes that Y6 is
is

and Yl OFF.

.V/Y6

.Z100'^
'^'^^'^

the program by allowing

Z1
1

types all variables needed to solve the subroutine,
(The user may
and enters them in the OFF state
re-enter them with an XN command if he wants
Only those variables
them to be considered
.)
which have not been listed previously for the veri.

^"^^^
•"^^^
*

cation, are listed when the user enters a subroutine

•XNl 5

,3254

in the verification.

,,,

Y006
•

•Xf"l ^
•^'^^'^^

Y006

The user types

Z followed by the address of the subroutine. SIM-14

X0 10
X0

SIM-14 to solve the sub-

routine with user supplied input.

!^^

Yp,0,
.

After removing program bugs by arbitrarily assigning states to subroutines, the user begins to debug

.r.

The user begins verification and SIM-14 replies that
when computed with the supplied
the output is

input.

8-24

The user continues verification with varying

•YFl
. XN/i-5

input until he is convinced that the program

•

working properly.

Verification of the out-

put continues below.
Y'^^16

.CV
YNl
•

.S254
•

.YFl

.XF5
.S254
Y00 6

.XN3
.S254
Y00 6

•CV
•XN5

.S854
Y0^6

.CV
.XF3
1

.X[\)4

•CV

.325 A
Y0 6

.XF4
.XNl 5

TRUTH TABLE GENERATION COMMANDS (LOCAL MODE)

Once the user has verified an equation of his program with the preceding commands, he may generate a truth
table for all possible values of input as a permanent record of the equation.
state of an output for all combinations of variable states.

SIM-14 will record the resultant

SIM-14 types an array of Os and Is to indicate the

OFF or ON state, respectively, of an input or output. The maximum number of variables in the truth table is
63.

The user typed commands are:

TA5

Generate the truth table for output 5 and print all cases;
and OFF output results.

TN6

Generate the truth table for output 6 and print only the

TF20

Generate the truth table for output 20 and print only the OFF cases.

X5-11

.e . , both

ON cases.

Inputs 5 through 11 are variables of the equation whose truth table is to

be generated.

Y6-7
S230

Outputs 6 and 7 are variables of the equation whose truth table is to be
generated.
Start execution of the PDP-14 program at location 230.

(Used in truth

table generation to specify the starting location of the equation whose
truth table

to be generated.)

8-25

Generating a Truth Table without Subroutines

The following truth tables are generated from the PDP-14 program instructions listed below by an LS command.
There is no command in SIM-14 which will enable the user to type the truth table of a subroutine which does not
set an output itself (Z-function) .

The user may, however, generate the truth table for the equation which

contains the subroutine and thus check out the subroutine itself.

The generation of truth tables containing sub-

routines is described in the next section.

The program for which the following truth tables are generated is:

.LS6n(^-61 3

TXN
TXF
M6f^2 TXN
60 3 JFF
n6f^4 TXN
<^c,<^b TYN

<^f,(^i^

n6H

023
01 7

210

32
00 A
'160 6 •TYF
57
^60 7 JFN 2 2
6 <^ :SYN 073
'1611 •SKP
73
612 •SYF
6 3 JFF 220
1

SIM-14 types a heading for the truth table which associates each variable with a letter in a list, and then types
the letters at the head of the truth table columns

The first column of the truth table contains the values for the

variable listed beside the letter A; the second column corresponds to the variable which is next to B; etc.
variables are listed in the order in which they were typed by the user.
in the form

The

Thus, the user may arrange his truth table

most meaningful to him by typing the variables In a specific order.

the user begins the generation of a truth table and later wants to prematurely terminate the table being gener-

ON This switch may be used to
ON and then OFF. SIM-14 will
prematurely terminate any typing being done by SIM-14. The user must set

ated, he may do so by setting switch 5 of the PDP-8 console switch register

then type a period, and await a new command.

the user types C (continue), the remaining part of the inter-

rupted truth table will be typed.

/rA73
.X5'1

.X2 3

The user requests that all values of the truth table
for output 73 be typed. He then supplies the
variables of the equation. The truth table will
be typed in the order that the variables are
supplied. The first column of the truth table
be the values of the first supplied variable.

.XI 7

will

.X32

When the user has specified the starting address

.Y4

of the equation to be solved,

.Y57

.S600

SIM-14 types out

the heading and the lines of the truth table.

For

illustration purposes, the truth table has been

shown in three columns; it is actually typed in
one long column on the Teletype.

8-26

A X'-lbiA
R X0)23
C X?7)l 7
D X<')32
17

Y'^^A

Y0 5 7

010 01=1

ABCDEF

<^c]f!)iy\i?]r/i

'A(7iiA0]^

= 1

lAr^P)r]

'^10 1 10 = 1
Ol'^l 1 1 =1

^V^'ir^l

.'•1

'')

r/T

1001
ri 1

(,)

= 1

10000=0
10001=1
10010=0
1

110101 =0
110 110=0
=0
1101

1000 10=0

=^)

100 1=1

1010=0

= 1

100 00=0
1=1
100
1

10 10 00=0
10 10 1 = 1
10 10 10=0

= 1

Q 1 = 1

'-1

1 10ri00 = 1
n 1

100 1 00=0
100 1 1 =0
100 10=0
=0
100 1

If^ = '^

'10 1111 =

.1 1

'i^l

10100=0

f) 1

Mill 10=0
0111 1 =0

00 1000 =
'-Ki 100
=
00 10 10-= 10
=
00 10
00 l'-^0 =
10 101 =
1

1001

000 10 1:=
000 110:=
r:i00 1

100 =

f/U/)P)

00=0
0110 01 =
10=0
=0
0110
O
00=0
(^1 1'^

1 17):=

10 10 11 =0
10 1 100=0
10 1 101 =0
10 11 10=0
101 1 1 1 =0

1000=0

1110 11 =
1

100=0

10 1 =0

=0
=0

The long trufh table shown in the previous example is sometimes cumbersome and it takes a relatively long time
to output the entries on the Teletype.

cases, respectively, as seen below.

The user may use the TN or TF commands to generate only the

ON or OFF

A truth table generated for only the ON (or OFF) cases is just as useful as

that which contains all cases, since the user need only remember that all cases not typed must therefore be of

The TF truth table on the right below is not complete, but is broken in the middle for

the opposite state.

illustration purposes.

.TN73

.TF73

.Y4

.Y4
.Y5 7

.Y57

XI 7
.X^^3

.XI 7

.X23
.X50
.

•

X'^

.Xb0
.X32

X3 ?
:

S60'-l

Y'1'14
Y''157

Y0'-1/!

Y0 3 7
X0 7

X'-l

X0 23
X0 50
X0 32

X0O3
X0 50
X0 32

8-27

ABCDEF
000000=0

ABCDEF
P)00 100 =
'1(^0 10 1 =

'TlfT in0 =

=0
0000
0=n
000
=0
000
0';i0
10=0

n 1 n 1 =

(100 1 1 1 =0

(110 110 =
'1110
=
01 10 10 =

00 1000=0
00 '-10 =il
00 10 10=0
=0
00 10

00(10 =
'1 100 10 =
'^

]

01 1 100 =
01 1 1 10 =

100 100 =

100101 =
1

10 100 =

110101 =

10 1 1 =0

100=0

10 1=0

111110=0
1

Generating Truth Tables for Equations Containing Subroutines
As previously stated, the user may not directly generate a subroutine truth table if the subroutine does not set an

However, the following commands may be used in SIM-14 to generate truth tables for equations

output directly.

which contain subroutines.

Z1400

The subroutine (Z -function) which starts at location 1400 is a
variable of the truth table.

(All

variables in the subroutine

no\ previously listed by the user are added to the truth table.)

ZU1450

Tho subroutine (Z -function) which starts at location 1450 Is to
be considered as a unit variable of the truth table. The separate
variables which determine the value of Z1450 are not included
in the truth table (as in the Z1400 command above). The value
of the Z function is arbitrarily considered

ON or OFF without

actually solving the subroutine.

With the first command, the user may generate for an equation a truth table which contains all the variables

which comprise the subroutine. With the second command, individual variables are not considered, and the
state of the whole subroutine is varied arbitrarily.

The resultant state of the output Is determined.

This second

command Is likely to include impossible states in the truth table if there are variables which are both In the subroutine and In the main equation.

The truth tables generated are for the program which was debugged with the equation verification feature previously, namely:

8-28

Y6 =Z1012 + (/Yl *Z1000)
where

ZIOOO = X4*X12* (X5 +Y1)
Z1012 =X15*(X3 +X4)
.TN6
.7AJl<7] 1 2

•

The user generates a truth table in which the two
The

subroutines are considered unit variables.

values of the subroutines are arbitrarily varied

without actually solving the subroutines for

.S254

specific variables.

A Z1

Z1012

B
C

ABC
I'/l

« 1 1 =
1(710 =
1

K-l =

111==

.TN6

The user generates a truth table for the equation

which considers the varying states of the variables
which are represented by the subroutine. The

f:^

X00 4
X0

part has been moved to the right of the upper

X0 10
•

X0
X0

is generated for the
cases only.
The table has been cut in half and the lower

truth table

X00 5

The complete table appears as one
column when typed by the teletype.
part.

5
3

.Yl

.S254
1

X00 4

X0 12

X005
Y001
X0 10
X0

10=
=
1000
110 110=
110 111=
110 10 10=
110 10 11=
110

X003

ABCDEFG
000001
0000 111:
000 10 11:
000 1111:
001001
--

1101111=
10000 =

110 1110=

00 101 1:
001 101
001 1111:
1

1011111=

010001
01001

110 =

10 10 1 =
10 1 10 10 =
10 110 11=
10 1111 =

1
1
1
1

1000 =
100 10 =
=
1 1001
1 10 100 =
1

1110101=

10 10 11:

010 1111:

8-29

ill

1^01

r^ 1

01 10^
01 1 1
10 10:
rii 1

=
=

01110 11=
0111111=
10000 10=
=
10000
1000 110 =
=
1000
1

1111

100 10 10 =
1

'10 10 1

10=
100
1001
10 100 10=
=
10 100
1

SIMULATED PROGRAM EXECUTION IN LOCAL MODE
and has generated a truth table

Once the user has debugged his program with the equation verification feature
for each

in total

equation solved by the program, he should use the simulated execution

feature to test out the program

The user supplies input values and starts the execution of the program.

SlM-14 reports any changes

in the state of outputs.

LM Execution Commands
Simulated execution of programs with SIM-14 is initiated by the following

commands.

AS50

Assign an address stop at location 50. (Stop is performed only when
switch register 6 is on.) Only one stop is allowed at any one time.

XNl-5

Assign inputs 1 through 5

XF6-12

Assign inputs 6 through 12 OFF for program execution.

YNl-4

Assign outputs 1 through 4

YF5-15

Assign outputs 5 through 15 OFF for program execution.

Clear all inputs; i.e., set all inputs OFF.

Clear all outputs; i.e., set all outputs OFF.

1X5-11

Interrogate the state of simulated inputs 5 through 11
inputs

IYl-20

ON for program execution.

.e. , are these

ON or OFF).

Interrogate the state of simulated outputs

outputs

S400

ON for program execution.

through 20 (i.e., are these

ON or OFF).

Begin program execution at location 400. The change of state of any
output will be announced by SIM-14 by typing the output and its new
state (0 or

1 )

Continue PDP-14 program execution from the point at which it was
interrupted (by either switch register 5, 6, or 9).

8-30

SIM-14 maintains two tables of input and output values. The first table is used for equation verification purposes,
and the second table is used for simulated execution.
enter variables for both features.

The table of values to be affected by a particular command is determined by

which feature is currently being used.

If the user

tion table is affected by the command.

If the

cution table is affected.
(e .g . , it

The same commands (XN, XF, YN, and YF) are used to

has typed a VY,

CV, or VZ command, the equation verificacommands, the simulated exe-

user has not typed one of the verify

Thus, the same variable may have two different values at the same time in local mode

may be ON for equation verification, but OFF for simulated execution)

The reader should also

remember that the same input has a real state (ON or OFF) which is used in on-line execution.
The YN and YF commands above allow the user to specify the states of outputs. While these commands may be
used in simulated execution, the user is advised to restrict himself to the

XN and XF commands.

the states of inputs, the program will specify the state of same outputs.

These resultant outputs with other inputs

may in turn specify other output states.

In brief,

By specifying

since the equipment to be controlled can only specify input

states, the user should also restrict himself to specifying input states when testing the program.

Switch Register Options in Simulated Execution

The execution of a program in local mode is controlled by five switches on the PDP-8 computer console.
use of each switch

summarized below.

Switch
5

Function

Terminate Typing - Switch 5 may be used to prematurely terminate
the output currently being typed by SIM-14. When this switch is
ON, typing is terminated; control returns to SIM-14 when the
switch is turned OFF, thereby allowing the user to type further

commands to SIM-14.
6

Enable Address Stop - Switch 6 controls the address stop feature
of local mode execution, honoring the address stop only if switch
6 is ON.

Report Address, Contents, and Test Flag - When switch 7 is

during program execution, each return to SIM-14 will cause the
following information to be typed: the address of the last instruction, the last instruction and the resultant state of the TEST flag.
If switch 7 is OFF, only the address of the previously executed
instruction is typed.

and
Automatic Return to PDP-14 Program - When switch 8 is
a return to SIM-14 occurs during program execution, information
is typed according to switch 7 and PDP-14 program execution automatically continues. When switch 8 is OFF, program execution
must be continued with an S or C command.

8-31

The

Function

Switch

Return to SIM-14 - Control returns to SIM-14 after executing the
Returns are affected by
if switch 9 is

ON.

current instruction,

switches 7 and 8 as above.
ll'.e

Thus,

if switches

8 and 9 are ON,

PDP-14 program will be executed one instruction at a time,

v'hile reporting information to the user on the Teletype.

Figure 8-2 illustrates the 12 switches which comprise the PDP-8 switch register.

The function of switches 10

and n (used in on-line mode only) will be described later in this chapter.

suggested that the user affix

labels to the PDP-8 console (above the switches) when using

It is

These labels should contain the informa-

SIM-14.

tion given in Figure 8-2 (the use of each switch and the modes in which they are recognized)

incorporating similar information is attached at the back of this manual

O
O

<]}

.2^

P
Ui

:f
_j

E
D
D)

(1)

-D

-t-

Q>».

»
^-

10)

D
0)

pod
1—

__1

^5 < o
LU _J

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D
3

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A useful card

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"cally.

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£ ^
3 *O
01
D

•-

o c
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Enable

PDP-8 Switch Register Switch Numbers

Figure 8-2

Switch Register Functions in SIM-14

Types of Simulated Execution

The command AS allows the user fo specify an address at which he wants to have the simulated program execution
stopped.

The stop is honored only when switch 6 is

If the

address stop is encountered and switch 6 is ON,

the instruction 'n 'hal location will not be executed, and control will return to SIM-14 which will type the
location from which

from the user.

If the

returned.

After typing the address, SIM-14 types a period and awaits further instructions

user types C (continue), the instructions beginning with the address stop instruction will be

executed, until the address stop is again encountered.
after each address stop.

The user may change the input and continue execution

SIM-14 will type all changes of state in the output values, by typing a message of the

form:

8-32

Y123 1

(Output 123 changed from OFF to ON.)

Y123

(Output 123 changed from

ON to OFF.)

Thus, the user may monitor the results achieved by his program for varying input.

When TXD, TYD, or TRM instructions are encountered during simulated execution, SIM-14 types the following
messages:

meaning TXD 23 encountered and X23 is OFF

TXD 023
TYD 125

meaning TYD 125 encountered and Y125 is ON.

TRM 4015

meaning TRM 4015 encountered.

As state above, SIM-14 types the address from which it returned when PDP-14 simulated execution was interrupted.

If switch

the TEST Flag

7 is ON, SIM-14 also types the instruction contained in that location, and the current state of
(i

.e., before execution of the typed instruction)

If switch

7 is OFF, only the address is typed.

The message typed when switch 7 is OFF is:

(Program execution was interrupted at location 1234)

1234

The message typed when switch 7 is ON is:
1234 TXN 027

(Program execution was interrupted at location 1234 which
The TEST flag was
(1)

contains the instruction TXN 27.

when the interruption occurred.)
0013 SYN 142

(Program execution was interrupted at location 13 which
contains the instruction SYN 142.

The TEST flag was OFF (0)

when the interruption occurred.)
Note that the information typed above concerns the next instruction to be executed, if the interruption was
caused by an address stop (enabled by switch 6)

However, if the interruption is caused by switch 9, as

described below, the information typed above concerns the instruction just executed, not the instruction to be

executed.

This distinction

crucial

when one is examining the state of the TEST flag.

If execution is

by switch 6 and an address stop, the TEST flag value typed is for before instruction execution.
is

stopped

the execution

stopped by switch 9, the TEST flag value is for after instruction execution.

The user may monitor program execution without using program stops by using switch 9. When switch 9 is ON
during simulated execution, control
address typed

(or

returned to SIM-14 after the execution of the next instruction.

The

the address, instruction and TEST flag value typed) are for the instruction just executed (not

the instruction to be executed as in switch 6 and address stops).

The user may use switch 9 in two ways:

stop the current execution of a PDP-14 program unconditionally, or to allow the program to be executed one
instruction at a time .

The second case is often used with switch 8 to achieve a trace of the PDP-14 program

8-33

Switch 8 is used to allow immediate return to the PDP-14 after
switch 8 is

an interruption (by switch 9, usually). When

ON and a return to SIM-14 occurs, the address causing the return

immediately to the PDP-14 program.

(It is

typed, and control is returned

equivalent to the user typing C after each return.

does not permit

the user to change any input values.)

The following is a list of commonly used switch combinations.
Function

Switch

cause the program to be stopped at the
Switches 6 and 7
address stop location. The instruction and TEST flag value
caused the return. Any
is typed in addition to the address that
This allows the user
typed
also
are
states
output
changes in
through the program.
pass
complete
each
for
variables
to change

6^7

cause the program to be executed one
Switches 8 and 9
instruction at a time. The address of the last executed instruction is typed, as well as any changes in output states. This
allows the user to generate a complete list of the locations
encountered during the execution of the program. The user
terminates this form of execution by changing switch 8 to the

8,9

OFF position.
Only switch 9 ON, causes the program to execute one instruction for each time the user types the C command. The user may

thus change the values of variables at any point in the program.
This switch may be used to return control to SIM-14 at any

time

ON cause the program to be executed one

Switches 7, 8 and 9
instruction at a time.

7^8,9

The address, instruction and resultant

TEST flag value of each instruction executed will be typed.
The user may stop this form of execution by changing switch
8 to the OFF position.

.TXl -3

The user checks the current state of inputs and

O'U

outputs with the IX and lY commands. SIM-14
types the number of the input or output followed

002
0^3

.[XA -10
0-^/)

by its state (1 for

0'^5

;;-]

6
17

''1

010
.

-3

0r^l

0).AO

003

8-34

ON and

for OFF)

.AS0
.XFl-•3
.XN4-•10
.YF0-•376

He then directs execution to start at location 0, after
setting switch 6

.S0

0000

ON.

SIM-14 immediately stops at location

the address stop.

Y101

Y105

Y003

since this is

The user requests execution to

continue

0000

SIM-14 again stops at location after typing the
changes in state of four outputs. The user changes
some input values and continues execution.

.XF4-10
.XNl--3
.0

Y10'^

and

The user assigns an address stop at location

supplies values for the variables used in the program.

Y101
Y105

Y106

YP0(-

Y0 5 3

Y0^-]

Y0 0R

Y0f^i3

''(101)
•
•

Again the execution stops at location 0. The user
changes the value of an input, and sets switch 7

XFl
I

ON (switch 6

is still

ON).

'•'1

Yri0p.

Y0(-i3

00
TXN 00
.XNl
.XFf5-S

When execution is stopped at location 0, the
instruction and TEST flag value are typed.
user changes some input values.

6 and 7 OFF, and sets switches 8 and 9
Thus, each location encountered is listed.
Changes in output states are also typed.

''-^R^'T)

Y100

()M02
^10

5
6

Y 1 '^ 1

00 7
00 10
00 12
00 1 3

Y105

8-35

The

He sets switches

The user sets switch 7 ON to have SIM-14
type the instructions and TEST flag values

0014 SYN 10 5
Y106
00 15 SYF 106
Y200
00 16 SYN 200
Y053

as well as the address.

00 17

0020

The user sets switch 7 OFF while execution

1500

continues.

150

1502

The user sets switch 8 OFF to terminate the
execution. He could now change the values
and restart or continue verification.

Simulated Timer Execution
If the user

manner.

program contains outputs which are timers, SIM-14 can simulate the timer action

in the

following

When the SYN instruction which turns ON a declared timer in SIM-14 is encountered during simulated

execution, the timer output is not turned

ON until the SYN instruction has been encountered seven times. Thus,

user; each assigned timer is
SIM-14 simulates a time delay for the output. The delay may not be varied by the
following are the commands which
until its SYN instruction is encountered seven times. The

not turned

declare and clear simulated timer assignments.

DT20-23

Define outputs 20-23 as timers. SIM-14 will treat any output so
as to simulate the action of a timer. The output will not "turn ON"
until the SYN instruction is encountered for the seventh time.

Clear all previously assigned timer outputs.

A maximum of 63 timers may be assigned for simulated execution

ON-LINE MODE DEBUGGING
Once the user has thoroughly debugged his program with the features of local mode,
while actually controlling the machine by sampling true inputs and setting
ever, the installation of the PDP-14 system must be completed.
installed.

he may debug his program

true outputs.

Before doing so, how-

The PDP-8 to PDP-14 interface must also be

Only after these steps have been taken and the PDP-14 is running, can the user actually

line mode.

If the

user types

enter on-

OM under any other conditions, he will receive the error message NR (not running)

When the user executes a PDP-14 program in on-line mode, SIM-14 supplies instructions which are executed by
the PDP-14.

The supplied program tests the actual machine inputs and sets outputs through the PDP-14

I- and

ROM once
O-boxes. SIM-14 serves the function in on-line mode which will be served by the
section at a time,
debugged. On-line mode, however, allows the user to execute the PDP-14 program one
the program is

fully

8-36

by placing in the program, stops which return control to SIM-14.
abled by the user.

A program stop is only executed when en-

Thus the program is executed in part or in total as controlled by the user.

When a PDP-14

program is interrupted by a program stop, the machine is no longer being controlled because the PDP-14 is no
longer testing inputs or setting outputs.

Thus, the user must carefully select the points at which he interrupts

program execution, so that the machine is not damaged when control is stopped.

The user has the option of specifying a set of operations to be performed when a program stop is encountered and
before control is returned to SIM-14.

This set of operations is called a stop equation and enables the user to

place program stops at points in the PDP-14 program where control could not be stopped otherwise.
equation serves as a shut down routine for the equipment before control is terminated.

The stop

The on-line mode pro-

cedure is outlined in Figure 8-3.

On-Line Mode Commands
The following Is a list of commands used exclusively in on-line mode.

The user may also use the program modi-

However, the user is cautioned

fication and manipulation commands previously introduced in on-line mode.

not to use these commands to make changes to a

PDP-14 program in on-line mode without first checking out the

changes with local mode debugging.

Command

Function

IXl-15

Interrogate the current state
inputs

lY 12-57

(ON or OFF) of actual machine

through 15.

Interrogate the current state

(ON or OFF) of the actual

machine outputs 12 through 57

SS234

Set a program stop at location 234.

This location must

contain a SYN or SYF instruction; otherwise, the program
stop will not be set.

SE1567

Specify a stop equation at location 1567. The equation
beginning with location 1567 and ending with the number
0010 will be solved (when enabled by switch 10) before

any return to SIM-14 control

Type all stop locations presently specified.

RS234

Remove the stop presently set at location 234.

Clear all stops presently set.

S200

Start on-line execution at location 200.

(A program stop

must be set before a program may be executed; the program
stop need not be enabled, however.)

Continue on-line execution from point at which it was interrupted,

8-37

The IX and lY commands interrogate the state of the actual machine inputs and outputs, respectively.
these same commands interrogate the state of simulated inputs and outputs when used in local

Since

mode, the user must

consider the current mode whenever these commands are used.

The SS (set stop; ccnmand is used to place stop points at any SYN or SYF instruction.

The user can type all

He may remove a single program stop with the RS com-

currently specified stop locations with the TS command.

mand, or he may clear all stops with the CS command.

On-Line Mode Switch Options
The following switch register options are used in conjunction with the on-line mode instructions to control online debugging

Function

Switch

Terminate Typing - Switch 5 may be used to prematurely terminate
the current typing of information by SIM-14. When this switch is
ON, typing is terminated; control returns to SIM-14 when the
switch is ttrned OFF, thereby allowing the user to type further
commands to SIM-14. This switch may not be used to terminate

on-line program execution.

Enable Stop Equation - Switch 10 controls the stop equation, causing
at the time a program stop
its execution only when switch 10 is
is encountered in the PDP-14 program.

and a set output
Enable Program Stop - When switch 11 is
stop
is encountered,
program
as
a
specified
which
is
instruction,
the instruction will not be executed if It will cause a change in

the state of the output.
not executed; control

If a
is

change will occur, the instruction

returned to SIM-14.

Program Stops

When the user executes a PDP-14 program in SIM-14 on-line mode, he must specify at least one program stop.
If the

user attempts to start execution without at least one program stop set,

PS? (program stop?)

SIM-14 will type the error message

The user is not required to enable the program stop, but at least one stop must be set to

allow return to SIM-14 when desired by the user.

If a stop is

not set,

PDP-14 program execution could not be

terminated.

When a program stop is encountered at a set output instruction, SIM-14 checks enabling switch 11.
is

ON, the program stop is enabled.

output will occur.

If switch

However, execution will not be stopped unless a change in the state of the

SIM-14 will only stop execution if the output is now ON and will be set OFF, or if the out-

put is OFF and will be set

The stop is not executed if no change will occur, regardless of switch 1 1

8-38

When an enabled program stop is encountered and a change in output state will result, the set output instruction
is

not executed.

Control is immediately returned to SIM-14 after executing an enabled stop equation

(if any)

The set output instruction which caused the return to SIM-14 will be executed when the user types C (continue).

Stop Equations

The stop equation allows the PDP-14 user to perform a set of operations after interrupting program execution and
before returning control to SIM-14.
tions continue after control

The stop equation must return the machine to a stable state so that no opera-

terminated.

The stop equation can either be a special set of instructions which will not be part of the final program, or a
section of the regular program which is a shut down routine.

The only requirement for a stop equation is that it

SIM-14 to terminate execution of

must be terminated with a location containing 0010.

This number will cause

the stop equation and return control to SIM-14.

number is executed as a NOP if it is encountered other

(This

than in the stop equation of SIM-14, or if it is included in the final PDP-14 ROM.)

The stop equation may be changed at will using the SE command
as the start of the stop equation.

Any location in the program can be specified

The user may specify one stop equation when testing one PDP-14 program

section in on-line mode, and another stop equation for another program section.

The stop equation is enabled by switch 10.
is

The stop equation is executed only when an enabled program stop

encountered, which would cause a change of state in the output, and when switch 10 is on.

CAUTION
Switch 10 must never be set
specified a stop equation.

ON when the user has not
10 and 11 are ON

If switch

and no stop equation is specified, SIM-14 will assume
location

as the start of the stop equation when a pro-

gram stop is encountered

On-Line Mode Execution

When the user begins to execute his PDP-14 program in on-line mode he must:
a.

Interrogate the inputs and outputs with the IX and lY commands to determine what

operation should be executed next
b.

Set a program stop at the SYN or SYF which will start that operation.

stops may also be set.
c .

Enable the program stop with switch

Specify a stop equation, if necessary.

Enable the stop equation with switch 10.

1 1

8-39

Other program

start program execution with the S (start)

f .

When the program stop is encountered, the SYN or SYF which

state will not be executed.

h
i

command, specifying the initial address.

stop equation is necessary,

would cause a change of

SlM-14.

Specify a new program stop at the SYN or SYF
If a

Control will return to

which will start the next operation

make certain that the stop equation is appropriate and

enabled.

Type C (continue)

Proceed to check each operation by changing the

program stop and stop equation as

necessary

OFF, thus disabling
Once each part of the program has been checked, turn switch 11
to terminate
wishes
user
the
If
The program may then be run in total
ail program stops
I

necessary)
(with the stop equation enabled by switch 10, .f
execution, he turns switch 1 1
change
a
cause
will
which
encountered
The program is terminated on the next program stop
of state in an output.

on-line mode, but he should
bugs are detected, the user may change the program in
program on-line.
the
executing
again
return to local mode for further debugging before

If any

Once the program has been successfully executed in on-line mode,

binary program

the user sends the

be woven) to DEC.
tape generated by SIM-14 (from which the ROM will
until the

ROM is received

The fully tested program may be used to operate the equipment
used to prevent accidentally
The PANEL lock feature of the PDP-8/L or PDP-8/I may be

stopping the program.

NOTE
Because of the processing time required by SIM-14
when operating in on-line mode, the PDP-14 will
operate approximately three times slower than it will

when it operates from the ROM stored program.

Thus,

momentary contact inputs which would not be missed
by the PDP-14 operating with an ROM may be missed
If this happens, the user
in SIM-14 on-line mode
.

may counteract the slowdown by using subroutines
to check crucial inputs more frequently when in the
on-line mode

SIM-14 SUMMARY
The following is a summary of the commands, switch options and
of SIM-14.

error messages for local

Specific numbers for inputs, outputs, and program numbers have

and error messages.

mode and on-line nrK>de

been used to describe the commands

or output number may be
should be noted that any PDP-14 location address, input number

substituted in place of those used for illustration.

NOTES
SIM-14 commands which reference more than one address.
Input, or output (such as XN4-12) may be shortened when
only one variable is referenced (XN5, not XN5-5).

8-40

Attach interface between
PDP-8 computer and
PDP-14 and complete

PDP-14 installation as

Return to local mode of SIM- 14 to test

described in Chapter 1 1

the corrections

I
Place program stops at SYN or

SYF instructions as desired.
Correct the error within SIM-14.

When

the correction has been checked out,
the bug should be corrected in the program source to BOOL-14 or PAL-14.
Do not make changes to the PDP-14

Specify the stop equation

programs with SIM-14 without correcting the program as it wos input to

(shut-down sequence).

BOOL-14 or PAL-14.

Execute the PDP-14 program
in sections.

(Shut-down se-

Yes

quence is executed before return to SIM- 14.) Any errors
found?

Execute complete program,
Any errors found ?

Yes

Program is debugged.

Request

ROM by supplying program
tape to DEC.

Figure 8-3

On-Line Mode Debugging Procedure

8-41

Commands which use the low-speed punch require that
the user press the PDP-8

CO NT switch both after typing

the command, and after the tape is punched. Commands
which use the low-speed reader require that the user press
the

CO NT switch after the tape

All

commands must be terminated by a carriage return

read.

before they will be executed.

Commands Common to Local and On-Line Modes
General Commands

Enter local

Enter on-line mode

'rubout:

mode

Ignore the previously typed command (up to the last carriage
return)

Verify the paper tape in the low-speed reader by comparing
it with PDP-14 simulated memory and noting any discrepancies.

Verify the paper tape in the high-speed reader by comparing
it with the PDP-14 simulated memory and noting any discrepancies

Program Manipulation and Modification
23:

Open location 23 symbolically and allow the user to modify its
contents

57/

Open location 57 numerically and allow the user to modify its
contents

RETURN)

Close the currently open location and enter any legal modifications typed by the user.

(Line feed)

close the currently open location; enter any legal modifications
typed by the user; open the next sequential PDP-14 location in
the same form (i .e , symbolically or numerically) and allow the
.

user to modify its contents.

LSO-30

List the

contents of locations

through 30 symbolically (i .e., by

typing the instructions in mnemonic form).

LNO-10

List the contents of locations

through 10 numerically (i.e., by

typing the instructions in their numeric (octal form).

PO-700

Punch a paper tape record of the contents of locations
700 on the low-speed reader.

PH40-70

Punch a paper tape record of the contents of locations 40 through
70 on the high-speed punch
.

Read a paper tape from the low-speed reader.

Read a paper tape from the high-speed reader.

Open mask location and allow modification.

Open word location and allow modification

8-42

through

Local

Mode Commands

Command

MB2

Function

The PDP-14 memory has two memory banks of IK words.
a 4K

PDP-8 is used to simulate operation.
3 , or 4 if an 8K PDP-8 is used .)
1

(MB must be

MB may equal 1,2,

Equation Verification Feature

VY5

Verify output 5, using the input which follows.

VZ1400

Verify subroutine (Z function) starting at location 1400.

XN4-12

Inputs 4 through 12 are

XF15-17

Inputs 15 through 17 are OFF for the equation being verified.

YNl-3

Outputs

YF7-11

Outputs 7 through

Z1400

through 3 are

ON for the equation being verified.
ON for the equation being verified.

11 are

OFF for the equation being verified.

A subroutine (Z-function) which begins at location 1400 is part
of the equation being verified.

(SIM-14 types any variables in the
subroutine which have not been previously listed by the user. All
variables listed by this command are considered OFF unless they

are later assigned

ZN1450

ON by one of the above XN, or YN instructions.)

A subroutine (Z-function) which begins at location 1450 is part of

ON.

the equation being verified and is considered
(The actual subroutine is not solved; the result of the subroutine is arbitrarily con-

sidered

ZF1500

ON for equation verification purposes.)

A subroutine (Z-function) which begins at location 1500 is part of
the equation being verified and Is considered OFF. (The actual
subroutine is not solved; the result of the subroutine is arbitrarily

considered OFF for equation verification purposes.)

S50

Start

Continue verification of same output with new input. Variables
may be added and states of variables may be changed with the

PDP-14 execution at location 50. (Used with the verify
feature to specify the start of the equation to be verified.)

XN, XF, YN or YF commands above. However, variables may
not be deleted.

The S command Initiates the verification as above.

Truth Table Feature

TA5

Generate the truth table for output 5 and print all cases; I.e.,
ON and OFF output results.

both

TN6

Generate the truth table for output 6, and print only the ON cases.

TF20

Generate the truth table for output 20, and print only the OFF coses.

X5-11

Inputs 5 through 11 are variables of the equation whose truth table
Is

Y6-7

to be generated

Outputs 6 and 7 are variables of the equation whose truth table Is
to be generated

8-43

Z1400

The subroutine (Z -function) which starts at location 1400 is a variable
of the truth table. (All variables not previously listed by the user are

added to the truth table.)

ZU1450

The subroutine (Z-function) which starts at location 1450 is to be
considered as a unit variable of the truth table. The separate variables
which determine the value of Z1450 are not included in the truth table
The value of the Z-function is arbi(as in the Z1400 command above)
.

ON or OFF without actually solving the subroutine.

trarily considered

S230

Start execution of the

PDP-14 program at location 230.

(Used in truth

table generation to specify the starting location of the equation whose
truth table is to be generated.)

Program Execution Feature

AS50

Assign an address stop at location 50. (Stop is performed only when
switch register 6 is ON.) Only one address stop is in effect at one

time

ON for program execution.

XNl-5

Assign inputs

XF6-12

Assign inputs 6 through 12 OFF for program execution.

YNl-4

Assign outputs 1 through 4

through 5

ON for program execution.

(Use of this

command should be avoided.)
YF5-15

Assign outputs 5 through 15 OFF for program execution.
this

(Use of

command should be avoided.)
.e., set all inputs OFF.

Clear all inputs;

Clear all outputs; i.e., set all outputs OFF

DT20-23

Define outputs 20 through 23 as timers. SIM-14 will specially treat
any output so assigned so as to simulate the action of a timer. The
output will not "turn on" until the SYN instruction is encountered
for the

CT
1X5-1 1

seventh time.

Clear all previously assigned timer outputs.
Interrogate the state of simulated Inputs 5 through 11 (I.e., are

these inputs

IYl-20

ON or OFF).

Interrogate the state of simulated outputs
these outputs

S400

through 20 (i.e., are

or OFF)

Begin program execution at location 400. The change of state of
any output will be announced by SIM-14 by typing the output and
its

new state (0 or 1)

Continue PDP-14 program execution from the point at which It was
interrupted (by either switch register 5, 6, or 9).

8-44

On-Line Mode Commands
Function

Command
IXl-15

Interrogate the current state
inputs

IY12-57

(ON or OFF) of actual machine

through 15.

Interrogate the current state

(ON or OFF) of the actual machine

outputs 12 through 57.

SS234

Set a program stop at location 234.

This location must contain a

SYN or SYF instruction; otherwise, the program stop will not be set.
The stop is enabled by switch 1 1

SE1567

Specify a stop equation at location 1567. The equation beginning
with location 1567 and ending with the number 0010 will be solved
(when enabled by switch 10) before any return to SIM-14 control

Type all stop locations presently specified.

RS234

Remove the stop presently set at location 234.

Clear all stops presently set.

S200

Start on-line execution at location 200.

(A program stop must be set

before a program may be executed; the program stop need not be enabled,

however.)
Continue on-line execution from the point at which it was interrupted.

Local

Mode Switch Options
Function

Switch

Terminate Typing - Switch 5 may be used to prematurely terminate
the output currently being typed by SIM-14. When this switch is
ON, typing is terminated; control returns to SIM-14 when the switch
commands
is turned OFF, thereby allowing the user to type further
to SIM-14.

Enable Address Stop - Switch 6 controls the address stop feature of
local mode execution, and honors the address stop only if switch 6
(Only one address stop may be in effect at one time.)
is ON.

Report Address, Contents, and Test Flop - When switch 7 is
during program execution, each return to SIM-14 will cause the
following information to be typed: the address of the last instruction,

and the resultant state of the test flop. If switch 7 is OFF, only the
address of the previously executed instruction is typed.

and a
Automatic Return to PDP-14 Program - When switch 8 is
return to SIM-14 occurs during program execution, information is
typed according to switch 7 and PDP-14 program execution automatically continues. When switch 8 is OFF, program execution must
be continued with an S or C command

i-45

Funcfion

Switch

Return to SIM-14 - Return to SIM-14 after executing the current
Returns are affected by switches
instruction if switch 9 is

7 and 8 above; thus, if switches 8 and 9 are ON, the PDP-14
program will be executed one instruction at a time, while reporting information to the user on the teletype.

On-Line Mode Switch Options

Function

Switch

Terminate Typing - Switch 5 may be used to prematurely terminate
the current typing of information by SIM-14. When this switch

ON, typing is terminated; control returns to SIM-14 when the

switch is turned OFF, thereby allowing the user to type further
commands to SIM-14. This switch may not be used to terminate

on-line program execution.

Enable Stop Equation - Switch 10 controls the stop equation,
when a program

causing its execution only when switch 10 is
stop is encountered in the PDP-14 program.

Enable Program Stop - When switch

11 is

ON, and a set output

instruction which is specified as a program stop is encountered,

the instruction will not be executed if it will cause a change in
the state of the output.
is

not executed; control

If a
is

change will occur, the instruction

returned to SIM-14 which types out

the location and the instruction which caused the return.

OFF, or if no change in the state of the output will
result, the execution of the PDP-14 program will continue unswitch 11

interrupted.

Error Messages

The following is a list summarizing all possible error messages typed by SIM-14 and their causes.

Error Message

Cause
Syntax error - The user has violated a syntax rule for SIM-14 commands
Each command of SIM-14 is of one of the following forms:
1

One or two letters with no following numbers (e .g

One or two letters followed by a number (e.g

SI 234)

One or two letters followed by two numbers separated by a
The first number must be less than
minus sign (e.g ., XNl-23)

the second number

When a command is not typed in its specified format the S? error
results.
(e .g . ,

Commands of form 3 may be typed in form 2 without error

XN5 is the same as XN5-5)

8-46

Error Message

Cause

Number error - The user has included an illegal number in his program.
The following conditions produce the code N ?:
1

A non-octal digit used in a program

8 or 9)

A test or set instruction references an illegal input or output

number (i.e., greater than 377)
3.

The address of a JFF or JFN is illegal

A JMP or JMS instruction references a location which is not

.e. , greater than 377)

in the simulated memory.

The second part of a two-word instruction is typed on the same

line as the first part

(e .g . ,

JMP 1567)

Mode error - The user has typed a command which is illegal in the
SIM-14 has four such modes: local mode,
on-line mode, truth table mode, and equation verify mode.
present mode of SIM-14.

Command error - The user has typed a command that SIM-14 does not
recognize.

X123 Lor
Y123 L
XT 23 Eor
Y123 E

Listed but not encountered error - Input (output) 123 was listed as a

variable in an equation to be verified, but was not encountered when
SIM-14 actually solved the equation.

Encountered but not listed error - Input (output) 123 was not listed as
a variable in an equation to be verified, but was encountered when

SIM-14 actually solved the equation

Y123?

Output error - The user has requested equation verify or truth table
generation for an output other than 123, and SIM-14 has encountered
a SYN 123 or a SYF 123 before the requested output has been solved.

OPER 1234?

Operation error - The instruction stored in location 1234 of the user
program, if executed, would cause a transfer out of simulated memory;
or SIM-14 encounters an instruction in location 1234 of the user pro-

gram which it does not recognize.

RDER?

Read error - A checksum error has occurred on a tape read by SIM-14
The tape should be reread.

with the R, RH, V or VH command.

PS?

Program stop error - The user has attempted on-line execution of a
program without a program stop specified in the program. SIM-14
demands that there be at least one program stop present; otherwise,
return to SIM-14 from the user program would be impossible.

TOV

Table overflow - The user has exceeded the highest possible number
of variables in equation verify or truth table generation, or the

maximum number of assigned timers for simulation.

MOV

Memory overflow - The user has attempted to load a PDP-14 program
from a paper tape into memory which is not available for simulation.
(The user should allow more memory with the MB command.)

NR?

Not running - The user has attempted to enter on-line mode when
either there is no connected PDP-14 or the connected PDP-14 is not

running

8-47

CHAPTER 9

MONITORING THE PDP-14

This chapter introduces the instructions which allow a PDP-14 to be monitored externally by a PDP-8 family

computer.

These instructions are of two types:

those which are executed within the PDP-14, and those which

are executed within the PDP-8 (but which affect the PDP-14).

The only instructions in this chapter which can

be simulated by SIM-14 in on-line mode are the TXD, TYD and TRM.

This chapter also describes possible ap-

proaches and techniques for monitoring the PDP-14 system with a PDP-8.

When used in a monitored or computer interfaced form of operation, the PDP-14 has three facilities for the
transfer of information:

The Input Register - may be used to supply input data to any internal register of the PDP-14.
may only be loaded by an external computer.

The Output Register - may be used to hold data to be transferred to the external computer.

The Memory Port - may be used to directly supply instructions to the PDP-14 without passing through
Instructions are loaded from the external computer. The PDP-14 executes the instruction and sets a flag when execution is complete.

the Input Register.

Three general approaches may be used to monitor an operation through the PDP-14.

The PDP-14 could contain instructions which output information to the monitoring computer through
These instructions do not interrupt the programmed
operation of the PDP-14. The monitoring computer (PDP-8) merely reads the information, on either a
programmed or an interrupt basis, as it appears in the output register of the PDP-14

the output register, such as TXD, TYD, or TRM.

b.
The second technique requires the monitoring computer to interrupt the PDP-14, and then supply
an instruction to the PDP-14 for execution through the memory port. The PDP-14 executes the externally supplied instruction and then returns to Its programmed operation, as stored in the ROM.

The third technique requires the monitoring computer to request an interrupt from the PDP-14 and

supply an instruction which causes the PDP-14 to enter the external mode of operation. In this mode,
as many instructions as necessary may be supplied to the PDP-14 through the memory port. The PDP-14
will suspend execution of

ROM instructions until it is supplied with an instruction causing it to leave

external mode.

Thus, the input and output registers may be used without interrupting the execution of the program stored in
the ROM.

9-1

The memory port may be used to supply instructions to the
externally supplied instruction is executed.

PDP-14 on a cycle-stealing basis, in which one

The memory port may also be used to allow the PDP-8 to

completely

to be executed.
take over the PDP-14's operation, by supplying all instructions

A two-location PDP-14 instruction may not be executed using technique (b) preceding.
be entered before a two-location instruction may be executed on

External

mode must

an interrupt basis.

PDP-14 INTERNAL REGISTERS
The monitor instructions involve the PDP-14 internal
ore used in the PDP-14 instructions to refer to the

registers listed in Table 9-1 .

respective registers.

The following register locks

The module type for each register is

also noted below.

Table 9-1

PDP-14 Internal Registers
Register

PCI

Module

M747

Description

Octal Code

Program Counter 1 - specifies the location of the next location
in sequence to be accessed. This location contains the next
instruction to be executed, except when it is the second part
of a two-location instruction.

Transfers which use this register

as destination may increment or decrement during transfer.
(Decrementing PCI can cause program loops which are impro-

per for the PDP-14.)

PC2

M746

Program Counter 2 - used to store the contents of Program
Counter 1 while subroutines are being executed to enable a
return to the main program. PC2 may also be used to store
the value of PCI whenever the PDP-14 operates in external

mode.

INPUT

M746

Input Register - used to accept information from a monitoring
PDP-8 family computer. This register is loaded externally and
its

contents may be transferred to other PDP-14 registers.

In-

formation cannot be transferred to the Input Register by
PDP~14 executed instructions (supplied as part of computer
interface).

OUTPUT

M746

Output Register - used to send information to a monitoring
PDP-8 family computer. This register is loaded from other
PDP-14 registers, or from PDP-14 memory directly, and is
read by a monitoring PDP-8 family computer. Information
cannot be transferred from the Output Register by PDP-14
executed instructions (supplied as part of computer interface).

M746

Memory Buffer - the interface between the PDP-14 memory
and other internal registers. It is used to hold instructions
read from the PDP-14 memory, or loaded from the monitoring
computer. The memory buffer also holds the second part of a

PDP-14 two-location instruction during its execution.

9-2

Table 9-1 (Cont)

PDP-14 Internal Registers
Module Type

Octal Code

M746

Description
Instruction Register - used to hold and decode PDP-14 instructions.

Instructions which are brought into the Memory Buffer

from PDP-14 memory, or which are supplied externally, are
transferred into the IR to be decoded and executed.

M747

SPARE

Spare Register - used for monitoring and diagnostic functions.
Spare Register is an incrementing type, transfers which
use it as destination may increment or decrement during the
If the

transfer.

DUMMY

(Not part of basic PDP-14.)

Dummy - used to transfer all Ts to any register. Dummy is

None

not an actual register but when addressed as the source of a
transfer it will act as a register which contains all Ts.

PDP-14 EXTENDED INSTRUCTIONS
The following are the PDP-14 instructions which may be used for diagnostic or moniix)r functions.

They are not

required for the basic control uses of the PDP-14 and, except where noted, are not simulated in local mode of

SIM-14.

External

Mode Instructions

The following instructions cause the PDP-14 to enter or leave the external mode of operation in which all instructions are supplied externally.

Purpose

Instruction

The EEM instruction causes the PDP-14 to receive
The Program Counter 1,
Memory Buffer, and Instruction Register will be affected during the external mode operation. Therefore, the monitoring computer must set
Program Counter 1 before returning the PDP-14 to normal operation with
the next instruction.
Enter External

Mode.

(0600 octal)

all instructions

from the monitoring computer.

LEM

Leave External Mode. The LEM instruction will return control to the
PDP-14 which will then execute the instructions in its memory beginning with the instruction specified by PCI.

EEM

(0400 octal)

EES
(0645 octal)

Enter External Mode and Store PCI

operation, the value of PCI

LER
(0454 octal)

The EES instruction causes the

PDP-14 to enter external mode and store the current value of PCI (the
address of the next instruction to be executed in the PDP-14 program)
in PC2.
Upon leaving external mode and returning to normal PDP-14
is

restored by the following instruction.

Leave External Mode and Restore PCI. The LER instruction causes
PDP-14 to continue normal program execution at the location
specified by the value of PC2. This value, which could be stored
the

9-3

Purpose

Instruction

LER (Cont)

PC2 by an EES instruction of by a register transfer instruction, is
PCI before the PDP-14 returns to its normal execution.

transferred to

NOTE
EES/LER instruction pair are used, the monitorsupplied instructions executed during external mode must
not change the content of PC2 (e.g. , there must be no
If the

PDP-14 JMS instructions within the monitor - supplied
program)

Memory Transfer Instructions
The following instructions transfer a 12-bit word from memory to some PDP-14 internal register.
Purpose

Instruction

Transfer Memor/ to Output.

TRM
(4226

NNNN

octal)

TRM is a two-location instruction which

transfers the contents of the second word to the Output Register of

PDP-14 where it may be read by a monitoring PDP-8 family comThe value of NNNN which is output to the monitor may be
any octal number specified by the user at the time the PDP-14 program is assembled by PAL-14, or compiled by BOOL-14. This instruction may be simulated by SIM- 14.

the

puter.

(4225

TRS is a two-location PDP-14 instruction
which transfers the contents of the second location of the instruction
to the PC2 register. It may be used to extract test patterns from memory during diagnostic work, or to alter the return address after execuTransfer to Storage (PC2).

TRS

NNNN octal)

tions of subroutines or external

mode operations.

Conditional Skip Instructions

The following instructions cause a conditional skip of one PDP-14 memory location.

Purpose

Instruction

SKZ R

The next PDP-14 location will be skipped if the
The value of R is the code
value for the previously introduced PDP-14 registers (0 through 6 octal).
Skip on Register Zero.

(63R4 octal)

SKE R

The contents of the register specified by octal
Skip on Register Equal
code R is compared with the contents of PC2. If the two contents are
equal, the location following the SKE is skipped. Otherwise, the following location is executed as an irtstruction.

(67R4 octal)

The above instructions may not be part of a SIM- 14 program for both on-line and local mode.

They will not be

recognized, simulated or executed and must not be part of a program which is executed in on-line mode of

SIM- 14.

9-4

Test and Display Instructions

The test and display instructions may be used

to test inputs or outputs and display information in the Output

Information

Bit Position

Present state of the TEST Flag (0 = OFF,
Result of the test -

= ON)

the output or input is OFF,

if the

output or input is ON.

Presently unspecified (always a 0).

Type of instruction 1

4-11

if a

if a TXD instruction was executed,
TYD instruction was executed.

Octal number of the input or output tested by the instruction,

Input or output tested
State of input

or output

= TXD (an input was tested)
= TYD (an output was tested)

Always

tested

Purpose

Instruction

TXD

Test Input and Display.

(7000+ NNN octal)

tested and the information previously described

The input specified by the value of
is

NNN

transferred to the

PDP-14 Output Register, where it may be read by a monitoring PDP-8
family computer.

The TEST flag is not affected by this instruction.

The output specified by the value of NNN
PDP-14
Output Register, where it may be read by a monitoring PDP-8 family
computer. The TEST flag is not affected by this instruction.

TYD

Test Output and Display.

(7400+ NNN octal)

tested and the information described above is transferred to the

These instructions are recognized and simulated in local mode of SIM- 14.

They are also executed in on-line

mode.

NOTE
TRM instructions are used in the same program with TYD's or
TXD's, bit 2 of the TRM transferred word should be a 1 to indicate to the monitor that it was not generated by a TXD or a
TYD. Any four-digit number with an odd first digit (1 , 3, 5,
or 7) cannot be generated by a TXD or a TYD.
If

9-5

PDP-14 register to another.

Transfers

which use the PCI or the Spare Registers as destination may also increment or decrement (by one) during the
transfer.

The previously introduced registers and their codes are used to construct the transfer instructions ac-

cording to the following format.

Not all possible transfer instructions are meaningful.

Op Code
Operation

Source

Destination

Specification
Bits

The operation code for a transfer instruction is 0000 in bits 0, 1,2, and 3.

Bits 4 and 5 contain the operation specification.

The following list gives the possible values for bits 4 and 5
Operation

Bits

00 or 10

Transfer the information contained in the source register to the

destination register.
Transfer the information in the source register, decremented by

The destination register must be
1 , to the destination register.
an incrementing type register, such as PCI or Spare (M747).
Transfer the information in the source register, incremented by

into the destination register. The destination register must
1
be an incrementing type register, such as PCI or Spare (M747).
,

The source and destination registers are specified by their respective codes given earlier in this chapter and
summarized below:
Register

Source Code

Destination Code

Dummy

000 = Oo

000 = Og

001 = I3

010=23

010 = 2g

Spare

Oll = 3g

Oil =3^

PCI

100 = 4g

100 = 4^

PC2

101=53

101

Input

110=63

Output

—

=5,

110 = 6
8

9-6

NOTES

A transfer register instruction which has a destination code
(Dummy) produces a PDP-14 instruction NOP (provided bit

3=0).
b.
The PCI register may be cleared by incrementing Dummy
while transferring it into the PCI register. Therefore, the
instruction to clear PCI is 0304 octal
The same is true for
the Spare register. Clearing Spare is accomplished by the
.

instruction 0303 octal

The destination register code 111 (7^) is used to produce the HLT instruction.

Any register transfer instruction

which has this destination code will halt the PDP-14 program execution.

The simplest form of HLT is described

below.

The HLT instruction may be used to stop the

HLT

Halt the processor.

(0007 octal)

processor until the start or continue switch of the PDP-14 is actiThis instruction should only be used for diagnostic purposes
and should not be part of a user's control program.

vated.

PDP-8 INTERFACE INSTRUCTIONS
The following instructions may be used when the PDP-14 is interfaced with a PDP-8 for monitoring purposes,
These instructions are executed within the PDP-8 family computer, but affect the operation of the PDP-14.

Skip Instructions

The following instructions allow the PDP-8 to determine conditions within the PDP-14 using conditional skips
of one PDP-8 location.
Instruction

SEP
(6161 octal)

Purpose

Skip on EXTERNAL Flag - The EXTERNAL flag is set by the PDP-14
whenever a GNI or LDE initiated operation is completed or whenever the PDP-14 executes an internally stored EEM or EES instruction. The EXTERNAL flag is on the PDP-8 program interrupt (PI)

The setting of this flag indicates that the controlling
computer can again interrupt the PDP-14, or enter a new external
mode instruction into the memory part of the PDP-14. Execution
of this instruction will cause the next PDP-8 instruction to be skipped
request bus.

SOF
(6171 octal)

the EXTERNAL flag is set.

Skip on OUTPUT REGISTER Flag - The OUTPUT REGISTER flag is set
whenever the PDP-14 transfers information to the Output Register.
The OUTPUT flag, like the EXTERNAL flag, is on the PDP-8 program
interrupt (PI) request bus. This instruction enables testing the Output

9-7

Purpose

Instruction

SOF (Cont)

The instruction following the SOF will be skipped only if

the OUTPUT flag is set.

STF
(6173 octal)

Skip on TEST Flag Set - This instruction will cause a program skip of
PDP-14 TEST flag is set. Thus

the following PDP-8 instruction if the

the monitor may determine if the TEST flag is set when the PDP-14

program is interrupted and,

if necessary,

may return the TEST flag to

the proper state when leaving external mode.

SCR
(6175 octal)

Skip on Controller Run - This instruction will cause a program skip of
PDP-8 instruction if the PDP-14 is running. When the

the following

PDP-14 is not running, it is not possible to enter external mode, or
PDP-14.

to start the

Input and Output Register Instructions

The following instructions allow the PDP-8 and PDP-14 to communicate through the Input and Output registers
of the PDP-14.

Purpose

Instruction

LIR

(6162 octal)

Load Input Register - This instruction transfers the contents of the accumulator of the controlling computer to the Input Register of the
PDP-14. Data transferred in this manner is expected to be used to

change the contents of internal PDP-14 registers. Register transfer
instructions to accomplish this may be executed from either internal
memory or the external memory port.

ROR

Read Output Register - This instruction clears the PDP-14 OUTPUT

(6176 octal)

flag, causes the accumulator of the monitoring

PDP-8 family com-

puter to be cleared and the contents of the PDP-14 Output Register
transferred into

it.

The PDP-8 program may check for the presence

of information in the Output Register by checking the OUTPUT flag
or the OUTPUT flag could request a program interrupt.
flag

ON, the Output Register may be read.

When the

Since ROR clears the

OUTPUT flag, each new transfer of information to the output register
will set the OUTPUT flag again.

The monitor must read the Output

the first word will be lost.

Load PDP-14 Instructions

The following instructions are used to load the PDP-14 with an externally supplied instruction.

Program ex-

amples assume a basic understanding of the PDP-8 programming.

Purpose

Instruction

GNI
(6165 octal)

Generate an Interrupt - This cycle -stealing instruction interrupts the
PDP-14, loads the MB of the PDP-14 with the content of the PDP-8

9-8

Instruction

Purpose

GNI (Cont)

accumulator, and clears the EXTERNAL flag. The PDP-14 takes its
instruction from the accumulator of the interfaced computer through
the memory port. The EXTERNAL flag is set when the PDP-14 instruction has been executed.

GNI does not increment PCI

will modify only the MB and IR,

unless otherwise specified by the instruction.

The instruction to be

loaded with the GNI must be held in the accumulator of the PDP-8
until the

EXTERNAL flag is set.

The suggested PDP-8 instruction sequence is:

CLA
TAD INSTRUCTION

/CLEAR THE ACCUMULATOR.
/GET THE INSTRUCTION INTO THE AC.

GNI

/GENERATE THE INTERRUPT.
/WAIT FOR THE INSTRUCTION TO
/BE EXECUTED BEFORE PROCEEDING.

SEF

JMP .-1

It should be noted that the PDP-14 will execute at least one programmed instruction after each interrupt. Thus, repeated use of the
GNI by the external computer will cause the PDP-14 to execute

externally supplied instructions on a cycle-stealing basis with one
external instruction executed followed by the execution of at least

one ROM-supplied instruction.
If it is

desired to inhibit the PDP-14 from executing instructions while

a sequence of external instructions are supplied and executed, an interrupt should be given to enter an

EEM or EES instruction.

It is

then

possible to enter successive instructions using the LDE instruction.

The LDE instruction given in the following example is usually used
while the PDP-14 is in external mode. Control is returned to the
PDP-14 program with a LEM or LER instruction supplied to the PDP-14
with a LDE instruction.

NOTE
The GNI instruction may be used while the PDP-14 is in
The result is described immediately after
the LDE instruction which follows.

external mode.

LDE
(6164 octal)

Load MB and Execute Instruction While in External Mode - Clear

EXTERNAL Flag - When the PDP-14 is in external mode, this instruction is used to load the instruction stored in the accumulator of the

PDP-8 family computer into the PDP-14 and execute it.

A new in-

EXTERNAL flag
held,
not
be
as
in GNI. Thus,
instruction
need
the
However,

struction can be loaded and executed every time the
is

set.

the suggested

PDP-8 instruction sequence is:

SEF

JMP

-1

TAD INSTRUCTION
LDE

9-9

/FLAG IS SET AFTER A GNI
/INITIATED ACTION IS COMPLETED.
/GET THE INSTRUCTION INTO THE AC.
/LOAD AND EXECUTE IT IN THE PDP-14.

Purpose

Instruction

/CLEAR THE AC AND PROCEED WITH
Ahe pdp-8 processing, another
/PDP-14 instruction MAY BE LOADED
/AND EXECUTED AS SOON AS THE FLAG

CLA

LDE (Cont)

/IS SET.

The instructions could also be supplied on a PDP-8 program interrupt basis.
Execution of LDE will not change the contents of any internal PDP-14
register except the MB, PCI , and IR, unless so specified in the instruction.
(When two-part instructions such as JMP, JMS, or TRM are loaded and executed with the LDE instruction, the EXTERNAL flag is set at the completion of each part of the instruction.)

The GNI instruction, in general, is used to interrupt the PDP-14 and it must wait for the PDP-14 to finish executing its current instruction before horroring the interrupt.

The LDE instruction is used after an EEM (or EES)

has been executed with a GNI and the PDP-14 is, therefore, in external mode.

When in external mode, either the LDE or the GNI instruction could be used to cause the PDP-14 to execute onelocation instructions (e.g. , TXD,

TYD and register transfers). The difference is that the LDE instruction will

increment PCI and keep track of instructions; the GNI will not increment PCI and the monitor must keep track
of the instruction sequence.

If,

while in external mode, the GNI is used to execute a two-location instruction (e.g., TRM, JMP, JMS),

the PDP-14 will take the second half of the instruction from its own
the

ROM

not present.

If a

ROM memory which will be a zero word if

two-location instruction is loaded with an LDE, the second half will be loaded

with the next LDE.

Remember that the TRM instruction causes the second half of the instruction to be transferred to the Output Register.

The fact that the second half of a TRM instruction is obtained from ROM memory whenever the PDP-14 is

in external

mode and the GNI instruction is used to load the TRM is very useful

amine a part of or the whole ROM memory.

allows the monitor to ex-

PCI will be incremented once each time a word is read from the

PDP-14 memory, enabling a search or dump of contiguous memory.
-N
CLA
TAD EEM
GNI
>

For example:

Put the PDP-14 into external mode.

SEF

JMP .-1
CLA
TAD

DCA

COUNT

Set up a counter, and supply the starting

TAD

START

address transferring it to the PCI

-N

NUMBER

TAD

GNI

(K264

contains 0264, transfer input to PCI.)

LIR

K264

9-10

DUMP,

SEF

JMP
CLA
TAD
GNI
CLA

.-1

Load fhe PDP-14 with a TRM and waif for

TRM

the output register to be loaded.

(The TRM

need not be held in the AC since the PDP-14
is in external mode.)

SOF
JMP .-1
ROR

y
Process the information:

compare it; list it; store it; etc.
ISZ

COUNT

JMP

DUMP

Check to see if you are done.

}

Using PDP-8 Program Interrupt to Monitor

A program interrupt request will be generated by the PDP-8 monitor computer if either the OUTPUT flag or the
EXTERNAL flag is set. The OUTPUT flag indicates that data is present in the Output Register. The EXTERNAL
flag signals that the

PDP-14 has completed execution of an external mode or interrupt instruction and is ready

for further instructions.

Thus, the PDP-14 can be monitored on a program -shared basis, with one PDP-8 serving

many PDP-14's.
The monitoring PDP-8 computer, when processing an interrupt request, must be able to clear the DEVICE flag

which caused the interrupt.

The instructions which follow perform this function.

CEF

Clear EXTERNAL Flag - By using CEF, the flag set upon completion

(6167 octal)

of PDP-14 instructions initiated by GNI or LDE can be cleared in-

dependently of GNI and LDE instructions.

CLF

Clear OUTPUT Flag - The OUTPUT flag which indicates that the

(6172 octal)

PDP-14 Output Register holds data for the PDP-8 can be cleared
independently of the ROR instruction using CLF. This instruction
also clears the PDP-8 accumulator.

should be noted that the execution of some instructions will cause both the OUTPUT flag and the EXTERNAL

flag to be set when monitoring a

PDP-14 using program interrupt.

The monitor should clear both flags before

turning the interrupt facility back on after an interrupt caused by such an instruction.

Otherwise an unwanted

double interrupt will occur.

MONITOR DESCRIPTIONS
The monitor for each PDP-14 system will be somewhat unique and will require individual programming.
general ideas and approaches for different applications are offered here.

9-11

Some

Transition Checking With BOOL-14

That is, for example, when is a solenoid

The most common need in monitoring is to know when an event occurs.
energized; when is a motor started; when is a limit switch tripped?

BOOL-14 provides for this type of PDP-14

monitoring.

The specific instructions added are de-

The commands and operation of BOOL-14 were described in Chapter 6.
scribed below.

To set

BOOL-14 terminates non-monitored equations by the following instruction sequence:

In general,

ON
To set OFF

L^SYF

OUTPUT

SKP

^ SYN

OUTPUT

The testing instructions proceed until the state of the output is determined.
set the output

ON, or fails to jump causing the output to be set OFF.

tered at one of two points:

A JFF or JFN instruction jumps to

Thus, the terminal instructions are en-

either to turn the output OFF or to turn the output ON.

When an output is monitored, this terminating sequence of instructions is altered. TYN or TYF instructions <jre
added to check for the occurrence of transitions.

TYD or TRM instructions are added to report the transition by

loading the output register and setting the OUTPUT flag.

should be noted that R-functions may be monitored as well as normal outputs or storage outputs.

The only

difference is that the last instruction of the terminal sequence is a JMR.

The terminating instructions for monitoring are entered in the same way as the terminal sequence of a non-

Namely, a JFF or JFN instruction has always been executed, clearing the TEST flag.

monitored equation.

Whenever the TEST flag is known to be OFF, a JFF instruction may be used as an unconditional jump.
conditional JFF instruction

often used in the termitKiting sequence for monitoring.

Monitoring for OFF (.MF) - The terminating sequence for .MF or .MF

NNNN (where NNNN

an octal num-

ber of 4 digits or less) is:

To set ON
To set OFF

OUTPUT
OUTPUT
NEXT
OUTPUT

•-^TYN
SYF
JFF

TYD
°'"

TRM

^NNNN
SKP

-^ SYN

This un-

OUTPUT

Test the present state of the output for

ON, then

turn the output OFF

If the output had been OFF, the test will be false
and the remaining instructions are bypassed. If
the output is ON, the TYD or TRM is executed to
report the transition. The SKP is then executed

to bypass the

9-12

SYN instruction.

Monitoring for

ON (.MN) - The terminating sequence for .MN or .MN NNNN (where NNNN

is an octal

number of 4 digits or less) is:

To set

ON
Set the output OFF and since the TEST flag must be OFF,

OUTPUT
NEXT
OUTPUT
OUTPUT
NEXT
OUTPUT

use a JFF to bypass remaining instructions.
Test present state of output for OFF

then turn the output ON.
If the output

had been

ON the test was false and

the remaining instruction is bypassed; if the

output had been OFF , the TYD or TRM is ex-

ecuted to report the transition

Monitoring All Transitions (.MFN) - The terminating sequence for .MFN or .MFN

MMMM and NNNN are octal numbers of 4 digits or less)
To set

NNNN, MMMM (where

is:

ON
OUTPUT
OUTPUT
NEXT
OUTPUT

Test the present state of the output for

ON,

then turn the output OFF.
^
If the output had

been OFF, the test will be false and

the remaining instructions are bypassed.

If the out-

put was ON, the TYD or TRM instruction is executed
to report the transition.

NEXT
OUTPUT
OUTPUT
NEXT
output'

The JFF is then executed to

bypass the remaining instructions.

Test the present state of the output for OFF, then set

the output ON.
If the output had

been ON, the test was false and

the remaining instructions are bypassed.

If the

output had been OFF, the TYD or TRM is executed
to report the transition.

Supervisory System

There are PDP-14 applications in which a power and light company wishes to scan a set of contact inputs, all
of which should be OFF.

If any

contact is ON, the monitor should be notified.

The following instruction sequence may be used for this monitoring application:

TXN

INPUT!

JFF

NEXT2

TXD

INPUT!
INPUT2

NEXT2,

TXN
JFF

NEXT3

NEXT3,

TXD

INPUT2

9-!3

If an

TXD instruction through the
input contact closes, the monitor will receive the 12-bit word sent by the

output register.

Notice that no control is performed in the above example, the PDP-14 simply serves a

watch-

man function.

Decision Making

When two or more PDP-14's are monitored by the PDP-8 to forni a network for material handling, each PDP-14
must interact with others.
decisions;

This means that the PDP-14 does not have enough information to make all necessary

does not know what other PDP-14's are doing.

Each PDP-14 is assigned two device

A simple approach is to have the PDP-14 request help from the monitor.
codes which differ from those assigned to other PDP-l4's.
For example,

if a

This allows the monitor to "address" each

PDP-14.

crate has been moved on an incremental conveyor to a point where it may be moved left or

right or continue straight ahead, the

PDP-8 must make the decision.

The PDP-14 requests this decision by send-

ing a distinctive word to the output register with a TXD, TYD or TRM.

This word

is sent

whenever a crate

reaches the position for decision as marked by a limit switch.

Upon receiving the direction word, the PDP-8 begins the decision-making process.
continues its other processing duties leaving the crate unmoved.

Meanwhile, the PDP-14

The PDP-8 determines positional information

concerning other PDP-14's with the TXD and TYD instructions executed through the cycle -stealing GNI.

When the monitoring PDP-8 reaches its decision, it sets one of three storage outputs in the S-box of the PDP-14.
The storage outputs are variables in the equations to move right, left, or proceed. When the PDP-14 solves
these equations after the PDP-8 supplied input, the crate will be moved in the proper direction.

The PDP-8

will then clear the storage output and wait for the next decision request.

Input Interrogating

machine tool applications, there are periods of time during which a set of inputs remains unchanged.

While

a slide moves forward, many inputs on the machine should be in a definite known state.

The monitor stores a list of the proper states for several points in the control sequence.
tion for testing begins, the

PDP-14 reports to the PDP-8 monitor.

When a suitable opera-

The monitor determines from the word received,

which operation is being performed and thus, which set of input conditions is applicable.
The PDP-8 then proceeds to check inputs with the TXD instruction executed on an interrupt basis using GNI's.
If any actual

input (e.g. , limit switch) state differs from the predicted state, the input failure is detected by the

monitor and an appropriate message is typed on the Teletype console.

9-14

CHAPTER 10
PDP-14 SYSTEM SOFTWARE OPERATION

This chapter describes the use of the five software elements of the PDP-14 system (Loader, Editor,

BOOL-14,

PAL-14 and SIM- 14). These system programs operate on a PDP-8 family computer, usually a PDP-8/I or 8/L.
The operation of the PDP-8 hardware system (computer console and ASR33 Teletype) is described in the PDP-8/I
System User's Guide (Order No.

DEC-08-NGCB-D).

PDP-8 SWITCH AND SWITCH REGISTER OPERATIONS
The PDP-8 is operated by a series of switches on the computer console.
user should be familiar with the START,

and EXAM (examine) switches.
switches at the proper time.

For PDP-14 programming purposes, the

STOP, CONT (Continue), LOAD ADD (load address), DEP (deposit)

The descriptions in this chapter will direct the user to operate each of these

These switches are all spring-loaded and will return to their normal positions after

release.

The PDP-14 software will not run if the SING STEP or SING INST switches are set on the PDP-8 console.

SING INST is not present on the PDP-8/L console.)

These switches should always remain off.

the top of these two switches should be in the OUT position, with the bottom IN.

In the

(In the

(The

PDP-8/I,

PDP-8/L the SING

STEP switch should be in the UP position.)

The twelve switches of the PDP-8 switch register are in four groups of three switches each.

Each group of

switches is the same color to differentiate them from the adjacent groups.

Every possible switch pattern for a 3-switch group is pictured in Figure 10-1

numbered

through 7.

There are eight such patterns,

The chart is essentially the octal-binary equivalents for the digits

their switch representations.

through 7, and

For example, to set a 3-switch group to the number 4, the first switch is set on,

and the second and third switches are set off.

NOTE
A PDP-8/1 switch is on when the top is OUT and the bottom
is IN.
A PDP-8/L switch is on when it is in the UP position.

10-1

OCTAL
NUMBER

LIGHTS

DISPLAY

-1

DOWN

Fi ri

OUT

OFF

m m
*

OFF

'-^^^--^

DOWN

OFF

n
i

Lu=

OUT

DOWN

OFF

OUT

DOWN

y[
I

OUT

DOWN

a m m

ri
n

OUT

DOWN

OFF

LJ
1

OUT

DOWN

OFF

=J L.1

OUT

uu
li.,,..jj

LL_

Figure 10-1

10-2

Examine Figure 10-1 and study the equivalents.

If you

are not familiar with the binary and octal number systems,

regard the table as a coding scheme which enables concise directions for switch settings.

For example in place

of stating:

SWITCH l = ON
SWITCH 2 = OFF
SWITCH 3 = ON

we can write "set the switches to 5"

thereby specifying the following switch configurations (Figure 10-2):

POP- 8/1
E^

pDP-e/L

Figure 10-2

As previously stated, the switch register is a group of 12 switches in the form of four 3-switch groups.
Figure 10-1 , we may use four numbers (with a range

through 7) to completely define all switch register set-

tings.

For example (Figure 10-3):

Set switch register to 1634:

1634

16 011100

001 110

POP- 8/1

PDP-8/L

Using

ijyyyyyyyy

Figure 10-3 (Part 1)

10-3

Set switch register to 2200:

2200

010 010 000000

POP- 8/1

PDP-8/L

upu uyu

bJil

II,

iiyyuyiiNuii;

14-0033

Set switch register to 200:

200

2
000 010 000000

POP -8/1

PDP-8/L

Figure 10-3 (Part 2)

PDP-8 LOADER PROGRAM
loader program must
Before any PDP-8 based program can be loaded into the PDP-8 memory, a
will read the binar/ format paper tape on which these programs are stored.

bring

be stored which

The loader program is then used to

BOOL-14, SIM-14 and all other system software into the PDP-8 memory.

NOTE
The loader program to be used with PDP-14 software is the

HELP Loader.

Readers who are familiar with other PDP-8

software should be aware that the HELP Loader contains the
more familiar RIM and BIN loaders. Once HELP is loaded,

RIM and BIN are both in memory. Binary paper tapes are
actually loaded by the BIN loader, not by HELP. This distinction is not necessary for the new PDP-8 user to understand.

Loading the HELP Loader
The procedure used to store the HELP loader itself in memory is described below.

The numbers represent PDP-8 instructions which are used to load a short paper tape.

This paper tape contains

the loader program for binary format tapes, such as BOOL-14 or SIM-14.

The data field and instruction field switches should be set to

memory.

If a

while the Loader is being stored in the PDP-8

PDP-8/L is being used, the MEM PROT switch must be in the DOWN or off position while the

loader program is being stored in memory.

10-4

The user sets the following switch register configurations, and then presses the

switch noted at the right of the

configuration.

Switch Register Setting

Operat ion Switch

0027

LOAD ADD (Load Address)

6031

DEP

(Deposit)

5027

DEP

(Deposit)

6036

DEP

7450

DEP

5027

DEP

7012

DEP

7010

DEP

3007

DEP

2036

DEP

5027

DEP

(Deposit)

The first number above is the first address where the instructions are to be stored, and the

following numbers are

the instructions to be deposited in the PDP-8 memory.

Once the instructions are ail loaded, the user should check to see that the program was loaded correctly by
examining the stored instructions.
stored instruction when the

The lights of the Memory Buffer console display will light to indicate the

EXAM switch is pressed.

The lights will have patterns corresponding to the numbers

given below, if the instructions have been correctly loaded.

If the

Switch Register Setting

Operation Switch

0027

LOAD ADD

Operation Switch

Memory Buffer Display

EXAM

6031

EXAM

5027

EXAM

6036

EXAM

7450

EXAM

5027

EXAM

7012

EXAM

7010

EXAM

3007

EXAM

2036

EXAM

5027

instructions have been loaded incorrectly, the user should restart the switch setting process.

10-5

When the switches are correctly loaded, the user should place the HELP Bootstrap Loader paper tape (DEC-08LHAl-PB) in the paper tape reader of the Teletype unit, and set the reader control switch to START.

The user

then sets the switch register to 0027, and presses the LOAD ADD and START switches of the PDP-8 computer
console.

The paper tape rontaining the loader will then be read.

the loader program in memory, any system program (e.g., SIM-14,

If a

BOOL-14, etc.) may be loaded.

PDP-8/L is used for programming, the MEM PROT switch of the PDP-B/L console should be put in the UP

position, once the loader is in memory.
is

Once the tape has been read, thus placing

This prevents unwanted destruction of the loader program.

This switch

not present on other family-of-8 computers.

Loading a Binary Tape into the PDP-8

To load a system software paper tape into the PDP-8 memory, place the tape in the paper tape reader of the
Teletype unit, and set the reader control switch to START.

The tape must always be positioned with the leader

tape over the reading head. Then set the PDP-8 switch register to 1711 , press the LOAD ADD and START switches
of the PDP-8 computer console.

If the

preceding directions have been followed correctly, the tope will now be

read into memory. When the tape reaches the end,

will stop.

any light of the accumulator display on the

PDP-8 console (not LINK display) remains on, a reading error occured and the tape must be re-read. If a light
remains on, a checksum error has occurred.

If the

PDP-8 system is equipped wilh a high-speed paper tape reader, a similar procedure is followed. The paper

tape is positioned in the endtr with the leader tape over the reading sensors.

7777, and the LOAD AD*

START sv/itch is depressed

-tc''

i;ie

depressed.

The PDP-8 switch register is set to

The first left-hand switch is then set OFF (SR = 3777), and the

binary tape will then be read.

BEGINNING
OF TAPE

)

BLANK TAPE

LEADER TAPE
END OF TAPE

Figure 10-4

10-6

PDP-8 EDITOR
PDP-14 users of BOOL- 14 and PAL- 14 must prepare a paper fape record of their program.
referred to as a program source tape or source language tape.
into the machine language or binary tape used by the

This paper tape is

BOOL-14 and PAL-14 translate the source tape

PDP-14 itself.

Machine language is the form in which

PDP-14 programs are debugged with SIM-14.

Composing Source Programs
The PDP-8 Editor program may be used to compose progroms in the BOOL-14 and PAL-14 source language.
Editor allows the
occur,,

The

PDP-14 user to type the program on the Teletype keyboard and correct typing errors as they

Sections of the program may be moved or removed by typing single Editor commands.

Program source

tapes are generated by Editor which are, in turn, used as input to BOOL-14 or PAL-14.

Updating Source Programs

A second, and very important, function of the Editor is updating user programs.
program, many changes will be made to the original version.

During the life of a PDP-14

Bugs uncovered with SIM-14, changes in machine

function, and additions of new inputs or outputs to the machine all require changes to the PDP-14 program.

These changes may be made with SIM-14; however,
program.

in this case

there is no permanent record of the altered

The user should always correct the source tape of his program by reading it back into the Editor,

making the necessary changes and corrections to the source program, and generating a new program listing and
tape.

Text Buffer

A Buffer is a computer storage area. The text buffer stores the text of PDP-14 programs typed by the user.
text buffer is organized by lines of text.

can-iage return at the end of the line.
referred to by its line number.

The

A text line is a collection of typed characters up to and including the

The lines of the text buffer are numbered decimally and each line is

By referring to these specific line numbers, the Editor commands delete lines of

text, insert lines of text before a specified line,

change lines of text,

list

lines of text and more.

Modes of Operation
Since Editor accepts both commands and text from the Teletype keyboard,

must know whether the characters

currently being typed are text of the program being created or modified by the user, or are commands directing

the Editor to perform some function upon the text.

between two modes.

In the

The Editor makes this distinction by dividing its operation

command mode, all characters typed on the Teletype keyboard will be interpreted

10-7

as commands to the Editor to perform some operation on the content of the text

operate upon the text.

buffer, or to allow the user to

text buffer.
In the text mode, all characters typed on the keyboard are entered into the

Typed text may replace, be inserted into, or be added at the end of the current content of the text buffer.
The current mode of the Editor must always be kept in mind.

a command is typed while the Editor is in text

mode, it will not be recognized as a command by the Editor and will be entered into the text buffer.
if text is typed

Likewise,

while the Editor is in command mode, it will be treated as a command.

Transition Between Modes

The Editor is in command mode when it is first loaded and is ready to accept the first command from

the user.

Only legal commands are accepted; any other typed characters cause the Editor to type a question mark (?) and
wait for a legal command to be typed.

Some commands cause the Editor to enter text mode, where all charac-

ters typed are entered in the text buffer.

When the user has finished typing his program and wishes to leave the

the
text mode, he simply holds the CTRL key of the Teletype keyboard depressed while he strikes

FORM key

(CTRL/FORM). The Editor will respond by ringing the Teletype bell and waiting for the user to type a new

command (Figure 10-5).

/IMAND THEN
TYPE A COMM
PRESS RE TURN KEY.

MMAND MODE

TEXT MODE

TYPE DESIRED PROGRAM
TEXT, THEN PRESS THE

CTRL/FORM KEYS.

Figure 10-5

Adding Text to the Buffer
To compose PDP-14 programs with the Editor, simply type "A^

The A command instructs the Editor to enter

text mode and add all text typed on the keyboard to the text buffer.

The new text is added at the end of any

text currently in the buffer.

Editing Keys

Typing errors, which invariably occur, may be erased with the RUBOUT key.
acter or space to the left each time it is struck.
of text.

This key will delete one char-

The RUBOUT key can only delete characters in the same line

The Editor types a backslash (\) for each time the RUBOUT is struck.

10-8

Characfer removed by
each RUBOUT

Y50 = X23 * X17 \\\ Y17 * (X43 + Y50) ^
J

)

3 RUBOUTs

3 characters
or

T^WV YN SOLA^

START, TXN LSI

Character removed by
'each RUBOUT

WWW

6 RUBOUTs

5 characters
and 1 space

In the foregoing examples, the user entered text mode with the

gram above or a PAL-14 program below.
striking the

A command and began typing a BOOL-14 pro-

He typed the wrong information, however, and changed it by repeatedly

RUBOUT key and "erasing" all characters back to the "*" in the BOOL-14 program and back to the

"T" in the PAL-14 program.

He then typed the correct characters, terminating the line by typing RETURN.

The corrected versions of the foregoing examples are now:

Y50 = X23 * Y17 * (X43 + Y50) J
or

START, TYN SOLA ^
The backarrow (*-) is also used to erase typed characters from the text buffer.
key while striking the letter O key.
left margin

It is

typed by holding the SHIFT

This special character deletes the complete line of characters between the

and itself.

Y5 = X2 + / (X16 * Y3) -; THE FOLLOWING EQUATION CONTROLS SOLENOID A. )
In the above example, a complete line of text was deleted using the backarrow,
its

place.

and a comment was inserted in

The line of the text buffer is now:

;THE FOLLOWING EQUATION CONTROLS SOLENOID A.

Reading a Paper Tape
Source tapes previously generated by the Editor may be read into the text buffer for modification or addition by
using the command:

10-9

If the

The paper tape will be read from the low-speed reader into the fext buffer.

buffer is not empty, the

information will be added at the end of the previously stored text.

After the R is typed and the tape is read, the Editor will ring the Teletype bell and enter command mode.

The R command will read a paper tape from the high-speed reader when the last switch of the switch register
(SR 11) is set ON.

Otherwise the tape will be read from the low-speed reader of the Teletype.

Listing a Program

Once the program has been typed or read from a tape, the complete text can be typed by issuing the L command.

The complete content of the text buffer will be typed on the Teletype printer.

The L command may be modified to type only certain lines by specifying limits for the list.
preceding the "L" and are separated by a comma.

1,15L }
12L

List

For example:

the content of text buffer lines

List line

The limits are typed

through 15 inclusive.

12 of the text buffer.

Remember that the lines of the text buffer are numbered decimally starting with line 1

After the Editor has

typed the text, it will enter the command mode.

Inserting a

New Line of Text

PDP-14 programs may be modified with the Editor by inserting new lines of text using the I command.

This

command is typed, preceded by the decimal number of the line before which the new text will be placed.
For example,

151

will allow one or more new lines of text to be typed before line 15 of the current text buffer.

Editor will remain in text mode and accept all characters and lines typed by the user into the text buffer.

When

the user has completed typing the lines to be inserted, he should type CTRL/FORM to return to command mode.

The Editor "pushes down" text in the buffer when the I command is used.

The new text will be automatically

numbered, thereby changing the previously assigned line numbers.

(viz. , 151

Thus,

one line is inserted before line 15

J) old line 15 will become line 16 and the newly typed line will become line 15.

10-10

Deleting Lines from the Text Buffer

PDP-14 programs may also be modified by deleting lines with the D command. The command is typed, preceded
by the line or lines to be deleted.

For example,

removes the first 15 lines of the text buffer.

Line 16 immediately becomes line

and all other line numbers are

adjusted accordingly.

After executing the D command, the Editor returns to command mode.

Remember that when a line has been deleted, the line numbers for the remaining lines are immediately adjusted.
For example, the following two commands will actually delete lines 16 and 17 of the original text buffer.

16D ^

16D^
The complete buffer is deleted by using the K (kill) command.

may be used after punching one program and

before reading another program tape.

Changing Lines of Text
The C (change) command is a combination of the D and I commands and allows the replacement of a line or
group of lines by text typed on the keyboard.

For example:

]5,UCJ
deletes lines 15 through 17 and then causes Editor to enter text mode.
serted as lines 15, 16, 17, 18, etc.

The text typed by the user is then in-

The user may type as many lines as needed.

When the new text has been

typed, strike the CTRL/FORM to return to command mode.

The C command may replace one line with many lines, or many lines with only one; there need be no relation

between the amount of lines deleted and the amount of lines added in their place.

NOTE
Line numbers are automatically adjusted for the new text
when the user presses the CTRL/FORM to return to text mode.

10-11

Moving Lines of Program Text
Occasionally PDP-14 programs need to be completely reorganized (e.g., to better fit the "page structure" of
the PDP-14).

This reorganization can easily be accomplished with the

M (move) command. The M command

has a special command format which specifies the line or group of lines to be moved and the line number before

which these moved lines will be placed.

For example:

15,27$30M

will

move lines 15 through 27 before line 30. The line numbers are automatically adjusted and the Editor re-

turns to command

mode.

In the foregoing example, line 30 will

lines 15 through 27 will

remain line 30; line 28 will become line

15; line 29 will

become line 16;

become lines 17 through 29,

Remember, the M command can move one or more lines before the line number which is preceded by a "$" in
the command.

The Editor automatically returns to command mode after an M command is executed.

Search Feature

A very helpful feature available with the Editor is the search feature, which allows the user to modify a line of
text without completely retyping the line.

"S" and a carriage return.

The line number for the line to be searched is typed followed by

The user then must type the "search character".

board character (e.g. , a letter, number or symbol).
the key is struck.

This character may be any key-

The search character is not printed on the teleprinter when

Instead, the Editor begins typing the searched line up to and including the first occurrence

of the designated search character.

When the Editor locates and types the search character, typing stops and

all, or any combination of, the following operations may be typed by the user:

New text and terminate line with the RETURN key to change the entire line to the right,

-to delete the entire line to the left,

RETURN to delete the entire line to the right,

RUBOUT to delete from right to left one character for each RUBOUT typed,

LINE FEED to insert a carriage return/line feed, thereby dividing the line into two lines,

CTRL/FORM to search for the next occurrence of the search character.

For example, consider the following equation:

Yll = X21 * X34 * YIO * (X31 + X21 + X44)
assume that the "(X31" should be "(Y31".

10-12

The letter X could be selected as the search character.

However, since there are two occurrences of the

letter X prior to the one to be altered, the CTRL/FORM keys must be used to pass by the two preceding letter

X's.

Once the third X is reached a RUBOUT is struck to delete the X and then the letter Y is struck to replace
The CTRL/FORM keys are used to continue the search until the end of the line, thereby completely

the X.

If the

retyping the line.

RETURN key were used after the letter was changed, the remainder of the line would

have been deleted.

RUBOUT

Yll = X21 * X35 * YIO * (X\Y31 + X21 + X44)

'CTRL/FORM J^--^
If the

user had selected the number 3 as the search character, he would have used one CTRL/FORM to get to

the second "3".

He then could type two RUBOUTs (thereby removing the 3 and the X), and type Y3 and then

CTRL/FORM to repeat the remainder of the line.

Thus, the intelligent choice of a search character can ease

the editing task when the search feature is used.

Special Characters

The use of the Editor commands in most cases requires the user to type line numbers.

These line numbers are

computed by counting the number of preceding lines, or the following special characters may be used

.(period)

has a value equal to the line number of the last edited line.
after a line

edited,

Thus

may be listed by typing ".L" and a car-

riage return.

/ (slash)

has a value equal to the line number of the last line in the buffer.

Thus "/D" means delete the last line.

+ , - (plus, minus)

may be used with the ". " or "/" characters to represent line numbers.
For example, ".+5L" means list the fifth line after the last edited
line.

= (equals)

may be used with the ". " or "/" characters to find the value of these

When the user types ". = ", the Editor will type the
decimal line number of the current line. When the user types "/=",
the Editor will type the decimal value of the last line in the buffer.
characters.

Punching a Source Tape

Once the PDP-14 program has been prepared with the Editor, a paper tape is punched with the P command,
This command may punch the complete program (P) or a group of lines within the program

10-13

(15,30P^ ).

The procedure for generating a source tape using the low-speed punch (LSP) of the Teletype is:
Quickly press the LSP ON.

Type T^

Press the

Type the punch command:

Turn LSP ON.

Press

Press the

Press F and

Leader/trailer tape will be punched.

LSP OFF.
P y

nP v

or m,nP

CONT switch located on the PDP-8 console.

(where m and n are decimal line numbers).

The program text will now be punched.

LSP OFF.

RETURN keys.

Turn LSP ON.

A special character is placed to signal the end of

Turn LSP ON.

Leader/trailer tape will be generated.

the tape for the Editor.
8.

Turn the LSP OFF.

Type T and RETURN keys.

10.

Turn the LSP OFF and remove the source tape.

The procedure for generating a source tape using the high-speed punch (HSP) is:
Set the next-to-last switch of the switch register (SR 10) ON.
Press the HSP

ON.

Type T and RETURN keys.
Type the punch command:
Press the

PDP-8 CONT switch.

np ^ ,

m,nP^

(where m and n are decimal line numbers)

The program text will now be punched.

Type F and RETURN keys.

Type T and RETURN keys.

Remove the generated source tape.

A program may be segmented and punched in sections using the .EOT (BOOL-14) or EOT (PAL-14) control statements to conclude all but the final segment.

a PDP-14 program.

Thus, the above procedure may be used to punch all, or part of,

This allows the user to edit and generate tapes for programs which are not small enough to

fit completely within

the text buffer.

Editor Summary Tables

Tables 10-1 and 10-2 summarize the characters and symbols used with the Editor.

have different meanings when used in command or text mode.

10-14

Note that the characters

Table 10-1
Special Editor Keys

Command Mode

Key

RETURN

Text Mode

Execute preceding command

Enter line in text buffer

Cancel preceding command (Editor
responds with a ? followed by a
carriage return and line feed)

Cancel line to the left margin

RUBOUT

Same as *-

Delete to the left one character for
each depression; a \ (backslash) is
echoed (not used in Read (R) command)

CTRL/FORM

Respond with question mark and remain in command mode

Return to command mode and ring teleprinter bell

Value equal to decimal value of
current line (used alone or with +
or - and a number, e.g., .+8)

Legal text character

Value equal to number of last line
in buffer; used as an argument

Legal text character

LINE FEED

List next line

Used in Search (S) command to insert

CR/LF into line

List next line

List previous line

Used with
value

or /to obtain their

Same as = (gives value of legitimate

argument)

ctrlAab

Produces a tab which on output is interpreted as 8 spaces or a tab/rubout ,

depending on SR option

Table 10-2

Summary of Editor Commands
Type
Input

Editing

Command

Function

Append incoming text from keyboard into text buffer

Append incoming text from tape reader into text buffer

List entire text buffer

List line n

m,nL

List lines

Change line n

m,nC

Change lines m through n inclusively

Insert before first line

m through n inclusively

10-15

Table 10-2 (Cont)

Summary of Editor Commands
Function

Type

Command

Editing

Insert before line n

Delete line n

m,nD

Delete lines m through n inclusively

m,n$kM

Move lines m through n to before line k

Search buffer for character specified after RETURN key and
allow modification (search character is not echoed on printer)

Search line n, as above

m,nS

Search lines m through n inclusively, as above

Punch entire text buffer

Punch line n

m,nP

Punch lines m through n inclusively

Punch about 6 inches of leader/trailer tape

Punch a FORM FEED onto tape

(Cont)

Output

m and n are decimal numbers, and m is smaller than n; k is a decimal number
The P command halts the Editor to allow the programmer to select I/O control; press CONT to
execute these commands.

Commands are executed when the RETURN key is depressed, excluding the P and N commands.

Loading the Editor

The Editor is supplied as a binary paper tape (No. DEC-08-ESAB-PB) and is loaded with the loader program.
It

will operate in any field of a

PDP-8.

Starting the Editor

When the Editor has been loaded and no checksum error has occurred, the PDP-8 switch register is set to 200
and the instruction field is set equal to the data field,
switches are then depressed in that order.

from the user.

an 8K PDP-8 is used.

The LOAD ADD and START

The Editor will type a carriage return and await a typed command

All further operation is controlled by commands.

The paper tape output and input are controlled by the last two switches of the switch register.
reader/punch is to be used, these switches should be set ON.
used, these switches should remain OFF.

10-16

If the

high-speed

low-speed reader/punch of the Teletype is

NOTE
Further Information on the Editor, including features not

described in this manual, is available in the DEC publications:

Symbolic Editor Manual (DEC-08-ESAB-D), and
System Users Guide (D EC-08 - NGC B-D )

BOOL-14 OPERATION
BOOL-14 reads paper tape records of programs in an equation format, or equations typed directly on the
type keyboard.

translates them into a paper tape in machine code (binary) form which contains the

Tele-

instruc-

tions necessary to solve the equations.

Loading BOOL-14

BOOL-14 is supplied as a binary tape and is loaded into the PDP-8 memory with the loader program.
the paper tape reader on the ASR-33 Teletype or the high-speed reader may be used

If programs
is

required.

Either

to load the tape.

PDP-8 system
requiring greater than IK of PDP-14 memory are to be compiled by BOOL-14, an 8K
In this case,

BOOL-14 is loaded into field

of the PDP-8 (by setting the data field switches to 1)

Starting BOOL-14

When BOOL-14 has been loaded and no checksum error has occun-ed, the PDP-8 switch register is set to 2200
START
and the instruction field switches are set to the value of the data field switches. The LOAD ADD, and
switches are then pressed in that order.

If the

high-speed reader is to be used, the source program paper tape

should be loaded in the high-speed reader before the queries are answered.

When started, BOOL-14 will respond by typing sequence of queries, for example:
Meaning

Query

*BIN-NLH?

What device is to be used for the binary output tape?

binary requested (N); binary on the low-speed

*LST-NYW?

What listing form is required? No listing is required (N).
In this case, only error messages will be typed.

Yes, a listing

requested (Y) which will contain any reduced forms determined by BOOL-14. Yes, a listing is requested, but without
is

the reduced equation forms (w)

*SRC-KLH?

What is the source device from which the program will be supplied
to

BOOL-14? Will it be the keyboard (K), the low-speed reader

of the Teletype (L), or the high-speed

*EDT-NY?

editing requested.

10-17

paper tape reader (H)?

No (N), or Yes (Y)?

When the *EDT-NY? query has been answered, compilation will begin.

If the

program is to be supplied from

the keyboard, the user will type the first equation or control statement following the quotation mark (").

the low-speed reader is used to read a source paper tape, the reader must be switched to START before the compilation will begin.

the high-speed reader is used and it was not loaded prior to answering the final query,

the user must stop BOOL-14 and restart at 2200, after he has loaded the tape to be translated into the reader.

the editing option is requested and the low-speed reader is the SRC device,

BOOL-14 will halt after an error;

the reader must be switched to STOP and the PDP-8 CONT switch must be pressed.

After the editing is com-

pleted, the compilation will continue when the user switches the low-speed reader to START.

BOOL-14 will complete the compilation after reading the source paper tape once. However, if the program
has been segmented with the

EOT statement, BOOL-14 will halt after the incomplete tape and type "EOT".

The next tape should then be loaded and the PDP-8 CONT switch depressed.

When the compilation is complete, BOOL-14 will type the message "TURN PUNCH ON" if a binary tape is to
be punched.

The proper punch should then be turned

ON and the PDP-8 CONT switch depressed. The binary

output tape will then be punched.

If more

than one source tape is to be assembled, the user may simply press the PDP-8 CONT switch after the

binary paper tape is punched.

BOOL-14 will then begin the option queries by typing "*BIN-NLH?"

PAL- 14 OPERATION
PAL-14 reads paper tape program records in a symbolic form and translates them into a paper tape in machine
code (binary) form which is acceptable to SIM-14.

The paper tape which is input to PAL-14 is a symbolic or

source tape and may be generated using a Teletype (in LOCAL mode with the punch turned ON) or by using
the PDP-8 Editor program.

Once this symbolic tape has been generated, the program is assembled through the

following procedure.

Loading PAL-14

PAL-14 is supplied as a binary tape and is loaded into the PDP-8 memory with the loader program.

Either the

paper tape reader on the Teletype or the high-speed reader may be used to load the tape.

an 8K PDP-8 is used for the assembly process, the symbol table storage capacity is expanded when PAL-14 is

loaded into field

(by setting the data field switches to

10-18

during loading).

Starting

PAL-14

To start PAL-14, set the PDP-8 switch register to 200, set the inrfruction field switches equal to the data field,

and press the console switches LOAD ADD and START, in that order.

PAL-14 will tfien type the following

queries to determine the devices to be used during assembly.

*BIN

Type the letter signifying the device on which the binary tape,
which is the assembly output, will be punched.

*LST

Type the letter signifying the device on which the assembly
listing will be typed (or punched).

*SMB

Type the letter signifying the device on which the symbol
table will be typed (or punched).
Type the letter signifying the device on which the program

*SRC

source tape will be read.

The responses are:
L

The low-speed Teletype unit is to be used as the device.

The high-speed paper tape reader/punch is to be used as
the device.

The particular output is not wanted; the RETURN key is typed
without being preceded by either an L or H
If the

PDP-8 system is not equipped with a high-speed reader/punch unit and all outputs ore wanted, the re-

sponses to all questions will be L and the query sequence will be:

*BIN-L }
*LST-L )

*SMB-L^
*SRC-L ^
To generate an error listing only, request no binary, no listing, and no symbol table, specifying only the source
device.

If the

user makes a mistake when typing a response to a query, he may change the response before he has typed

the terminating carriage return simply by typing the correct response.
For example:

*BIN-LH }
*LST-HL )

the same as typing:

*BIN-H ^
*LST-L

)

10-19

Only the last character is recognized.

The user may erase all previous query responses and restart the sequence of queries by typing the response X.
For example:

*BIN-L ^
*LST-L )

*SMB-X }
*BIN- }

The query sequence has been restarted.

Two additional responses are used to control the output of optional error listings. These character responses
may be typed along with the required response to any query. They may be erased by typing the X response and
restarting the query sequence.

No separate error listing is desired on the Teletype. PAL-14

will suppress the output of the Pass

error listing to the Teletype.

high-speed punch is used to output the assembly listing,
the output of Pass 2 errors to the Teletype will also be suppressed.
If the

If the

high-speed punch is used to output the assembly listing,
1 error listing be punched on the

typing E requests that the Pass

high-speed punch, also.

For example, the following sequence of queries and responses results in binary output on the high-speed punch
1)

the assembly listing will be punched on the high-speed punch, 2) the symbol table will be typed on the

Teletype, 3) the source tape will be read from the high-speed reader, 4) there will be no Pass
listings typed on the

or Pass 2 error

Teletype, and 5) the Pass 1 error listing will be punched on the high-speed punch.

*BIN-HN^
*LST-HE )
*SMB-L i
*SRC-H )

Assembly Passes

PAL-14 must read the program source tape two or possibly three times dependent upon the selection of assembly
devices.

The first pass of PAL-14 defines symbols and checks for errors.

symbol table.

If separate devices are designated

punched on the second pass.

If the

The second pass types the listing and

for the listing and the binary output, the binary will also be

same device (e.g. , the Teletype) is used for listing and binary output, a

third pass will be required to punch the binary tape and thereby complete the assembly process.

PAL-14 will type the message:

*PAS
and halt when it has completed an assembly pass.
in the reader and presses the PDP-8

CO NT switch.

If a

further pass is needed , the user reloads the paper tape

If the

low-speed reader is used as the SRC device, the

10-20

reader must be switched to START before the pass will start.

Before beginning the pass which will punch the

binary tape output (either pass 2 or 3), the punch designated in the BIN query must be turned ON.

More than one program may be assembled without reloading PAL-14 by pressing CONT in response to the "*PAS"
statement typed after the binary output has been punched.

PAL-14 will respond by typing the initial queries

(*BIN, *LST, *SMB, and *SRC), and the assembly process may be restarted.

If a

PAL-14 source program is contained on two or more source tapes, the assembler will stop after reading all

but the last source tape and type:

*EOT

(end of tape)

The user should load the next sequential tape and press the PDP-8 CONT switch whenever this message is typed.

Error Halt

The only error which will halt the assembly is symbol table overflow.

If this

occurs, PAL-14 will type:

*SMB OFLW
Recovery is only possible by:

the user is presently assembling using a 4K PDP-8, he will increase the symbol table area by

using an 8K PDP-8 and loading
b.

If an

PAL-14 in Field 1

8K PDP-8 is not available, or if such a system is presently being used, the user must segment

his program and

assemble it in parts.

In both of the above cases, the assembly must be restarted.

SIM-14 OPERATION

SIM- 14 reads the paper topes as output from BOOL-14 or PAL-14 and allows the user to thoroughly test the
program thus generated.

SIM-14 outputs a birwry tape to be sent for the weaving of the Read-Only-Memory

(ROM).

Loading SIM-14

SIM-14 is supplied as a binary tape and is loaded into the PDP-8 memory with the loader program.
paper tape reader on the ASR-33 Teletype of a high-speed reader may be used to load the tape.

10-21

Either the

SIM-14 is loaded into Field

if the

PDP-14 will have a IK memory.

If the

PDP-14 program will require greater

than IK of PDP-14 memory, a PDP-8 with 8K of memory is needed to simulate the PDP-14 memory.
the SIM-14 program is loaded into Field

of the 8K

In this case,

PDP-8, by setting the data field switches on the PDP-8

when SIM-14 is loaded.

equal to

Starting

SIM-14

When SIM-14 has been loaded and no checksum error has occurred, the PDP-8 switch register is set to 2200,
and the instruction field is set equal to the data field if an 8K PDP-8 is used.

The user then presses (1) the

LOAD ADD switch (load address) and (2) the START switch, in that order. SIM-14 responds by typing its version number (e.g. , V3 means version 3 of SIM-14), and a period to signal its readiness to accept commands

from the user.

When it is started at location 2200 as above, SIM-14 will load all PDP-14 simulated memory with the instruction

NOP (0000).

All instructions must

Thus, unwanted instructions can never be in the simulated program.

be entered by the user.

SIM-14 also sets the values of all inputs and outputs for local mode execution to OFF

state

SIM-14 may be restarted without destroying the user's program or assigned input and output values by setting
the switch register to 2201 and then pressing the LOAD ADD and START switches.

SIM-14 ever appears to be out of control in the local mode and the user cannot type commands, SIM-14

probably is executing the PDP-14 program and is in a closed loop.
switch register

The user should set switch 9 of the PDP-8

ON (with switch 8 OFF), and control will return to SIM-14.

New commands may then be typed.

To prematurely terminate typing by SIM-14, simply set switch 5 of the PDP-8 switch register

ON and then OFF.

SWITCH REGISTER KEY

A very useful aid for operating the PDP-8 switch register is pictured below.
12 switches of any PDP-8 family computer.

The key may be mounted over the

The starting address switch settings for the Loader, Editor, BOOL-14,

SIM-14, and PAL-14, are identified with symbols.

The switches operated when using SIM-14 are also marked

(Rgure 10-6).

TO START:

SET SWITCHES ON: PDP-14 KEY FOR PDP-8 SWITCH REGISTER §ON-LINE ONLY

LOADER

all

PAL-14 & EorroR
SIM-14 & BOOL-14
SIM-14 RESTART

•

STOP

A
A

TYPING

ADDRESS
STOP

4X A
Figure 10-6

10-22

TYPE
LAST
INSTR

AUTO.

RETURN

PROGRAM

RETURN

SIM-14

ENAB ;^ ^ ENAB ^
STOP g ^ PROG
STOP ^
EQ

CHAPTER n

INSTALLATION
BASIC FACTORS AFFECTING SYSTEM INSTALLATION
The three basic factors that affect the PDP-14 system installation:
a.

electrical noise

heat dissipation

cabling and maintenance clearance.

The following discussion explains the importance of each of

these factors, as an introduction to an orderly in-

stallation scheme.
Electrical Noise

Electrical noise abounds in many common industrial environments.

Large electrical noise pulses are generated

by motor controls, brush-type motors, and any other devices which abruptly switch
create arcing.

large amounts of power and

Plasma flame cutters and high-power RF heating unit^ are the source of the worst

noise.

These

noise signals can travel many yards from their source, into cables and anything
else in the vicinity.
Electronic switching circuits use electrical pulses in their normal operation.

accepting electrical noises from the environment which might be accepted

They must be protected against

as valid control signals.

Although

the obvious place to eliminate hash is at its source, this is not always
feasible, and can be quite expensive.

Early designs of solid-state control equipment were extremely sensitive to
hash, and required elaborate protection from the hostile environment they were supposed to be
in an air-conditioned and

controlling.

If a

computer was used, it was placed

humidity-controlled engineering area, often far from the controlled equipment.

many cases, such cumbersome solutions to hash problems just weren't practical

And so, solid-state control

equipment acquired a bad reputation and was put on the shelf.

The PDP-14 AND Electrical Noise
Solid-state design has advanced greatly since the early 1960's.

If the

installation instructions in this chapter

are complied with, you can put the PDP-14 control system in nearly any industrial environment without concern
for noise problems.

If the

installation

be located near absurdly high sources of electrical noise (such as

plasma cutting equipment), some additional precautions may be needed, and you should consult a PDP-14 Applications Engineer.

The PDP-14 control system is protected in three ways:
a.

Circuit design techniques which reject false pulses of electrical energy

Hash filtering or shielding on cables and other sensitive points

An installation arrangement which provides an overall shield protection.
11-1

Installation considerations which reduce noise problems are as follows:

The entire system is to be mounted in a standard NEMA 12 enclosure, and operated with the
enclosure door closed (except for maintenance operations, when this is not possible). The NEAAA 12
a.

an effective noise shield.

b.
The Control Unit
shielding.

(CU) cover is to be in place for all normal operations, as a second level of

I,
c.
O, A, and S boxes are to be placed nominally between the CU and the entering AC signal
cables, to reduce noise transfer.

An arrangement of AC and control cables, given later in the chapter, helps reduce noise transfer
d.
even further.
These requirements are similar to those of any ordinary control system.

Heat Dissipation
The PDP-14 system is designed to be cooled by natural convection and does not require special equipment.

The

system produces heat from two sources;
a.

Current from the low-voltage power supply dissipated in the electronic circuits of theCU and I,

AC current dissipated in the circuits of the

and A units;

AC is dissipated in both I- and O-box circuits.
active would consume 1.5 x 32, =

and O boxes.

Since each input of the

48 VA, or about 44 watts.

box is a 1.5 VA load,

all

32 inputs

A more reasonable estimate would be that only

half the inputs would be active on the average, or a load of 22 watts.
possible

The total dissipation of all eight

boxes is, thus, about 22 watts x 8, = 176 watts.

The resistive dissipation of each O-box triac AC circuit is about 8 watts with a maximum 5 ampere load.
the maximum distributed load
puts are turned on,

2.5 ampers per circuit, or 4 watts.

Assuming that an average of half the out-

each O box consumes 4 watts x 8 outputs, or 32 watts.

All 16

16 X 32 watts, or 512 watts.

The CU requires from 90 to 175 watts for its low-voltage power supplies.
The basic system power dissipation is thus:

CU power

90 Watts

one

25 Watts

box

one O box

32 Watts
1

47 Watts

The maximum system dissipation for a full-size PDP-14 system is (rounded figures):
control system power

eight

sixteen

175 Watts

boxes

175 Watts

O boxes

510 Watts
Total

860 Watts

11-2

But

O boxes dissipate about

This figure will increase

extended time.

you have a control requirement which allows most of the outputs to be on for an

Reduce this figure for less

O boxes.

Cooling requirements affect installation in these ways:
The CD is mounted at the bottom of the

NEMA 12 for best cooling, and clearance is provided on all

sides.

The
bottom.
b.

O, A, and S boxes are mounted in vertical columns with unobstructed air flow at top and

The NEAAA 12 is specified at a minimum size for proper convection cooling (minimum airspace and

surface area)

A maximum enclosure surface temperature is specified. Note that the surrounding air must be
somewhat cooler than the maximum enclosure temperature to allow heat transfer from the control
d.

system.

Cabling and Maintenance Clearance

A PDP-14 system installation will involve these three kinds of wiring:
a.

Flexible wiring supplies 115 Vac to the CU

Flat ("ribbon") cables carry control signals between the

CU and the various boxes.

AWG

No. 14
leads carry ac signal and power circuits from terminals on the
from the controlled device.

The CU mainframe is hinged at its left side to swing open for service.

and O boxes to and

Since the AC feed and all control cables

enter the CU on the left, clearance is needed for both the free swing of the mainframe and the bundle of cables.

Modules plugged into the mainframe will protrude several inches to the left when the unit is fully open for
service.

Each

Allowance must be made for this space.
O,

or A box requires one ribbon control cable.

whether it is a half or a full box.
row of boxes,

until

Each cable plugs into a box, and bends either left or right, along the entire

meets the CU.

Thus, one end of the row will have a thick group of several control cables

which must fit in the space above the end box.
boxes) for these cables.
spaces among

A minimum clearance must be left above each box (or row of

AC wiring will normally be groups of No. 14 AWG leads passing in the vertical

and O boxes.

right of each box.

An S box requires either one or two, depending on

These wire groups may be stiff and bulky, and need clearance to the left and

will be useful to leave some extra space

beyond minimums in these areas.

Maintenance clearance is simply the space left around all parts of the control system to allow work to be done
and parts to be changed.
hinges for removal.

The CU must be able to swing out 90° from the enclosure, and also to lift from its

Generally speaking, a control system which is mounted in somewhat greater space than

bare minimum requirements, will be much easier to install and service.

ENVIRONMENTAL SPECIFICATIONS
The entire PDP-14 System has been designed to operate reliably in rigorous industrial environments when
properly installed.

Table 11-1 contains the DEC System Specifications as:

1-3

Table 11-1

PDP-14 Environmental Specifications

The entire PDP-14 system complies to J. I.C. electronic industrial standards applicable
at time of manufacture.

The PDP-14 CU, and all I, O, and Auxiliary Boxes are to be mounted in a standard
NEMA 12 enclosure system. The NEMA 12 is assumed to be normally sealed - this
means also that the door must be closed when the PDP-14 is operating (except for
maintenance)
Corrosive atmospheres shall be kept from the PDP-14 System by the design and proper
use of the NEMA 12 enclosure. Extensive exposure to corrosive atmospheres might
cause system failure.

The surface temperature of the NEMA 12 must be between 0° and 55° Centigrade
(32 to 130°F) at all times. This temperature range assumes all thermal effect of the
surrounding atmosphere and of any radiation (such as sunlight) which may strike
the NEMA 12. Assuming proper free-air space within the enclosure, the PDP-14
System is designed to be cooled by closed convection, with no need for forced air
or air-conditioning.

Relative humidity shall be within 10 to 85 percent.
of individual modules is required.

A vibration of

.25 g' s maximum at frequencies from

No special moisture-proofing
to

100 Hz sinusoidal

each of the three normal axes, can be tolerated.
The PpP-l4 System is highly noise-immune. However, absurdly strong sources of
electrical noise should not be placed in the immediate area of the
12

NEMA

enclosure.

TYPICAL INSTALLATION
The previous discussion of installation factors indicates a general mounting scheme.

shown in Figure 11-1, embodies these requirements.
the general considerations already given,

The sample installation,

Other layouts are of course permissable,

they follow

and do not exceed the environmental specifications of Table 11-1.

ENCLOSURE
The entire PDP-14 system, including the CU and all

O, A, and S boxes,

mounted in a standard NEMA 12

enclosure.

The steel box keeps the control system clean, and provides both mechanical and electrical noise

protection.

The minimum size enclosure which provides enough free cooling air and mounting space for a

basic system is:

48 in. high

36 In. wide
12 in. deep or greater

Since the bosic system consists of one CU, one
systems with more units.

and one O box, you will require a larger enclosure for

You may also wish to use a larger enclosure to make mounting and maintenance

easier.

11-4

440 VAC

115 VAC
INPUT LEADS

VAC
FILTER

^-^

115

(IF REQ'D)

TERMINATIONS

115 VAC
OUTPUT LEADS

CONTROL
TRANSFORMER
115 VAC 10
OUTPUT

CI RCUIT

BREAKER

CONTROL CABLE
(RIBBON)

NO. 14 WIRES

ADDITIONAL
115 VAC

LEADS

NEMA 12
ENCLOSURE

Figure 11-1

PDP-14 System Layout Example

n-5

CAUTION
drilling operations
Installing the PDP-14 system involves
articles. These
paint
and
metal
produce
will
which
components and cause
particles could short out electronic

PDP-14 system.

permanent damage if allowed to enter the
warranty.
This damage is not covered in the

Therefore,

THEN mount the parts of the PpP-l4 system.

Protect all

DO ALL DRILLING FIRST, CLEAN UP the area, and

system components from contamination.

ELECTRICAL GROUNDS
For proper electrical shielding, the

NEMA 12 enclosure must be bonded to the normal ac grounds system,

the ac metal condu.t
This grounding normally occurs when
which must be low impedance to true earth ground.
to establish good
removed or that paint-cutting fittings are used
installed. Ensure that insulating paint is
is

grounding to the chassis.

Install

a bonding strap between the rear mounting

panel and the enclosure frame.

by establishing metal-tokept at the same relative ground potential,
which attaches the various units penepanel. Ensure that the hardware
rr^tal contact through the mounting
small spots of paint or use lockcontact with the metal surface. Remove
trates the panel paint to rrK.ke firm

Each unit of the PDP-14 system must be

washers which will penetrate the paint under

bolt pressure.

SYSTEM POWER AND OTHER DEVICES
The ac power chain and the other devices shown in Figure
In this example,

assembly.
(hash),

11-1 (top center) are optional for each installation.
circuit breaker

440 Vac enters the enclosure at upper right and is controlled by a fused
line transients
reduced to 115 Vac by a control transformer, and filtered to remove

The voltage is

if necessary.

This power is available at upper left to power both the

Box ac power requirements are discussed in Chapter 3.
activated and their load.

CU and

and O box ac circuits.

They will depend on the number of ac circuits

The control transformer could be as small as 250 VA for a very small

above 50 KVA for a very large one.

system, and

15 Vac may, of course, be provided from outside the enclosure.

requirements.
computer is to be attached to the same circuit, be sure to add its power

and teletype require 500 VA.)

CONTROL UNIT MOUNTING

11-6

(The PDP-8/L computer

BASE FRAME

MAIN FRAME

SHIELD COVER
Figure 11-2

Control Unit Housing Components

11-7

The other devices indicated in the figure may be electromechanical timers,
contactors.

counters, or if necessary, small

Large-current switching devices should always be mounted outside

The CU is installed in the lowest (assumed coolest) part of the enclosure.

the enclosure.

Thus it is as far as possible from

interfering hash which could enter the enclosure through the AC wiring at the top.

The CU, although shown as one mechanical unit, consists of three separate articles, as shown in Figure 11-2.

A heavy metal base frame is attached to the mounting panel of the NEMA 12 using l/4-inch dia.
The keyhole cutouts are placed over the bolts and the base frame drops in
place; the bolts are then tightened. The base frame should be mounted flush to the NEMA
mounting panel, so that the wiring normally within the frame is protected from falling debris.
mounting bolts.

The base frame provides wiring protection and a hinged mounting support for the CU mainframe,
with open hinge pins, which drop into the base frame from above. This mainframe contains
a wired panel of connector sockets accepting all CU circuits and cable modules. All
permanent cabling enters the mainframe at the left, or hinge, side. Strain reliefs are
provided to form a small clearance loop in each cable. The mainframe swings open to
access its rear wiring, and is normally held closed by a locking pin at the right side.
This cover
The entire mainframe assembly is covered by a SHIELD COVER of sheet metal
provides isolation from electrical noise and physical protection for the CU modules. It
attaches to two locating pins at the sides of the mainframe, and is released by pressing the
pushbuttons of both handles at the same time while pulling straight outward.
.

The mainframe is completely covered except for an aperture for control cables and

AC power on the left side, vent openings, and a maintenance access port in the
A small metal panel is screwed in place over this port when it is not used.
front.
The CU should always be operated with its shield cover in place except during
maintenance.

CU MOUNTINGDIMENSIONS
Figure 11-3 shows both mounting dimensions and clearances required for the CU.

The unit requires mini-

mum mounting clearances of:
a.

Two inches above, to allow the mainframe hinge pins to enter their mating hinge supports
on the frame and drop in place, and for cooling air to leave the top vent.

Six inches to the left, for cables to leave the mainframe and be routed toward the
boxes and to the ac power source (including two inches for a cable duct).

and

About two feet forward (and slightly to the left), to allow the mainframe to swing out for
servicing. This clearance need only be available when the NEMA-12 enclosure door is
open for servicing.

Six inches below, for cooling air to enter,

and for wire terminations on the bottom of the

NEMA 12, if used.
e.

One inch to the right, for cooling air.

These clearances may be increased to make installation and servicing even easier.
1

Mount the CU within

degrees of vertical

CU MOUNTING SEQUENCE
All

mounting holes should be drilled before installation begins.

be dismantled for installation.

First,

The CU is shipped as one package, and must

l/4-inch mounting bolts are prepared for the

11-8

NEMA 12 on centers

(TOP)

LOCK PIN

REAR WALL OF
NEMA 12 ENCLOSURE

MINIMUM SWING
CLEARANCE TO LEFT

TOP CLEARANCE
2"

(RIGHT side:

BOTTOM

RIGHT SIDE

CLEARANCE,

CLEARANCE
USE t/4-20 HARDWARE
WITH LOCKWASHERS
(4 PLACES)

ALL DIMENSIONS IN INCHES

* INCLUDING COVER

CLEARANCE SHOWN REFERENCE
NEMA MOUNTING PANEL

Figure 11-3

Confrol Unit Mounting Dimensions

shown in Figure 11-3.

The CU is unpacked, and the shield cover released by depressing the handle push-

buttons and lifting the cover away.

The mainframe and base frame may be left together, but for handling

ease, temporarily detach the mainframe and place it aside.

CAUTION
Be careful not to bend wiring pins which extend from the
back of the mainframe.

The base frame is then bolted to the rear mounting panel of the NEMA 12 enclosure.

hardware, to prevent vibration from loosening the installation.

Be sure to use locking

Slip the mainframe in place on

its

open hinge

When all other mechanical

Replace the shield cover.

pins (Figure 11-4),

and latch in place with its pin.

installations in the

NEMA 12 are completed, the cover will be removed again for cable insertions.

This

completes installation of the CU.

AUXILIARY BOX MOUNTING

The A and S boxes are mounted above the CU so that their control cables will have the shortest run to the

mainframe sockets.
as shown above.

This usually places them in the furthest left column of all

A and S box clearance is the same as for

and O boxes.

O, A, and S box mounting,

Note that each A-box control

cable enters at the top left of the box, while each S box may require two control cables, at top and bottom left.

n-10

;****'

SHIELD

COVER
MOUNTJNO
PIN

TCHING
IN

UPpEft HtNGE PIN

ON MAINFRAME

Figure 11-4

Conirol Unit Mainframe Mounting

n~n

__i__4-

D:
'

•Trr727:^;^yi:r77

'^"^

/A//

if y

^1^

•

A^^

i.-s
I t»ll

Jj /A

Figure C

AND O BOX MOUNTING
l-and-O boxes are mounted in even rows and columns above the CU, as shown above. Clearance is allowed
above and below the columns for cooling air, and between each box and on the sides for ac signal wiring.
Space must be provided above and below each box for control cables which pass from right

box rows.

to left along the

Each l-or O-box has one control cable, which enters the box from the top left.

O, A AND S BOX MOUNTING DIMENSIONS

Figure 11-5 shows all mounting dimensions for a single
left show how columns and rows of boxes

O box.

Optional boxes indicated at top and at

may be extended to any required length.

Mount all boxes within

10 degrees of vertical, to promote proper convection cooling.

Approximately one inch must be left between box rows to allow cables to pass across the tops of the
If

boxes.
boxes share vertical mounting centers, as shown, about 7/8-inch usable space remains between
two boxes.

Boxes may be mounted in vertical columns and horizontal rows up to the limits of the enclosure.
cables should run horizontally across the box rows to the left, and then down to the CU.

All control

Allow space along

the left side of the mounting for this cable drop, along the right for AC wire
ducts, and at least two inches

above and below the box group for free air flow.

O, A, AND S BOX MOUNTING SEQUENCE

First

determine the type and quantity of all boxes to be mounted, according to the demands of the
system.

Allow space for more boxes if the possibility exists that the system may be expanded later.
mounting panel and drill
all

all

Lay out the NEMA

holes for l/4-inch mounting bolts on centers shown in Figure 11-5.

boxes in place, using locking hardware.

This completes the box installation.

installed in a later step.

11-12

Then bolt

Control cables will be

-<t-

Hiii

(OPTIONAL)

UPPER BOX

•51/4-

l^^l

4 1/4REF

41/2
I

>!l"REF

JTf
11

1/2

!
I

3 1/2i
!

10 7/16

REF
I

BOX
TO
LEFT

_q_

(OPTIONAL)
I

3 1/2

USE 1/4LOCKING HARDWARE
(3 PLACES)

J
ALL DIMENSIONS IN INCHES

Figure 11-5

O Box Mounting Dimensions

WIRINGAND CABLE INSTALLATION
This section shows how to install both control cables and

AC wiring.

The same procedure is used for initial

work and for later additions to the system.

CAUTION
Insertion or removal of any PDP-14 system wiring must
always be done with all power off. This includes both
control cables and AC leads, as well as maintenance
and computer interface connections. Failure to observe
this caution could result in permanent damage to the
circuits which is not covered by the warranty.

n-13

AC Wiring
Note that ac wiring duct is placed above

The sample installation above shows the position of wiring ducts.

between the box columns
and below the l-and O-box group, and single power leads are then run vertically
rows if space is provided. The control
to their individual terminals. More ducting may be placed between box
then down a separate duct (shown
cables, in contrast, run horizontally along the box rows to the left, and
minimizes transfer of noise
crosshatched) until they exit, in two bundles, to the CU. This cable dressing
possible. The ac power supply
from the ac wiring to the control cables, and should be followed as closely as

chain at top center in the drawing has already been discussed.

supplies both the CU and the box ac circuits

with filtered 115 Vac.

To power the CU, run a flexible service cable (two No.
top left of the CU.

4 to 16

AWG leads) from the ac terminations at

Remove the CU cover, and swing the mainframe out fully.

Figure 11-6 shows the back

turn and slide the
Loosen the two Phillips screws, which hold the protective cover, one full
Run the cable through the
is now exposed.
cover off. A power connector strip with two screw terminals
themon the connector strip. Leave a
grommet in the left side of the mainframe, strip the ends, and install
plate and close and lock the mainframe.
small service loop in the cable. Reinstall the protective

panel exposed.

11-14

LOW-VOLTAGE

POWER SUPPLY
MOUNTING PLATE

Figure 11-6

PROTECTIVE COVER
FOR
AC TERMINALS

Mainframe Back Panel

n-15

NOTE
An ac convenience outlet is provided on the CD mainframe. This outlet is directly across the incoming ac,
and is neither fused nor grounded through the CU.
This outlet is ordinarily used for electronic diagnostic

equipment or a computer, and external fusing should
be provided to protect such equipment.

All

box AC wiring is done with single conductor number 14

Initial

checkout of the

AWG copper with standard insulation.

and O boxes in the system requires that no ac wiring be installed on their terminals.

This means that control cables are temporarily installed, as described in the next section, then computer
test

The control cables are disconnected, the AC wiring connected, and the control

programs are run.

cables then permanently reconnected.

The wiring is installed behind the space reserved for control cables.

may extend from the mounting panel forward no more than three inches as it leaves the duct.
Once the individual leads leave the duct and clear the control cables, they may be run forward to meet the

This means

screw terminals along each box front.

Each terminal accepts one or two leads stripped about l/4-inch and

inserted under its integral clamping plate.

Figure 11-7 shows terminal connections to each

The entire box front is covered with a transparent

box.

plastic cover which protects from electrical shock and forms a wiring duct.

by unscrewing four thumbscrews and pulling straight out.

The cover is removed for wiring

Each of the four K578 input modules has a

9-terminal barrier strip mounted on its front face.

One terminal must be returned to 115 Vac neutral, as marked.

Ordinarily,

easiest to loop all four

neutral terminals on a single box and then return only one lead to the ac supply neutral.

eight terminals on the K578 is for an ac input circuit.

Each of the other

Switched 115 Vac is to be provided to each terminal

from whatever input sensors are used on the controlled device.

A neon lamp corresponding to each terminal

glows only when AC is being provided by the input sensor to the terminal.
Input circuits are identified by a alphanumeric combination.
possible eight (letters A through H),

Figure 11-7 showed
the left side.

The letter refers to the specific

and the number to the box terminal

through 32).

box from a

For example,

box "D", then input D15 would be connected to the second from the lowest terminal on

A list of the input circuits and sensors is produced in the programming operations discussed in
one

Chapters 4 through 10.

This list should be provided for wiring operations on "Input Assignment Sheets",

for each

box should be assigned a letter according to programming instructions and should be

box.

Each

marked with a small tag.

All are then wired according to the assignment sheets.

so that the control cables may be later inserted.

11-16

Leave protective covers off

MODULE SOCKETS

TERMINAL STRIPS
115

INPUT AC
INDICATOR LAMPS

VAC

NEUTRAL

INPUT
CONDITIONING

MODULE
K578

MOUNTING EARS
(3) ON BASE

INPUTS PER BOX
VA EACH

32 AC
1,5

Figure 11-7

Input Box Terminal Connections

11--17

Output circuits are connected in the same general way as inputs.

that if necessary,

Each output switching circuit is electrically independent from every other, so
an entire box from one
supplied from a separate source of 1 15 Vac. Ordinarily, you will supply

box.

for one
it

Figure 11-8 shows the output terminals

may be

power source, and loop the 115 Vac hot lead to each circuit, as shown in Figure 11-7.
As in the

box, each terminal strip has a single connection for ac neutral.

o common return for all circuits in the module.

lamps.

In this

case,

But in the

box, this neutral was

simply a common for the neon indicator

The four neutral terminals in each O box should be looped together and tied to AC neutral

(this is

not

shown in the drawing)

and are

The four switched output terminals on each K614 module alternate with the looped ac hot leads,
be provided on
identified with a circuit number, as shown in Figure 11-7. Output circuit assignments should

"Output Assignment Sheets", one for each box.

An O box should be given a letter at this time (A thru S,

O, andQ), and marked with a tag.

Every O-box terminal can now be defined by an alpha-

excluding

numeric combination.

For example,

upper right would be circuit N9.

Assignment Sheets.
later.

All

Figure 11-8 showed O-box

"N", then the switched terminal on the

O boxes should now be wired with the circuits specified by the Output

Leave the protective plastic covers off the boxes so that control cables can be installed

These steps complete all ac wiring for the PDP-14 control system.

Figure E

Control Cable Installation
Control cables carry the CU command signals as well as low voltage power to the

They are flat, multiconductor wire packages called "ribbon" cables.
arrangement.

O and auxiliary boxes,

Figure 11-9 shows the connection

Note that each cable extends from the left-hand side of the CU to one

O box.

Each control cable is a length of ribbon cable terminated at each end by a cable connector module which
acts as a flat plug for the sockets in the CU and box.

The cable assembly (Figure 11-10)

11-18

DEC part

AC
11 5 VAC

COMMON

TERMINAL STRIPS

MODULE SOCKETS
EXAMPLE CKTN9

OUTPUT AC NEON
INDICATOR LAMPS

j—n
115 VAC "hot"

OUTPUT LEAD#I
15 VAC"HOT"

(LOOP TO ONE SIDE
OF ALL OUTPUT PAIRS)

(LOOP TO ONE
SIDE OF ALL
OUTPUT PAIRS)

SEE NOTE

ISOLATED
AC SWITCH

MODULE K614

OUTPUT LEAD #12
115 VAC COMMON

MOUNTING EARS
(3) ON BASE

115 VAC

^
115

HOT

VAC HOT

SEE NOTE

115 VAC COMMON

OUTPUTS PER BOX
500 VA EACH OR 4000 VA
PER BOX

16 AC

note: AC POWER STRAPS TO

ALTERNATE TERMINALS
ARE USER- INSTALLED
Figure 11-8

Output Box Terminal Connections

AC INPUT

OUTPUT
BOXES
120 VAC "HOT"

CABLE

120 VAC NEUT

32 INPUTS
PER BOX'

CONNECTOR

CONTROLLER

MODULE

NEUTRAL
CONNECTIONS
NOT SHOWN)

20 VAC

60 HZ

I.5VA EACH

PDP-14

(0 BOX

tlNGED EDGE

PDP-14 CONTROL UNIT

D
OUTPUT CABLE

SOCKETS
I

16 Cables Max.

OUTPUT CABLE GROUP

Figure 11-9

PDP-14 System Control Cable Arrangement

OUTPUTS

PER BOX
S500 VA EACH
OR
4000 VA
PER BOX
'

RIBBON

vABL&

0777
CONNECTOR
BOX
MODULE
.

i^rOHT- ANGLE)

CU CONNECTOR MODULE
(IN-LINE)

Hgure 11-10

DEC BC-14A Control Cable Assembly

11-21

BC14A-XX* available and is supplied in standard lengths of 03, 05, 10, 15, and 25 feetspecified, the

0-foot length is supplied.

If no

length is

The box connector module is at right angles to the cable and has

a green handle marked "G777"; the CD module is in-line with the ribbon wire.

Each box is supplied with proper control cabling whose length should be stipulated on the box order.

The

cable assembly ordered should be long enough to extend from the particular box to the lower left-hand side
of the CU, with about one foot of slack.

This length of course depends on the individual mounting plan.

One such cable is used for a half S box, and two for a full S box.

Box Cable Connections
Begin connecting control cables to the boxes closest to the CU (usually the A and S boxes).

Starting with

the box furthest left in the lowest row, insert the right-angle cable connector in the top left module slot in

the box so that the cable comes out the top, as shown in Figure 11-11.
slot at bottom left;

this

cable comes out the bottom of the box. )

carefully but firmly straight back until the handle

(The full S box has an additional

The module is inserted in the slot by pushing

in line with the other modules in the box.

ribbon cable to the left over the top of the box and into cable duct at the left side of the

Run the

NEMA enclosure.

Now mark the cable connector for
the CU with the box type and letter, using a grease pencil or a small tag; for example, "A BOX B"
ConIn a later step, the

cable will be run down the duct and into the CU.

tinue to the next box along the row to the right, install in the box and run the cable directly over the first

box and into the duct.

When the bottom row of boxes is completed, go on to the next upper row, until all

cables are installed.

NOTE
Although the insulation on control cables is highly
abrasion-resistant, do not run cables over sharp edges.

Always be sure to use the proper length cable to reach the CU, and mark the box identifier on the CU
cable connector.

All protective plastic box covers should now be reinstalled.

Line up the finger screws

with the box standoffs, as shown in Figure 11-12, and hand-tighten all four screws uniformly.

CU CABLE CONNECTIONS
The control cables connected to the boxes in the previous step are now in the duct, with the cable connectors

marked.

These cables can now be plugged one at a time into the CU mainframe.

cover to expose the mainframe.

box allocations.
with each box.

Remove the CU shield

Figure 11-13 shows the cable slots along the left side of the unit and their

The l-box slots are lettered A through H, and the O box slots A through S, to correspond
This lettering does not appear on the

CU.

Since A and S boxes use O-box cable slots,

you will need a list formed in the programming operation to indicate the proper slots for these boxeso

*The "XX" is the length in feet.

11-22

GT77 CABLE
CONNECTOR MODULE
RIBBON CABLE

BOX
CABLE SLOT

Figure 11-11

Box Control Cable Insertion (O Box Shown)

11-23

STANDOFFS

F\NGER
SCREW

Figure 11-12

(4 PER BOX)

Installing Box Protective Cover

n-24

CONTROL
SWITCHES
ON /OFF

START/STOP

TOP

CONTINUE

TT^

NO.

OPEN PIN
HINGES
(2)

lis

NO. 2

CONTROL
POWER SUPPLY
5 VDC,7 AMPS

VAC

nil

CONVENIENCE

OUTLET

CONTROL
POWER SUPPLY
5 VDC,7 AMPS
(OPTIONAL)

»
CONTROL

I BOX
_CABLE_ SPARE
«>
SOCKETS

CABLE

CLAMPS
(2)

(8)

CONTROL
OPTIONS

BANK

•MEMORY UNIT SOCKETS

L N R

BOX
«)

CABLE
SOCKETS

MAINTENANCE
PANEL

CONTROL
LOGIC

(16)

0000

2000

4000

6000

1777

3777

5777

7777

®
®

LOCK PIN

MTG
HOLES

BASE FRAME
HINGED

MAINFRAME

BOTTOM

Figure 11-13

CU Cable Socket Allocations

cable is inserted in the CD in the same manner as in the boxes with the side of the module to
cable wires are soldered to the right.

which the

Two key notches are cut in each connector module along the plug

edges/ and the shortest key notch should be at the top.
Figure 11-14 shows the connector for 1-box "A" being inserted into the CU slot.

Install

cables in this order:

-box cables

1 .

All

O-box cables

All

S-box cables (in

box slots)

All

A-box cables (in

box slots)

Finally, the cables are formed into two flat bundles and run through the U-shaped cable clamps,

shown in Figure 11-15, and into the duct.

Leave a small service loop between the mainframe and the

duct so that the cables can move without binding when the frame is swung open.
the duct, to complete the control cable installation.

"A" properly installed.

Place all slack cable

Figure 11-16 shows cables for l-box "A" and O-box

a computer interface is also to be installed, leave the CU shield cover off and

proceed to the next section;

not, reinstall the cover.

CU POWER SUPPLY, COMPUTER INTERFACE, AND ROM INSTALLATION
Figure 11-17 shows the placement of equipment on the CU mainframe.

will be used in the following

installation discussions.

CU POWER SUPPLY INSTALLATION
The CU power supplies, shown at the top of Figure 11-17, provide highly regulated dc to operate the circuits
in the

mainframe and also l-and O-boxes.

7 Amperes.

Number

sized control system.

Each of the two power supplies shown is rated at 5 Vdc at

power supply is shipped installed in the CU, and is sufficient to power a moderate
For increased numbers of

and O boxes, more control current is required, and must

be provided by the optional Number 2 power supply.

The following table of power consumption will

allow you to calculate when a second power supply should be installed:

n-26

Figure 11-14

CU Control Cable Insertion

11-27

N3
00

ngure

i-io

^u <wOnrroi L.aDie ^wiamp Use

Figure 11-16

CU Control Cables Installed

CONTROL

SWITCHES

TOP

CONTINUE

START/STOP

ON/OFF

\ i &

NO.

OPEN PIN
HINGES
(2)

115

NO. 2

CONTROL
POWER SUPPLY
5 VDC,7 AMPS

VAC

hBt

CONVENIENCE

OUTLET

(OPTIONAL)

BOX
_CABLE_ SPARE
(t>
SOCKETS

CONTROL
CABLE
CLAMPS

(8)

(2)
I

BANK

MAINTENANCE
PANEL

LOCK PIN

®^

MEMORY UNIT SOCKETS
J

BANK

CONTROL
OPT IONS

w
fi

BANK

«
«

L N R

BOX
(Z)

CABLE
SOCKETS

CONTROL
LOGIC

0000
1

(16)

2000

4000

6000

777

3777

5777

7777

MTG
HOLES

BASE FRAME
HINGED

MAINFRAME

BOTTOM

Figure 11-17

CU Mainframe Allocations

PDP-14 SYSTEM POWER CONSUMPTION

DC Amps @ 5V

Unit

2.50

14 Control Unit

Memory
I

0.50

0.05

Box

O Box

0.60 max, 0.50 avg

A Box

0.60

Half S Box

0.40

Box

0.80

Computer Interface

0.40

Full S

Here are three examples of calculations for systems of various sizes:

DC Amps @ 5V

Examples:

Machine

Basic

2.50
0.50

14 CONTROL

IK MEMORY
1

BOX

0.05
0.60 (max)
3.65 amps

O BOX

Largest system with one power supply:

14 CONTROL

2.50
1.00
0.10
2.40 (max)
0.60
0.40

2K MEMORY
2 BOXES
4 - O BOXES
I

- A BOX
COMPUTER INTERFACE
1

7,00 amps

Largest possible system:

2.50
2.00
0.40
8.00 (avg)
0.40
13.30 amps

14 CONTROL

4K MEMORY
BOXES
8 16 - O BOXES
COMPUTER INTERFACE
I

Note that a large system should not be expected to have all outputs activated at once, and therefore wil
not use full control current for each box.

This means that an average

for calculations.

11-31

O-box current value may be used

Installation of Number 2 power supply is a simple bolt-in process.

First,

disconnect oi

AC power.

Swing

four bolts provided. Attach
open the mainframe and attach the power supply in the space shown with the
right side of Number 1 power supply.
the supply connecting leads to the screw terminals provided on the

(Follow the connection diagram packed with the power supply. )

Close and latch the mainframe.

ROM INSTALLATION
The Read-Only Memory (ROM) stores all the instructions for operating the control
for one to four

system.

The CU has space

ROM banks DEC port no. MR-14, as shown in Figure 11-16.

G923

SENSE
BOARD-

SELECTION
BOARD

^ It \

KEEPER PLATE
BRAID (ENCAPSULATED)
y
BRAID BOARD

WIRE CHANGE SIDE

14-0013

The G923 Sense Board is attached directly to the G922 Braid Board, and they form one plug-in assembly.
The G922 module contains the braid, or actual memory storage unit, and is different for each bank.

bank also requires a G924 Selection Board, which is included in the MR-14 package.

Each

When more than one

MR-14 is used, each Sense-Braid assembly is marked with an "M" or bank number as shown in Figure 11-17.
This number appears on a sticker attached to the keeper plate.

When a G922 module is provided, be sure to

immediately determine its bank number so that it is installed properly.

Memory

Instructions

Bank

Stored

0-1777

2000-1///

4000-5///

6000-7777

n-32

To install a ROM bank,

first

obtain all Sense-Braid assemblies (G923) and G924 boards.

frame contains four slots for each ROM bank.

Beginning with Bank 1 ,

sockets furthest to the left, as shown in Figure 11-18.
will contact the second slot,

The G924 board is next installed in the

Although the boards are shown angled in the photos to show place-

ment, do not angle them for insertion or removal.

make sure all sockets accept the board ends.
completely in the sockets.

Instead, place the module squarely in the slots and

Then press the module firmly straight back until it is seated

A side-to-side rocking motion may aid insertion.

will require considerable pressure, so be sure not to allow an individual

pressure of insertion.

G923 assembly in the

The G923 will slide into the first slot, the G922

and the third slot remains unused.

fourth slot, as shown in Figure 11-19.

install the

The G923 double assembly

board end to bend under the full

Continue the installation for Banks 2 through 4, if tbey are used.

ROM installation.

mZZ /G923
ROM MODULE
ASSEMBLY

Figure 11-18

The CU main-

Installing

G922/G923 ROM Modules Assembly

11-33

This completes the

G924
ROM MODULE

G922/G923
(INSTALLED

Figure 11-19

Installing G924/ROM Module

11-34

COMPUTER INTERFACE INSTALLATION
The computer interface for the PDP-8/1 or 8/L consists of these modules:

MljZfe

M745

M746

and these control cables:
for the

PDP-81, 3 - BC08C-15

for the

PDP-8L

or PDP-12,

3- BC^8A-15

The control cables and modules are installed in the CU mainframe in the same manner described for other
similar units.

For the proper module and cable socket positions, refer to the "CU Socket Allocations" chart sup-

plied with each CU.

Ordinarily, the computer interface is the last to be installed in the mainframe, since

other modules are shipped installed.

CU.

The computer interface is shipped installed if initially ordered with the

Figure 11-20 shows a completed computer interface installation.

from those used for control cables.

This flat cable

These cables are slightly different

called "flexprint".

CAUTION
Any computer or other electronic equipment connected
by control cables to the PDP-14 system must share the
A
same AC neutral and metallic ground potential
difference in neutrals, such as caused by use of two AC
power sources, could cause large current flows in control cables and permarrently damage electronic equipment. The convenience outlet in the CU mainframe
provides external equipment the same AC power as the
.

system

The M921 Device Selector jumper module allows each PDP-14 to respond to a unique device code transmitted

by the computer.

The Device Selector shipped will respond to codes 16 and 17, since these have been

specifically assigned.

more than one PDP-14 system is to be connected to one computer, an expander is

required, and is available as DEC DB-14.

device code for identification.

Each PDP-14 in the expanded system must be assigned a different

The Device Selector in each interface must be rewired for the proper code.

A PDP-14 Applications Engineer can explain the wiring changes and provide a list of suggested devices codes
for use in a particular computer system.

INITIAL CHECKOUT
Before applying power to any new
installation.

PDP-14 system, an orderly check should be made of the complete

Be sure that:

11-35

COMPUTER
INTERFACE

CONTROL
CABLE

Figure 11-20

Computer Interface Installations

11-36

No metal or paint chips or other foreign matter has fallen into equipment or is left in the

NEMA enclosure
b.

Proper grounding has been maintained between all units

Output circuits are not shorted and loads will be properly distributed among K6l4 modules

Control cables are completely seated in their proper slots, and all other modules are firmly

in their sockets

An optional low-voltage power supply has been installed if needed

Only 115 Vac, 60 Hz will be supplied to the PDP-14 system when power is energized

People around the installation know that the
g.
times. A lock is suggested
h.

NEMA enclosure is to be kept closed at all

ROM banks are available for this installation, they are correctly in place.

The first powered operation of the PDP-14 system should be to check out electrical operation of all

components.

its

This initial test is done with the PDP-8/1 or 8/L computer, using these programs:

must
TEST-14, which checks the CU, and 1, O, and S boxes; -(1 and O box AC wiring
be disconnected for them to be tested with this program);

VER-14, which checks the ROM contents and operation; and

A BOX-14, which checks all A boxes.

according to the
The computer is connected to the system through its interface, and the test programs are run
Teletype printer connected
instructions provided with them. The result of this testing will be printed on the
to the computer, including faults,
for further maintenance

any.

module changes are considered necessary, refer to Chapter 12

information.

INITIAL STARTUP
The CU automatically starts the PDP-U system whenever ac power is applied.
operates constantly, waiting for commands from the control device.

The control system then

power is interrupted, the control

sequence simply starts from the beginning whenever power is reapplied.
The CU control panel

shown in Figure 11-21.

The large toggle switch to the left is the power switch,

which interrupts ac to the low-voltage power supplies.
the

NEMA door

normally left in the

ON position,

breaker
closed, and power is applied to the entire control system through the circuit

interlocked to the door.
is

This switch

The CU will then automatically start its control sequence.

turned OFF, the control operation stops and all outputs are also turned off.

right of the control panel are

marked START/STOP and CONTINUE.

control sequence on and off, but without turning any outputs off.

11-37

the toggle switch

The smaller switches on the

The START/STOP switch turns the

AC POWER SWITCH

START/STOP
CONTINUE

115 VAC

CONVENIENCE
OUTLET
(SEE CAUTIONS)

Figure 11-21

CU Control Panel

11-38

CAUTION
The STOP position of the START/STOP switch does not
stop activity of the controlled device; It merely suspends
control at an Indefinite place In the sequence. Do not
use it as an emergency stop switch.

One special use of the START/STOP switch Is when you wish to activate the CU power supplies without
starting the control operation.

For example, for initial checkout using the computer programs, the CU must

Figure 11-22 shows the use of

be on to activate Its Interface, but control operations should not be started.
the switches.

Begin with the power switch OFF but ac supplied to the CU.

START/STOP switch in Its STOP position, turn the power switch ON.
released.

Then, while holding the

The START/STOP switch may then be

The low-voltage power supplies are now powered, but the control sequence Is Interrupted.

Remember that the control operation will start if power is momentarily Interrupted.

Further use of the

START/STOP and CONTINUE switches is reserved for programming and diagnostic purposes.
The PDP-14 system installation should now be complete and operating.

This chapter has been able to deal

only with a generalized Installation scheme, since so many variations are possible.

You may wish to design

your system and then consult with a PDP-14 Applications Engineer before making all plans final.

Figure 11-22

Special Startup Procedure

11-39

CHAPTER 12

MAINTENANCE CONCEPT

when a device controlled by a PDP-14 fails to
This chapter explains the general maintenance concepts applied
perform properly.

Modifications to the ROM are described at the end of the chapter.

Only the general method of servicing PDP-14 contolled equipment
diagnostic aids available.

described herein, along with some of the

A detailed explanation of troubleshooting for the electrical serviceman and complete

equipment,
electronic circuit information for repair technicians, to service digital logic

located in the

maintenance manual.

APPROACH
Every control system is unique; when failure occurs,

can be for countless reasons.

servicing scheme should be employed to reduce downtime.
to servicing

Therefore, an orderly

This section discusses some of the general approaches

which may speed the job.

The first step in servicing equipment controlled by a PDP-14 system is to distinguish equipment failures in the
controlled device from those in the control system.

The equipment of the controlled device is always first to be

Equipment malfunction can be caused by mechanical problems,

loss of power to cir-

cuits, stoppage of hydraulic or pneumatic actuators, and by other defective components.

Input sensors, (such

suspected of malfunction.

as limit switches) are especially prone to failure, since they are usually mechanical

and subject to wear and

corrosion.
totally free of defect, the PDP-14 control system can then be checked.

This testing

the controlled device

divided conveniently between the major elements of the system; the CU, the ROM, and the I- and O-box

group.
Figure 12-1 explains the general sequence that testing should follow.

The maintenance procedure can be considered as an orderly sequence of the following three basic steps:
The mechanical and electrical operation of the controlled device is checked completely in
is high that
order to isolate the controlled device faults from the control unit faults. The probability
this equipment
Testing
failure.
the
for
responsible
are
actuators
and
sensors
mechanical
and
electrical
a.

first will

tend to reduce much needless search for defects in the control system.

12-1

The controlled device fault diagnosis is greatly aided by the indicator lamps in the and O boxes and
by the complete lists of machine control sequences formed in the PDP-14 programming operation.
I

If the controlled device is entirely free of defect, the CU and ROM are tested by automatic
computer programs, which quickly pinpoint a circuit failure.

The Input and Output box system Is last to be checked.

Since all other equipment has now been

tested, box error can be found by simple substitution of modular components.

CONTROL UNIT
CONTROLLED

ROM

DEVICE

INPUT/OUTPUT

COMPONENTS
Figure 12-1

General Testing Sequence

The following discussion explains some of the general procedures followed for each of the three basic servicing
sequences.

Determining controlled device malfunclion

When a failure of a controlled device occurs, the servicing objectives are to quickly:
a.

Define which operation did not occur,

Reduce the operation to a limited number of circuits to be tested,

Isolate the defective circuit,

Make the repair.

Re-check the operation for other errors.

Usually, trouble is apparent in a single output or small group of them.
limited group of conditions is required.

To switch one output on or off, a

Certain inputs and other outputs (and possibly timers) must be on or off.

This situation can be shown in the ladder diagram

Rgure 12-2.

12-2

Another program list would state that:

Y14 = SOLA
= LS17
X5
MOT
Y143

=
= PBll
I

X37

These program lists are an extremely effective diagnostic aid, since they show the control equations affecting

every output circuit in the controlled device.
system for reference.

The lists should always be kept convenient to the PDP-14

They may be attached directly to the inside of the NEMA 12 door.

Usually, the problem of why a single output is not turning on or off, as required,

solved by checking the

limited group of inputs and outputs specified by the equation which controls that output.

The problem is

manageable because it contains a limited number of items to be tested.
The state of each control equation element is determined by examining the neon lamps corresponding to each
input or output circuit specified.
since they Indicate the actual

These lamps are extremely convenient and accurate troubleshooting aids,

AC power condition of all circuits.

Checking the CU and ROM
Diagnostic programs run on a PDP-8/l or PDP-8/L computer provide complete testing of all circuits in the CU.
Similar programs for the
the

ROM will verify that the memory system is working properly and that the contents of

ROM braid (the control instructions) are correct.

Each diagnostic program is supplied as a paper tape.

A complete explanation of the various tests performed and the meaning of their error
the tape.

messages is provided with

These messages are printed on the computer Teletype and can then be correlated to specific circuit

repair or module replacement.

To operate such a program, a computer interface is first installed in the CU

mainframe as described in Chapter 11.

A computer is attached through control cables to the interface, the

program is inserted in the computer, and the diagnostic is run.

The total operation of the computer requires

no more than several minutes, and checks every possible instruction in every circuit many times over.

Because of this repetitive testing, the computer diagnostics effectively check the possibility of intermittents.

Checking the Input and Output Boxes
The I- and O-box components are last in the testing sequence because it should now be known that both the

ROM are operating properly. By elimination, the indication is that further
and O boxes or their cables. Since the failure of control has been isolated

controlled device and the CU and

malfunction must be in the

earlier to a single control equation or group of them, only a very few box modules are suspect.
are simply substituted, one at a time, until the defect is eliminated.
that they may be available for quick replacement.

12-3

These modules

Substitute modules should be stocked so

Summary of Maintenance Apprcxjch
The general maintenance approach to PDP-14 controlled equipment implies the following steps:

The controlled device is tested, and is assumed to be the cause of error unless demonstrated

otherwise.
b.

The CD and ROM are checked, and faulty circuit operation serviced by module replacement.

Finally, the

and O box system is serviced by simple module and cable substitution.

ROM MODIFICATIONS
Industrial control requirements can change.

These changes are often limited and may be due to errors or

ommissions in the system design.

When the entire control operation is to be redefined, it is probably easiest

to program for a completely new

ROM braid and insert it into the CD.

However, when lesser changes must

be made, the ROM program can be modified by manually placing wires corresponding to the new program.

These wires selectively replace the wires which are permanently sealed in an ROM braid assembly.

Since the manual ROM reprogramming process is relatively slow,

it is

recommended only when a maximum of

10 percent of the total instructions (approximately 120) must be changed.

necessary,

all instructions

can be

manually changed.
The ROM change operation has two general stages:

First,

the new program, including changes,

determined and the program is converted to a

series of binary numbers.

Wires are then hand- positioned in the ROM assembly according to the pattern determined by the
binary numbers.

Programming for ROM Changes

A specific program instruction is described by two numbers; it has a numbered position (a location or address)
and also the number code which is the actual instruction (the contents of the location).

An example would be

a stack of parts boxes numbered consecutively from top to bottom, with a specific number of parts in each box.

Each box could be described by its number (giving its location or address in the stack) and by the quantity of
parts inside (its contents).

A program list is nothing more than all the locations in consecutive order, and their

contents (the instruction commands themselves).

ROM changes which alter locations in the middle of a braid must occupy the same number of locations as the old
program, or less.

For example,

if a

TXN 26 instruction is an error, and should be a TXF 6, both instructions

12-4

SOL A

Figure 12-2

in this example,

Ladder Diagram Showing Output Controlled
and Inputs and Output Tested

SOL A is the output controlled, and PBIl, LS17 and

MOT are the inputs and output tested.

One "rung" of the ladder diagram is equivalent to one control equation in the PDP-14 system.
The PDP-14 control system provides a ready-made documentation of every operation which is to occur in the
controlled device.

Detailed program lists are produced when the ROM program is designed.

diagram, these lists represent control equations in a symbolic form.

Like the ladder

For example, a control designer might

begin his programming by thinking as follows:

"Motion of a table to the left requires that the table be at the right, and that a certain motor be on, or that
a manual pushbutton be depressed".

He would translate this statement into terms of actual sensor and actuator devices:

SOL A

= LS17AND
OR

MOT

PBll

where,

SOL A controls motion of the table to the left;
LSI 7 senses that the table
1

in position at the right;

MOT is the motor circuit supplying hydraulic power to the table (through SOL A); and

PBll

is, the

manual operator pushbutton

The PDP-14 program lists later would show all these inputs and outputs in a symbolic relationship,

Y14

X5 (AND) Y143 (OR) X 37

12-5

for example:

simply changed to correct the
use one memory location, and its contents are

error.

But if a two-location

instruction must be added to the previous program,
instruction, such as a JMP, or a new one-location

must be made for the added location required.
location must be deleted.

In other words,

room

a NOP or other unused instruction in a nearby

which deletes
Conversely, a NOP can be inserted in a program change

instructions

and leaves an unused location.
Each of the four possible ROM banks in the Control unit
to 1777.

has "IK" or 1024 locations, numbered (in octal) from

The first three digits identify a ROM address wire (0 through 177),

specific row of transformer cores (0 through 7) .

wire and selecting one transformer row.

The ROM reads a specific address by selecting and pulsing orve

For example (see Figure 12-3):

This allows you to determine the position of an instruction

LOCATION

and the last digit gives a

physically in the

ROM from its location number.

1346

WIRE NO.

134

and

ROW

TRANSFORMER

ROWS

WIRE PIN

AREA

COMMON
PIN

Rgure 12-3

Wire Placement in ROM Transformer Rows

12-6

Each ROM wire runs through all eight transformer rows and makes available eight instructions each time

Only one transformer row is selected to be read at a time, and thus only one instruction.

pulsed.

it is

the pre-

vious example, wire 134 is pulsed and the output from row 6 is used as the instruction.

As you can see, each time an instruction is changed by replacing a wire, all eight instructions must be replaced.
Therefore, the program list should contain locations in the group (both those changed and

others unchanged).

Here is an example:

LOCATION
OCTAL

ROW NO.

WIRE NO.

INSTRUCTION
TXF
TXF

Co
1

This

list

2006
2014
5076
2407
2554
5477
3406
4224

6
14

JFF

TXN
TXN

JFN

SYN

JMP

062

INSTRUCTION CODE

154
77
6

should include all program changes.

A two-location instruction uses two transformer rows.

In the

above case, the second location of the JMP

(which specifies the JMP address) is in the next consecutive memory location, 063 and is therefore on the next
wire.

this instruction

were changed, two wires would be affected.

The next programming step is to convert the octal instruction code to a binary number.
of the Figure 12-4

"ROM Change Sheet".

Refer to the left side

The example shows the octal instruction numbers for wire 062.

octal digit is converted to three binary digits, as given in the conversion table (Figure 12-4).
octal digits, one at a time.

Convert the four

For example, in location 622, the instruction 5076 is:

101

000
111

110
or,

101

000

111

For ease in handling, the binary number is written in four groups of three digits each, corresponding to the

previous octal numbers.

The binary numbers can now be written directly on the braid board outline on the right of the sheet, as a
reference when adding the new wire.

The electrical layout of the ROM transformers reverses the binary

12-7

Each

2006

MEMORY LOCATION
ROW

INSTRUCTION

WIRE NO.

CONVERSION
BINARY
OCTAL

000
1

Figure 12-4

ROM Change Sheet - Example

bits in each alternate

location 620,

row.

The asterisk (*) indicates the beginning of the binary code.

we have:

OCTAL

BINARY

1
A
000

I
2006
In

For example, in

000

010

TRANSFORMER ROW

r7
110

Oil

000

]l
000

location 621, the binary code is simply transferred to the braid board just as read.

010*

But in location 622

(and all even-numbered locations), the order of bits is reversed, end-to-end, as in the
example.

The

"Rev Bits" remarks (Figure 12-4) remind you to make this reversal when transferring the number to the
drawing.

board

Now complete the chart.

When all binary numbers are on the board drawing of Figure 12-4, the entire process should be rechecked.
This completes the programming section of the

ROM changes operation.

ROM Wire Additions
The clue to ROM wire additions is that a binary 1 (as written on the drawing) corresponds
through the center of an individual transformer core, and a binary
It

to a wire

makes no difference to which side of the core the wire runs to form a 0.

to a wire

placed

around the outside of the core,

See Figure 12-5 for example.

TRANSFORMER CORES
PER ROW

/
BRAID BOARD G922A

1/0

o/ O

O \ O

o/o o\o

O /O

ROW
WIRE

OUT

Figure 12-5

ROM Wire Placement Example For One Transformer ROW

12-9

WIRE
IN

Preparing the

ROM Braid Board

Before removing a

contaminants.

ROM bank from the CU, prepare an area which is free from dirt, metal particles and other

A clean, flat table should be provided, covered with soft, lint-free cloth or paper. Good

required.
lighting and an ac receptacle for a small soldering iron will also be

Locate the proper ROM bank in the CU by its "M" or bank number printed on a

sticker on the

G922 keeper

plate.

Board, as described
The ROM consists of a double board assembly, G922 and G923, and a separate G924 Sense
in Chapter 11.

The boords are separated from each

Remove only the G922-923 assembly from the Control Unit.

other to expose the wire changes side of the

G922 "Braid Board".

WARNING
Transformer cores which will be exposed in this operation are fragile. They are formed of ferrite, or
powdered iron, and can be chipped or broken if abused.

Never force cores in any direction, and avoid resting
assemblies on their core surfaces. Do not touch cores
with any hard object, or with oil or other contaminants.

DO NOT DROP ROM ASSEMBLIES.

Place the double assembly down with its aluminum keeper plate on the bottom.

holding the two boards together and lift the G923 straight up and off the G922.
cores.

Lay the G923 down in a protected place, with its cores facing up.

the aluminum keeper plate to the G922.

Side 2".

Place this assembly to the

Do not bend the transformer

Do not disturb the screws holding

The surface now exposed on the table is the "G922 Braid Board,

left of Figure

The example shows wire 062 installed.

Remove the fifteen screws

First,

to its proper pin, as shown in Figure 12-6.

12-4, with its pins on the right side.

cut 5 feet of no. 36 enameled wire.

Tin one end, and solder

Use a small, clean, pencil-type iron of not more than 40 watts,

and 60/40 rosin core solder.

In our Figure 12-6, pin 62 is not marked on the board,

from right to left, bottom to top.

57 - 60 - 61 - 62.
first

and is found by counting from the last marked pin {57)

Remember to skip 8 and 9 when counting octal numbers.

The pins are:

Bring the wire to the ST (start) position in the top right row and weave it through the

row of cores (row 0) as shown.

Lay the wire at the bottom of each plastic sleeve, and do not pull it tight.

Continue through all eight rows, alternating entry of the wire onto the rows,
position at bottom right.

Then, clip the excess wire,

tin the end,

COMMON pins. This completes the wire addition.

12-10

until the wire

at the

END

and solder it to any one of the four

Figure 12-6

Pin Location Example - Pin 62

Removing the Old Braid Wire
Locate the wire pin for the wire

under side.
cutters.

just

replaced.

This pin extends through the braid board to the braid on the

One braid wire is connected to the pin at this point and should be clipped off with small wire

Bend the wire back gently so that it cannot touch other wire pins, and insulate it with tape.

Be very

careful not to break the other fine braid wires.

Continue making wire changes until all new wires are installed and old ones clipped.

Replacing ROM Braid Board

The G923 board should now be slid gently in place on the G922 and screwed in place.
is

shown on edge in Figure 12-6 to illustrate the arrangement of parts.

The board package

The three screws in the center of the

board are tightened first.

Work toward the outside of the board, tightening by hand pressure only.

exerting extreme pressure.

The board assembly can now be installed in the Control Unit to complete the ROM

modification operation.

12-n

Avoid

REMOVE 15 SCREWS

BRAID

ON THIS SIDE FOR

ROM CHANGES

KEEPER
PLATE

METAL STANDOFF

FOAM BACKING
PAD
PLASTIC SLEEVES

FERRITE CORES
FERRITE CORES

SENSE WINDINGS
THIS SIDE

DOWN
FOR ROM
CHANGES
i8iM>%rw4iiMiifi»

Figure 12-7

ROM Board Assembly - G922-G923
12-12

(Edge View)

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OUTPUT NUMBERS
FOR SIXTEEN OUTPUT BOXES

Box Terminal Number

Box

47 :m.

:|52_

67 ifo„.

;72

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

154 155

156

157

160

161

162

163

164 165

166

167 170

171

172

173

174 175

176

177

200

201

202

203

204 205

206

207 2m

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

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

tl3

tl5

Box

Box Terminal Number
Notes:

No "8" or "9" Digits appear in program numbers
No boxes lettered "I", "O", or "Q" are used, to avoid confusion

with numbers
Special output-unused for

A-2

O boxes.

PDP-14

INPUT
INPUT

INPUT
NUMBER

ASSIGNMENT SHEET -PI
(A THROUGH H)

BOX
ASSIGNMENT

PROGRAM
NUMBER

NORM
COND.

A-3

PDP-14

INPUT ASSIGNMENT SHEET -P2
INPUT

INPUT
NUMBER

(A THROUGH H)

BOX
ASSIGNMENT

NORM

PROGRAM
NUMBER

COND.

•

A-4

PDP-14 OUTPUT ASSIGNMENT SHEET
(A THROUGH S

OUTPUT BOX
OUTPUT

NUMBER

EXCLUDING 1,0 SO)
ASSIGNMENT

PROGRAM
NUMBER

A-5

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