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DEC-14-GGZA-D

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Document:	DEC-14-GGZA-D PDP14UM Nov69
Order Number:	DEC-14-GGZA-D
Revision:	0
Pages:	299
Original Filename:	DEC-14-GGZA-D_PDP14UM_Nov69.pdf

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

tomers in the use of our products.

DIGITAL

EQUIPMENT

CORPORATION

MAYNARD,

MASSACHUSETTS

1st Printing November 1969

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

PDP

FLIP CHIP

FOCAL

DIGITAL

COMPUTER LAB

CONTENTS
Page

CHAPTER 1

GENERAL CONCEPTS OF INDUSTRIAL CONTROL SYSTEMS

General Control Systems

1-1

Catagories of Control Systems

1-2

Numeric Confrol

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
The PDP-14 System
General PDP-14 System
I Box Function

I Box Mechanical
Control Unit

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

Auxiliary Box Operation

Additional Module Information

3-11
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

4-4

Equations Containing "NOT"

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

5-1

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 1)

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

6-10

Storage Outputs

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

Start of Program - .LOC

6-14

Spacing Between Equations - .FIXS or .VARS

6-14

Spacing Examples

6-15

Monitoring Provisions in BOOL-14
Monitor Transitions to ON - .MN

6-15

Monitor Transitions to OFF - .MF

6-16

Monitor All Transitions - .MFN

6-16

Monitoring Input Transitions

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

7-6

PAL-14 Program Conventions
Comments

7-7

Two=-Location Instructions

7-7

Permanent Symbol Table

7-8

CONTENTS (Cont)

Page
Special Characters and Operators

7-10

PAL-14 Output

7-16

Binary Output

7-16

Assembly Listing

7-16

Symbol Table

7-17

Error Messages

7-17

Error Listing

7-20

Sample Output

CHAPTER 8

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

8-2

SIM-14 Command Description

8-3

PDP-14 General Commands

8-4

LM Command
OM Command
RUBOUT

Local Mode Program Debugging

MB Command
Program Manipulation and Modification Commands

R Command
RH Command

Open Location Commands
LS Command

LN Command
P Command
PH Command

Verification of a Paper Tape Program Record
Equation Verification Commands (Local Mode)

Continue Verification

vii

CONTENTS (Cont)
Page

8-22

Verifying an Equation which Contains Subroutines

8-25

Truth Table Generation Commands (Local Mode)
Generating a Truth Table without Subroutines

8-26

Generating Truth Tables for Equations Containing Subroutines

8-28
8-30

Simulated Program Execution in Local Mode
LM Execution Commands

8-30

Switch Register Options in Simulated Execution

8-31

Types of Simulated Execution

8-32

Simulated Timer Execution

8-36
8-36

On-Line Mode Debugging
On=-Line Mode Commands

8-37

On-Line Mode Switch Options

8-38

Program Stops

8-38

Stop Equations

8-39

On-Line Mode Execution

8-39

8-40

SIM-14 Summary

8-42

Commands Common to Local and On-Line Modes
Local Mode Commands

On-Line Mode Commands

8-45

Local Mode Switch Options

8-45

On-Line Mode Switch Options
8-46

Error Messages

CHAPTER 9

MONITORING THE PDP-14

PDP-14 Internal Registers

9-2

PDP-14 Extended Instructions

9-3

External Mode Instructions

9-3

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

viii

CONTENTS (Cont)
Page

Using PDP-8 Program Interrupt to Monitor
Monitor Descriptions

- 9-11

9-11

Transition 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 infto the PDP-8

10-6

PDP-8 Editor

10-7

Composing Source Programs

10-7

Updating Source Programs

10-7

Text Buffer

10-7

Modes of Operation

10-7

Transition Between Modes

10-8

Adding Text to the Buffer

10-8

Editing Keys

10-8

Reading a Paper Tape

10-9

Listing a Program

10-10

Inserting a New Line of Text

10-10

Deleting Lines from the Text Buffer

10-11

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-14

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 11

INSTALLATION

Basic Factors Affecting System Installation
The PDP-14 AND Electrical Noise
Heat Dissipation

Cabling and Maintenance Clearance
Environmental Specifications

Typical Installation
Enclosure
Electrical Grounds

System Power and Other Devices
Control Unit Mounting

CU Mounting Dimensions
CU Mounting Sequence
Auxiliary Box Mounting
I and O Box Mounting

I, O, A and S Box Mounting Dimensions

I, O, A, and S Box Mounting Sequence
Wiring and Cable Installation
AC Wiring

Control Cable Installation
Box Cable Connections

CU Cadble Connectors

CU Power Supply, Computer Interface, and ROM Installation
CU Power Supply Installation

CONTENTS (Cont)
Page

ROM Installation

11-32

Computer Interface Installation

11-35

Initial Checkout

11-35

Initial Startup

11-37

CHAPTER 12

MAINTENANCE CONCEPT

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

12-9

Preparing the ROM Braid Board

12-10

Removing the Old Braid Wire

12-11

Replacing ROM Braid Board

12-11
ILLUSTRATIONS

Figure

Page

1-1

General Control Systems

1-2

Binary Control Systems (Electric)

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

Auxiliary Boxes - Pictorial

2-12

2-9

Auxiliary Box Dimensions

2-13

3-1

Box Input Circuit - Simplified

3-1

3-2

I Box Selection System

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

2-8

1-1

ILLUSTRATIONS (Cont)
Page

Timer Module

3-13

K302

A Box Socket Functions and Allocations

3-14

Retentive Memory Module K272

3-15

Input Assignment Sheet

4-3

Output Assignment Sheet

4-5

Ladder Diagram

4-6

Ladder Diagram

4-6

Ladder Diagram

4-7

Program Description

4-10
5-7

Ladder Diagram

5-16

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

5-11

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 1)

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

xii

ILLUSTRATIONS (Cont)
Figure

Page

11-3

Control Unit Mounting Dimensions

11-9

11-4

Control Unit Mainframe Mounting

11-11

11-5

I or O Box Mounting Dimensions

11-13

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 Qutput Tested

12-5

12-3

Wire Placement in ROM Transformer Rows

12-6

12-4

ROM Change Sheet - Example

12-8

12-5

ROM Wire Placement Example For One Transformer ROW

12-9

12-6

Pin Location Example - Pin 62

12-11

12-7

ROM Board Assembly - G922-G923 (Edge View)

12-12

TABLES

Table

Page

5-1

PDP-14 Test Instructions

5-2.

5-2

PDP-14 Set Output Instructions

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

Xiii

TABLES (Cont)
Table

Page

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

7-2

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

xiv

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 fo 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.

That

is, status inputs are either on or off, and the control operation selects outputs
and turns them on or off.

This type of control sequence is used in most mass-

production equipment and materials handling systems.

It is also used in such

diverse industries as automotive, steel, food processing, petrochemical, appliances, 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 conirol needs.
can be 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 moni-

toring 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 oper-

ations.TM
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 operators with only limited training in electronic systems.
The PDP-14 system is extremely compact, and requires very little operating

power.

Installation is quick and simple, and requires no special training.

PDP-14 Industrial Control System

CHAPTER 1
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

INPUTS

POWER

OUTPUTS

CONTROLLED

DEVICE

~—

14-0036

Figure 1-1

General Conirol Systems

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

Specific input con-

ditions cause the conirol unit to send signals to the controlled device to effect its operation.

The operation

results in changes in the device status, and thus changes in the input signals to the control unit.
unit then reacts to this new status by changing outputs, etc.

The conirol

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, by itself, does no useful work. The external data are
status information which do not result from changes in device condition (for example, from operator controls
and prepared instruction commands).

CATEGORIES OF CONTROL SYSTEMS

Industrial control systems are often divided into two general categories according to the type of control signals:
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. The variation of input magnitude causes a fixed, proportional change in output
magnitude. Equipment which responds precisely to varying signals is then required to transform control commands 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 is 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-

115 VAC

A C INPUT

:\/I\

440 VAC

CONTROL

‘

COUNTERS

T'_‘>

MOTOR
STARTERS

CONTACTORS
-=

TIMERS

POWER

COUNTERS

WIRES
AIR

OIL

VAVAY

CONTROL

)

CONTROLLED

HYDRAULIC

DEVICE

PNEUMATIC

ACTIVATORS

LIMIT SWITCHES
OPERATORS
PANEL

O
o

E]
PUCH

BUTTON

MOTORS
HEATERS

O ‘é'é["f? HIGH ENERGY
O

ELECTRICAL

DEVICES

SELECTOR

Figure 1-2

4-ooet

Binary Control Systems (Electric)

The control unit has three types of inputs:

those responding to the status or position of various sections of the controlled 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 inpufs 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 conirol decision).

1-3

Each in-

In electrical binary controls, decision making is 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 fo 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.

when this operation proceeds to a new condition which requires a change in actions.

Input sensors determine

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. It is the first really new system
of its type to appear in several decades.

It 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.

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 individual 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.

In 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 fo 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.

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

if 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 conirol 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 modifying 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

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.
job well.

Since each relay systems is custom-designed, it can do its

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

ponent layouts and wiring changes must be overlaid on the existing control structure.

(Just documentating

system modifications can be a major effort.) 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 modification.

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.

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.

Here is a major area for improvement.

Diagnosis of faults

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

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

To replace

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.

These

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

This means that an interface apparatus

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

worth when these limitations are imposed.

Adding

Monitoring and

Monitoring can be easily more trouble than it's

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

augmented as production operations change.

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 inferest has centered around numeric control computer programs and the popular K-series

control modules.

We had created custom control systems of many sorfs, but no general-purpose industrial

equipment.

In the fall of 1968, one of our industrial customers approached us with a request for an
industrial controller.

all-purpose, solid-state

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 final ly, DEC mass production skill was concen-

When we finished deve lopment, we found that we could supply

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

This is the PDP-14.

TRAINING FOR THE PDP-14

The PDP-14 is functionally equivalent to nearly all binary control systems in industrial use.

This means that one

should understand in 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

the system for specific control needs, and about installation and computer monitoring operations. DEC also
offers intensive training courses on various PDP-14 topics to supplement this manual. 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. It becomes a system when these units are properly combined
to provide a control function. 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.

Control modifications and retrofit can be made at any time with minimum downtime and without

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. Figure 2-1
shows a general system layout.

115 vac
]

lL
I
BOX

J
////////////////////////

/////////

440 VAC
l£

BOX
|

MOTOR

—

STARTERS

CONTACTORS

PDP-14
L
CONTROL
BoX
UNIT
7

: BOX
I

BOX

s
BOX

BOX

TIMERS

CONTROLLED DEVICE
[]

AIR

PANEL-

PNEUMATIC

SWITCHES

OPERATORS

{}

HYDRAULIC
&

T
7

0OIL

{}

ACTUATORS

MOTORS

©lLamps

(e}

HEATERs

BELLS

ETC.

14-0023

Figure 2-1

The Input (1) boxes and Output (O) boxes
trol signals from the controlled devic

General PDP~14 Control Arrangement

provide an "interface" or electrical buffe

e and the electronic circuits of the

control system we have:

r between the 115 Vac con-

Control Unit.

In the conventional

115 VAC POWER

—>
wsvac ___3]
INPUT

SIGNALS

—

INTERMEDIATE

INPUT-

peiie

ACTIVATED

RELAYS

‘4
outpuT

>
L,

SWITCHING

C tiMErs ;

[

COUNTERS
|

TIMERS

CONTROL

RELAYS

15vaAC
SWITCHED

ouTPuTs

—

SYSTEM
14-0017

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

115 VAC POWER

/
o

¢ — BOX

’

1|L5P$

SIGNALS

—{ BOX
—¥

——

PDP- 14

CONTROL UNIT

MEMORY

LOW-VOLTAGE

CONTROL

TIMERS AND

—3

zzzzzd

15 VAC

SWITCHED
OUTPUTS

o [—*

BOX

CABLES

ELECTRONIC

BOX

SaA

BOXES

RETENTIVE
MEMORIES

14-0017

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. Each I or O box handles a

small number of AC circuits and has its own control cable to the CU. This means that by selecting the proper
number of 1 and O boxes, only the input and output circuits actually needed for the specific control operaticn,
need be purchased.

The PDP-14 system is a unified assembly of five basic units consisting of a Control Unit, with its Memory, Input
(1) Boxes, QOutput (O) Boxes, Auxilary Boxes, (timers, retentive memories, etc.), Storage Boxes.
This system does exactly what ordinary systems do; it 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 if in a different way.

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

2-4

But

115 VAC
INPUT SIGNALS

—®

BOX

7777777777,

7777777
PDP-14

/,’
7

———

5
.

]

> BOX

115 VAC

"HoT"

]

CONTROL UNIT

RN \\

7777

CONTROL CABLE —»

PRESSURE
SWITCH

I_E

_—%
—_—

—

NEON

AL, PUSH BUTTON

INDICATOR LAMPS

I——]LIMIT SWITCH
L)

INPUTS

1.5 VA LOAD EACH

115 VAC COMMON —»

CONTROL MODULES
14 - 0031

Figure 2-2

Input Box Pictorial

2-5

I 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 lomp on each input circuit shows

when ac power is being supplied to the box terminals.

I Box Mechanical

14-0030

Figure 2-3

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.

The box contains a wired socket on

Wire connections are made to screw-type terminal

strips mounted on the front of the box, which accept number 14 AWG leads.
minals and modules.

A plastic shield covers the ter-

Control Unit (Figure 2-4)

The circuits of the Control Unit and the memory perform the three basic operations of any control system.
1.

TEST inputs for state (ON or OFF);

DECIDE what control function is required; and

SET outputs ON or OFF (execute the control decision).

They:

Read-Only Memory

The memory used in the PDP-14 system is called a Read-Only Memory, or ROM.
cause it cannot be altered electrically (that is written on).
woven together.

1t is termed "read-only" be-

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

This pattern is 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 (fo 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 program.

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

//_‘\

JA LS TITL LSS SIS SIS

N\
L
A

PDP-14

CONTROL UNIT
Ll

MEMORY

l
LLl
L

L/
e

—

CONTROL
CABLES

Figure 2-4

Control Unit=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 conirol 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

BOX

SWITCHED

QUTPUTS

WSSV

PDP-14

CONTROL UNIT

~ = <

LR 2Ll LA

7777773

l\
\

CONTROL CABLE —p

sox| )
/

115 VAC

fifi SOLENOIDS
{

—~ LAMPS
)

afs

MOTOR
STARTERS

CONTACTORS

NEON

INDICATOR LAMPS

AC COMMON

QUTPUTS

500 VA MAX EACH

(SEE TEXT)

TERMINAL STR{P

—/

CONTROL MODULES
14 -0028

Figure 2-6

Output Box-Pictorial

2-10

O Box Function (Figure 2-6)
The O box contains isolated 115 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.)

is actually being supplied to a terminal strip.

A lamp on each output switch shows when ac power

Each O box contains 16 independent output circuits.

signals pass from the CU along control cables to each O box.

Command

The CU will accept as many as 16 O box cables

for a total 256 outputs per system (actually, the last output is special=purpose, and is not normally used.)

O Box Mechanical (Figure 2-7)

Y
v

S L[

;

10 /¢

o
d

-y
14-0030

Figure 2-7

The O box shell is identical to the I box.

used.

Output Box Dimensions

It 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.

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

1IN
ABS \l

BOXES

\\, —’

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 fo 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 slofs.
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.

The S box is available in

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

The full-size is

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

2-12

Auxiliary Box Mechanical (Figure 2-9)

ra
v
S

[
11

o a¥ -—.I
14-0030

Figure 2-9

Auxiliary Box Dimensions

Both the A and § 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.

The full S box has several

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

is 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 CU, and certain monitoring
modules are also in-

stalled.

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-8/1, or PDP-8/L. They
are convenient to use and install, and inexpensive. The monitoring modules to adapt these computers are available 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 VA

OUTPUTS

16 O-boxes with 16 outputs each, total of 255 outputs

(one output unusable).

All outputs 115 Vac, 500 VA max. , or total distributed
load of 250 VA each. (See Chapter 3 for details.)

CONTROL UNIT

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

CHAPTER 3

PDP-14 SYSTEM PARTS AND FUNCTION

INPUT BOX OPERATION

The I box has two general functions:
a.

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

AC HOT

TRANSFORMER

15 VAC
INPUT SIGNAL

1.5 VA

AC NEUT

|
|

RE%“EWER
FILTER
__L 5 vDC

c—

LAMP
COMMON
14-0020

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.

In 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 cir-

cuits.

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 K578 input converter module. Four of these plug-in modules (with
their screw terminal strips) are inserted in the left and right sides of an I box, for a total of 32 circuits per box.

The remaining I box modules provide for the selection of one input from the 32 available. Figure 3-2 shows

the general selection system for one I box.
A SELECTION CODE is sent from the Control Unit to the 1 box along the control cable.

The PACKAGE SELECT

signal is used by the Control Unit to select one I box for testing from the eight possible boxes in a complete system.

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 K161, one on each of two K578

modules.

Each tested input provides a SAMPLE RETURN signal.

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 K578 modules.

The Control Unit selects one of two SAMPLE RETURN signals for testing. 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. Even so, it is much less complex than a
conventional small computer. The CU and the Read Only Memory (ROM) interact in what might be called
"electronic catch." CU begins the ball game by demanding that the ROM "pitch" one instruction. The ROM
responds, and the instruction is "caught" by the CU, which must now "run the play. This instruction determines 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. However, in this case, no referee can
call an arbitrary "time-out."
The CU functions to:

Interrogate the ROM for an operating instruction

Generate signals that address or select specific inputs or outputs

3-2

CONTROL

CABLE

SELECTION CODE

(3 LINES)

PKG
SELECT

K161

INPUTS
4

—

5 —
4

€-€

NEON LAMPS—G/
7

—

——

K13

Ki61

DECODER

/
4

2
%

Z
g

AC NEUT —

CLO!} O(L OCL‘O(L OJ)O$O(L Oé)

DECODER

2
;

7
g

7
2

K578 @1//// 777777

e oo2VA T
g

YS! OJ)'OJ)OJ)OCL o(g O(Jz

~
16

——

O—or— 2

O—o—. 21

()——O —— 22

O—+t— 23

NEON LAMPS

INPUTS

O—3———24

—— AC NEUT.

)

g
%

|
LAMPS

//@ KS78

(

O—1— 28

O—t— 27

a‘
/7/77777/7/777”7777@ Ki?B

Og——— 2
O—F4—— 29

7 777 7272 707 7

>—-O

3
o
NEON

O
%

Ki’ 8 Q///////// UL Ll 27 7 77 77 2 22722 7727 7

13 74

F__

INPUTS

O—

o
O—f—18

Of———NEON LAMPS

INPUTS

OF—— 30
%

O——— 3

[SOLATED
115 VAC INPUT CONVERTER

o)
O—O——- 32

-O

#2(INPUTS17-32)

SAMPLE RETURN
— # 1 (INPUTS 1-16)
14-0004

Figure 3-2

I Box Selection System

¢]

[0}

Test a selected input or output to determine whether it is on or off
Combine the results of one or more test steps

Interrogate the ROM for a new operating instruction.

Tum an output on or off depending on the combined results of the testing operations

Inputs and outputs to be tested

Alternate commands to be followed depending on the results of the testing

In these operations, the ROM is functionally an electronic list of:

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 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 the ROM. The computer
can request the condition of an input or the result of testing, or it can actually control the operation of selected
outputs. In another monitoring approach, the ROM can include instructions which force the CU to send status
information to a waiting computer. The computer doesn't need fo make a request. The active element which
temporarily stores the results of several test operations and allows alternate output control instructions to be performed is called the TEST FLAG.
Boolean Logic

The PDP-14 control system operates by a formal binary logic termed Boolean. This logic is a simple way of
expressing binary equipment operation, as in this example:

IF a pushbutton is pressed OR the drill head is turning, THEN move the drill head
to the left. The operator of the machine wants to be able fo move the drill head
left at any point in its automatic cycle by pressing a button. In any case, the
drill head should automatically move left whenever it is turning.

This simple Boolean statement has three functional parts; corresponding to the operation of any control system:
— IF pushbutton is pressed

TEST ———

— 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 ON

OR
output 7 is ON

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.

INPUT 36.

It receives the electronic command; TEST

2.
The CU addresses input 36 by sending the proper address code along the control cables to I box A.
(Input 36 is input number 31 in 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.
3.

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

The CU requests a SAMPLE RETURN from output 7

(In this case, no output command signals are sent.

(in O box A) just as it did for input 36 in step 2.

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.
5.

The CU requests more instructions from the ROM.

the results of the testing operation (to the TEST flag).

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 number 3 in O box G.) It also sends the ENABLE SET signal, which will turn on output 142 when it is addressed.

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.

/’Q

<, ff\\)}\[
\\

[\ %/

>
IRON CORE

"SENSE" WINDING

()

\_ AC "AMMETER"
14-0013

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 is induced in

This voltage is measuredby a mete

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
e

POWER f

ray

yAV

PULSE

)

H
g

POWER RETURN
«-TRANSFORMER CORE

o’

OFF

® (0}

SENSE WINDING

)

g WE—

‘®

VOLTMETER

14-0013

ROM circuit operation is 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.

If a quick-acting voltmeter were applied,

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

show none.

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

110

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
e

G923

SENSE

SELECTION
BOARD

BOARD—H*

WIRE CHANGE SIDE

G922

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

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

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

wire to select (and which group of 12 transformers).
pulse on the selected wire in the braid.

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. If
a wire is placed inside a core, it 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 implement 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 1K units of memory. The CU can accept four memory banks, or 4K of memory. When the CU is operating, the individual memory banks are all used as one large memory in sequential program operation.
O BOX OPERATION (Figure 3-4)

The O box functions much like an I box, but with these general operations:
a.

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.

At the same time the Con-

trol Unit sends its SELECTION CODE, it can also issue one of three function commands, ENABLE SET, ENABLE
RESET and CLEAR.
3-8

o
CONTROL
CABLE

SELECTION CODE
3 LINES

PKG

SELECT

6-€

OUTPUTS

O1 | ket ér/

——0

NEON

LAMP

3 —6—‘0

O
4 —1—O

o 1

5 —1—O

O
OUTPUTS

O
O

Ki14

@/ ST

ITIS ISSIS ISSIS
IS IS,

STORAGE

‘/// REGISTER

K207

SRR
R HARA NG ASAARRANNANAN AN

1 —+—O

K207

<
2

(4)

O— T 9

%
/

~O—51—— AC HOT

O—t1+—10

% 72

T % K614 +O O
*

o ©
O——F— 12
O

sO—t+— AC

|
i

Oo—t—13

PRO—
v
14
|

ISP

IIII SIS 1//> Ketig !

O ©

OUTPUTS

{ O—O—‘— 16

ISOLATED

120 VAC

~-O—+—— AC NEUT.

QUTPUTS

o—t—n

EAEE

AC HOT —O—O—

K207

O—e

<
ATASATAAAAREAHATAET
A TTATTAEAE TGS SR LSRRGS AR A RA R R R RN RARRANNS

ENABLE RESET
CLEAR ALL

NEUT.

Ki61

DECODER

AANAARNNRRRANRRNNN

ENABLE SET

K161

DECODER

SWITCH

8 —+—O

-0
» SAMPLE RETURN

(OUTPUTS

1-186)
14-000%

Figure 3-4

O Box Selection System

ENABLE SET will turn on a K207 control circuit corresponding to the selected output. ENABLE RESET will turn
the circuit off. The CLEAR signal will turn every output circuit off regardless of selection.
The K207 output control circuits receive the CU 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 if 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. If 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. If a function command was also
issued, the SAMPLE 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
5A

——)

TRANSFORMER
K207

CONTROL

CIRCUIT

ON OR OFF

TRIGGER

TRIAC

CIRCUIT

OUTPUT

TO 500 VA
AC

PULSE

SWITCHING

AC HOT
115 VAC

PULSE

«—— FERRITE

CORE

NEUT

LOAD
14-0022

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, it is a high-voltage switch

operated by a low-voltage control signal.

The K207 control circuit is first directed ON or OFF by the selection and control sequence.
condition indefinitely.

It 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
.

The transformer

The

A 5-ampere replaceable pigtail fuse is provided directly on the K614 module to protect the triac 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.
Qutput

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

Example

D
300 VA

500 VA

250 VA

400 VA

500 VA

250 VA

200 VA

100 VA

no load
no load

250 VA
250 VA

400 VA
no load

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 K614 module is loaded more than 1000 VA.

The maximum evenly distributed load of 250 VA per circuit

is 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.

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

terminals, as shown in Chapter 11. It is not recommended that outputs be paralleled to form higher current

‘rafings. 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 C110.

Copies

are available on request.

AUXILIARY BOX OPERATION

The A and S box shells are physically identical to those of the 1 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).

Fi gure 3~ 6

AorS 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).

Figure 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, which can be turned with a small screwdriver when
the module is installed. Timing error due fo temperature variations is typically less than + 1% for a 5°C (9°F)
change. Repeatability is better than 95%, allowing a minimum recovery time of 0.3% of the maximum

time

available in the range.

one
The K 272 retentive memory modules use a magnetically-latching mercury relay, which must be mounted in
ng one
position to keep the mercury where it belongs inside the sealed unit. Therefore, K272 modules, containi
output circuit each, are mounted only along the right side of the A box. Thus the 16 output circuits of this box
8 timers,
may contain: Eight K302 timer modules (2 circuits) = 16 timers, or four K302 timer modules (2 circuits) =
and four K272 retentive memory modules (1 circuit) = 4 retentive memories.
They may also contain reduced amounts of K302 or K272 modules, but never more than four K272 modules per
box (Figure 3-8).
TOP

K302

h— (2 TIMERS)

252272

(2 TIMERS)

(1 MEMORY)

K302

(2 TIMERS)

K302

on TIMERS)
e (2

K27

{1 MEMORY)

K302

(2 TIMERS)

K302

- OR

(2 TIMERS)

K27

(1MEMORY)

(ALWAYS MOUNT

BOX VERTICALLY)

K302

(2 TIMERS)

(@ OR

(1MEMORY)
K27

14-0032

Figure 3-8

A Box Socket Functions and Allocations

3-14

As in all output 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 @ RESET command turns it off.

The output then

In other words, the timer is 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).

Figure 3-9

Retentive Memory Module K272

The S box, or- "storage" box, contains groups of K207 output holding circuits, exactly
out the K614 ac switch modules.

as an O box, but with-

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

teen), and uses one control cable.

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

circuits, the equivalent of two 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 - ifs addressing and control commands are

exactly the same, but with-

out actual ac power switching.

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.

Additional Module Information

Eor further information about modules used in 1 and O boxes, consult the DEC publication, "The Control

Handboo"k, Catalog C~110, 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. I has been shown how the CU requests input and output samples and uses them to make a proper control decision. This same information may

also be sent to a general-purpose computer for interpretation and processing in many ways. For example, the

computer can prepare a complete status report of equipment operation, and signal slowdowns and other undesirable situations before they become major catastrophes. This points out the importance of preventive maintenance.

EXTERNAL DATA

INPUTS

ANA N AR ANRN NANg

PDP-14

CONTROL SYSTEM

POWER

OUTPUTS

'
CONTROLLED

DEVICE

14-0016

MONITORING

The PDP-14 can be used for monitoring only, if desired, with no control operations. In this mode, the ROM
contains instructions for inputs and outputs to test, and the proper format to send the information to the com-

puter. The system can also be run without an ROM; the computer controls all testing operations. That is, the

PDP-14 functions as a giant "“interface," providing ac coupling and addressing circuits for the computer. For ex-

tended monitoring, special options allow several PDP-14 systems to send data through long lines to a single
waiting computer, where the data are assembled into a report for an entire network of equipment.
3-16

COMPUTER
PDP-14

CONTROL
SYSTEM

INPUT

DEVICE

(MANUAL OR INTERNAL
CONTROL)

14-0018

CONTROL AND MONITORING

When both 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 well as a group of special monitoring instructions.
results for transfer to the computer.

These instructions allow the CU to select specific TEST

Part of the ROM program may be designed for emergency conditions only

(to signal the 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

o222

ppp-14
CONTROL

sysTem

| OUTPUTS

INPUTS

CONTROLLED

DEVICE

-- 0018

Shared Control

This approach, like control and monitoring, is 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

CONTROLLED DEVICE

ANALOG

SIGNALS
14-0019

Adding the Computer

The most convenient computer to use with the PDP-14 system is either the PDP-8/1 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.

If 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 fo one for complete computer
monitoring.

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 eleciric 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

the smallest part of a program. An instruction causes the PDP-14 to perform one specific

operation, such as testing an input or setting an output. An instruction may be onelocation (requires one memory location for storage) or two-location (requires two locations for storage). The actual instructions executed by the PDP-14 are binary numbers,
but they are usually given symbolic names.

Operand

that which is operated upon by an instruction. For example, the operand of a test in-

struction is the specific input to be tested for ON or OFF. The operand of a set output
instruction is the specific output which is set ON or OFF.

Program

a plan for solving a problem. A PDP-14 program is basically a series of instructions
which tests inputs and sets outputs ON or OFF dependent upon the result of the tests.
PDP-14 programs have three basic forms:

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

by the PDP-14.

(2) PAL-14 Source Program - a program containing symbolic representations for
instruction operands which must be translated into machine code before it can be

executed by PDP-14.

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

translated into machine code before it can be executed by the PDP-14.

INPUT AND OUTPUT ORGANIZATION

Machine inputs and outputs must be assigned to the PDP-14 input (1) 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 1 and O boxes are contained in Chapter 3. There are eight possible input
boxes, lettered A through H. Each I box contains 32 inputs, thereby allowing a maximum of 256 PDP-14 program inputs. There are sixteen possible output boxes which are designated A through S (excluding I, O, and Q
to prevent possible confusion). Each O box contains 16 output drivers. A total of 255 separate outputs are
possible; the 256th output (the 16th output of O-box ) is 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.

Each input has a value

of either ON or OFF at any one time. These machine inputs are wired to an I-box terminal. An input is ON
if there is 115 Vac present at the specific input terminal. The input is OFF to show the absence of 115 Vac.

For programming purposes, all PDP-14 inputs are denoted by an "X" followed by an octal (base 8) number. This
convention of identifying inputs with the letter "X" is used throughout the PDP-14 system. The number is determined by the selection of the I box and terminal to which the machine input is wired.
PDP-14 input 15.

For example, X15 is

Specifically X15 is the PDP-14 representation of a machine input (e.g., a limit switch) which

4-2

PDP-14

INPUT

ASSIGNMENT SHEET

INPUT

(A THROUGH H)

BOX__°:

NUMBER

-Pf

ASSIGNMENT

COND | NUMBER

LS201 - Activated when slide 2 at full return position

n/c

X40

LS202 - Activated when slide 2 at full depth.

n/c

X41

1
)

PDP-14

INPUT

ASSIGNMENT SHEET

BOX

INPUT

NUMBER

-P2

(A THROUGH H)

ASSIGNMENT

17
18

COND.

NUMBER

PB5 - Cycle start pushbutton.

n/c

X60

PB12 - Start motors pushbutton.

n/c

X61

INPUT NUMBERS
Box

Box Terminal Number

40|

41|

42|

43|

100

{1071|

102]

103|104

140 | 141

142

143|

44|

A
'8

IS5}

16|

17]

18|

19|

20|

21|

22|

23|

17|

20§

21|

22|

23]

24]

25|

26|

46|

57]

60|

61|

62|

63|

64|

65|

66|

|105(106|

107

117[120]

121{122|123|

124

)125]|

126]

127

14711

157|160]

161}

164 ] 165]

166|

167

45|

144 | 145|146|

Figure 4-1

4-3

162{163]

is wired to terminal 14 of I-box A. Note that program inputs are numbered octally (there are no "8's" or "9's"
used in the number system). Input screw terminals are numbered in the familiar decimal number system.

The normal procedure to be followed when assigning input numbers is to complete an Input Assignment Sheet,
as shown in Figure 4-1. This sheet is completed for each I box used in the PDP-14 system. The Input Assignment Sheet for one I box has two pages, each page containing 16 input assignments. The sheet records the
machine input (e.g., LS 201 for limit switch 201) which is wired to a particular terminal and notes the implication of this input (e.g., "activated when slide 2 is in full return position"). A separate column records the
normal condition of the contacts which are wired to the PDP-14 I box (normally open or normally closed). The
last column of the sheet contains the input numbers used for PDP-14 programming purposes. These input numbers
are read from the chart in Appendix A (part of which is reproduced in Figure 4-1) and are obtained by listing in
the last column of the Input Assignment Sheet all the numbers which are found in the row for that particular
I box in the Input Assignment Chart.

PDP-14 Qutputs

The outputs of the PDP-14 system are solenoids, motor contactors, timers, small motors, indicators, signal
devices, etc. These outputs are set ON or OFF by the PD P-14, dependent upon the current state of inputs or
outputs. PDP-14 outputs are denoted by a "Y" followed by a number. Thus, Y123 is PDP-14 output 123; Y301
is PDP-14 output 301; etc. 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 input numbers. A sample Output Assignment Sheet is shown in Figure 4-2. This sheet should be completed for each O box in the PDP-14 system. The
machine output (solenoid, motfor contactor, etc.) which is wired to each O-box terminal is recorded with its
function in the machine being controlled (e.g., "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 Appendix A (reproduced in part in Figure 4-2).

PDP-14 Timers and retentive memories which are in A boxes are assigned to output box positions using the same
procedure. 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 control functions. These repre
sentations are comprised of operators and variables. The variables of PDP-14 control equations are inputs (X's)
and outputs (Y's). The variables have two states; namely, ON and OFF. The operators in these equations are
* (AND), + (OR) and / (NOT). Parentheses may be used within equations to group variables.

4-4

PDP-14 OUTPUT ASSIGNMENT SHEET

OUTPUT BOX

OUTPUT
NUMBER

_¢£

(A THROUGH S

EXCLUDING I,0 & Q)

ASSIGNMENT

PROGRAM

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
jox

Box Terminal Number

20|

21|

22|

23 |

24|

25|

40|

41|

42|

43|

60|

61|

62|

63 |

Box

44|

45 | 46

64|

65|

J 100 | 101 | 102 | 103 [ 104{105 | 106

F | 120 [ 121 | 122 | 123 | 124125 | 126

140 | 141 | 142 | 143 | 144(145 [ 146

H | 160

léu 162 | 163 | 164(165 | 166

Figure 4-2

4-5

For example, the equation:
Y10 = X23 + X21 * Y7

is read "output 10 is set ON when input 23 is ON, or when both output 7 and input 21 are ON." This equation
instructs the PDP-14 to test input 23 and if it is ON, set output 10 ON.

input 21.

If they are both ON, set output 10 ON.

If input 23 is OFF, test output 7 and

If 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
/\/

\ B 7CR

‘

|
14-0034

Figure 4-3

where SOL F corresponds to Y 10; 2LS corresponds to X23; 7CR corresponds to Y7; and 3LS corresponds to X21.

[t is important to remember that input and output numbers are determined when the inputs and outputs are assigned to PDP-14 1 and O boxes, respectively.

Equations Containing "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

A,/

14 -0034

Figure 4-4

where SOL A corresponds to Y27; 5LS corresponds to X5; and X30 corresponds to 12PB.

Note that a normally

closed set of contacts for 12PB is shown in the ladder diagram. The NOT sign in the equation means not tripped
or not pushed; it is a physical description.

4-6

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

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

it, depending upon the user's choice.

or the OFF state.

It does not relate

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.

When normally

open contacts are used, the equation "Y5 = X15" means that output 5 will be set ON when machine input 15

is 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 is not activated.

Because normally closed contacts result in equations which seem contrary to common sense, it is suggested that
all normally open contacts be used in the PDP-14 system.

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 is determined.

For example, consider the following equation:

Y1=X1*X2+ X3

Does the above equation represent Y1 = (X1 * X2) + X3 or Y1 = X1 * (X2 + X3)?

By drawing two ladder dia-

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

EJ'—‘

xel _@_

14-0034

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, (X1 * X2) + X3 (the second ladder

diagram) is the correct interpretation of the expression X1 * X2+ X3.
Y1=X1%* X2+ X3 is equivalent to Y1 = X3 + X1 * X2,

4-7

It should also be observed that

Examples:

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

X11 * X23 + X31 * X14= (X11 * X23) + (X31 * X14)
(X12 + X15) * /X21 + X22 = [(X12+ X15) */X21] + 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 groupsof 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 ON or OFF) and the result is to be treated as a single variable of the whole equation. 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. The following truth table summarizes the function:
X121

X26

X121*X26

Y21=/(X121%X26)

OFF

Notice that output Y21 is ON if either X121 or Y26 is OFF, or if both inputs are OFF. The following equation
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 truth table to determine the state of output Y22 for all states of inputs follows.

X107

X12

(X107+X12)

Y22=/(X107+X12)

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
= X1+ (X1 * X2)+ (X3 * X5)
Note that the expression X1 * X2 adds no meaning to the equation.
regardless of the state of X2.

If X1is ON, output Y5 will be set ON

If X1 is OFF, again the state of X2 cannot affect Y5.

simplified to:

Y5= X1+ (X3 * X5)
and the following rule is established:
A+ (A*B)=A

The following equation may also be simplified:

Y6
= (X1 * X2+ X3) * X4 * /X3

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 ON and OFF at the
same time.

The simplified equation is

Yé6=X1*X2* X4*/X3
Thus the following rules are established:

A is always true
A * /A can never be true, and A +/

PDP-14 PROGRAM DESCRIPTION

After recording the input and output assignmenfs and their functions, the programmer codes the program for the

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

instruction group solves a Boolean equation by testing PDP-14 inputs and outputs and, at its conclusion, sets an
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. Thus the PDP-14 Program is a closed loop.

For example, if a machine control requires twenty outputs, there must be twenty instruction groups in the control program. The following diagram illustrates the construction of the program (Figure 4-6).

SOLVE
FOR

OuUTPUT
1

SET YV

OFF

[——*
e

SOLVE
FOR

OUTPUT
>

SET Y2

OFF
[——®TM
L

l
[}
1

SOLVE
FOR

OFF

OUTPUT

[ coTov

14-0035%5

Figure 4-6
4-10

The disjoint instruction groups are often separated by several NOP's.
No OPeration*.

The PDP-14 NOP instruction specifies

The NOP instruction is simply a space filler which leaves room for future program modifica-

tions or corrections.

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

If 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.
It 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

machine instructions.

A compiler translates expressions into machine code.

How-

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.

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.
In other words, the PAL-14 assembler translates the symbolic representations of the
instructions of the PDP-14 into the PDP-14 machine code.
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 par-

ticular part of the program) is 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.
structions used to solve control equations are described in Chapter 5.

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

The in-

Instructions used by an external PDP-8

Chapter 10 describes operating procedures

for the 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.

4-11

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.
erated instructions are then tested or debugged with SIM=-14.

The gen-

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.

PAL-14 is an assembler

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

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.

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 format.

BOOL-14 and Editor programs.
b.

A paper tape uses punched holes to represent

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

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

or to SIM-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.
c.
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
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 the PDP-14, many handwritten sheets of paper, Teletype listings and paper tapes will be
generated.

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

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

Note the date, your name, the system

being programmed, the type of tape (e.g., "BOOL-14 source tape," "SIM-14 binary tape"), and other pertinent 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.

It can save

hours of time.
Forms Used During Programming of PDP-14

Form

Input Assignment and
Output Assignment Sheets

Description

These sheets note which machine input or output (e.g., LS1) is wired to
each PDP-14 terminal (e.g., X15). It should be constantly updated with
any changes.

List of Equations

The handwritten list of equations (e.g., SOLA = LS1* 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.

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

(e.g., SOLA = LS1*LS2).
Source Program Paper Tape

This 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.

BOOL-14 Compiler
or

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

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
Binary Tape

This tape is input to SIM-14 and should correspond to the above compiler
or assembly listing.

SIM-14 Listing

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

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

SIM-14 Binary Tape

Description

This binary tape is punched in 1K segments and is the form required fo

generate an ROM. It is punched from SIM-14 when no errors have been
detected in the BOOL-14 or PAL-14 program. 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.

(Additional 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:
a.

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 is changed by the controlled

equipment, not by the PDP-14 itself.)

Jump Instructions - used to execute instructions out of sequence.

program.

That is, to "branch" the PDP-14

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.

The

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

(True tests and false tests are defined below.) The condition of the TEST flag is sampled by jump instruc-

tions to determine set output operations.

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 is represented by a solidstate flip-flop.

5-1

PDP-14 TEST INSTRUCTIONS

Test an input for the ON state.

Test an input for the OFF state.

The PDP-14 test instructions are:

Test an output for the ON state.

Test an output for the OFF 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

Definition

TXN XXX

2400 + XXX

Test input XXX for the ON state.

TXF XXX

2000 + XXX

Test input XXX for the OFF state. If
input XXX is OFF and the TEST flag is

input XXX is ON and the TEST flag is
currently OFF, the TEST flag is set ON.
Otherwise the flag remains unchanged.

currently OFF, the TEST flag is set ON.
Otherwise the flag remains unchanged.

TYNYYY

1400 + YYY

Test output YYY for the ON state.

TYF YYY

1000 + YYY

Test output YYY for the OFF state.

output YYY is ON and the TEST flag is
currently OFF, the TEST flag is set ON.
Otherwise the flag remains unchanged.
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 4 be explained
byY defining the terms "true test" and "false test" as given in the following
Xp
table.
State of Input or Output

OFF

Test for ON
(TXN or TYN)

True test

False test

Test for OFF
(TXF or TYF)

False test

True test

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

OFF

True test

State of

False test

OFF

TEST Flag

Resultant

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.

The symbolic and nu-

The SYN and SYF instructions

reference output numbers (YYY) from O through 377 (octal), and are determined by the selection of O box sockets

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

3000+YYY

Set output YYY to the OFF state.
Ovutput YYY remains OFF until
it is set ON by a SYN instruction.

CLR

3377

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

The instruction CLR is equivalent to SYF 377 and causes all timers, storage outputs and regular outputs to be
set OFF. Refentive memories are only set OFF when addressed individually. 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 fransfer 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 storage process is not of concern at this point in
the discussion. 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 is a first location, a second, a third, etc., through to
the last memory location). 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. They are numbered in "octal",
a numbering system which does not use the digits "8" or "9". 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 100.

Octal numbers are usually given a subscript (8) to avoid confusion with decimal numbers. Thus "108" is not the
same as the decimal number "10".

NOO
b WON —

The following sequence of numbers illustrates the octal counting technique.

Since the octal number system contains no

11
12

eights or nines, after counting to the
digit 7, simply place a zero in the ones

column and carry 1.

14
15
16
17
20

66
67

70
71

72
73

74
75

76
77

100

The carry out of the ones' place produces

101

a second carry out of the next place.

102

Hence, 77 + 1 = 100 in the octal number

103

system.

PDP-14 Memory Organization
The locations of a PDP-14 memory are numbered in octal as previously described.
tains 1024 locations in which program instructions may be stored.

17778.

A 1K PDP-14 memory con-

These locations are numbered 0 3 through

The locations of a 2K PDP-14 memory (2048 locations) are numbered O8 through 37778; 3K memory

locations (3072 locations) are numbered O8 through 57778; and 4K memory locations (4096 locations) are numbered O8 through 7777

A PDP-14 memory is constructed of blocks of 256 locations.

called "pages".

A 1K PDP-14 memory contains four of these blocks,

The 256 locations of each page are numbered from 08 through 3778'

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 memory (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.

For example,

Note that there are many

locations with the same relative or page address, but each PDP-14 location has its own unique absolute address.
The page address of a location can easily be determined from its absolute address by means of the following
procedure:

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

If the number resulting from step 1 is less than 400, it is the page address.

If the number resulting from step 1 is 400 or greater, the page address is found by subtracting 400

from the step 1 result.

The examples below illustrate the procedure.
Absolute address

Step a. result

Page address

1234
3347

234
347

2652

652

252

7521

521

121

7400

400

5000

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 location 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 1

Absolute
Address

BANK 2

R((T)l:;:)’e

Absolute

Address

0000

0377

377

0400

1 Page =

256

R((;l:;:)/e

Address

2000

locations

256

377

"IK" of PDP-14
?Memory = 1024
0777

377

1000

1377

256

2377

2400

locations = 4
memory

377

1400

1777

pages

2777

377

3000

3377

377

3400

377

3777

377

BANK 3

Absolute

Address

BANK 4

R(?)l:;;\)/e

4000

4377

377

4400

4777

5000

5377

5400

5777

Absolute

Address

377
0

377

6377

377

6400

6777

377

7000

7377

377

7400

377

7777

5-7

5-1

Address

6000

Figure

R(fl;;:),e

377

Conditional jump instructions are used to cause an SYN (set output ON) instruction to occur
the TEST flag and an SYF (set output OFF) for the other TEST flag state.

for one state of

NOTE

OFF.
The JEF and JEN instructions always set the TEST flag flag
TEST
the
ction,
instru
JFN
After execution of a JFF or
was
is always OFF, regardless of whether or not the jump

executed.

Table 5-3

PDP-14 Conditional Jump Instructions
Instruction

Symbolic

JFEN NNN

Numeric

5400 + NNN

Definition

Jump to location NNN if the TEST flag

is now ON and execute the instructions

beginning with the instruction in location NNN. (If the flag is OFF, the in-

structions following the JFN continue to

be executed in sequence.) The TEST

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

JFF NNN

Jump to location NNN if the TEST flag

5000 + NNN

is now OFF and execute the instructions

beginning with the instruction in loca-

tion NNN. (If the TEST flag is ON,
the instructions following the JFF con-

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

or page address to which
NOTE: The expression NNN represents the relative
377 (octal).

control may be transferred. Legal values are 0 to

es O through

Conditional jump instructions are limited. They can only reference the 256 locations (page address
377) on their own page (often called the current page) .

n of a

Because of internal restrictions, a JFF or JFN instruction must never be stored in the last memory locatio
page (e.g., locations 377, 777, 1377, 1777, etc.).

The instruction JEN 300 illustrates the use of a conditional jump instruction. This instruction means that

if the

es
TEST flag is ON, jump to relative location 300 on the current page. Recall that several absolute address
it is
have the same relative or page address. Thus, a conditional jump instruction has different meanings when
phs in order
stored on different pages of PDP-14 memory. Observe the examples given in the following paragra
to properly understand location to be addressed.

5-8

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.

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

If the result of step b is less than 400, the relative (page) address is that number.

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

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. (Off-page reference)

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 done. (Off-page reference)

Location of Instruction:

435

Location to be Addressed:

776

Correct Instruction:

JFN 376

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 uncondi-

tional 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

Symbolic

Instruction

JMP NNNN

Numeric

4224 NNNN

efinition
-

Jump to location NNINN unconditionally.

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

JMP is a two-

location instruction; the absolute address of
the "jump-to" location is stored in the location following that which contains the
JMP instruction.

SKP

Skip the following memory location uncon-

0344

ditionally. This instruction causes the
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 following 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. The first part of the instruction tells the PDP-14
fo jump to the address given in the second part of the instruction. The first instruction executed after the jump
will be the one stored in the location with that address.

5-10

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

JMP

1376

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 is passed need not be specified.
need to reference memory.

The SKP instruction has no

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

It may therefore

be used to skip any one-location PDP-14 instruction only, but may not be used to skip a two-location instruction

(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 retum 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

Symbolic

Numeric

Definition

4645 NNNN

Jump to the subroutine beginning in location

Instruction

JMS NNNN

NNNN.

The PDP-14 executes in sequence

the instructions beginning with the instruc-

tion stored in location NNNN, and terminated by a JMR instruction. The JMS instruc-

tion is a two=location instruction which may

directly address all PDP-14 memory.

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 subrou-

tine. 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 at one time.

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

original program would be impossible.

PDP-14 subroutines are written in the following manner:
Main Program

Subroutine
1200 TXN 27

1201 TXN 30
TXN 5

TXF7

JFF 250

1200

JMS

JMR

JFN 250
TXN 12

The JMS in the above example causes transfer to the subroutine which starts at location 1200. The instructions
of the subroutine are then executed in sequence until the JMR instruction is encountered. Control is then returned to the instruction which follows the second part of the two-location JMS instruction.

SAMPLE PDP-14 PROGRAM AND ANALY SIS

The following equation represents a typical control requirement to be programmed:
Y1= X123 + X54 * Y3

This equation could represent the control function "Solenoid A (Y1) is 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

Comment

300

TXN 123

301

JFN 307

If input 123 is ON, the flag is set ON. If
the flag is ON, jump to 307 and set Y1 ON.

302

TXF 54

303
304
305
306
307
310

TYF 3
JFF 307
SYF 1
SKP
SYN 1
JMP

311

300

Otherwise, if either input 54 is OFF, or if
output 3 is OFF, the flag is set ON. If the
flag is OFF, jump to 307 and set Y1 ON.
Otherwise set output 1 OFF and skip the set
output ON instruction. This instruction sets
Y1 ON. After determining the state for
output 1 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.

In each case, the TEST flag is assumed to be OFF as the

result of a previously executed JFF or JFN instruction.
Case 1 - Input 123 OFF, input 54 OFF, and output 3 OFF; Result:
Location

Content

300

TXN 123

Y1 OFF

Program Execution

Input 123 is tested for the ON state.

Since it is OFF, the TEST flag

remains OFF, and program execution proceeds to the instruction contained

in location 301.

301

JFN 307

If the TEST flag is ON at this point, the program will proceed to location
307.

The flag is OFF, however, and program execution proceeds to the

instruction contained in location 302.
302

TXF 54

The program tests input 54 for the OFF state.
TEST flag is now set ON.
contained in location 303.

5-13

Since input 54 is OFF, the

Program execution proceeds to the instruction

Case 1 (Cont)
Location

303

Program Execution

Content
TYF 3

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

304

JFF 307

If the 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 is set OFF (as it should be).

Program execution proceeds to the

instruction contained in location 306.
SKP

This instruction causes program execution to skip location 307 and proceed
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.

306

NOTE

The instruction in location 307 is not executed.

Case 2 - Input 123 ON, input 54 ON, and output 3 OFF; Result: Y1 ON
Location

Content

300

TXN 123

Program Execution

Input 123 is tested for the ON state. Since input 123 is ON, the TEST flag
is set ON and program execution proceeds to the instruction contained in
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 1

Output 1 is set ON (as it should be). Program execution proceeds to the
instruction contained in location 310.

310

JMP
300

311

NOTE

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

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

Content

300

TXN 123

Y1 ON

Program Execution

Input 123 is tested for the ON state and since it is OFF, the TEST flag
Program execution proceeds to location 301.

remains OFF.

301

JFEN 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.

303

TYF 3

Output 3 is tested for the OFF state.

Since output 3 is ON, the TEST flag

again remains OFF and program execution proceeds to the instruction contained in location 304.

304

JFF 307

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

307

SYN 1

Output 1 is set ON (as it should be). Program execution then proceeds 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 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.

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

The PDP-14 program for the control function.

In 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 1. To solve this problem with a PDP-14, test for either input's ON
state. 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. Thus, testing for ON means testing
for an activated switch. Testing for OFF means testing for a not activated switch.
EXAMPLE 1

Control Function

If either limit switch 1 or limit switch 2 is ON, energize Solenoid D (otherwise, Solenoid D should be OFF).
Ladder Diagram (Figure 5-2)

soL D
1t LS
Ac\"o—_j

2 LS

_—_.No__.———d

Figure 5-2

Boolean Equivalent

Outputs:

Inputs:

ILS (n/o)

XI11

2LS (n/o)

X12

SOLD Y7

Equation: Y7 = X11 + X12

EXAMPLE 1 (Cont)

PDP-14 Wiring (Figure 5-3)

1Ls(n/0)

SOL D

X11

<z | POP

——-——Qfig—-—————-

/\F

2LS (n/o)

Figure 5-3
PDP-14 Program
Location

Content

Comments

TXN 11

Test input 11 and 12; if either is ON, set

TXN 12

output ON; if not, set output OFF.

JEN

SYF

SKP

SYN 7

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

In other words, both limit switch 3 and pushbutton 1 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 if either is OFF.

if the TEST flag is ON, to the set output OFF instruction.

The program jumps,

If the flag remains OFF during the testing, the output

for Solenoid A is turned ON, and the solenoid is energized.

EXAMPLE 2

Control Function

If pushbutton 1 and limit switch 3 are ON, energize Solenoid A (otherwise Solenoid A should be de-energized).

EXAMPLE 2 (Cont)

Ladder Diagram (Figure 5-4)

6PB_ |

3LS
l
e |
A
SOL

Figure 5-4
Boolean Equivalent
Inputs:

1PB (n/o)
3LS (nfo)

Output:

XI
XI13

SOLA

Equation: Y4
= X1 * X13

PDP-14 Wiring (Figure 5-5)

0——1—3

1PB (n/0)

O[O

3LS (n/o)

X1
X13

SoL A

pop

1Y4 /\/

Figure 5-5

PDP-14 Program

Location

Content

6
7

TXF
TXF

1
13

10
11

JFF

SYF

SKP

SYN 4

Comment
Test inputs 1 and 13; if either is OFF, the
output will not be set.

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. The PDP-14 does not require two types of

contacts for such control functions. All normally open contacts may be used, as illustrated in Example 3.
Normally open contacts for both pushbutton 7 and limit switch 5 are wired to the PDP-14. Thus, an ON input
means that the button or switch is activated. An OFF input means that the button or switch is not 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 fo test normally closed contacts. The program would merely test for
the opposite state (ON or OFF) of the input. Thus, if normally closed contacts are used in the wiring, all TXF's
become TXN's for the input and all TXN's become TXF's. An ON input from normally closed contacts means
that the switch is not activated while an OFF input means it is activated.

EXAMPLE 3

Control Function

If pushbutton 6 and limit switch 4 are on, or if pushbutton 7 and limit switch 5 are both OFF, then Solenoid C
is energized (otherwise Solenoid C is de-energized).

Ladder Diagram (Figure 5-6)

soL C

6 PB_
—O0

4 LS

|
O-

alo
7 PB

5 LS

Figure 5-6

EXAMPLE 3 (Cont)
Boolean Equivalent

Output:

Inputs:

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

SOLC

X6
X7
X14
X15

Yé

Equation: Y6 = (X6 * X14) + (X7 * X15)
PDP-14 Wiring (Figure 5-7)

6 PB (n/0)

7PB(n/o)__]
—0

X6
o

° °

4LS(nso)

5LS (n/0)

SoL ¢

|6 /\/
pop
x14|
14

l
l

X15

Figure 5-7

PDP-14 Program

Location

Content

Comment

14
15

TXF 6
TXF 14

If either X6 or X14 is OFF, other leg must be
tested. If both ON, output should be ON.

JFF

TXN 7

SYF 6

SKP

20
21

TXN 15
JFF 24

SYN 6

If either X7 or X15 is ON and other leg

failed, set output OFF.

Set output OFF if both legs fail.
Set output ON if either leg solves.

Latching Control Function - Example 4 is a motor contactor latching function. Pushbutton 2 is the start button,
and pushbutton 3 is the stop button for energizing a motor contactor. Again, normally open contacts are as-

sumed for all inputs. 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 is not pressed.

The output will remain on

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

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)

iM
| L
11

3 PB

Figure 5-8

Boolean Equivalent

Inputs:

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

Output:

X2
X3

Y10

Equation: Y10 = X2+ (X3 * Y10)

PDP-14 Wiring (Figure 5-9)

2PB (n/o0)

——————0

3PB (n/o)
—————
0

X2
O—

pop

Oo—

Figure 5-9

5-21

|10

PDP-14 Program

Location

Content

25
26
27

TXN 2
JFN 34
TXN 3

TYF

31
32

JFF
SYF

34
10

SKP

SYN

Comments

If X2 is ON, jump to set output ON; otherwise, if X3 is OFF and Y10 is already ON,
leave it ON; otherwise, set the output OFF.

Relay Controlled Function - Example 5 uses a control relay to energize a solenoid. All normally open contacts

are used as inputs fo the PDP-14. (As explained in the two preceding examples, normally closed contacts could
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 is actuated, and either pushbutton 5 is ON or control relay 2 is
ON already, then control relay 2 is set ON.

If control relay 2 is ON, solenoid B is energized.

Ladder Diagram (Figure 5-10)

14-0012

Figure 5-10

5-22

EXAMPLE 5 (Cont)

Boolean Equivalent
Inputs:

Outputs:

4PB (n/o) ;54—
5PB (n/o)
2LS (n/o)

X5
X12

2CR

YIi

SOLB

Equations: Y1 = X4 * (X5+ Y1) * X12
Y5=YI1

PDP-14 Wiring (Figure 5-11)

4 PB (n/o)

—0

5PB(n/o0)_

O—

X51{

PDP
14

2 LS (n/0)

X12

SoL
B

Figure 5-11

PDP-14 Program
Location

Content

TXN

TXF

JFN 4

TXN

TYN

JFN

SYF

SKP

SYN

Comments

If either X4 is ON or X12 is OFF, the output should be OFF.

If X4 is OFF, and X12 is ON, then either
X5 or Y1 must be ON for the output to be ON.

TYN

JFN

If output 1 is ON, jump to set output 5 ON.

SYF

Otherwise, set output 5 OFF.

SKP

SYN

The Example 5 illustrates an important PDP-14 concept.

Note that although the original equation was

Y1=X4 * (X5+ Y1) * X12, the program was written for the equation Y1 =X4 * X12 * (X5 + Y1),

Programming

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

5-23

that control
Simplifications - The control program for Example 5 could be greatly simplified by the observation
on. In
relay 2 is an unnecessary output. The control relay is needed in the ladder diagram to latch the circuit

as shown in
the PDP-14 however, the output fo energize the solenoid may itself be tested as an input. Thus,
test
Example 5 Simplified (following), output Y1 may be eliminated and the control relay may be removed. The
of output Y5 is equivalent to testing output Y1 in this case.
EXAMPLE 5, SIMPLIFIED

Control Function

If pushbutton 4 is not ON and limit switch is actuated, and either pushbutton 5 is ON or solenoid B is ON

ready, then solenoid B is engated.

Boolean Equivalent

Inputs:

Output:

4PB (n/o) X4

SOLB Y5

5PB (n/o0) X5
2LS (n/o) X12

Equation: Y5 = X4 * (Y5+ Y1) * X12

PDP-14 Wiring (Figure 5-12)

4 PB(n/0)

—0

SOL B

5 PB (n/oJ)\) | 5

2 LS(n/o)

X12

P104P

14-0012

Figure 5-12
PDP-14 Program

Location

Content

TXN 4

JFN

TXF

Comments

If either X4 is ON or X12 is OFF, the output

should be OFF.

5-24

al-

Location

Content

Comments

TXN 5

Either X5 or Y5 itself must be ON for Y5 to

TYN 5

be set ON.

JFF

43
44

SYF
SKP

SYN

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. For other applications; however, timing
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.

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

By considering timing, this condition will be prevented.

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

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

average time, the following program execution times are determined:
1K program

20 ms

2K program

40 ms

3K program

60 ms

4K program

80 ms

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, if 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=Y0 * (X1 + X2+ X3),

and it is compiled by BOOL-14, the inputs X1, 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.

If either of the first two inputs are OFF,

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

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

1K program
2K program
3K program
4K program

75%

50%

15 ms
30 ms
45 ms
60 ms

10 ms
20 ms
30 ms
40 ms

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 equation could be checked more

than once, thereby decreasing the time between input samplings. To determine the choice of execution assumption (50% or 75%), consider the following analysis:

How much memory is not used (i.e.,

it is filled with NOP's) and is jumped around?

Are there many subroutines in the program? These effectively increase the memory size when they

Are there any sizable routines (e.g., start-up, shut-down, or manual) which are not executed

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

are executed.

under normal conditions?

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.
(us)

SKE, SKZ
TXD, TYD

5-26

6 NoNalNS,
B, N 18]

wed

SYF, SYN
JMP, JMS, TRM
JFF, JFN

TXF, TXN

—

]

4.0
A MO0 O

SKP, JMR, EEM, LEM
TYF, TYN

Time

Instructions

—

NOOG
D WN —-O

Operation Code

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. Thus, when the
user debugs his program with 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.

This feature is useful for

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.

Failure to do so may result

in lost hours when 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
9
Each character in the control equation has special meaning to BOOL-14.

For example, the non-printing car-

riage return character ( ) ) is 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.

The

This table includes all legal 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

into EDITOR.

[- and O-boxes.

Correct the program

Express the machine

sequence in equation

errors.

form.

Type the equations

in program form with
EDITOR.

Generate the source
tape for BOOL-14.

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

Errors may be corrected
with the BOOL-14 Edit
option and compilation
will continue. These
errors should also be
corrected in the source

Yes

lNo

tape.

Load the compiled
program paper tape

into SIM-14.

Check for program
errors.

e
-

Operational

Errors found.

No errors found.

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

End of statement (often represented by " ) ")
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 0 and 377.

puts.

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.

These inputs and outputs are combined as vari-

Operators

The BOOL-14 operators are * (Boolean AND), + (Boolean OR, inclusive), and / (Boolean NOT). These
operators combine input and output values to determine the value of an output. Thus the equation:
Y17 =Y17 * / X4 + X23

means that output 17 is set ON if (a) Y17 is already ON and X4 is not ON, or (b) X23 is ON; otherwise, Y17
is set OFF.

Note that the equation specifies the ON and OFF conditions for an output. Namely, the output is set ON if
the conditions are met (true) and it is set OFF otherwise (the conditions are false). The fact that an output is
set OFF when the conditions are not met is not always expressed explicitly, but it is always implied in a
BOOL-14 equation.

The NOT operator (/) may negate the sense of single variables or variable groups. It may also negate the left
member of an equation, in which case the equation specifies the set OFF conditions rather than the set ON
condifions.

For example:

/Y21 = X12+ /X31

means that output Y21 is set OFF if (a) X12 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. (The square bracket "["
is SHIFT/K and "1" is SHIFT/M on the Teletype keyboard.) For example:
Y12 =(X12 + X13) * [X27 + Y15l

There is no difference in the treatment of square brackets and parentheses by BOOL-14. They are available for
the user's convenience in distinguishing between variable groups. The only requirement by BOOL-14 is that
these symbols must be used in pairs. Any grouping which is opened with a square bracket must also be closed
with a square bracket.

For example:

Y12 = (X12 + X131 * [X27 + Y15)

will generate an error because both groupings are closed with the wrong bracket type.

However, the equations:

and

Y12 = (X12 + X13) * [X27 + Y 15]
Y13 =(X
+ 22
Y17 * [X42
+ X31) * X15

are in proper form.

Statement Continuation

Extremely long equations which will not fit on one line in the source program may
be broken into two or more

parts using "$" as the statement continuation character.

Each incomplete line is terminated with a dollar sign.

If the equation is being typed directly to BOOL-14 from the keyboard, BOOL-14 will
carriage return after the "$".

automatically provide a

If the equation is part of a source program paper tape generated with the Editor,

the user has typed a carriage return after the "$" on the source tape.

Whenever a dollar sign precedes a car-

riage return, BOOL-14 will not treat the carriage return as an end of statement
indicator.

It simply provides

a new input line and accepts the additional characters until it encounters o carriage
return which is not preceded

by a dollar sign.

Example:

Y21 =/ (X1+ X2+ X3) * ( (X4
+ [X5 * X6) * /X7%

)+ Y12 % (X27 + X5 +/X21)

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 of an equation
or to document the program in general.

program.

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 (;).

all characters to the right as a comment.

sign ($).

When BOOL-14 encounters q semicolon, it treats

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 = X1+ X2 * (X3 + /X4)

+ / LS14)

;SOLA = PB1 + PB2 * (LS13%

;LS14 TRIPPED WHEN SLIDE IS FULL FORWARD.

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 divided using a Z-function as described later in this chapter,
and recompiled.

SUBROUTINES AND STORAGE OUTPUTS

Subroutines serve two functions in BOOL-14 equations:

1. Z-functions solve for an intermediate value or result. A Z-function does not directly turn an output ON or OFF; rather, it is part of a larger equation which does.

2. R-functions 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.

A BOOL-14 program may contain a maximum of é4 subroutines (viz., R- and Z-functions).

Intermediate Results

" of an intermediate result. For example, one
There are many cases in PDP-14 programs whichrequire the "storage

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. These control relays are then used

in various combinations with other inputs and 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

Storage outputs

A normal output equation is written which sets an output in an S-box ON

or 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 in many different equations.

For example, suppose the following equations were compiled by BOOL-14:

Y1=X1*(X21+ X13 * /X42
+ Y17 * X11)
Y2= X2 *(X21+ X13 * /X42 + Y17 * X11)
Y3
= X3 * (X21+ X13 * /X42+
Y17 * X11)
Y4= X4 * (X21+ X13 * /X42+ Y17 * X11)
If given this set of equations, BOOL-14 would generate PDP-14 machine code to test each variable for each
equation.

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.

Z1=X21+
X13* /X42 + Y17 * X11
Y1=X1*Z]
Y2=X2*Z1

Y3=
X3 * Z1

Y4=X4*
Z1

The new form is analagous to a control relay in a ladder network which represents the combined state of a group
of inputs (Z1).

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 0 and 2047.
only be defined once.

The Z function must

It may be referenced as many times as necessary.

If given this group of equations, BOOL-14 will generate the series of instructions to establish Z1 as a subroutine.

The Z1 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 ON 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 Equation

Z-function
Test and

Conditional

jump

instructions

SYF output
SKP
N output
SY

TYN 377
TYF 377
JMR

If the result of the Z-function is 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. If the result of the Z-function
is frue, the TYN 377 and TYF 377 instructions will be executed. Since output 377 must be in one of the two
states, 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 . 1In
place of the instructions to test the variables in the Z-function, BOOL-14 will generate a JMS (jump to subroutine) to the beginning location of the subroutine that solves the Z-function. The subroutine will return to
the main program with the result reflected in the TEST flag. The main program will test the result with a JFF
or JFN instruction. 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.

This means that a subroutine may not contain a

In terms of BOOL-14, this means that a Z-function may not contain another Z-function as a

variable of its equation. If a second level is 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 ON or OFF (as opposed fo Z-functions
which set the TEST flag). 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.

This technique

is inefficient if the same equation is solved more than once, however. Defining an R-function causes BOOL-14
to generate the equation as a subroutine. Whenever the output state is to be determined, BOOL-14 generates a

JMS (iuhp 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=X1* ...

where n is any decimal number between 0 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 following

statement defines an R-function to set output Y53.

R81:

Y53 = X32 * (X41 + X12 * Y13) + X21

BOOL-14 generates the machine code instructions to solve the equation for Y53 in the same form as o normal
output equation.

After the set output instructions, BOOL=-14 compiles a JMR instruction:

SYF 053
SKP

SYN 053

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 program and not following an output equation.

Any R- or Z-function which is defined following an output equa-

tion (e.g., Y1 = X4) will generate an error.

Each 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

Z8 = X2+ X4 * Y7
+ X12
79 = X31 + X4

Z8 = X21 * Y7

Y1=X21+R8
R21: Y10=21 * X17

Z1 = X1+ X31 * Y21

Z2 = X3 * (X21 + X31) + Z1

Error because the Z8 function has already been defined.
Error because R-functions cannot be variables in equations.

(Only Z-functions may.)

Error because an R-function may not contain a Z-function as
a variable. (A subroutine may not jump to another subroutine.)
Error because the equation for a Z-function may not contain
another Z-function. (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

Storage outputs are outputs in an S-box of the PDP-14. They are programmed exactly like other Y-functions.
The only difference is that the output does not drive a solenoid, motor starter, or such.

Once a storage output

is set, 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

are executed only once for each pass through the program. The storage output itself may then be tested whenever 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 Y 16.

6-10

CONTROL STATEMENTS
Control statements 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 PDP-14 program

instructions generated by BOOL-14 and mark the end of source program tapes.

End of Program - .END or .ENDN

Each BOOL-14 source program must be terminated with an .END or .ENDN statement to indicate the end of
compilation.

The .END statement completes the BOOL-14 program by compiling a JMP instruction.

dress of the JMP is specified by the user such that the program is a "closed loop".
written following the .END.

The ad-

The address of the JMP is

Any octal number between 0 and 7777 may be specified as the value of the . END

statement, or a default value of 0 is assumed.

The value is often the same as the value of the .LOC statement
.

The .ENDN (end-no jump) statement may be used to terminate an incomplete program where no JMP instruction
is needed.

This statement marks the end of the source program but generates no machine code instruction.

.END and .ENDN Examples

Statement

Instruction Generated

.END 50

JMP

50
.END 2000

JMP

2000
.END

JMP

0
.END 2008

error-octal numbers only

.ENDN

non generated

.ENDN 50

error-no value allowed

End of Tape - .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 PDP-8 CONT switch permits the compilation to

proceed.

6-11

For example, if the program is on three tapes, the end of the tapes will be

[

Tape 1 is terminated by an .EOT statement

.EOT
J

[

Tape 2 is also terminated by an .EOT statement.

.EOT)

[

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

The JMP instruction goes to the first instruction of

231

the first output equation (in this case Y12).

The Z~ and R-function definitions may be in any order

.
15

Z15

and may be assigned any identifying number less than
or equal to 2047.

R29

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
Y73

1723
1735

JMP

The program was terminated by an

1736

"_.END" statement causing a JMP 0.

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 0 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 PDP-14 memory locations for the machine code instructions to solve the equation, BOOL-14
will compile 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.

The content of the locations be
-

ginning with O must control "start up", either with instructions to initialize the system, or with a JMP to an initialize 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
Y1= X1+ X2

yields the compiled instructions:

0050
0051

2401
2402

TXN 001
TXN 002

Note that the instructions begin in location 50. If no .LOC
statement were given, a .LOC 0 would be assumed and the

0052

5455

JFN

055

first instruction would be placed in location 0.

0053

3001

SYF

001

0054

0344

SKP

0055

3401

SYN

001

Only one .LOC statement is permitted in a BOOL-14 program.
of the program.
units are:

It must precede the first subroutine or equation

The value of .LOC may be any octal number between 0 and 7777.

(Remember that the memory

MB1, 0 to 1777; MB2, 2000 to 3777; MB3, 4000 to 5777; 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 0 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 aoffects 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 statement.

The value of . VARS is a decimal number between 0 and 2047.

The .VARS statement may be used to suppress the

output of NOP instructions after an equation by specifying a value of 0:

.VARS 0

Spacing Examples
Equation and Control

Number of NOP's after

Statements

The Equation

Z1=(X27 * YO) * X13 + X4

none

.FIXS 5

R12:

Y1=X23
* X14 + X0

.VARS 2

Y1=X23*Z1

R12

.FIXS 10
Y2 = X27 * X3+ X30 * X2

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, BOOL-14 can be directed to automatically supply monitoring instructions if the operation of the 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.

Specifically,

instructions may be added to monitor transitions to 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.

The TYD instruction outputs a spe-

cific 12-bit word to the monitoring computer; the word is determined by the PDP-14 (see Chapter 9).

The TRM

is a two location instruction which outputs a 12-bit word specified by the user.

Monitor Transitions fo 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-bit word into the PDP-14 output

The output register is not loaded as long as there is no

transition, or when the transition is from ON to OFF.

Example:
.MN

Y5=/X2* (X3
+ Y5)
(the instructions generated will include a TYD 005)

Only the immediately following equation will contain the sequence of monitoring instructions. The instructions
generated are described in Chapter 9.

If 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:

.MN 4123
Y5=/X2* (X3 +Y5)

(the instructions generated will include a TRM 4123)

If the user supplies less then four digits after the control statement, BOOL-14 will assume leading zeros.

Monitor Transitions to OFF - . MF

The . MF control statement allows the user to monitor the transition in an output from ON to OFF.

Instructions

are added which will load a 12-bit word into the output register whenever the output is changed from ON to
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+ /X10 * X11)
(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).
If 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+ /X10 * X11)
(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 ON to OFF and

OFF to ON).

Instructions will be added which will load a 12-bit word into the PDP-14 output register on all

transitions in the state of the output.

The output register is not loaded as long as the output remains ON or OFF.

6-16

Example:

.MFN
YN
= X271+ X15 * Y5

(the instructions generated will include two TYD 007's)
If 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 (. MEN) and the second number is

used in transitions to ON (. MFN).

Monitoring Input Transitions

As stated above, BOOL-14 allows monitoring of output states.

If the user wishes to monitor the fransitions 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 = X1

(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

X1.

Table 6-2
Summary of Control Statements

Command

Control Operation

.LOC 250

Start the program compilation at PDP-14 location 250.

.FIXS 5

Leave 5 (decimal) NOP's after all equations beginning
with the next equation.

.VARS 30

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

.MF

Monitor the next equation for transitions to the

.MFN

Monitor the next equation for all transitions

.EOT

ON state.

OFF state.

End of tape - interrupt the compilation while a

new tape is loaded.

.END

End of program - compile a JMP 0 instruction.

.END 50

End of program - compile a JMP 50 instruction.

.ENDN

End of program - do not compile any JMP
instruction.

BOOL-14 OPTIONS

The options available to the user are requested through a series of four queries as described below. These
queries are typed to start the BOOL-14 compilation process. If the user types other than a legal response to
a query, BOOL-14 will retype the query.
Example:

*SRC-KLH? N
*SRC-KLH?

N is not a legal response to the SRC query. BOOL-14

retypes the query.

If the user types more than one character in response to a query, BOOL-14 will recognize only the last character typed before the carriage return. 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.
H

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.

For example, the user may not want

By typing N, he may compile the program and get an error

listing without wasting time generating an incomplete binary tape.

The other two possible responses request the

binary output and specify the device to be used.
If the user requests binary output from a 4K PDP-8 system and the compiled program requires more than 1K of
PDP-14 memory, the message "BINARY OVERFLOW" is typed and no binary will be punched.

The compilation

will continue, however.

Compiler Listing

The compiler listing, which contains error messages and generated machine code instructions for solving the
equations of the source program, is 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.
w

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 N.

If only an error listing is wanted, the

BOOL-14 will type only those lines of the source program which contain errors.

For example,

BOOL~14 might type:

Y10 = X27 (Y3 + X21) * X4

Note that an operator is missing

EOT1

after "X27".

The user could then correct this and any other error detected during compilation and generate an updated and
correct source program fape 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.

The Y response causes BOOL-14 to generate the complete compiler listing. All lines of the source program

are typed (followed by an error number if the line contains an error). If 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. In these cases
BOOL-14 types the converted form to assist the user in debugging his program.
which the NOT (/) operator applies to single variables only.

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.

If 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.

13=X2%xX4+Y13% (/X4+/X5)
AA12 202 TXF 202
AN13 2004 TXF 004
AN14 S024 JFF 024
PN01S 1913 TYF 913
2016 5422 JFN 022
Q17 2004 TXF D04
pAa2n 2005 TXF 205
P21 5424 JFN 024
pn22 3013 SYF 713

AAaa 2431 TXN 201
PA7A1 5411 JFN 211
ona2 2032 TXF 032
PR3 20023 TXF 003
PR4 511 JFF 911
POAS 1412 TYN D12
P0n6 5411 JFN 11
AR7 3001 SYF 001
A010@ @344 SKP
3401

The third column is the

For example:

Y1=X1+(X32%¥X3+Y12)

PA11

These in-

NA23 @344 SKP

SYN 071

na24

3413

SYN

9213

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:
K

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.

If 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. Characters on the current
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 (\).

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, N and Y, mean No and Yes respectively.
If the 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:

"Y1= X1+ X9
E002

>Y1= X1+ X10

Retyped by the user

TXN 1

TXN 10

Generated machine code

If the source program is read from the low-speed reader and the editing option is requested, BOOL-14 will halt
after typing the ">".

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 be

completely ignored.

If 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 genercted

for erroneous equations, unless they are first corrected.

Error Number
1

Cause
A required number is missing after an input (X), output (Y), Z-function,
R-function or control statement.

Examples:

Y1=X
Y = X1
YI5=X2+Y

* CTRL/D is formed by holding the CRTL key depressed while striking the letter D.
6-22

Error Number

1 (Cont)

Cause
Z=X3+Y1

Y17=X5*Z
R:

Y12 =X27 * X]

.FIXS

A non-octal digit is encountered after an X, Y, . END, or .LOC.

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 .LOC or .END
statement.

The first or second character of an equation is not valid. The first character may be a NOT sign (/), or a "Y". If the first character is
A
the second character must be a "Y".
Examples:
B=XI

/G114
= X27 * Y3
The equals sign (=) is either missing or not in the proper place within an

equation, Z-function, or R-function.

Examples:
Y1

X1* X2

Y15/
= X3
A variable grouping is not closed with the character type with which it

was opened.

Examples:

[
X1+ X2)
[ X3 + (X5 * X6] +Y7)
The character following a negation sign (/) is not valid.
Example:

Y23=/11* X2
The character following a left parenthesis or left bracket is not valid.
Example:

Y10 = (R5 * X2)
The character following an AND (*) or OR (+) sign is not valid.
Examples:
Y11= X1+ *

Y12 = X10 * R1

The character following an equals sign (=) is not valid.
Example:

Y21 =RI

6-23

Cause

Error Number
11

The character following a number is not valid.
Example:

Y32=X1/* X2
12

The character following a right parenthesis or right bracket is not valid.
Example:

X2
/ *)
Y7 = X12 * (X5+ X7
13

A Z-function is confained as a variable in an R-function or Z-function.
Examples:

Z29 = X3 + Z50

R10: Y73 = X1 * Z12

An R-function or Z-function is referenced which has not been defined

An equation contains more right parentheses and brackets than left paren-

previously .

theses and brackets.
Example:

Y37 = X1 * (X2 * X24 + X25] * X4)
16

An equation contains less right parentheses and brackets than left parentheses and brackets.
Example:

V42 = X12 * X2 * (X2 * [23 + X171 * X14
17

A control statement is not recognized.
Examples:
.MZN
.MNF

.SAZ
18

A control statement contains an illegal character.
Examples:

.MEN
.M.N

There is no control statement after the period (. ).

The .LOC statement must precede all equations, R-functions and Z-functions.
Examples:

Z12= X1 * X2
.LOC 50
21.

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

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

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 (:) is 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.

equation.

The first two rules affect the number of memory locations used to solve the

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:
Y1=X1+X2+ (X3* X4* X5)+Y12+
X15

should be rewritten:
Y1=X1+X2+YI12+ X154+ (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:
YI5=X3*Y5+ X6* Y5+ X12*Y5+YI17
*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)]1 * 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 is more often true
should preceed the other expression.
Example:

Y5=(X12 * X4+ / X27) + (X21 * (X3 + / 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.
longer to test than a single variable.

Remember that subroutines take

Example:

Y11=(Z3 * / X21) + ((Z7 + X4) * X3 * X5)) + X1 * X2
should be rewritten:

+ Z7))
+ (X3 * X5 * (X4
(/ X21 * Z3)
Y11= X1* X2+
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.

The

rules attempt to limit the amount of testing which 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

3BOOL-14

SAMPLE

5COMMENTS

5CONTOL

PROGRAM

IDENTIFY

STATEMENTS

THE

WHICH

PROGRAM

AFFECT

WOULD

THE

APPEAR

WHOLE

HERE.

PROGRAM

FOLILOW.

.L0C250
FIXSS5

5SUBROUTINES

PRCEED

THE

MAIN

PRO GRAM.

52CR=/ 6PB*/ 7TPB*/ 1PS*/ 1 FS*/ 5CR

722=/KI3%/X14x
K6/ KXT*x/Y11
/

5SOLE=3CR=(8PB*CRH+CRA)*7CR*&8CR*9CR*/3LS*/4LS*/
5LS
R1:Y4=(X1S5*YT+Y6I*Y12%Y13%/Y14%/X2%/
X3%/ X4
3SOLF=4CR=/7CR* (CRA%5CR+/ 9CR+9PB*CRH)
R2:Y5=/Y12%(Y6*xY11+Y14+X16%Y7)

5NORMAL

EQUATIONS

FOLLOW.

32LT=CRA=RESET(AUTO
*/CRH*
+CRA)

Y6=X10*Y7T*(X11+Y6)
5CALL

REPETITIVE

EQUATIONS.

.VARS®

3NORMAL

EQUATICNS

CONTINUE

BELOW.

53LT=CRH=RESET* (MAN+CRH)

Y7=X10*(X12+Y7)
5SOLA=SOLC=CR1=/6CR*(6PB
1 LS*/2LS*5LS
*7PB*2
*6LS*7CR+1C
CR*/
R)

YO=/Y3%(X13*%X
X%/ X1
14%Z2%x
*XA*KS5*Y12+Y0/
7)

Yo =X0
541, T=/ 6PB*/ TPB*( 1PS+1FS)

Y10=/X13%X1ad*(XE+XT)
35SLT=5CR=3LS%/4LS+5CR*&CR

Y11=X2%/X3+Y11%Y13
5SOLB=S0LD=6CR=
5LS*/ 6L.S* 7CR*(
(6CR+5CR*8CR)
CRA*/
+PR1A*CRI)
Yo=Y
X4/
12%(
X5%(Y2+Y11%Y1
Y6x/
3)+X1T74Y7)

56LT=7CR=4LS

Y12=X3
57LT=8CR=1LS*2LS

Y13=X0*X1
3/8LT=9CR=/11PB*(9CR+12PB)*
(7CR+8CR)

/Y14=/X2P*(Y14+XK21)%(Y12+Y13)
5CALL

REPETITIVE

EQUATIONS.

.VARSOQ
R1

R2
«END

250

6-27

V1
*BIN=-NLH?L

*LST-NYW?Y

*SRC-KLH?”L
*EDT=-NY?
N

513J)0L-14

SAMPLE

PROGRAM

5OOMMENTS TO IDENTIFY THE PROGRAM WOULD APPEAR HERE.
5CONTOL STATEMENTS WHICH AFFECT THE WHOLE PROGRAM FOLLOW.
1.0C250

SFIXS5

5SUBROUTINES

PRCEED

THE

MAIN

PROGRAM.

;2CR=/6PB*x/
7TPBx/ | PS*x/ 1 FS*x/ 5CR
72=/X13%/
K1 4%/ Xex/XT*x/Y11
P52

2413

TXN

013

M2e53

2414

TXN

Al4

Necd

2406

TXN

006

Bess

2407

TXN

207

pese

1411

TyN

011

7nesT

5662

JKFN

262

pe6n

1377

TYF

377

neel

1777

TyYN

377

neez2

B354

JMR

5SOLE=3CR=(8PB*CRH+CRA)*7CR*8CR*9CR*/3LS5*/
4L.5*%/5L5S
RlL:Y4=(X1I5*%YT+Y6)I*xY12*xY13%/Y14*%x/X2*%x/
K3*%/ X4
A270

2015

TXF

A15

271

1007

TYFE

007

AR72

5275

JFF

275

M273

1406

TYN

(06

5304

JFEF

3004

275

1012

TYEF

uiz2

peve

1013

TYF

0013

pe7T

1414

TYN

014

A300

2402

TXN

002

A301

2403

TXN

103

p302

2404

TXN

N303

530¢

JFF

306

N304

3004

SYF

004

W30S

N344

SKP

A306

3404

SYN

@307

B354

JMR

004

5SOLF=4CR=/T7CR*(CRAX*5CR+/9CR+9PB*CRH)
R2:Y5=/Y12%x(Y6xY11+Y14+X16%YT)
315

1412

TYN

0l2

p316

5727

JFN

327

317

1006

TYF

006

0320

1011

TYF

011

w321

5331

JFF

331

A322

1414

TYN

Ol4

323

5731

JFN

331

0324

2016

TXF

016

0325

1007

TYF

007

w326

5331

JFF

331

0327

3005

SYF

005

N330

0344

SKP

®#331

3405

SYN

w332

B354

JMR

005

6-28

;NORMAL

EQUATIONS

FOLLOW.

32LT=CRA=RESET*/CRH*
(AUTO +CRA)
Y6=X10*YT7T*x(X11+Y6)

0250

4224

JMP

B251

0340

P340

B340

2010

TXF

010

p341

1207

TYF

0067

p342

S5T46

JFN

346

@343

2411

TXN

011

P344

1406

TYN

006

@345

5750

JFN

350

0346

3006

SYF

Q06

0347

0344

SKP

@350

3406

SYN

sCALL

P06

REPETITIVE

EQUATIONS.

+VARSQ

P356

4645

JMS

B357

270

0270

8360

4645

JMS

0361

P315

@315

5NORMAL

EQUATIONS

CONTINUE

BELOW.

353LT=CRH=RESET* (MAN+CRH)
Y7=X10*%(X12+Y7)

0367

2010

TXF

210

8370

S5TT74

JEN

374

0371

2412

TXN

@12

p372

1407

TYN

007

@373

5776

JFN

376

P374

3007

SYF

007

@375

0344

SKP

0376

3407

SYN

00817

5SOLA=SOLC=CR1=/6CR*(6PB*x7PB*2CR*/ 1LS*x/2LS5*5LS*6LS*7CR+1CR)

YO=/Y3%(X13%X14%Z2%/XO*/
X1 *xX4*xX5%xY12+YD)
Qud4

1403

TYN

003

2405

5424

JFN

024

B406

2013

TXF

913

o407

2014

TXF

@14

0410

5422

JFN

022

gall

4645

JMS

R4al12

pase

pasa

2413

5022

JFF

pg22

oal4a

2400

TXN

000

415

2401

TXN

001

P416

2004

TXF

004

Qa1

2005

TXF

085

6-29

pua20

1gl2

TYF

012

pa21

5026

JFF

026

pac2

1400

TYN

000

423

5426

JFN

026

aa24

3000

SYF

000

@425

A344

SKP

426

3400

SYN

000

Ba34

2400

TXN

000

B4a35

S44¢

JFN

040

pa3é6

3002

SYF

002

Qua37

¥344

SKP

440

3402

SYN

Y2=X0

@02

541L.T=/ 6PB*/ 7TPB* (1PS+1F5)
Y1@0=/X13*X14%x(X6+X7)
paa6

2413

TXN

aaa7

2014

TXE

013
014

A45@

5454

JFN

054

P45l

2406

TXN

006

pase

2407

TXN

007

A453

5456

JFN

056

pas54

3010

SYF

010

M4asS5

A344

SKP

Auas56

3410

SYN

@10

35LT=5CR=3LS*/4L.5+5CR*8CR
Y11=X2*/X3+Y11*xY13
pae64

2002

TXE

002

Da6s5

2403

TXN

003

A4a66

5SO7T4

JFE

074

pa67

1011

TYF

@11

naty

1913

TYE

013

aaT7l

S@T4

JFF

074

472

3011

SYF

011

@473

0344

SKP

Aa74

3411

SYN

Q11

3;S0LB=SOLD=6CR=7CR*(CRA*/5LS*x/6L5*(6CR+5CR*8CR)+PB1@*xCRH)
Y2=Y12%(YOX/
X4X/ X5 (Y2+Y11xY13)+X17*xYT)
502

1012

TYF

¥5@3

5520

JFN

@12
120

w504

1006

TYF

006

D505

2404

TXN

004

@506

2405

TXN

005

@507

5515

JFN

115

510

1402

TYN

002

@511

5522

JFN

122

P512

1011

TYF

011
013

@513

1013

TYF

P514

5122

JFF

122

515

2017

TXF

@17

0516

1007

TYEF

Q07

@517

5122

JFF

122

@520

3002

SYF

@@2

521

0344

SKP

P522

3402

SYN

Q@2

6-30

56LT=7CR=4LS
Y12=%3

@530 2403 TXN 003
M531 5534 JFN 134
3012
0344

532
(1533

0l2

SYIT
SKP

SYN 0l2

(1534 3412

57LT=8CR=1LS5*2L5S
Y13=X0*xXl1

2000 TXF 000
2001 TXF 001
5147 JFF 147
3013 SYF 013
@344 SKP
3413 SYN 013

0542

P543
p544
@545
546
@547

R)
)*
(7CR+8C
5/8LT=9CR=/11PB*(9CR+12PB

/Y14=/K20*x (Y14+K21)I*x(Y12+Y13)
555

2420

@556
@557
M560
@561
562
563

5565
ltal4a
2421
5165
1412
1413

020
JFN 165
TYN 014
TXN 021
JFF 165
TYN @12
TYN 013

@564
565
0566
567

5567
3414
@344
3014

JFN
SYN
SKP
SYF

TXN

167
@l4

@14

REPETITIVE EQUATIONS.

sCALL TO
-VARSO

R1
@575

4645

JMS

@576

270

0270

@577

4645

JMS

D600

©B315

@315

+END

250

pev6

4224

JMP

PepT

B250

V250

LINES:

0000

ERROR
EDITED

LINES:

PRO GRAM
TURN
BEeW

0000

BREAK:

PUNCH

0607

OXN

277,

%5/ +/+%55/
&7 (D&%8&%
/>%5
5 &% %k (

(555,

SPURTIOUS

$s5555C(<(<?

-))%-

TYPFD

PUNCHFD

)

Y'F-505

-T1T5&%8&7%

6-31

CHARACTFKS

WHILF

KINAKY

AKFE
IS5

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 program. 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

Each instruction is assigned to a numbered location.

2. The JFN and JMP instructions refer to locations by
specific address numbers.
3.

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 program. To correct the program with SIM-14, each instruction is moved to the next sequential location (by typing
it 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. Originally the
jump caused transfer to the SYN 12 instruction; now it causes transfer to the SKP. The JFN instruction must be
changed to a JFN 234 to preserve the original sense of the program. Thus, there are dangers in simply relocatin
programs with SIM=-14. 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. The need to specify the address of each

instruction is therefore unnecessary. The locations may be assigned by PAL-14 using an origin statement for the
sequence of instructions. The statement is "LOC NNNN" where NNNN is 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.,

LOC 227
TXN 15
TYN 27
JFN 234
SYF 12
SKP

SYN 12
JMP
437

7-2

Assign inputs and
outputs to PDP-14 1and O-boxes

v
Express the machine
sequence in equation
form.

y
Translate the equations

Read source tape back

into instruction form.

into the EDITOR.

Type the instructions

Correct the program

in program form with
the EDITOR.

errors.

v
Generate the source
tape for PAL-14.

Assemble the PDP-14
program with PAL~14.

’stembl y errors founD—-—‘

v
Load the assembled
program paper tape
into SIM-14.

Y
Check for program

errors.

D@era’rional errors Found>—’

< No errors found.
Y
Generate paper tape
and send to DEC for

ROM.

Figure 7-1

7-3

PAL-14 recognizes the LOC 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
JFN 234 is stored in 231; etc. Thus, the need to write location numbers is eliminated by PAL-14.

Symbolic Addresses

The LOC statement by itself does not eliminate the problems arising when PDP-14 programs are altered. However, automatic location assignment using the LOC 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 jump 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

The location to be jumped fo is assigned the

address label "TAG", by writing TAG followed by a comma, preceding the referenced instruction.

TAG,

JEN

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" (LC). The LOC
statement sefs the LC to a value (e.g., LOC 200 sets the LC to 200).

PAL-14 then assigns each successive

instruction of the source program to the locations specified by the LC.

The LC is incremented for each instruc~

tion, thereby storing the program in sequential locations of PDP~14 memory. Whenever a symbolic address

(recognized because it is followed by a comma) is encountered, it is assigned the value of the LC. Thus, if the
LC 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.

Note that programs in this form may readily be changed to eliminate bugs.

located by changing the LOC 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.

An address

error will result if a 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, SETYTON 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 SETYTON and SET1OF

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 are identical in
these first six characters.

The error results because the same symbol is defined twice in the program.

Note that

the symbols SOLAON and SOLAQOFF 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.
3.

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 mean-

ingful to PAL-14. Although more characters may be
used, they are not meaningful to PAL-14,
5.

No spaces or tabs are allowed within the symbol .

Assighment Statements

PAL-14 assignment statements equate a six character symbol with a numeric value.
statements are subject to the rules given in Table 7-1.
symbolic address is illegal in PAL-14.

Symbols used in assignment

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.

The most common use of assignment statements in PAL-14 programs is to identify input and output assignments.

It is more convenient fo remember that "LS1 is limit switch 1" as opposed to "17 is limit switch 1", Since
PDP-14 programs must refer to inputs and outputs by the numbers which are determined by the I- and 0-box
assignments (e.g., 17), the following PAL-14 assignment statement is used.
LS1=17

Instructions may then test "LS1" in place of testing "17". The PDP-14 program may include, usually ot its

beginning, a list of such assignments which are used throughout the program. This allows the program to be
written in a completely symbolic form. For example:
LS1=17

L52=30

SOLA=11
SOLB=12
PB1=10

PB2=11

LOC

250

Y11,

TXN LS1
TXF LS2
JFN SOLAN
TXF PB1
TYN

JFF

SOLAN,

SYN

SOLB
SOLAF

SOLA

SKP

SOLAF,

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 used throughout the
program. (The above example only controls one output.) Also note that LS1 = "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 format the program as desired.

At least one space (or a TAB) must be used between an instruction (e.g., TXN or SYF) and the referenced symbol
or operand (e.g., LST or SOLB). 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. For example:
SOLA

LS1

TXF

7-6

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.

/THE FOLLOWING PROGRAM CONTROLS SOLENOID A
LOC 200

Y1,

TXF LSI
TXN PB1

/LS1
/PB1

ACTIVATED WHEN SLIDE 2 IS FULL FORWARD.
1S 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,

STATN=2002

Y5,

LOC 200

200 TRM
201 2002

TRM

STAIN

202

JMS

203

1323

JMP

204

JMP

205

1401

TXN

LS16

JMS

NEXT,

TYN

SOLB

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 is acceptable to SIM=14 or to the
ROM generator.

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., LS1=27) and symbolic addresses (whose values are defined by the location counter and LOC
statements) .

In addition to user defined symbols, PAL-14 has a table of permanently defined symbols and their
numeric equiva-

lents.

The permanent symbol table allows the user to write statements such as "TXN 15" without having previous-

ly defined the symbol TXN.
PAL-14.

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

7-8

10 (pages 10-21).

Table 7-2
PAL-14 Permanent Symbol Table
PDP-14 Instructions
Max. Arg.

Value

Symbolic

Octal

Meaning

Argument

TXF

2000

Test input for OFF

Input Numbe:

377

TXN

2400

Test input for ON

Input Number

377

TYF

1000

Test output for OFF

Output Number

377

TYN

1400

Test output for ON

Output Number

377

SYF

3000

Set output OFF

Output Number

376

CLR

3377

Clear all outputs

None

-—

SYN

3400

Set output ON

Output Number

377

JFF

5000

Jump if test flag OFF

Page Address

377

JFN

5400

Jump if test flag ON

Page Address

377

JMP

4224

Jump unconditional

Absolute Address

7777

SKP

0344

Skip next location

None

JMS

4645

Jump to subroutine

Absolute Address

7777

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 Number

377

TYD

7400

Test output and display

Output Number

377

EEM

0600

Enter external mode

None

~——

EES

0645

Enter external mode, store PC1

None

—-——

LEM

0400

Leave external mode

None

-—

LER

0454

Leave external mode, restore PC1

None

TRM

4226

Transfer memory to Output

Any data word

7777

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 registers given below.

7-9

in Octal

PDP-14 Internal Registers
Register Name

Octal Code

DUMMY

0000

PC1

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

LOC

Set location counter

PAGEJ

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

(logical OR)

combines symbols or values by a logical OR

shift)

shifts a value one octal digit left

—

(space)

separates instructions from operands and otherwise formats

the source program

(tab)

separates instructions from operands and otherwise formats
the source program

)

(carriage
return)

(slash)

terminates a statement
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 "JMP 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).
LOC

100

START,

TXN

PBI

JFN

OUT

TXN

PB3

JMP

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.

The location counter of PAL-14 will assign values to all labels and then PAL-14

will 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.

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:

translates into

TRM 15 1 27

TRM
37

The values of symbols may be combined with the

character also.

ON =1

SOLA = 1500

TRM SOLA |

translates to

TRM
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. Zeros are shifted into vacated positions on the right and the most significant digit is
lost.

For example:
0231 > =2310
0010> =0100
> =2340
1234

The shift character will often be used with the PDP-14 instruction TRR and internal register names. PAL-14
maintains the following register assignments in its permanent symbol table.

SPARE

PC1

= O

DUMMY
IR

Octal Equivalent

hWON

PAL-14 Register Name

OUTPUT

PC2
INPUT

The above register names may be used as operands in PAL-14. For example:
TRR

PC2>

OUTPUT

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

TRRI

PC2>!

OUTPUT

The shift character only affects the symbol or number which immediately precedes it.
STATN3 =300

translates to

TRM 1+300 >

Thus

TRM
3001

(not 3010)

Period - The period is a special symbolic address used in PAL-14.

Its value changes for each instruction and is

always equal to the present value of the PAL-14 location counter.

Jump instruction operands may contain the

period (often read "dot") and the +, -, and ! operators.

For example, JFF .+12 (read, JFF dot plus 12) means

JFF to the twelfth octal (tenth decimal) location after the JFF instruction.

The period is most used with small

(less than 10) octal numbers; large jumps are best done in PAL-14 with true symbolic addresses.

A variation of this instruction is "JFF .+1".
ed for both states of the TEST flag.

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.
.12 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.
translates to

LOC
JMP

200

201

JMP
203

TXN

202

TXN

203

TXN

200

(201 +2)

The following instruction could be used to have a TRM instruction output its own address:

LOC
TRM

1400
-1

translates to

Thus JMP

1400
1401

TRM
1400

Pseudo-Instructions

ly proPseudo-instructions are included in PAL-14 program listing on the source paper tape to direct the assemb
instruccess. They are not themselves translated into PDP-14 machine code; they affect the translation of other
tions into machine code. There are four pseudo-instructions in PAL-14 including the LOC and

END statements

described previously in this chapter.

te the
END- The END pseudo-—instruction marks the end of a source program and directs PAL- 14 to termina

ent upon
current assembly pass. The complete assembly process requires either two or three "passes” (depend
ion to
the assignment of input/output devices) during which the source tape is read by PAL-14 and the franslat

PDP-14 machine code is made. The END statement terminates the current pass and causes PAL-14 to halt while

the source tape is reloaded to begin the next assembly pass.

Since the END statement halts the reading of a paper tape during the assembly, any information present on the
source tape after the END statement will not be read by PAL-14. However, the comments are a permanent part
comments
of the source program and may be read with the Editor. The assembly process will be faster if lengthy
and program documentation are wriften here.

on
_EOT- The pseudo-—instruction EOT (end of tape) allows a long PAL-14 program to be segmented and recorded
more than one source paper tape. The EOTis typed as the last statement on all tapes except the last one which
must be concluded with the END pseudo=instruction. PAL-14 will stop upon the reading EOT at the end of each
tape during an assembly pass and type "*EOT". The next source tape is then loaded and the assembly continues.
This procedure is repeated for each source tape in the complete program.

LOC - The LOC pseudo-instruction directs PAL-14 to set its location counter to the operand value of the LOC.
As many LOC statements as desired may be used. However, if no LOC statement is present, a "LOC 0000"

statement at the beginning of the program is assumed by PAL-14.

t re-

The LOC statement may advance or reset the location counter to any desired value. If the LOC statemen

turns the location counter to an earlier value, any previously assembled instruction at that location will be lost.
For example,
LOC

50
TXN
TXN

LS1
LS2

LOC

50
SYN

SOLA

results in the assembly of two instructions for the same location.

The first instruction (TXN LS1) is lost from the

assembly; PDP-14 location 50 will contain the assembled instruction for SYN SOLA.

The LOC 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 LOCATIONS BEFORE STARTING NEXT PROGRAM SEGMENT.
LOC SOLAF+10

The value of SOLAF will be assigned at the time of assembly and the LOC statement will set the location counte
to the value of SOLAF plus 10 (octal).

Thus the value of a LOC statement may be determined at the time of

assembly .
The pseudo-instruction "LOC .1377 +1" causes PAL-14 to advance the location counter to the first location
of the next PDP-14 memory page.

The statement is evaluated by PAL-14 as:

counter (.) OR'd with 377 (octal) plus 1.

the current value of the location

If the location counter is 1312 for example, the result of the OR will

be 1377 and the LOC statement will set the location counter to 1400 (]3778 + 18) .

PAGEJ ~ 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.

Current Locafion

Instruction Generated

First location in a memory page

none

Last location in a memory page

NOP

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
supply a JMP instruction, the operand of which is 1 plus the OR of the current location counter value and 377.
This JMP always goes to the first location of the next PDP-14 memory page.

The PAGEJ pseudo-instruction also acts as a "LOC .1377 +1" in the cases where a JMP instruction was assembled. 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, a symbol table and a punched binary

tape. 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.

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
a punched code at its end (checksum) which is read by SIM-14 when the tape is read into memory to verify reading accuracy.

Assembly Listing

The assembly listing contains the original source statements, the numeric value of the generated PDP-14 machine
code and error codes. PAL-14 formats the assembly listing into pages of 66 lines (approximately 11 inches long).
It types the page number (in octal) at the top of each output page.

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.

Only

assembled instructions have entries in this field.

Code field

contains the numeric value of the code for assembled
instructions, assignment statements or the LOC 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-14 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
(This is not the largest address;

by the assembled program.

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.

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,

if the statement "PB1=PBO + 1" and there is no statement which defines PBO, the symbol table will contain "PBO
~U" and "PB1

+0".

The values of directly assigned symbols are typed as five digit numbers (with leading zeros)

to distinguish them from symbolic address values which are typed as four digit numbers.

Error Messages

Error messages are single letters typed as the first entry of the same line as the source statement which contains
the error.

If more than one error is detected, a list of all error codes is typed in alphabetical order.

of six error codes is typed for each line.

A maximum

If the same 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.

These errors will, of course, be detected after the cause of the syntax error is removed and the statement

is 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
JFF Oor JFN 0. The code for the
example is JFN 0, therefore.

Example:

At location 376

LEAVE, JFN .+3

Double Defined Symbol Error - an
instruction references a symbol which
has been defined more than once in

PAL-14 uses the first definition.
The JMP A in the example would
jump to the TYN SOLA instruc-

the source program.

tion.

TYNSOLA

JFNOUT

JMP A

Illegal Character Error - The statement contains a character which is
not acceptable to PAL-14.

PAL-14 ignores the illegal
character. Thus the example is

Example:

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)
or the left hand member of an assign-

The label or assignment is ignored
by PAL-14.

ment statement is numeric.

Example:

50=LS1

47,

JMP

RESTART

Multiple Definition Error - a label
is defined more than once in the
source program.

Examples:
M

TYN

SOLB

JFN

SOLBN

Operation Error - the source program contains an illegal operation
(e.g., two instructions in the same

statement) .

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.

PAL-14 will ignore the illegal and
all subsequent information. In the
example, the machine code is generated as if the statement were:

Example:

START,

JMP TEST

JMP

START,

JMP

TEST

Action Taken

Meaning

Error Code

Phase Error - a label has a
different Pass 1 and Pass 2 value.
This error is normally caused by
a symbolic LOC statement the
operand of which is defined after
it is used.

Example:
P

LOC

XYZ,

The current value of the location
counter is used to define the label
for each pass. Since CDE is undefined at the start of assembly, LOC
0 is 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

CDE

JMP .+2

errors.

CDE=50

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:

LOC 50

R
ABC,

JMP=400
TXN LST

ABC=70

Syntax Error - the source state-

The statement is evaluated from left

ment is not meaningful to the

to right up to the point where the
error occurred.

assembler.,

Thus:

Examples:

ABC,

LS1+LS2,

LS1=

SOLA,

JFN

JMP

TXN+=3
SOLAN,

JMP

assigns ABC the current value of the
location counter and generates the
machine code for "JMP .". The
value of LST plus LS2 will be stored
in the next memory location (with=out any symbolic address). 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",
Truncation Error - a single
value exceeds 7777 octal, or

In assigned values, the excess right
hand digits are ignored. Thus the

the maximum argument value

result of A=40543 +C is

for the instruction (see Table

If the truncated value is used as the
operand of an instruction, PAL-14
substitutes the value 0 when the value
is too large. Thus the value of:

7-2) if maximum is less than
7777 .

A=4054+C.

Error Code

Action Taken

Meaning

ABC=375+100

Examples:

TYN

C=3
T

is the following:

A =40543+C

—

ABC=375+100
TYN

ABC

SKZ

ABC

ABC =475

TYN

The instruction SKZ 40 becomes
SKZ

Undefined Symbol Error - an

The undefined portion of the

instruction references an un-

statement is set equal to 0.

Thus:

defined symbol .
Example:
XYZ =50

JMP

XZZ +3

becomes

JMP

0+3 or

JMP

XZZ +3

where XZZ is not defined

Illegal Value Error = A value

The illegal digit is ignored, and

given in the source program

the remainder of the expression is

cannot be evaluated by PAL-14

evaluated.

Example:

Thus:

ABC=8402 +5

ALS, 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.

This

Furthermore, the

listing 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).

It 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 1 error listing may be incomplete, it 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

If 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.

If the assembly listing is to be output on the high-speed

punch, typing E will cause pass 1 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

FOLLOWING

PROGRAM

SOLVES

THE

EQUATIJN

/SOLA=(LS1*PR2%x/PB3+S0LA=/1L52)*%/PPB5
/
/

SOLA=5
LS1=415

L52=16
PB2=17

PB3=10

PB5-12
LOC

200

SOLAS

TXF

LS1

TXF

PB2

TXN

P*B3

JFF

CK5

TYF

SOLA

TXN

LS®2

JFN

SOLAF

SCHK.>

TXN

PBS5

JFF

SOLAYN

SOLAF,

SYF

SOLA

/TURN

SOLA

TURN

SOL.A

Source
Program

OFF.

SKP
SOLANs,

SYN

SOLA

ON.

END
*BIN-L
*LST-L,

Command String

*SMB-L,
*SRC-L

FRR

200

2000

202

2410

0207

2400

213

3400

LINES-0004

UNDEFINED

CK5S

SOLA,

TXEF

LS1

TXN

PxB3

SCHK,

TXN

PBS5

SOLAN,

SYN

SOLA

MEM

Pass 1

Errors
TURN

SOLA

ON.

BRK-0M115

SYMBOLS

-U

PB5

-U

TURN

-U

Pass 1

Symbol Table

7-21

*PAS

op@a1

PAGLEE-

PAL-14

/THE FOLLOWING PROGRAM SOLVES THE EQUATION
/SOLA=(LS1#PB2%/PR3+50LA*x/L52)%/PPR5
/

SULA=5

LUV

Mn4a15

LS1=415

B16

LS2=16

EIIoN

PR2="7

PR3=10

a141414)

7766

PRS5-12

200

LOC

A2Mn

2000

SOLAS

TXF

LS1

2ml

27077

TXF

P32

nene

2410

TX:

P*B3

1273

50300

JIE

CKD

1200

TYF

SOLA

3205

2416

TXN

L52

R06

5611

207

2470

1219

50213

M1l

39270

I212

134

1213

34001

Pass 2
Listing

2017

HCHIG

SIHTLAY,

JFN

SOLAF

TXN

PR5

JFF

SIOLAN

SYF

S5ouA

/TURYN

5J)LA

TUR'T

SOLA

OFF.

SKP

SOLAYS

SYN

SOLA

ONe

KND

Error Codes

KRR

L INES-0007

MEM

BRK-00O15

TABLE

SYMBOL

CK5

-U

.51

-3A415

.52

-0 16

-U

PR2

0007

PR3

-A0010

PB5

-uU

SO0LAF

f211

SOLAN

0213

SO0LA

0200

TURN

-uU

Pass 2

Symbol Table
(Addresses are 4-digit numbers;

assigned values are 5-digit numbers.)

*PAS

®? 6B (

Spurious characters are
typed while binary is punched.

)

*PAS

Pressing CONT will restart PAL-14.

7-22

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.

be used to compose programs directly by typing PDP-14 instructions under control of

It may also

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 machinery .

In fact, it is 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
actual equipment when placed in a PDP-14 memory.
gram contained within the PDP-8 computer.

local mode, will 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

specifying the location (or locations) 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

SIM-14 can be used to simulate PDP-14 programs of 1K, 2K, 3K or 4K words. However, if more than 1K of
PDP-14 program is to be simulated, SIM-14 must be loaded in a PDP-8 computer with at least 8K of core memory.
CONVENTIONS

The following conventions are used to describe the dialogue between the user and SIM-14.
a.

All characters typed by SIM=14 will be identified in this manual by an underline.

Examples:

NOP

Typed by SIM-14

TXN 1

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:

TXNT )

User concluded typing with
a carriage return

The non-printing character LINE FEED will be noted in this manual by a straight down

arrow
.

Example:

TXN 1 |

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 instructions 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). They are treated as NOP's
during equation verification or truth table generation. 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.)

Execution 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

TYN

1400-1777

JMP

TYF
TXN

4224

1000-1377
2400-2777

IMS

NNNN
N

TXF

2000-2377

TRM

4226

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

Octal Equivalent

NNNN

SIM-14 COMMAND DESCRIPTION

SIM-14 has many commands to control program debugging.

Some commands are recognized only in local mode;

others are 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

error). The command which caused the error will be ignored and the user may either change
modes
new command.

M ? (mode

or type a

(Commands which are not recognized by the truth table mode or the equation verification

will also generate an

mode,

M ? error message when used in the wrong mode
.)

All commands in SIM-14 are terminated by a carriage return.
act upon the command.

When the carriage return is typed, SIM-14 will

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.

The first

Any command which is of the last form may also be typed in form b. Specific examples of these command forms

will be covered in the following pages. It is important that the reader understand that there are three forms
and that a command must be typed in the form expected by SIM-14.

Commands in this manual are presented as specific examples without giving the general form. Note that commands which have limits (e.g., form c above) may be typed in form b if only one entity is affected by the
command .

The user may substitute any PDP-14 program address, PDP-14 input or output program number, or other paramete
for those given for illustration purposes in this manual .

PDP-14 GENERAL COMMANDS

Once SIM=-14 has been loaded into the PDP-8 computer and started (see Chapter 10 for these operating pro-

cedures), the user may type commands to SIM-14 and begin program debugging. 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 version 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
D

SIM-14 is now awaiting a local mode command.

OM Command

When the user has completely debugged his program in local mode and wants to test the program with the machin
ery to be controlled, he may enter on-line mode by typing the command OM, followed by a carriage return.
LOM)

SIM-14 is now awaiting an on-line mode command.

On-line mode execution is possible only when the PDP-14 has been completely installed, with the machine inputs and outputs wired to the I and O boxes of the PDP-14. The ROM for the PDP-14 is not in place, however,
and the PDP-8 inferface modules and cable must be installed. If any of these steps has not been taken, or if
the PDP-14 is not running, SIM-14 will type NR? and will not enter on-line mode .

RUBOUT

If the user types a command incorrectly or wishes to have SIM-14 disregard a command for any reason, he may
strike the teletype 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

.MB2@ S
_.MB3)

The user meant to type MB3 and therefore struck the RUBOUT key at
this point. SIM-14 ignored the command and typed the @, the
carriage return and period to signal readiness to accept a further
command. The user then typed MB3, followed by a carriage return.

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
al, 2,3, or4, tospecify the size of the PDP-14 program (1K, 2K, 3K or 4K).
.MB3
) SIM-14 will allow up to a maximum 3K program (i.e., addresses
0 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 MB1 command is legal (viz., only 1K 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.

No. of Memory Banks

Memory Addresses

0000 - 1777

0000 - 3777

0000 - 5777

0000 - 7777

8-5

Load the program into simulated PDP-14 memory
.

!
List the program with SIM=14| Yes
Any errors found
?

Correct the error within SIM-14, When
the correction has been checked out,

‘No

the bug should be corrected in the program source to BOOL-14 or PAL-14.

Verify each equation with
varying input.

Any errors

Do not make changes to PDP-14 programs
Yes

with SIM-14 without correcting the pro-

gram as it was input to BOOL~14 or

found ?

PAL-14.

‘ No

Generate a truth table for
each equation.

Any errors

Yes

?
found

‘No
Execute in local mode with
varying input.

Yes

Any errors

found?

‘No
Begin OM Debugging.

Figure 8-1

Local Mode Debugging Procedure

PROGRAM MANIPULATION AND MODIFICATION COMMANDS

The following set of SIM-14 commands enables the user to read paper tape programs, make changes fo 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).

If program changes of large magnitude are needed at a later date, the user

will 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 followed 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.

Press the CONT switch on the PDP-8 computer console.
R )

The leader section of

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.

RH Command

The RH command is used to read paper tapes with the high-speed reader, if the PDP-8 computer used for simulation is equipped with this device. The binary paper tape (output from SIM-14, BOOL-14, or PAL-14) is first

placed in the reader unit; the user then types RH followed by a carriage return. SIM-14 will read the paper tape
record into memory, and type the period at the left margin fo 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 )
.RH)

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

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 until the
whole tape is read. (For a full 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). The
user must either reorganize his program to fit 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 command. This error message indicates that the tape was incorrectly read and should be
reread. If the same tape generates this error consistently, the paper tape is bad and should be repunched from
BOOL-14 or PAL-14.

Open Location Commands

Open a 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). The user may then alter the content
of that location by typing a legal PDP-14 instruction next to the content typed by SIM-14, and ferminating the
line with a carriage return. If he does not wish to change the content of the location, he simply types a carriage
return after the instruction typed by SIM-14.

LT0:NOP TXN 7 )

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. Lines so terminated will cause the next sequential location to be automatically opened for modification. If a line which was opened symbolically is closed with a line feed, the next location will

also be opened symbolically. This feature may be used to scan a series of PDP=-14 instructions by continually
typing line feed.

J0:TXN_007
1T,

0011:NOP TXNI0 )

The user opened location 10 but did not modify the content .
Termination by a line feed caused the next sequential loca-

tion to be opened for modification. The user terminated

this second line with a carriage return and SIM-14 responded by typing a period to request a new command.

The following example shows the way in which a PDP-14 program could be completely typed.

Each line is ter-

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 :NOP

TXN2

PB61:NOP JFN65
QP62 :NOP TXN3

The user typed a carriage return after modifying location 60;

SIM-14 responded with a period. Since the user really

wanted to enter a group of instructions, he typed a line feed

P63 :NOP TYF10

and the next location (61) was opened. The user continued

PB65:NOP SYNLO

line feed.

0064:NOP JFN67
P66 :NOP

SKP

P@6T:NOP

SYF10

to type program instructions, terminating each line with a

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 |

The user opens three sequential locations numerically by

0067,/0100 )

modifications were performed although the user does have

0066/4224 |
.

following each but the last line with a line feed.

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 beet
made at any time.

8-9

The user opened location 63 symbolically, after it

6N /2492

N166 /4224

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

AA67T/73177

return.

NA617/75465
NA62/2493
D163/1%310

:TYF

D064:JFN

070

065t SYN

210

010

/3410

A3TA/3%19

A71/74224

LS Command

Once a program is loaded into memory, the LS command is used to list the program symbolically.
is listed with instruction mnemonics for all locations within the specified limits.
instructions (viz., JMS, JMP and TRM) are typed numerically.

The second part of two word

Any location within the limits which contains

a number other than those given in Table 8-1 is also typed numerically.
listing by following the LS with two numbers.

The program

The user specifies the limits of the

For illustration purposes, the listing is shown in two columns.

L5211 =239

Mg
s TAN

411

42091
¢ JFFE

2007

A2A2
¢ TXN

271

from 200 to 230 inclusive.

A20338TXN

2702

altered the content of M and W, all locations

JFF

2047

within these limits are typed.

A5t SYN

@My

n204:

SKP

The user requests SIM=14 to list the locations
If the user has not

The user lists the complete set of instructions

37T SYR

441

by not altering the initial values of M and W

M219

JFF

215

(namely M=0000 and W=NOP).

211

¢ NO¥

212

NOP

121 3:NOP

2142 NO?
421 5:JIMS
121621000
217 JFF

227

A227
2 JMS
221317312

P2
s JFE

20T

bee3iTYN

N224: JFF

227

P225:SYN

005

V226 :SKP
N227:5YF

@05

230

234

JFF

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.

The user controls the locations listed by

changing the contents of two special registers, 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.

The user wishes to list:

He changes M to:

He changes W to:

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

7777

JMP

or 4224

all JMS instructions

7777

JMS

or 4645

all JMR instructions

7777

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

7777

the instruction

all locations within limits

0000

NOP

a particular operand

0377

the operand

or 0000

The user alters the locations M and 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/@ 7000 )

The user changes the mask to 7000.

<W:NOP SYF 2

The user changes the word to SYF.

The following examples list different instructions within the same limits by changing the M and W locations.
M/ AAAD

JWiNOP SYF

LS2M =067

A:235¢SYN

@141

A207+SYF

7091

A225:SYN

995

A227:SYF

0725

A244:s SYN

2462 SYF

206

A264: SYN

707

A266:SYF

The user changes M and W to list all set output
instructions within the limits of the command.

M/ZTQB0

«W:SYF

T409

200

SYN

The user changes M and W so that only the SYN
instructions are listed.

L.8200-267

P2A5:SYN

201

B225:SYN

@05

B244:5YN

046

N264: SYN

A@7

MZT40D

TTTT

«W:SYN

2003

JMP

L.S200-267

The user changes M and W to list only the JMP
instructions within the limits of the command.

N267: JMP

M/ZTTTT

WiJM?

JFF264

JAS20M-267

The user changes the content of M and W to have
SIM-14 type all the JFF 264 instructions within

the limits.

There are no such instructions, how-

ever, and SIM=14 types the period to request a
new command.

The user changes the content of W to list the

M/ZTTTT

WeJFF

264

JFN264

LS200-267

N256
¢ JFN

264

JFN 264 instructions and SIM-14 types the

single such instruction within the specified
limits .

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.

+LN2AG-235

The user requests SIM-14 to list the locations

G204 /241 1

from 200 f? 235, irjclusive . All locations will

9201 /5207

be typed (in numeric form) if the user has not

A202 /2 4%

altered the content of M and W.

D2B3/24%2

each instruction within the limits will be taken

B204/527%7

2275/3471

n206/3344

N2A 7733151

#210/5215

2211 /23900

P212/0000
221370000

021473000
A215/74645

P216/1000
a217/75227

Otherwise,

from memory, masked with the content of M and

then compared with W, The original content of

all matches are then typed numerically on the
Tel

All loca-

efype.

B22h /4645
B221/71012
A222/5227
n223/71 491
M224/5227

A225/73495

M226/0344

N2277/3975
M2372/5234

M231 /39047
B232/8007%

#233/70000

B234/4645
A235719%9

M/ADAA T
<WiNOP JMS
LN2AG-235

The user requests SIM-14 to type numerically all
JMS instructions within the limits.

M215/74645

A2200 /4645
N234/4645

M/TTTT
We
5
.y&igi

The user requests SIM=14 to type all SKP instructions
GKE
ifP

i ally.
numeric

276/ 344

226/ 344

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 CONT switch of the PDP-8 computer console.

After the tape is punched, turn the punch unit OFF and remove the punched tape.
Press the PDP-8 CONT switch.

.P0-200 J
-

The user requests SIM-14 to punch a paper tape record
of the program instructions in locations 0 through 200,

inclusive. When the tape has been punched (by following 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 )
-

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. It may be shut off after the tape is
punched.

The tape will be punched by the P or PH command in 1K segments. The leader for the first 1K segment (addresses
0000 to 1777) will have a single row of punched holes on the right edge of the paper tape; the second 1K (20003777) will have two punched rows; the third 1K (4000-5777) will have three punched rows; and the leader for
the fourth 1K (6000-7777) will have four punched rows.

VERIFICATION OF A PAPER TAPE PROGRAM RECORD

Once the user has punched a paper tape 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.

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.

When the tape stops reading, switch the low-speed reader to FREE, and remove

the paper tape.

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 1K segment in the paper tape to be verified.

The tape verify commands compare the tape being read with the simulated memory within SIM=14.

If the content

of the tape does not represent the content of memory , 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 in 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 ROM generated, the user must verify the tape to be
certain that a punching error did not occur.

It is 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 prog
program with dangerous
results.
g

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).

The commands for verifying an equation are:

Verify the equation for output 20.

VY20

SIM-14 will now await user speci-.

fication of the variables used in the equation.

User specifies that inputs 5 through 7 are in the equation, and that

XNS-7

their state is ON.

User specifies that inputs 10 through 13 are in the equation, and that

XF 10-13

their state is OFF.

User specifies that outputs 5 and 6 are in the equation, and that their

YN 5-6

state is ON.

User specifies that output 11 is in the equation and that its state is

YF 11

OFF.

User instructs SIM=14 to begin execution of the program at location
200. This should be the starting address for the equation to be verified.

$200

All of the assignment commands above (XN, XF, YN, or YF) can be typed in either the multiple variable form
(e.g., XN 5-7) or the single variable form (e.g., YF 11).
The messages that may be typed by SIM-14 are:
Y020

Output 20 is turned ON by the user-supplied variables.

Y020

Output 20 is turned OFF by the user-supplied variables.

X005

Input 5 was encountered by SIM-14 when solving the equation, but it
was not listed by the user.

Y011

Y100

1023 ?

Output 11 was listed by the user but it was not encountered by SIM-14
when solving the equation.

A set output command for Y100 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. If this number is exceeded, SIM-14 types the
message TOV (table overflow). 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. After one verification, the user may change the states of variables with the XN, XF,
YN or YF commands. 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. Those variables which are not re-entered after the CV command
is typed, retain their previous state.

If an E emror (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 necessi-

tates 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).

«LS35%-364
M350 :TXF

@11

P351:TXF

A32

N352:JFF

355

N353:TXN

293

A354: JFN

362

D355:TXN

004

A356:TXN

035

M357:JFN

362

N369:SYN

2011

P361 :SKP

A362:SYN

292

M363: IMP
2364:0 430

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
X1 is ON and
X2 is ON and

X4 is OFF and

X3 is ON and
X4 is OFF and

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.
+VY1

The user begins the verification by typing

’;((F’YZ"3

the initial input and the starting address.

+«XNS

«S350

YOon2

3362

.362:SYN

OP2

SYNI

VY1
-XN1-3

SIM-14 encountered a SYN2 instruction at location
362 when verifying output 1. The user changes the
instruction to a SYNT1, and restarts verification.

- XF
4
SXNS

.S359

YOn1

Xa11

TXF1

9411

«35sTXF
«VY1
« XN1

«XN2-3
XF
4

«XNbD

« 5350
Yaal

«CV

given input. The user continues verification,
changing the value of X4 to ON. The user finds
that Y1 remains ON when it should be OFF. He
decides that there must be an extra SYNT instruc-

« XN
4
«S357

YAiA1

TTTT

MZAKGAG
<WeNOP

SYNI

tion in the program and changes the mask (M) and
word (W) to type all such instructions. The SYNI
instruction at location 362 should be an SYF1.

LS35M-365
M136M1¢SYN

141

M362:5YN
«362:SYN

N1
A1

SIM-14 reports that with the supplied input, Y1
is now ON; however, X1 was listed by the user
and not encountered in the program. XI11 was
encountered in the program, but was not listed
by the user. The user thus discovers that the
TXF11 instruction at location 350 should be a
TXF1. He then restarts verification. (He does
not continue the verification because variable 11
was entered in the input table by SIM-14 when
it was previously encountered. To delete any
variables, the verification must be restarted.)
SIM-14 reports that the output is ON with the

SYF1

The user then restarts verification.

(Assigning

input 4 ON and then OFF is the same as assign-

ing it OFF since only the last value is used by

«VY
1
«AN3-D

SIM-14.)

«XF
4

« S350

The user did not list inputs 1 or 2 and the output
is OFF with the supplied input. The program
still contains at least one bug since the output
should have been ON when inputs 3 and 5 are

YAl
XaAa1

X0z

ON and 4 is OFF.

M2 7777

TMA

«W:SYN

4111

NOP

LL.S35M-362

M350
¢ TXF

(371

M351¢sTXF

M02

The user decides that he should have a listing of
his program with its changes at this point. Since
he has changed the values of M and W, he must
now return them to the original values of 0000
(or NOP). The listing continues below.

M352:JFF

355

M353:TXN

2173

4354:JFN

362

136D

N355:TXN

1361
¢ SKP

A356: TXN

357t JFN

362

SYN

TM31

M362:SYF

«354:JFN

362

JFF362

VY1

After scanning the program, the user sees the bug
which caused the output to be set OFF instead

<XF1-2

of ON during the last verify case.

«XN3

He changes

the JFN to a JFF at location 354, since the out-

«XF
4

« XNS

puts should be OFF only if the flop is OFF (not

« S350

ON). He then restarts the verification and finds
that the output remains OFF. Confused at this

Yna1

.CV

point, he tries to solve the equation with the

«XN1-2

original set of input, and discovers that again

«XF3

the output is OFF.

XF
4
« XNS
« 5357

YON1

«356:TXN
VY1

«XN1-2
«XF3

«XNS

-CV
«XN3
« 5351

.CV
«XF
4

+ 5350

-CV
«XN4

« 5350

-CV
«XF
4
«XNS

« 5359

-CV
«XF5

-« 5350

YOA1

TXF5 and not TXNS5, since the JFN instruction

«XF1-2

Y31

Examining the program again, the user notices

that the instruction in location 356 should be

to it.

« 5359

YOl

TXFS

jumps to the set output OFF. With this final bug
removed, the program solves all input supplied

4
XF

Yot

MRS

The user continues to supply varying input to
test the program until he is satisfied that all
bugs are removed.

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 ON or OFF) may be debugged as a regular
PDP-14 output verification.

(This type of subroutine is 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.

The

subroutine (Z function) is specified by its starting address. Thus, to verify the subroutine starting at location
1000, the user types VZ1000.

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:

In BOOL-14, for example, an R-function would be written as:

Y15=X12 +Y23 */X13

To verify this function in SIM-14, simply verify output Y15 (i.e., VY15).
In 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-function 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 subroutine is listed with the LS command below.

1A =-1717
ST

1733
¢ TXF

A4
4

¢ TXF
1271

992

2
¢ JFN
199

721

¢ TXN
1933

1004: TYN

AM1

175+ JFF

1706 TXF

319

: TXN
1337

417

¢ JMR
1717

The user begins verification specifying states for the

<VZ 1900

«XN4-5

inputs fo the equation (X4, X12, X5 and Y1).
is used as a dummy variable and is not listed.

<YF
1

«XN12

X10

« 51970

71000

X312

XA732

X312

1AL
2 TXFE
NZ 1977
e XN4-H5

1012

TXF12

SIM=-14 computes the state of Z1000 and notes that
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
variable used to set the test flop.

SYF
1

«XN12

«S1A77

71973

XA1m

«VZ190¢
«XN4
«XF5S
«YN1
«XN12

Continued verifications indicate that the subroutine
is now fully debugged. The encountered X10 error
continues to be typed, but is ignored since it does
not indicate an error in the program.

«S1097

21997
X313

1
E

«NVZ 17307
XF4=-5
«XN12
«YN1

«S1MAMA

Z13a0

X210

NVZ123AD

«XN4=-5

«YN1
«XF12

«S1A07
21900

X010

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 an Equation which Contains Subroutines

The user program which contains subroutines (Z-functions) as elements of an equation may be verified in two
ways. The user may arbitrarily assign the result of the subroutine ON or OFF, or he may enter the states of
all the variables which determine the state of the subroutine. In the first case, the subroutine is not solved by
SIM-14; it is arbitrarily considered ON (or OFF) to determine the verification result. 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 ON
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 ON
for equation verification purposes.)

ZF1500

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.)

The following debugging example corrects the PDP-14 program to solve the equation:
Y6 =7Z1012 + (/Y1 *Z1000)
where the subroutines are defined as:

Z1000 = 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

L5S254-270

1002:JFN

M254: JMS

13733: TXN

ANRS

N255:1012

103
4: TYN

2031

N256:JFN

264

M257:TYN

291

N26N:JFF

266

210

1205:JFF

219

: TXF
126

219

1207:TXN

219

: JMR
1310

M261:JMS

LS1012-1021

N262: 17900
M263:JFF

266

1712:TXN

M2648SYN

297

1913:JFF

721

1714:TXN

293

1015:TXN

204

N265: SKP

N266:SYF

N267: IJMP

1316:JFF

M21

A277
¢ AQAA

101 7:TXF

9?10
710

SLS1AGA=-1710)

1720
: TXN

1097
: TXF

1721
: JMR

1971
¢ TXF

212

VY6

At the first stage of debugging, the user assigns

«ZN1M12

arbitrary values to the subroutines.

«ZF 17100

ZN1012 tells SIM=14 that the equation being veri-

«YNI

fied includes a subroutine beginning at location

« 5254

YAAT

The command

4264

648 SYN

1012 which should be considered ON when deter-

2
37

SYNA

SIM-14 responds by

saying that output 7 was discovered at location

M265: SKP
N266¢SYF

mining the state of output 6.

007

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

«ZN17 12

the verification.

«ZF 17137

Yé is ON when Z1012 is ON

by verification.

«YF1

YA
6

-CV

The user continues verification and finds that

ZF10012
+ZN17277

« 5254

YAR
6

«257:TYN
VY6

2031

TYF1

the output is OFF when Z1000 is ON, and Y1
is OFF (it should be ON). Examination of the
program shows that output 1 is tested for ON
when it should be tested for OFF. The program
is changed and the user restarts verification.

«ZN12%07)

SZF 112
<YF1

5254

8-23

Yoo
6

The output is now ON as it should be.
Continued verification indicates that all

<YN1

bugs have been removed.

«S254

YON6

.CV
oYF1

<ZF 10717

«5254

YAN6

«ZN17212
M?

-CV
«ZN172 12
5254

YA
6

The user forgot to type the CV command before
he supplied input to the verification. Since
SIM-14 does not recognize the ZN command
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. The user could
arbitrarily assign Z1000 ON, representing X4 ON, X12 ON, X5 OFF, and Y1 ON. The user could now verify
Y6 by assigning Y1 OFF and Z1012 OFF. Using these assignments SIM=14 concludes that Y6 is ON. Notice

that this result is misleading. The state assigned is an impossible state, since Y1 is required to be ON and OFF
at the same time. Thus, if Z1012 is OFF, the only way Y6 may be ON is to have X4 ON, X12 ON, X5 ON
and Y1 OFF.

VY6

After removing program bugs by arbitrarily assign-

< 21907

ig?g

ing states to subroutines, the user begins to debug

the program by allowing SIM=14 to solve the sub-

X0 S
YO0 1
X310

routine with user supplied input. The user types
Z followed by the address of the subroutine. SIM-14
types all variables needed to solve the subroutine,

X715

re-enter them with an XN command if he wants

<Z1912

X003

and enters them in the OFF state.

(The user may

them to be considered ON.) Only those variables

:)Y(::j;_q

which have not been listed previously for the veri-

.3254

in the verification.

.XN15

YAA6

-CV
<XF15

fication, are listed when the user enters a subroutine

The user begins verification and SIM-14 replies that
the output is ON when computed with the supplied

8-24

.CV

The user continues verification with varying

YF1

input until he is convinced that the program

e ANA-S

zg]m
Y"7)C"i6

is working properly. Verification of the out-

put continues below.

CV
«YNI1

4
e SPH
6
YN

)

«CV
«YF
1
«XF
5

JXN3

«S5254
E
YO

.$954

-CV

YO36
1
.cV

5254

Rvnes

< XN

1Ine 1

.5254

-CV

YAas

«XF 4

«XN15

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.

OFF or ON state, respectively, of an input or output.

SIM-14 will record the resultant

SIM-14 types an array of Os and 1s to indicate the

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; i.e., both ON
and OFF output results.

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 cases.

X5-11

Inputs 5 through 11 are variables of the equation whose truth table is to
be generated.

Y6-7

Outputs 6 and 7 are variables of the equation whose truth table is to be
generated.

$230

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.)

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 subroutines is described in the next section.
The program for which the following truth tables are generated is:
LSE6A-/A13

s TXN
4640

359

M6M1:TXFE

723

M6A2
e TXN

B17

1603 :JFF

210

N6AL4s TXN

M32

A6A5:TYN

774

66 TYR

T61
7T JFN

212

619 :SYN

773

9611 :5KP

N612:SYF

173

I613: JFF

2217

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.

The

Thus, the user may arrange his truth table

in the form most meaningful to him by typing the variables in a specific order.

If the user begins the generation of a truth table and later wants to prematurely terminate the table being generated, he may do so by setting switch 5 of the PDP-8 console switch register ON.
prematurely terminate any typing being done by SIM-14.
then type a period, and await a new command.

This switch may be used to

The user must set it ON and then OFF.

SIM-14 will

If the user types C (continue), the remaining part of the inter-

rupted truth table will be typed.

The user requests that all values of the truth table
for output 73 be typed. He then supplies the

TATA
X5
X233
«X17
-X32

variables of the equation. The truth table will
be typed in the order that the variables are

of the equation to be solved, SIM=14 types out

:Z;fl

supplied. The first column of the truth table
will be the values of the first supplied variable.
When the user has specified the starting address

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

s R

XA 51

XN23

X177

X232
YA
4

Y57

ABCDEF

719191
=1

171911
=9

=0
AN

219119=1

171179
=2

AGAAA]
=]

117111
=1

171101
=2

ARG
A =0

N11907=0

131119=m

39011
=0

311971=1

171111=9

AAA 1A% =07

411910
=0

112307
=7

MAA101
=9

M11011=05

119091=1

GOR
1 174 =0)

M11197=0

112210
=0
11011=9

“MAA111=7

111101=0

Ny Aa0
=0

“d111179=09

112109
=9

Ari1me]
=1

M11111="

113191=9

=0}
1A%

113119=9

1911
=9

199071
=1

119111=9

=10

7 =0
1A%

1117300
=0

31171
=9

130131
1 =0

111991
=1

91119=4

1794102
=0

1117914=0

1111
=0

19131
=0

111311
=4

1M
=1

1990411600
=5)

111179
=73

i} 1 30 1 = ‘[

197111
=0

111171=0

19=1

=0
171000

111117=9

111
=1

191971
=1

111111=7

1791919=0

The long truth 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 opposite state.

The TF truth table on the right below is not complete, but is broken in the middle for

illustration purposes.

«TNT73

<TF723

-Yz,’g

YHT

Y57

«X17

« X233

2 X023

e X517

e X0

X302

« X057

e 56N

X382
o S50

Yty

Y17

4
YR

X917

Y?57

X493

X317

X456

XA23

X930

[

X950

X132

8-27

ABCDEF

=0
NARAAA

MPN1073=1

=0
AN
=0
1A
NAA

MAg101=1
109nn=1

I10M10=1

NAnG11="

AR 19=0

11N =1

=
0111
=0
AN 1A
=1
171

717191 =1
11 19=1
111703 =1

711919=1

1
10141="

711109=1

11110 =1

=1
103100
1001031
=1

Ho1en=1

110171 =1

)

111011=0

1111730
=0

111101=9

111110=02

111111=9

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

output directly. However, the following commands may be used in SIM=-14 fo generate truth tables for equations
which contain subroutines.

Z 1400

The subroutine (Z-function) which starts at location 1400 is a
variable of the truth table. (All variables in the subroutine
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 (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 + (/Y1 *Z1000)
where
Z1000 = X4 *X12* (X5 +VY1)

Z1012 = X15* (X3 + X4)
«TNn

VAN
U171
2
Y1

<5254

The user generates a truth table in which the two
subroutines are considered unit variables. The
values of the subroutines are arbitrarily varied
without actually solving the subroutines for
specific variables.

Z 103707

Z1g12

Y71

ABC
117 =1

M11=1
1901 =1

1101=1
111=1

+TN6

2114737
XA%
4

XN12
X305

Y3731

The user generates a truth table for the equation
which considers the varying states of the variables
which are represented by the subroutine.

The
truth table is generated for the ON cases only.
The table has been cut in half and the lower

X719

part has been moved to the right of the upper

1M1
2

part.

X315
XA
3

The complete table appears as one
column when typed by the teletype.

SQwW
P

e 5254

1713 119=1

X717
4

14114111
=1

XA12

191101
=1

X275

1711911=1

YA
1

1911119=1

X210

1911111=1

X215

1191919
=1

X723

11997411
=1

ABCDEFG

1199111=1

AANAG11=1

117109179
=1

11973119=1

9007111
=1

1191011
=1

NAA1A11
=1

1121119=1

7731111
=1

1171111=1

31071 1=1

11109073
=1

019111
=1

11173901
=1

2011011=1

11190 19=1

2711111=1

11190911=1

2100311=1

11191929
=1

2107111
=1

1119101
=1

271710911
=1
7171111
=1

8-29

=1
1112110

=1
112711

1119111=1

M119111=1

1111010=1

m111711=1

11111711=1

A111111=1

1111119=1

10=1

1111111=1

=1
19079711
=1
177731179

17973111=1
=1
11319319
=1
1101911
1971119=1
1mp1111=1

=1
1710310
=1
113711

SIMULATED PROGRAM EXECUTION IN LOCAL MODE

Once the user has debugged his program with the equation verification feature and has generated a truth table
for each equation solved by the program, he should use the simulated execution feature to test out the program
in total . The user supplies input values and starts the execution of the program. SIM-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 fime.

XN1-5

Assign inputs 1 through 5 ON for program execution.

XF6-12

Assign inputs 6 through 12 OFF for program execution.

YNI1-4

Assign outputs 1 through 4 ON for program execution.

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.

IX5-11
1Y1-20
S400

Interrogate the state of simulated inputs 5 through 11 (i.e., are these
inputs ON or OFF).

Interrogate the state of simulated outputs 1 through 20 (i.e., are these

outputs 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. The same commands (XN, XF, YN, and YF) are used to
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 has typed a VY, CV, or VZ command, the equation verification table is affected by the command. If the user has not typed one of the verify commands, the simulated execution table is affected. Thus, the same variable may have two different values at the same time in local mode
(e.g., it 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. By specifying
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, 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. The
use of each switch is summarized below.

Switch

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,

Enable Address Stop - Switch é 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 ON
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.

Automatic Return to PDP-14 Program - When switch 8 is ON and
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

Function

Switch

Return to SIM=14 - Control returns to SIM-14 after executing the

current instruction, if switch 9 is ON. Returns are affected by
switches 7 and 8 as above. Thus, if switches 8 and ? are ON,

{ke PDP-14 program will be executed one instruction at a time,
while reporting informaiion 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 11 (used in on-line mode only) will be described later in this chapter. It is suggested that the user affix

labels to the PDP-8 console (above the switches) when using SIM-14. These labels should contain the informa-

tion given in Figure 8-2 (the use of each switch and the modes in which they are recognized). A useful card
incorporating similar information is attached at the back of this manual .

€

R
[o
b

o+l

]

Ll <

o
-~
17

o) O
+

telcBles|o

Cglaoln
0
o
]l o=}
o

-l

uS|<
98]l

R}
o

o> |o

Ne;

— E|
215
T

-l
N

EO
¢]
8|
8|
21 2|
=)
3
3
3
S|
.

<
Ul

O ¢ |~

—

5”’

o] O

—

Ne;

“
0
2& |l L
aZ|o.2].0
-1
=1 =

o
o}

5
s
Sol2s|2cgls

|23

5|55

%228z

sle

dlE0OlS0
9

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 to specify an address at which he wants to have the simulated program execution
stopped. The stop ic honored only when switch 6 is ON. If the address stop is encountered and switch 6 is ON,

the instruction in thai location will not be executed, and control will return to SIM-14 which will type the
location from which it returned. After typing the address, SIM=-14 types a period and awaits further instructions

from the user. If the user types C (continue), the instructions beginning with the address stop instruction will be
executed, until the address stop is again encountered. The user may change the input and continue execution

after each address stop. 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.)

Y1230

(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:

TXD 023

meaning TXD 23 encountered and X23 is OFF

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 interrupt-

ed.

Ifswitch 7 is ON, SIM-14 also types the instruction contained in that location, and the current state of

the TEST Flag (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:

1234

(Program execution was interrupted at location 1234)

The message typed when switch 7 is ON is:

1234 TXN 027

0013 SYN 142 0

(Program execution was interrupted at location 1234 which
contains the instruction TXN 27. The TEST flag was ON (1)
when the interruption occurred.)

(Program execution was interrupted at location 13 which
contains the instruction SYN 142,
when the interruption occurred.)

The TEST flag was OFF (0)

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 is crucial when one is examining the state of the TEST flag.

If execution is stopped

by switch 6 and an address stop, the TEST flag value typed is for before instruction execution.

If the execution

is 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 is returned to SIM=-14 after the execution of the next instruction. The

address typed (or 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: to

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 an interruption by switch 9, usually). When
switch 8 is ON and a return to SIM=14 occurs, the address causing the return is typed, and control is returned
immediately to the PDP-14 program. (It is equivalent to the user typing C aofter each return. It does not permit
the user to change any input values.)

The following is a list of commonly used switch combinations .
Function

Switch

Switches 6 and 7 ON cause the program to be stopped at the
address stop location. The instruction and TEST flag value
is typed in addition to the address that caused the return. Any
changes in output states are also typed. This allows the user
to change variables for each complete pass through the program.

6,7

Switches 8 and 9 ON cause the program to be executed one
instruction at a time. The address of the last executed instruction is typed, as well as any changes in output states. This

8,9

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
OFF position.

Only switch 9 ON, causes the program o execute one instruc-

tion 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.

Switches 7, 8 and 9 ON cause the program to be executed one
instruction at a time. 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

7,8,9

8 to the OFF position.

«IX1-3

GIE

na2

A13

i1 4

f?]l’?jb'

&Iy

n1n

071

703

)

The user checks the current state of inputs and

outputs with the IX and 1Y commands. SIM-14
types the number of the input or output followed
by its state (1 for ON and 0 for OFF).

8-34

~ASO

The user assigns an address stop at location 0 and

«AF1-3

supplies values for the variables used in the program.

YFA-376
.S

He then d:recfs execution to start at location
setting switch 6 ON,

e XN4=117

naan

tion

0, a

SIM-14 immediately stops at location O since this is

;(;@ -

the address stop. The user requests execution to

Y105

continue.

Yean

YON3

pAAd
Ak a-10

SIM-14 again stops at location O after typing the
changes in state of four outputs. The user changes

'?{\‘ -3

Y1aa

Yiatr

Yia5

Y106

Y53

some input values and continues execution.

GEAER
Yiie

YAana

Again the execution stops at location 0.

’?f'”

changes the value of an input, and sets switch 7

vipn

Yol

YAH3

0aA7n TXN 081
SXN 1

K2 =5

(;;'m
A1

Y109

When execution is stopped at location 0, the
instruction and TEST flag value are typed.

user changes some input values.

Thus, each location encountered is listed.

The

He sets switches

6 and 7 OFF, and sets switches 8 and 9 ON.
Changes in output states are also typed.

AMMA3
(as

pac

AB10
nA12
n213

Y105

The user

ON (switch 6 is still ON).

nane

Y171

after

8-35

0214 SYN 105 @

The user sets switch 7 ON to have SIM-14

P15

as well as the address.

Y106

0SYF

Yooo 1

106

NP16

SYN

200

YA53

0a17

type the instructions and TEST flag values
.

The user sets switch 7 OFF while execution

?ggg

continues

150 1

1572

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 program contains outputs which are timers, SIM-14 can simulate the timer action in the following
manner. 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,
SIM=14 simulates a time delay for the output. The delay may not be varied by the user; each assigned timer is
not turned ON until its SYN instruction is encountered seven times. The following are the commands which
declare and clear simulated timer assignments.

DT20-23

Define outputs 20-23 as timers. SIM-14 will freat any output so
as fo 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, he may debug his program
while actually controlling the machine by sampling frue inputs and setting true outputs. Before doing so, however, the installation of the PDP-14 system must be completed. The PDP-8 fo PDP-14 interface must also be
installed. Only after these steps have been taken and the PDP-14 is running, can the user actually enter online mode. If the user types 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
O-boxes. SIM-14 serves the function in on-line mode which will be served by the ROM once the program is

fully debugged. On-line mode, however, allows the user to execute the PDP-14 program one section at a time,
8-36

by placing in the program, stops which return control to SIM=14. A program stop is only executed when en-

abled by the user. 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. The stop
equation serves as a shut down routine for the equipment before control is terminated. The on-line mode procedure 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 modification and manipulation commands previously introduced in on-line mode. However, the user is cautioned
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

IX1-15

Function

Interrogate the current state (ON or OFF) of actual machine
inputs 1 through 15.

IY12-57

Interrogate the current state (ON or OFF) of the actual
machine outputs 12 through 57.

55234

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 af 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.

$200

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 IY commands interrogate the state of the actual machine inputs and outputs, respectively. Since

these same commands interrogate the state of simulated inputs and outputs when used in local mode, the user must
consider the currert mode whenever these commands are used.

The SS (set stop; command is used to place stop points at any SYN or SYF instruction. The user can type all
currently specified stop locations with the TS command. He may remove a single program stop with the RS command, 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 .

Switch

Function

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 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, causing
its execution only when switch 10 is ON at the time a program 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, If a change will occur, the instruction
is not executed; control is 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, SIM-14 will type the error message

PS ? (program stop ?). 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. If switch 11
is ON, the program stop is enabled. However, execution will not be stopped unless a change in the state of the
output will occur. SIM-14 will only stop execution if the output is now ON and will be set OFF, or if the output is OFF and will be set ON. The stop is not executed if no change will occur, regardless of switch 11.

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.

The stop equation must return the machine to a stable state so that no opera-

tions continue after control is 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.
must be terminated with a location containing 0010.
the stop equation and return control to SIM-14.

The only requirement for a stop equation is that it

This number will cause SIM-14 to terminate execution of

(This number is executed as a NOP if it is encountered other

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.

The stop equation is executed only when an enabled program stop

is encountered, which would cause a change of state in the output, and when switch 10 is on.
CAUTION

Switch 10 must never be set ON when the user has not
If switch 10 and 11 are ON
and no stop equation is specified, SIM-14 will assume
specified a stop equation.

location O as the start of the stop equation when a program 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 IY commands to determine what

operation should be executed next.

b.
Seta program stop at the SYN or SYF which will start that operation.
stops may also be set.
c.

Enable the program stop with switch 11,

Specify a stop equation, if necessary.

Enable the stop equation with switch 10.

8-39

Other program

f. Start program execution with the S (start) command, specifying the initial address.

or SYF which would cause a change of
g. When the program stop is encountered, the SYNSIM-14
,
state will not be executed. Control will return to

on.
h. Specify a new program stop at the SYN or SYF which will start the next operati

i. If a stop equation is necessary, make certain that the stop equation is appropriate and

enabled.

Type C (continue).

on as
k. Proceed to check each operation by changing the program stop and stop equati
necessary .

switch 11 OFF, thus disabling
|. Once each part of the program has been checked, turn
to terminate
all program stops. The program may then be run in total . If the user wishes
10, if necessary).
switch
by
execution, he turns switch 11 ON (with the stop equation enabled
a change
cause
will
which
ered
encount
The program is terminated on the next program stop
of state in an output.

on-line mode, but he should
m. If any bugs are detected, the user may change the program ngin the
program on-line.

return to local mode for further debugging before again executi
the user sends the
n. Once the program has been successfully executed in on-line mode,
to DEC.
woven)
be
binary program tape generated by SIM-14 (from which the ROM will
until the ROM is received.
o. The fully tested program may be used to operate the equipment
The PANEL lock feature of the PDP-8/L or PDP-8/1 may be used to prevent accidentally
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
in SIM=14 on-line mode. If this happens, the user
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 error messages for local mode and on-line mode
of SIM-14. Specific numbers for inputs, outputs, and program numbers have been used to describe the commands
and error messages. It should be noted that any PDP-14 location address, input number or output number may be
substituted in place of those used for illustration.
NOTES

SIM-14 commands which reference more than one address,
input, or output (uch 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 11.

the corrections

'
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 correct-

(shut-down sequence).

ing the program as it was input to
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.

Yes

Any errors found ?

[~
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 CONT 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 CONT switch after the tape is read.
All commands must be terminated by a carriage return
before they will be executed.

Commands Common to Local and On-Line Modes
General Commands
LM

Enter local mode.

Enter on-line mode.

Ignore the previously typed command (up to the last carriage
return) .
A%

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

Open location 23 symbolically and allow the user to modify its
contents.

Open location 57 numerically and allow the user to modify its
contents.

Close the currently open location and enter any legal modifications typed by the user.

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.

LS0-30

List the contents of locations 0 through 30 symbolically (i.e., by
typing the instructions in mnemonic form).

LNO-10

PO-700

List the contents of locations O through 10 numerically (i.e., by
typing the instructions in their numeric (octal form).
Punch a paper tape record of the contents of locations 0 through
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

Local Mode Commands

Command

MB2

Function

The PDP-14 memory has two memory banks of 1K words. (MB must be
1 if a 4K PDP-8 is used to simulate operation. MB may equal 1, 2,
3, or 4if an 8K PDP-8 is used.)
Equation Verification Feature

VY5

Verify output 5, using the input which follows.

VZ 1400

Verify subroutine (Z function) starting at location 1400,

XN4-12

Inputs 4 through 12 are ON for the equation being verified.

XF15-17

Inputs 15 through 17 are OFF for the equation being verified.

YNI1-3

Outputs 1 through 3 are ON for the equation being verified.

YF7-11

Outputs 7 through 11 are OFF for the equation being verified.

21400

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 ON by one of the above XN, or YN instructions.)

ZN1450

A subroutine (Z-function) which begins at location 1450 is part of

the equation being verified and is considered ON.

(The actual sub-

routine is not solved; the result of the subroutine is arbitrarily con-

sidered ON for equation verification purposes.)

ZF1500

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 PDP-14 execution at location 50.

(Used with the verify

feature to specify the start of the equation to be verified.)

Continue verification of same output with new input.

Variables
may be added and states of variables may be changed with the

XN, XF, YN or YF commands above.

not be deleted.

However, variables may

The S command initiates the verification as above.

Truth Table Feature
TAS

Generate the truth table for output 5 and print all cases; i.e.,

both ON and OFF output results.
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 cases.

X5-11

Inputs 5 through 11 are variables of the equation whose truth table

is to be generated.
Y6-7

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
(as in the Z1400 command above). The value of the Z-function is arbitrarily considered ON or OFF without actually solving the subroutine.

$230

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.

XN1-5

Assign inputs 1 through 5 ON for program execution.

XF6-12

Assign inputs 6 through 12 OFF for program execution.

YN1-4

Assign outputs 1 through 4 ON for program execution.

(Use of this

YF5-15

Assign outputs 5 through 15 OFF for program execution.

(Use of

Clear all inputs; i.e., set all inputs OFF.

cYy

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

command should be avoided.)

this command should be avoided.)

output will not "turn on" until the SYN instruction is encountered
for the seventh time.
CT

IX5-11

Clear all previously assigned timer outputs.

Interrogate the state of simulated inputs 5 through 11 (i.e., are

these inputs ON or OFF).

IY1-20

Interrogate the state of simulated outputs 1 through 20 (i.e., are

5400

Begin program execution at location 400. The change of state of
any output will be announced by SIM-14 by typing the output and

these outputs ON or OFF).

its new state O or 1).

Continue PDP-14 program execution from the point at which it was
interrupted (by either switch register 5, 6, or 9).

On-Line Mode Commands

Function

Command

IX1-15
1Y12-57

Interrogate the current state (ON or OFF) of actual machine
inputs 1 through 15.

Interrogate the current state (ON or OFF) of the actual machine

outputs 12 through 57.

Set a program stop at location 234. This location must contain a
SYN or SYF instruction; otherwise, the program stop will not be set.

55234

The stop is endbled by switch 11.

SE1567

Specify a stop equation at location 1567. The equation beginning

Type all stop locations presently specified.

RS234

Remove the stop presently set at location 234.

Clear all stops presently set.

with location 1567 and ending with the number 0010 will be solved
(when enabled by switch 10) before any return to SIM-14 control .

Start on-line execution at location 200. (A program stop must be set

$200

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 inferrupted.

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
is turned OFF, thereby allowing the user to type further commands

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
is ON. (Only one address stop may be in effect at one time.)
Report Address, Contents, and Test Flop - When switch 7 is ON
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.

Automatic Return to PDP-14 Program - When switch 8 is ON and 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.

Function

Switch

Return to SIM-14 - Return to SIM-14 after executing the current
instruction if switch 9 is ON. Returns are affected by switches
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
Switch

Function

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 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,
causing its execution only when switch 10 is ON when a program
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. If a change will occur, the instruction
is not executed; control is returned to SIM=14 which types out
the location and the instruction which caused the return. If
switch 11 is OFF, or if no change in the state of the output will
result, the execution of the PDP-14 program will continue uninterrupted.

Error Messages

The following is a list summarizing all possible error messages typed by SIM-14 and their causes.

Cause

Error Message

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:

One or two letters with no following numbers (e.g., C).

One or two letters followed by a number (e.g., S1234).

One or two letters followed by two numbers separated by a
minus sign (e.g., XN1-23). The first number must be less than
the second number .

When a command is not typed in its specified format the S ? error
results. Commands of form 3 may be typed in form 2 without error
(e.g., XN5 is the same as XN5-5).

8-46

Cause

Error Message

Number error - The user has included an illegal number in his program.

The following conditions produce the code N ?:

A non-octal digit used in a program (i.e., 8 or 9).

2. A test or set instruction references an illegal input or output
number (i.e., greater than 377).

The address of a JFF or JFN is illegal (i.e., greater than 377).

A JMP or JMS instruction references a location which is not

.
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

present mode of SIM-14. SIM-14 has four such modes: local mode,
on-line mode, truth table mode, and equation verify mode.
C?

Command error - The user has typed a command that SIM-14 does not
recognize.

X123 L or
Y123 L

X123 E or
Y123 E
?
Y123

(OPER 12347

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.

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.

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 program which it does not recognize.

RDER?
PS?

TOV

Read error - A checksum error has occurred on a tape read by SIM-14
with the R, RH, V or VH command. The tape should be reread.
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.

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

NR?

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.)

Not running - The user has attempted fo 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 aoffect 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 o PDP-8.

When used in a monitored or computer interfaced form of operation, the PDP-14 has three facilities for the
transfer of information:

a. 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.

c.
The Memory Port - may be used to directly supply instructions to the PDP-14 without passing through
the Input Register. Instructions are loaded from the external computer. The PDP-14 executes the instruction and sets a flag when execution is complete.

Three general approaches may be used to monitor an operation through the PDP-14.
a. The PDP-14 could contain instructions which output information to the monitoring computer through
the output register, such as TXD, TYD, or TRM. 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
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.

c.
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.

92-1

The memory port may be used to supply instructions to the PDP-14 on a cycle-stealing basis, in which one
externally supplied instruction is executed. The memory port may also be used to allow the PDP-8 to completely
take over the PDP-14's operation, by supplying all instructions to be executed.

A two-location PDP-14 instruction may not be executed using technique (b) preceding. External mode must
be entered before a two-location instruction may be executed on an interrupt basis.
PDP-14 INTERNAL REGISTERS

The monitor instructions involve the PDP-14 internal registers listed in Table 9-1. The following register locks
are used in the PDP-14 instructions to refer to the respective registers. The module type for each register is
also noted below.
Table 9-1

PDP-14 Internal Registers

Module

Octal Code

Description

PC1

M747

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 PC1 can cause program loops which are improper 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 PC1 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. Information 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.

Table 9-1 (Cont)
PDP-14 Internal Registers

Module Type

Octal Code

Description

M746

SPARE

M747

Spare Register - used for monitoring and diagnostic functions.
If the Spare Register is an incrementing type, transfers which
use it as destination may increment or decrement during the
transfer. (Not part of basic PDP-14.)

DUMMY

None

Dummy - used to transfer all 1's to any register.

Instruction Register - used to hold and decode PDP-14 instruc-

tions. Instructions which are brought into the Memory Buffer
from PDP-14 memory, or which are supplied externalily, are
transferred into the IR to be decoded and executed.

Dummy is

not an actual register but when addressed as the source of a
transfer it will act as a register which contains all 1's.

PDP-14 EXTENDED INSTRUCTIONS

The following are the PDP-14 instructions which may be used for diagnostic or monitor 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.
Instruction

EEM
(0600 octal)

Purpose

Enter External Mode. The EEM instruction causes the PDP-14 to receive
all instructions from the monitoring computer. The Program Counter 1,
Memory Buffer, and Instruction Register will be affected during the ex-

ternal mode operation.

Therefore, the monitoring computer must set
Program Counter 1 before returning the PDP-14 to normal operation with

the next instruction.

LEM

Leave External Mode.

(0400 octal)

PDP-14 which will then execute the instructions in its memory begin-

The LEM instruction will return control to the

ning with the instruction specified by PC1.

EES
(0645 octal)

Enter External Mode and Store PC1. The EES instruction causes the
PDP-14 to enter external mode and store the current value of PC1 (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
operation, the value of PC1 is restored by the following instruction.

LER
(0454 octal)

Leave External Mode and Restore PC1. The LER instruction causes
the PDP-14 to continue normal program execution at the location
specified by the value of PC2. This value, which could be stored

Purpose

Instruction

in PC2 by an EES instruction of by a register transfer instruction, is

LER (Cont)

transferred to PC1 before the PDP-14 returns to its normal execution.
NOTE

If the 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
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.
Instruction

Purpose

(4226 NNNN octal)

transfers the contents of the second word to the Output Register of
the PDP-14 where it may be read by a monitoring PDP-8 family computer. The 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.

TRM

TRS

(4225 NNNN octal)

Transfer Memory to Output. TRM is a two-location instruction which

Transfer to Storage (PC2). 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 ofter executions 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

(63R4 octal)
SKER

(67R4 octal)

Skip on Register Zero. The next PDP-14 location will be skipped if the
register specified by R has contents zero. The value of R is the code
value for the previously introduced PDP-14 registers (0 through 6 octal).
Skip on Register Equal. The contents of the register specified by octal
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 instruction.

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
Register of the PDP-14 according to the format below.

Information

Bit Position

Present state of the TEST Flag (0 = OFF, 1 = ON)
Result of the test - 0 if the output or input is OFF, 1 if the
output or input is ON.

Presently unspecified (always a 0).
Type of instruction - 0 if a TXD instruction was executed,
1 if a TYD instruction was executed.

Octal number of the input or output tested by the instruction.

4-11

Test flag

11 J
J

Input or output tested

0 = TXD (an input was tested)
1= TYD (an output was tested)

State of input
or output

Always 0

tested

Instruction

Purpose

(7000 + NNN octal)

Test Input and Display. The input specified by the value of NNN is
tested and the information previously described is transferred to the

TXD

PDP-14 Qutput Register, where it may be read by a monitoring PDP-8
family computer. The TEST flag is not affected by this instruction.
TYD

(7400 + NNN octal)

Test Output and Display. The output specified by the value of NNN
is tested and the information described above is 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.

These instructions are recognized and simulated in local mode of SIM=14.

They are also executed in on-line

mode.

NOTE

If 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.

Register transfer instructions may be used to transfer information from one PDP-14 register to another. Transfers
which use the PC1 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 according to the following format.
0

Not all possible transfer instructions are meaningful.
2

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.

Bits

Operation

00 or 10

Transfer the information contained in the source register to the
destination register.

Transfer the information in the source register, decremented by
1, to the destination register. The destination register must be
an incrementing type register, such as PC1 or Spare (M747).

Transfer the information in the source register, incremented by
1, into the destination register. The destination register must
be an incrementing type register, such as PC1 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 = 08

000 = Og

001 = ]8

J—

0]O=28

O]0=28

Spare

OH=38

omn =38

PC1

]OO=48

100 =48

PC2

101 = 58

Input

110 = 68

Output

-——

110 = 68

9-6

NOTES

a. A transfer register instruction which has a destination code
(Dummy) produces a PDP-14 instruction NOP (provided bit
3=0).
b.
The PC1 register may be cleared by incrementing Dummy
while transferring it into the PC1 register. Therefore, the
instruction to clear PC1 is 0304 octal. The same is true for
Clearing Spare is accomplished by the

the Spare register.

instruction 0303 octal.

The destination register code 111 (78) is used to produce the HLT instruction.

which has this destination code will halt the PDP-14 program execution.

Any register transfer instruction

The simplest form of HLT is described

below.

HLT
(0007 octal)

PDP-8

Halt the processor. The HLT instruction may be used to stop the
processor until the start or continue switch of the PDP-14 is activated. This instruction should only be used for diagnostic purposes
and should not be part of a user's control program.

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
SEF
(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 when-

ever the PDP-14 executes an internally stored EEM or EES instruction. The EXTERNAL flag is on the PDP-8 program interrupt (PI)
request bus.

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
if the EXTERNAL flag is set.
SOF

Skip on OUTPUT REGISTER Flag - The OUTPUT REGISTER flag is set

(6171 octal)

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

Purpose

Instruction

SOF (Cont)

flag is set.

The instruction following the SOF will be skipped only if

the OUTPUT flag is set.
STF

(6173 octal)

SCR

(6175 octal)

Skip on TEST Flag Set - This instruction will cause a program skip of
the following PDP-8 instruction if the PDP-14 TEST flag is set. Thus
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.
Skip on Controller Run - This instruction will cause a program skip of
the following PDP-8 instruction if the PDP-14 is running. When the
PDP-14 is not running, it is not possible to enter external mode, or
to start the PDP-14.

Input and Qutput 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)

ROR

(6176 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.
Read Output Register - This instruction clears the PDP-14 OUTPUT
flag, causes the accumulator of the monitoring PDP-8 family computer 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. When the
flag is ON, the Output Register may be read. 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
Register before the PDP-14 internally transfers a new word to it or
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

PurEose

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 PC1. It 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
GNI
SEF
JMP . -1

/CLEAR THE ACCUMULATOR.
/GET THE INSTRUCTION INTO THE AC.
/GENERATE THE INTERRUPT.
/WAIT FOR THE INSTRUCTION TO
/BE EXECUTED BEFORE PROCEEDING.

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
external mode. The result is described immediately after
the LDE instruction which follows.
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 instruction can be loaded and executed every time the EXTERNAL flag
is set. However, the instruction need not be held, as in GNI. Thus,
the suggested PDP-8 instruction sequence is:

SEF
JMP . -1
TAD INSTRUCTION
LDE

/FLAG 1S SET AFTER A GNI
/INITIATED ACTION IS COMPLETED.
/GET THE INSTRUCTION INTO THE AC.
/LOAD AND EXECUTE IT IN THE PDP-14.

Instruction

Purpose

LDE (Cont)

CLA
.

/CLEAR THE AC AND PROCEED WITH
/THE PDP-8 PROCESSING. ANOTHER
/PDP-14 INSTRUCTION MAY BE LOADED
/AND EXECUTED AS SOON AS THE FLAG
/15 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, PC1, and IR, unless so specified in the instruction.
(When two-part instructions such as JMP, JMS, or TRM are loaded and ex~
ecuted 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 honoring 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 one-

location instructions (e.g., TXD, TYD and register transfers).

The difference is that the LDE instruction will

increment PC1 and keep track of instructions; the GNI will not increment PC1 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 ROM memory which will be a zero word if
the ROM is not present.

If a 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 G NI instruction is used to load the TRM is very useful.
amine a part of or the whole ROM memory.

It allows the monitor to ex-

PC1 will be incremented once each time a word is read from the

PDP-14 memory, enabling a search or dump of contiguous memory.

For example:

CLA
TAD EEM

GNI

Put the PDP-14 into external mode.

SEF

JMP .-1

TAD
DCA
TAD

NUMBER
COUNT
START

LIR
TAD

K264

GNI

CLA

Set up a counter, and supply the starting
address transferring it to the PC1. (K264
contains 0264, transfer input to PC1.)

/
9-10

DUMP,

SEF

)

JMP .-1

?AL’S

GNI

CLA
SOF

Load the PDP-14 with a TRM and wait for

the output register to be loaded.

(The TRM

need not be held in the AC since the PDP-14
is in external mode.)

JMP . -1
ROR

)

Process the information:

compare it; list it; store it; etc.

fls;\fp

SSAL,{:IT }

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 independently 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
This instruction

independently of the ROR instruction using CLF.

also clears the PDP-8 accumulator.
It 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

The most common need in monitoring is to know when an event occurs. That is, for example, when is a solenoid
energized; when is a motor started; when is a limit switch tripped? BOOL-14 provides for this type of PDP-14
monitoring.

The commands and operation of BOOL-14 were described in Chapter 6. The specific instructions added are described below.

In general, BOOL-14 terminates non-monitored equations by the following instruction sequence:

To set ON
To set OFF

Le-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.

A JFF or JFN instruction jumps to

Thus, the terminal instructions are en-

tered at one of two points: either to turn the output OFF or to turn the output ON.
When an output is monitored, this terminating sequence of instructions is altered.

added to check for the occurrence of transitions.

TYN or TYF instructions are

TYD or TRM instructions are added to report the fransition by

loading the output register and setting the OUTPUT flag.

It 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 termminal sequence is a JMR.

The terminating instructions for monitoring are entered in the same way as the terminal sequence of a nonmonitored equation.

Namely, a JFF or JFN instruction has always been executed, clearing the TEST flag.

Whenever the TEST flag is known to be OFF, a JFF instruction may be used as an unconditional jump.

This un-

conditional JFF instruction is often used in the terminating sequence for monitoring.
Monitoring for OFF (.MF) - The terminating sequence for .MF or .MF NNNN (where NNNN is an octal num-

ber of 4 digits or less) is:
To set ON
To set OFF

Le-TYN

OUTPUT

SYF

OUTPUT

JFF

Test the present state of the output for ON, then
turn the output OFF.
)

TYD or OUTPUT

TRM

NNNN
SKP

& SYN
|

OUTPUT

If the output had been OFF, the test will be false

and the remaining instructions are bypassed.

the output is ON, the TYD or TRM is executed to
report the transition. The SKP is then executed

to bypass the 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
To set OFF

Lo SYF

OUTPUT

Set the output OFF and since the TEST flag must be OFF,

JFF

TYF

OUTPUT

SYN

OUTPUT

use a JFF to bypass remaining instructions.
Test present state of output for OFF
then turn the output ON.

JFF

TYD

OUTPUT
or

TRM
NNNN

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 fo report the transition.

Monitoring All Transitions (-MFN) - The terminating sequence for .MFN or .MFN NNNN, MMMM (where
MMMM and NNNN are octal numbers of 4 digits or less) is:
To set ON
To set OFF

leTYN

OUTPUT

SYF

OUTPUT

JFF

TYD

OUTPUT
or

NNNN
e

If the output had been OFF, the test will be false and
the remaining instructions are bypassed. If the output was ON, the TYD or TRM instruction is executed
to report the transition. The JFF is then executed to

TRM
NEXT

JFF

Test the present state of the output for ON,
then turn the output OFF.

»TYF

OUTPUT

SYN

OUTPUT

JFF

TYD

OUTPUT
or

TRM
MMMM

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:

NEXT2,
NEXT3,

TXN

INPUTI

JFF
TXD

INPUTI

TXN

JFF
TXD

NEXT2
INPUT2

NEXT3

INPUT2

9-13

If an input contact closes, the monitor will receive the 12-bit word sent by the TXD instruction through the
output register. Notice that no control is performed in the above example, the PDP-14 simply serves a watchman function.

Decision Making

When two or more PDP-14's are monitored by the PDP-8 to form a network for material handling, each PDP-14
must interact with others. This means that the PDP-14 does not have enough information to make all necessary
decisions; it does not know what other PDP-14's are doing.

A simple approach is to have the PDP-14 request help from the monitor. Each PDP-14 is assigned two device
codes which differ from those assigned to other PDP-14"s. This allows the monitor to "address" each PDP-14.
For example, if a 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 sending 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. Meanwhile, the PDP-14
continues its other processing duties leaving the crate unmoved. 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

In 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. When a suitable operation for testing begins, the PDP-14 reports to the PDP-8 monitor. 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-8/1 or 8/L.

The operation of the PDP-8 hardware system (computer console and ASR33 Telefype) is described in the PDP-8/1
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. For PDP-14 programming purposes, the
user should be familiar with the START, STOP, CONT (Continue), LOAD ADD (load address), DEP (deposit)
and EXAM (examine) switches. The descriptions in this chapter will direct the user to operate each of these
switches at the proper time.

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.

(The

SING INST is not present on the PDP-8/L console.) These switches should always remain off. (In the PDP-8/1,
the top of these two switches should be in the OUT position, with the bottom IN. In the 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. There are eight such pattems,
numbered O through 7.

The chart is essentially the octal-binary equivalents for the digits O through 7, and

their switch representations.

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

DISPLAY

PDP-8/L

DOWN

OFF

LIGHTS

’l .

| I
o]

DOWN

upP

OFF

)

upP

DOWN

@00

14- 00014

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 1= 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

PDP-8/L

Figure 10-2

As previously stated, the switch register is a group of 12 switches in the form of four 3-switch groups. Using

Figure 10-1, we may use four numbers (with a range 0 through 7) to completely define all switch register settings.

For example (Figure 10-3):
Set switch register to 1634:

1634

Figure 10-3 (Part 1)

10-3

Set switch register to 2200:

2200
PDP-8/1

PDP-8/L

Set switch register to 200:

200
PDP-8/1

PDP-8/L

k /Kjb }‘

L
14-0033

Figure 10-3 (Part 2)

PDP-8 LOADER PROGRAM

Before any PDP-8 based program can be loaded into the PDP-8 memory, a loader program must be stored which

will read the binary format paper tape on which these programs are stored. The loader program is then used fo
bring 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 dis-

tinction 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 0 while the Loader is being stored in the PDP-8
memory. If a 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

Operation 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 all loaded, the user should check to see that the program was loaded correctly by
examining the stored instructions. The lights of the Memory Buffer console display will light to indicate the
stored instruction when the EXAM switch is pressed. The lights will have patterns corresponding to the numbers
given below, if the instructions have been correctly loaded.
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

If the 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-08LHA1-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 containing the loader will then be read. Once the tape has been read, thus placing
the loader program in meniory, any system program (e.g., SIM-14, BOOL-14, etc.) may be loaded.
If o PDP-8/L is used for programming, the MEM PROT switch of the PDP-8/L console should be put in the UP
position, once the loader is in memory. This prevents unwanted destruction of the loader program. This switch
is not present on other family-of-8 computers.

Loading a Binary Tape into the PDP-8

To load a system software paper tape info 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 7777, press the LOAD ADD and START switches
of the PDP-8 computer console . If the preceding directions have been followed correctly, the tape will now be
read into memory. When the tape reaches the end, it will stop. If 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 with o high-speed paper tape reader, a similar procedure is followed. The paper
tape is pesitionad in the ~eader with the leader tape over the reading sersors. The PDP-8 switch register is set to

7777 and the LOAD ADt . iich & depresscd. The first left-hand switch is then set OFF (SR = 3777), and the
START switch is depressed.

i.ic binary tape will then be read.

BEGINNlNG‘

’V.\T

[]
[4

OF TAPE

BLANK TAPE

[]

[

[]

END OF TAPE|

[]

LEADER TAPE

14-C025

Figure 10-4

10-6

PDP-8 EDITOR

PDP-14 users of BOOL-14 and PAL-14 must prepare a paper tape record of their program.
referred to as a program source tape or source language tape.

This paper tape is

BOOL-14 and PAL-14 translate the source tape

into the machine language or binary tape used by the 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 programs in the BOOL-14 and PAL-14 source language.

The

Editor allows the PDP-14 user to type the program on the Teletype keyboard and correct typing errors as they
occur.

Sections of the program may be moved or removed by typing single Editor commands.

Program source

tapes are generated by Editor which are, in tum, 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, in this case there is no permanent record of the altered
program.

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.
carriage 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, it 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.

The Editor makes this distinction by dividing its operation

In the command mode, all characters typed on the Teletype keyboard will be interpreted

10-7

as commands fo the Editor to perform some operation on the content of the text buffer, or to allow the user to
operate upon the text. In the text mode, all characters typed on the keyboard are entered into the text buffer.
Typed text may replace, be inserted into, or be added atf the end of the current content of the text buffer.
The current mode of the Editor must always be kept in mind. If 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 info the text buffer. Likewise,
if text is typed 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 characters typed are entered in the text buffer. When the user has finished typing his program and wishes to leave the
text mode, he simply holds the CTRL key of the Teletype keyboard depressed while he strikes the 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).

TYPE A COMMAND THEN
PRESS RETURN KEY.

‘ TEXT MODE ’

‘ COMMAND MODE )
TYPE DESIRED PROGRAM
TEXT, THEN PRESS THE |«
CTRL/FORM KEYS.

14-0024

Figure 10-5

Adding Text to the Buffer

To compose PDP-14 programs with the Editor, simply type "AJ) ". 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. This key will delete one character or space to the left each time it is struck. The RUBOUT key can only delete characters in the same line
of text. The Editor types a backslash (\) for each time the RUBOUT is struck.

10-8

Character removed by

each RUBOUT

Y50 = X23 * X17 \\\ Y17 * (X43 + Y50))
N Y

3 characters
or

3 RUBOUTS
A

| l INN\\-

START, TXN LST \\\\\\ YN SOLA )
e~

each RUBOUT

Character removed by

——

/‘

6 RUBOUTs

5 characters
and 1 space

In the foregoing examples, the user entered text mode with the A command and began typing a BOOL-14 program above or a PAL-14 program below.

He typed the wrong information, however, and changed it by repeatedly

striking the 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) )
or

START, TYN SOLA )
The backarrow (+) is also used to erase typed characters from the text buffer.
key while striking the letter O key.

It is typed by holding the SHIFT

This special character deletes the complete line of characters between the

left margin 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, and a comment was inserted in
its place.

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

The paper tape will be read from the low-speed reader into the text buffer. If the 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.
L
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. The limits are typed
preceding the "L" and are separated by a comma. For example:

1,15L J

List the content of text buffer lines 1 through 15 inclusive.

12L J

List line 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 J
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.
numbered, thereby changing the previously assigned line numbers.

The new text will be automatically

Thus, if one line is inserted before line 15

(viz., 151 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.
by the line or lines to be deleted.

The command is typed, preceded

For example,

1,15D )
removes the first 15 lines of the text buffer.

Line 16 immediately becomes line 1 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 J
16D J)
The complete buffer is deleted by using the K (kill) command.

It 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 | commands and allows the replacement of a line or
group of lines by text typed on the keyboard.

For example:

15,17C
J
deletes lines 15 through 17 and then causes Editor to enter fext 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 remain line 30; line 28 will become line 15; line 29 will become line 16;
lines 15 through 27 will 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

New text and terminate line with the RETURN key to change the entire line to the right,

AW
N

all, or any combination of, the following operations may be typed by the user:

« to delete the entire line to the left,
RETURN to delete the entire line to the right,

LINE FEED to insert a carriage return/line feed, thereby dividing the line into two lines,

RUBOUT to delete from right to left one character for each RUBOUT typed,

CTRL/FORM to search for the next occurrence of the search character.

For example, consider the following equation:

Y11=X21* X34 * Y10 * (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 X.

The CTRL/FORM keys are used to continue the search until the end of the line, thereby completely

retyping the line.

If the RETURN key were used dofter the letter was changed, the remainder of the line would

have been deleted.
¢

RUBOUT

Y11= X21 * X35 * Y10 * (X \ Y31 + X21 + X44)
CTRL/FORM

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. Thus
after a line is edited, it may be listed by typing ".L" and a carriage 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
characters. 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.

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 (15,30P) ).

10-13

kW
G

Press CONT switch located on the PDP-8 console.
Press the LSP OFF.

Type T)) .

The procedure for generating a source tape using the low-speed punch (LSP) of the Teletype is:

Quickly press the LSP ON.

Leader/trailer tape will be punched.

Press the LSP OFF.

Type the punch command: P 2, nPJ, orm,nP J, (where m and n are decimal line numbers).
Turn LSP ON.

Press F and RETURN keys.

The program text will now be punched.

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.

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:

Type T and RETURN keys.

Press the PDP-8 CONT switch.

Press the HSP ON.

Type F and RETURN keys.

Set the next-to-last switch of the switch register (SR 10) ON.

Type T and RETURN keys.

Remove the generated source tape.

Type the punch command:

P) ,

np ),

or m,nP) ,

(where m and n are decimal line numbers).

The program text will now be punched.

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
Key

Command Mode

Text Mode

RETURN

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 re-

Return to command mode and ring tele-

main in command mode

printer 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

Legal text character

in buffer; used as an argument

LINE FEED

List next line

List previous line

Used in Search (S) command to insert

CR/LF into line

Used with . or / to obtain their
value
Same as = (gives value of legitimate
argument)

CTRL/TAB

Produces a tab which on output is in-

terpreted as 8 spaces or a tab/rubout,
depending on SR option

Table 10-2
Summary of Editor Commands

Type

Command

Input

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 m through n inclusively

Change line n

m,nC

Change lines m through n inclusively

Insert before first line

Editing

Function

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 1/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, if an 8K PDP-8 is used. The LOAD ADD and START

switches are then depressed in that order. The Editor will type a carriage return and await a 'fyped command
from the user.

All further operation is controlled by commands.

The paper tape output and input are controlled by the last two switches of the switch register.

If the high-speed

reader/punch is o be used, these switches should be set ON. If the low-speed reader/punch of the Teletype is
used, these switches should remain OFF.

10-16

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 (DEC-08-NGCB-D).

BOOL-14 OPERATION

BOOL-14 reads paper tape records of programs in an equation format, or equations typed directly on the Tele-

type keyboard. It translates them into a paper tape in machine code (binary) form which contains the instructions 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. Either

the paper tape reader on the ASR-33 Teletype or the high-speed reader may be used to load the tape.

If programs requiring greater than 1K of PDP-14 memory are to be compiled by BOOL-14, an 8K PDP-8 system
is required. In this case, BOOL-14 is loaded into field 1 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 occurred, the PDP-8 switch register is set to 2200
and the instruction field switches are set to the value of the data field switches. The LOAD ADD, and START
switches are then pressed in that order. If the high-speed reader is fo 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? Is no

*LST-NYW?

What listing form is required? No listing is required (N).

binary requested (N); binary on the low-speed

In this case, only error messages will be typed. Yes, a listing
is requested (Y) which will contain any reduced forms determined by BOOL-14. Yes, a listing is requested, but without
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 paper tape reader (H)?

*EDT-NY?

Is editing requested, No (N), or Yes (Y)?

10-17

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.

If 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, aofter he has loaded the tape to be translated into the reader.
If the editing option is requested and the low-speed reader is the SRC device, BOOL-14 will halt ofter 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.

If an 8K PDP-8 is used for the assembly process, the symbol table storage capacity is expanded when PAL-14 is

loaded into field 1 (by setting the data field switches to 1 during loading).

10-18

Starting PAL-14

To start PAL-14, set the PDP-8 switch register to 200, set the instruction field switches equal to the data field,
and press the console switches LOAD ADD and START, in that order.

PAL-14 will then 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 are wanted, the responses to all questions will be L and the query sequence will be:

*BIN-L J)
*|ST-L J)

*SMB-L
»

*SRC-L J)

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 J)
is the same as typing:

*BIN-H J)
*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 J _
*LST-L J

*SMB-X J
*BIN- J

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 1 error listing to the Teletype.
If the 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 high-speed punch is used to output the assembly listing,

typing E requests that the Pass 1 error listing be punched on the
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 1 or Pass 2 error
listings typed on the Teletype, and 5) the Pass 1 error listing will be punched on the high-speed punch.
*BIN-HN )
*LST-HE
*SMB-L

*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. The second pass types the listing and

symbol table. If separate devices are designated for the listing and the binary output, the binary will also be
punched on the second pass. If the 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. If a further pass is needed, the user reloads the paper tape
in the reader and presses the PDP-8 CONT switch. 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:
a.
If 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 PAL-14 in Field 1.
b.

If an 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 tapes as output from BOOL-14 or PAL-14 and allows the user to thoroughly test the
program thus generated.

SIM-14 outputs a binary 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 O if the PDP-14 will have a 1K memory. If the PDP-14 program will require greater
than 1K of PDP-14 memory, a PDP-8 with 8K of memory is needed to simulate the PDP-14 memory. In this case,
the SIM-14 program is loaded into Field 1 of the 8K PDP-8, by setting the data field switches on the PDP-8
equal to 1 when SIM-14 is loaded.

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 ver-

sion 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 ot location 2200 as above, SIM-14 will load all PDP-14 simulated memory with the instruction NOP (0000). Thus, unwanted instructions can never be in the simulated program. All instructions must
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.

If 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.

The user should set switch 9 of the PDP-8

switch register 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

(Figure 10-6).

SET SWITCHES ON: | PDP-14 KEY FOR PDP-8 SWITCH REGISTER[ZON-LINE ONLY:’

TO START:

SM-14 RESTART
A

AN W m

AUTO

TYPE

all

LOADER

a4\

_Aals

Figure 10-6

10-22

¢ EQ
10

STOP 7
1"

CHAPTER 11
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 units 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.

They must be protected against

accepting electrical noises from the environment which might be
accepted as valid control

the obvious place to eliminate hash is at its source, this is not always feasible,
Early designs of solid-state control equipment were extremely sensifive to

tion from the hostile environment they‘ were supposed to be controlling.
in an air-conditioned and humidity-controlled engineering area, often

signals.

Although

and can be quite expensive.

hash, and required elaborate protec-

If a computer was used, it was placed
far from the controlled equipment.

many cases, such cumbersome solutions fo 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 is to 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:

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:

a. 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 NEMA 12
is an effective noise shield.

The Control Unit (CU) cover is to be in place for all normal operations, as a second level of

shielding.

|, O, A, and S boxes are to be placed nominally between the CU and the entering AC signal

An arrangement of AC and control cables, given later in the chapter, helps reduce noise transfer

cables, to reduce noise transfer.

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:

Current from the low-voltage power supply dissipated in the electronic circuits of the CU and |,

AC current dissipated in the circuits of the | and O boxes.

O, S, and
A units;

AC is dissipated in both |- and O-box circuits.
active would consume 1.5 x 32, =

Since each input of the | box is a 1.5 VA load, all 32 inputs

48 VA, or about 44 watts.

A more reasonable estimate would be that only

half the inputs would be active on the average, or a load of 22 watts.

The total dissipation of all eight

possible | 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 is 2.5 ampers per circuit, or 4 watts.

Assuming that an average of half the cut-

puts are tumed on, each O box consumes 4 watts x 8 outputs, or 32 watts.

All 16 O boxes dissipate about

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 | box

25 Watts

one O box

32 Watts
147 Watts

The maximum system dissipation for a full-size PDP-14 system is (rounded figures):
-

control system power

175 Watts

eight | boxes

175 Watts

sixteen O boxes

510 Watts
Total

860 Watts

11-2

But

This figure will increase if you have a control requirement which allows most of the outputs to be on for an

extended time.

Reduce this figure for less | or O boxes.

Cooling requirements affect installation in these ways:

The CU is mounted at the bottom of the NEMA 12 for best cooling, and clearance is provided on all

sides.

b.
Thel, O, A, and S boxes are mounted in vertical columns with unobstructed air flow at top and
bottom.
c.
The NEMA 12 is specified at a minimum size for proper convection cooling (minimum airspace and
surface area).
d.
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
.

system.

Cabling and Maintenance Clearance
A PDP-14 system installation will involve these three kinds of wiring:

Flexible wiring supplies 115 Vac to the CU

Flat ("ribbon") cables carry control signals between the CU and the various boxes.

No. 14 AWG leads carry ac signal and power circuits from terminals on the | and O boxes to and

from the controlled device.
The CU mainframe is hinged at its left side to swing open for service.

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 info the mainframe will protrude several inches to the left when the unit is fully open for
service.

Each I,

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.

Each cable plugs into a box, and bends either left or right, along the entire

row of boxes, until it 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.

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

spaces among | 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

It 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 |ift 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:

Table 11-1

PDP-14 Environmental Specifications

The entire PDP-14 system complies to J.1.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.

cause system failure.

Extensive exposure to corrosive atmospheres might

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.

No special moisture-proofing

Avibration of 1.25 g's maximum at frequencies from 0 to 100 Hz sinusoidal in

each of the three normal axes, can be tolerated.

The PDP-14 System is highly noise-immune. However, absurdly strong sources of
electrical noise should not be placed in the immediate area of the NEMA 12
enclosure.

TYPICAL INSTALLATION

The previous discussion of installation factors indicates a general mounting scheme.
shown in Figure 11-1, embodies these requirements,

The sample installation,

Other layouts are of course permissable, if they follow

the general considerations already given, and do not exceed the environmental specifications of Table 11-1.
ENCL OSURE

The entire PDP-14 system, including the CU and all I, O, A, and S boxes, is 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 basic system consists of one CU, one I, and one O box, you will require a larger enclosure for

systems with more units.
easier.

You may also wish to use a larger enclosure to make mounting and maintenance

|NP:J1T5 X::DS

442 \¢/)Ac OU'::’?J"YAL%ADS

/
7

| ]

Tfi%?qurgg:fien

c1RCUIT

TERMINAL STRiIPS, OTHER DEVICES

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(IF Ral::o'%)

A
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/NS

7 NO.14 WIRES

7.
/

%
//

7
2

¥\

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0 [-/\E
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\g

AC WIRING DUCT

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15 VAC

WIRING DUCT

w% S
INPUT B

25953277
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CONTROL UNIT

et RBDITIONAL

/Z LEADS

/
NEMA 12
/
A" ENCLOSURE

/
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Y
Figure 11-1

PDP-14 System Layout Example
11-5

CAUTION

drilling Ofierafions
Installing the PDP-14 system involvesartic
les. These
paint
and
metal
ce
produ
will
which
ts and cause
onen
comp
ronic
particles could short out elect enter the PDP14 system.
to
wed
allo
if
ge
dama
permanent
fore,
There
nty.
warra
the
in
This damage is not covered
and
area,
the
UP
N
CLEA
,
FIRST
LING
DO ALL DRIL

system. Protect all
THEN mount the parts of the PDP-14
ion.

system components from contaminat
ELECTRICAL GROUNDS

normal ac grounds system,
For proper electrical shielding, the NEMA 12 enclosure must be bonded tollytheoccurs
when the ac metal conduit

which must be low impedance to true earth ground. This grounding normag fittings are used to establish good
is installed. Ensure that insulating paint is removed or that paint-cuttin panel and the enclosure frame.
grounding to the chassis. Install a bonding strap between the rear mounting

ive ground potential, by establishing metal-toEach unit of the PDP-14 system must be kept at the same relathardw
which attaches the various units penemetal contact through the mounting panel. Ensure that the ce.areRemo
ve small spots of paint or use locktrates the panel paint to make firm contact with the metal surfa
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 11-1 (top center) are optional for each installation.
In this example, 440 Vac enters the enclosure at upper right and is controlled by a fused circuit breaker
assembly. The voltage is reduced to 115 Vac by a control transformer, and filtered to remove line transients
(hash), if necessary. This power is available at upper left to power both the CU and | and O box ac circuits.
Box ac power requirements are discussed in Chapter 3. They will depend on the number of ac circuits
activated and their load. The control transformer could be as small as 250 VA for a very small system, and

a
above 50 KVA for a very large one. 115 Vac may, of course, be provided from outside the enclosure. If

computer is to be attached to the same circuit, be sure to add its power requirements. (The PDP-8/L computer
and teletype require 500 VA.)

CONTROL UNIT MOUNTING

BASE

MAIN

FRAME

SHIELD

Figure 11-2

Control Unit Housing Components

11-7

COVER

The other devices indicated in the figure may be electromechanical frimers, counters, or if necessary, small
contactors. Large-current switching devices should always be mounted outside the enclosure.

The CU is installed in the lowest (assumed coolest) part of 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 1/4-inch dia.
mounting bolts.

The keyhole cutouts are placed over the bolts and the base frame drops in

place; thebolts 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.

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 ot 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.

The entire mainframe assembly is covered by a SHIELD COVER of sheet metal. This cover
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 siraight 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

front.

A small metal panel is screwed in place over this port when it is not used.

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:

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 | and
O boxes and to the ac power source (including two inches for a cable duct).

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.

One inch to the right, for cooling air.

These clearances may be increased to make installation and servicing even easier.

Mount the CU within

10 degrees of vertical.
CU MOUNTING SEQUENCE

All mounting holes should be drilled before installation begins.

be dismantled for installation.

The CU is shipped as one package, and must

First, 1/4-inch mounting bolts are prepared for the NEMA 12 on centers

(TOP)

HINGE

<— LOCK PIN

PINS —»|®

(2)

|
|
|
|

|
|

REAR WALL OF
NEMA 12 ENCLOSURE

MiNIMUM

SWING

TO LEFT

CLEARANCE

TOP CLEARANCE

22 .5"

je—— g8'—

(FRONT)

6-11

6'—

BOTTOM

CLEARANCE

¢"

17.7

RIGHT SIDE
CLEARANCE
———————— |

USE

WITH

1/4-20

(RIGHT SIDE)

4»

HARDWARE

LOCKWASHERS

(4 PLACES)

ALL DIMENSIONS IN INCHES

CLEARANCE

% INCLUDING COVER

SHOWN REFERENCE

NEMA MOUNTING PANEL

14-0011

Figure 11-3

Control Unit Mounting Dimensions

shown in Figure 11-3. The CU is unpacked, and the shield cover released by depressing the handle pushbuttons 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. Be sure to use locking

hardware, to prevent vibration from loosening the installation. Slip the mainframe in place on its open hinge
pins (Figure 11-4), and latch in place with its pin. Replace the shield cover. When all other mechanical
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

(277D,

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 themin the furthest left column of all I, O, A, and S box mounting,

A and S box clearance is the same as for | and O boxes.

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.

11-10

F igure 11 -4

Control Unit Mainframe Mounting

11-11

Figure C

I AND O BOX MOUNTING

I-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 to left along the

box rows.

I, O,

Each I-or O-box has one control cable, which enters the box from the top left.

A AND S BOX MOUNTING DIMENSIONS

Figure 11-5 shows all mounting dimensions for a single | or O box.

Optional boxes indicated at top and at

left show how columns and rows of boxes 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

boxes.

If 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.

All control

cables should run horizontally across the box rows to the left, and then down to the
CU.

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.

I, 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.

Lay out the NEMA

mounting panel and drill all holes for 1/4-inch mounting bolts on centers shown
in Figure 11-5.

all boxes in place, using locking hardware.

This completes the box installation.

installed in a later step.

11-12

Then bolt

Control cables will be

]

| 1
T
| I

no|

UPPER BOX

(OPTIONAL)

| i

no,

i:|

T Sy
iy
hfi}—————5u4————%-L_iL____
|
n

=== =4 1/4REF
= |

I"REF

]

LEFT
(OPTIONAL)

ToT

BOX

AT ———

3172

[
} e
. ——
i o c—

—\-.

—_———

(3 PLACES)

USE 1/4-20
LOCKING HARDWARE

ALL DIMENSIONS IN INCHES

Figure 11-5

| or O Box Mounting Dimensions

WIRING AND 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.

11-13

AC Wiring

The sample installation above shows the position of wiring ducts. Note that ac wiring duct is placed above
and below the 1-and O-box group, and single power leads are then run vertically between the box columns
to their individual terminals. More ducting may be placed between box rows if space is provided. The control

cables, in contrast, run horizontally along the box rows to the left, and then down a separate duct (shown

crosshatched) until they exit, in two bundles, to the CU. This cable dressing minimizes transfer of noise
from the ac wiring to the control cables, and should be followed as closely as possible. The ac power supply
chain at top center in the drawing has already been discussed. It supplies both the CU and the box ac circuits
with filtered 115 Vac.

To power the CU, run a flexible service cable (two No. 14 to 16 AWG leads) from the ac terminations at

top left of the CU. Remove the CU cover, and swing the mainframe out fully. Figure 11-6 shows the back
panel exposed. Loosen the two Phillips screws, which hold the protective cover, one full turn and slide the

cover off. A power connector strip with two screw terminals is now exposed. Run the cable through the

grommet in the left side of the mainframe, strip the ends, and install themon the connector strip. Leave a
small service loop in the cable. Reinstall the protective plate and close and lock the mainframe.

11-14

PROTECTIVE

MOUNTING PLATE

Figure 11-6

COVER

AC TERMINALS

Mainframe Back Panel

11-15

NOTE

An ac convenience outlet is provided on the CU 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 AWG copper with standard insulation.

Initial checkout of the | 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 programs are run. The control cables are disconnected, the AC wiring connected, and the control
cables then permanently reconnected. The wiring is installed behind the space reserved for control cables.
This means it may extend from the mounting panel forward no more than three inches as it leaves the duct.

Once the individual leads leave the duct andclear the control cables, they may be run forward to meet the
screw terminals along each box front. Each terminal accepts one or two leads stripped about 1/4-inch and
inserted under its integral clamping plate.

Figure 11-7 shows terminal connections to each | box. The entire box front is covered with a transparent
plastic cover which protects from electrical shock and forms a wiring duct. The cover is removed for wiring
by unscrewing four thumbscrews and pulling straight out. 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, it is easiest to loop all four

neutral terminals on a single box and then return only one lead to the ac supply neutral. Each of the other
eight terminals on the K578 is for an ac input circuit. 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.

The letter refers to the specific | box from a

possible eight (letters A through H), and the number to the box terminal (1 through 32).

For example, if

Figure 11-7 showed | box "D", then input D15 would be connected to the second from the lowest terminal on
the left side.

A list of the input circuits and sensors is produced in the programming operations discussed in

Chapters 4 through 10.

for each | box.

This list should be provided for wiring operations on "Input Assignment Sheets", one

Each | box should be assigned a letter according to programming instructions and should be

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

15 VAC

NEUTRAL ———f—

17 ()

19 @

20@

|62

()

| Mot | i35 R

23 ()

24@

@ 3

INPUT

CONDITIONING
MODULE

K578 ——————

onn.

D slsH

@ 6 |@H

@ 7 |OH Used
[@H
Té—

4
____

NEUTRAL

| kis1 | xiel

|G —

1 Not

Not

- Used | Used

115 VAC

" NEUTRAL

O f— Yoo
ius eans

29()

S
l__———_l
--

|e—xs578

31@
32

Figure 11-7

LAMPS

=
115 VAC

i 21 @ ——K 578

|@H

INPUT

— INDICATOR

]
O

SOCKETS

)

MODULE

N A AARRRAAIAR
L RN A RIARIAR 20|

TERMINAL STRIPS

32 AC

INPUTS PER

EACH

115 VAC

NEUTRAL

BOX

Input Box Terminal Connections

11-17

Output circuits are connected in the same general way as inputs. Figure 11-8 shows the output terminals
for one 0 box. Each output switching circuit is electrically independent from every other, so that if necessary,
it may be supplied from a separate source of 115 Vac. Ordinarily, you will supply an entire box from one
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. But in the | box, this neutral was
a common return for all circuits in the module. In this case, it is simply a common for the neon indicator
lamps. The four neutral terminals in each O box should be looped together and tied to AC neutral (this is not
shown in the drawing) .

The four switched output terminals on each K614 module alternate with the looped ac hot leads, and are
identified with a circuit number, as shown in Figure 11-7. Output circuit assignments should be provided on

"Output Assignment Sheets", one for each box. An O box should be given a letter at this time (A thru S,
excluding I, O, andQ), and marked with'a tag. Every O-box terminal can now be defined by an alphanumeric combination. For example, if Figure 11-8 showed O-box “N*, then the switched terminal on the

upper right would be circuit N9. All O boxes should now be wired with the circuits specified by the Output
Assignment Sheets. Leave the protective plastic covers off the boxes so that control cables can be installed
later. These steps complete all ac wiring for the PDP-14 control system.
, L“_‘

Figure E

Control Cable Installation

Control cables carry the CU command signals as well as low voltage power to the I, O and auxiliary boxes.
They are flat, multiconductor wire packages called "ribbon" cables. Figure 11-9 shows the connection
arrangement. Note that each cable extends from the left-hand side of the CU to one | or 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) is DEC part

11-18

ééa%fi

TERMINAL STRIPS

MODULE SOCKETS

/O
@

OUTPUT LEAD#| —
115 VAC"HOT

(LOOP TO ONE

QUTPUT PAIRS) O
SIDE OF

ALL

Hcontrol
Cabie

Conn.

:@
[K135H S

——

115 VAC "HOT"
(LOOP TO

ONE

T
|
'AC INPUT

SIDE

OF ALL OUTPUT PAIRS)

S
-

ISOLATED

-— SEE

NOTE

AC SWITCH —®

MODULE K614

Hk207 | k207

OUTPUT LEAD

s@E

MOUNTING

(3)

115 VAC

COMMON

#12

115 VAC COMMON

61-11

EXAMPLE CKT N9

OUTPUT AC NEON
/INDICATOR LAMPS

115 VAC

“HOT

EARS

BASE

)

1 k1e1 | k161 B S
115 VAC *HOT" —

@
Z

S
| k207

|K207

SEE NOTE /

@
—— 115 VAC COMMON

S
i

16 AC OUTPUTS PER BOX
500 VA EACH OR 4000 VA

NOTE. AC POWER STRAPS TO
ALTERNATE

ARE

PER BOX

TERMINALS

USER-INSTALLED

Figure 11-8

Output Box Terminal Connections

Lo e 4

OUTPUT
BOXES

INPUT
BOXES

MODULES

VAC
120
60 HZ

DGE

—

A .

/NINGED EDG

INPUT

—

! ;
]

SOCKETS

i
|
.
|

' :
{

i6 Cables Max.
OUTPUT CABLE GROUP

.
'y

16
BOX
eOUTPUTS

500 VA EACH

L
:"""" ——————————— 51

L--—J’“"_—--—“_"_‘J

o
¢

s®
e
¢

OR
PER BOX

4000 VA

R
p

]

: I

CABLES

OUTPUT CABLE

'
(

CONTROL

® A :n_

8 Cables Max.‘

® g?

INPUT

GROUP\‘
'y

l¢

l DY[®] ®¢®

CON TROL L UNIT
PDP-14

CONTROL

CABLES—»

0c-11

CONTROLLER
—~

32PERINPUTS
BOX

1.5VA EACH

~—" |20 VAC "HOT"
(O BOX NEUTRAL

CABLE

120 VAC NEUT

[

b
| U _‘f"““!

Le——— b IR

®TO

[]

Y
®

::
[]

TO0®

Figure 11-9

PDP-14 System Control Cable Arrangement

Figure 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 feet.

specified, the 10-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 CU 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).

Startingwith

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.)

(The full S box has an additional

The module is inserted in the slot by pushing

carefully but firmly straight back until the handle is in line with the other modules in the box.

Run the

ribbon cable to the left over the top of the box and into cable duct at the left side of the NEMA enclosure.

In a later step, the cable will be run down the duct and into the CU.

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".

Con-

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 onthe 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 nowbe plugged one at a time into the CU mainframe. Remove the CU shield
cover to expose the mainframe.

Figure 11-13 shows the cable slots along the left side of the unit and their

box allocations.

The I-box slots are lettered A through H, and the O box slots A through S, to correspond

with each box.

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 boxes,

*The "XX" is the length in feet.

11-22

Figure 11-11

Box Control Cable Insertion (O Box Shown)

11-23

Figure 11-12

Installing Box Protective Cover

11-24

CONTROL

SWITCHES

ON/QFF START/STOP CONTINUE
<

v 8 &

TOP

NO.

NO. 2

CONTROL

POWER SUPPLY

115 VAC

POWER SUPPLY

5 VDC,7 AMPS

CONVENIENCE

(OPTIONAL)

OUTLET

)

A C[E G
]

CONTROL
CABLE
CLAMPS

(2)

GZ-11

—

1 BOX

|@|LEABLE] spaRrE
50‘(:'8‘)51'3

&
fi
.

SOt IONS

0 BOX
CABLE
CKE

— LOCK PIN

PANEL

MEMORY UNIT SOCKETS

JiL|n|r

—
@\ T-sockeTs ]

MAINTENANCE

olo|e|w

@
\

6'
LOGIC

CONTROL

0000

| 2000

1777

| 3777 |

| 4000

5777

2 —

6000

7777

—— BASE FRAME

HINGED

MAINFRAME

BOTTOM

Figure 11-13

MTG

B|o|F|H|k|m|P|s

HOLES

CU Cable Socket Allocations

cable is inserted in the CU in the same manner as in the boxes with the side of the module to which the
cable wires are soldered to the right. 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 l-box "A" being inserted into the CU slot.

HOW
N
-

Install cables in this order:
All lI-box cables
All O-box cables

All S-box cables (in O box slots)
All A-box cables (in 0 box slots) .

Finally, the cables are formed into two flat bundles and run through the U-shaped cable clamps, as

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. Place all slack cable in
the duct, to complete the control cable installation. Figure 11-16 shows cables for I-box "A" and O-box
"A" properly installed. If a computer interface is also to be installed, leave the CU shield cover off and

proceed to the next section; if not, reinstall the cover.
CU POWER SUPPLY, COMPUTER INTERFACE, AND ROM INSTALLATION

Figure 11-17 shows the placement of equipment on the CU mainframe. It 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. Each of the two power supplies shown is rated at 5 Vdc at
7 Amperes. Number 1 power supply is shipped installed in the CU, and is sufficient to power a moderate
sized control system. 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:

11-26

Figure 11=14

CU Conirol Cable Insertion

11-27

e Clamp Use
i

3TRV4AR1PSRNReNyeRheAErE|.YESfRAeeSNEESaAeYNnyErIIsERaLYeNEtEvrTRREBNLeEEELPTrRRASRnERIS-pscLsr¥frEpogEEgtrerTvsapsgEsgrRerCEgengyErvcynaTEysgyTReELrE
£

LRAYISycertritaey

11-28

11-29

7e§

Figure 11-16

CU Control Cables Installed

CONTROL

SWITCHES

TOP

ON/QFF START/STOP CONTINUE
7

NO.

CONTROL

POWER SUPPLY

5 VDC,7 AMPS

(OPTIONAL)

OUTLET

)

0€-11

5 VDC,7 AMPS

CONVENIENCE

(2)

POWER SUPPLY

15 VAC

CONTROL
CABLE
CLAMPS

NO. 2

CONTROL

BANK | BANK | BANK | BANK

AICIEIG

1 BOX
»|@|LCABLE| spaRe
sogg)t-:'rs

\\\@
\

)

SOTIONS

L Lock PIN

MAINTENANCE
PANEL

MEMORY UNIT SOCKETS

alclelelz L InlR

)

| 'caBLE '_|| conTROL | 0990 | 2000 | 4000 | €080
0

BOX

LOGIC

SOCKETS

1777 | 3777 | st | 7777

®l

8|o|F|n|k|m|P|s

&‘

MTG
HOLES

<«—+— BASE FRAME

HINGED

MAINFRAME

BOTTOM
14 -0002

Figure 11-17

CU Mainframe Allocations

PDP-14 SYSTEM POWER CONSUMPTION

DC Amps @ 5V

Unit
14 Control Unit

2.50

Memory 1K

0.50

| Box

0.05

O Box

0.60 max, 0.50 avg

A Box

0.60

Half S Box

0.40

Full S Box

0.80

Computer Interface

0.40

Here are three examples of calculations for systems of various sizes:

Examples:

DC Amps @ 5V

Basic Machine

2.50
0.50
0.05

14 CONTROL
1K MEMORY
1-1BOX

0.60 (max)

1- OBOX

3.65 amps

Largest system with one power supply:

14 CONTROL
2K MEMORY
2 - | BOXES

2.50
1.00
0.10

1-ABOX
COMPUTER INTERFACE

0.60
0.40

2.40 (max)

4 - O BOXES

.00 amps

Largest possible system:

2.50
2.00
0.40

14 CONTROL
4K MEMORY
8 - | BOXES

8.00 (avg)

16 - O BOXES

0.40

COMPUTER INTERFACE

13.30 amps

Note that a large system should not be expected to have all outputs activated at once, and therefore will
not use full conirol current for each box. This means that an average O-box current value may be used
for calculations.

11-31

Installation of Number 2 power supply is a simple bolt-in process. First, disconnect all AC power. Swing

open the mainframe and attach the power supply in the space shown with the four bolts provided. Attach
the supply connecting leads to the screw terminals provided on the right side of Number 1 power supply.
(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 system. The CU has space

for one to four ROM banks DEC part no. MR-14, as shown in Figure 11-16.

G923

G922

SENSE

SELECTION

“

/
/

BOARD

BOARD—

WIRE CHANGE SIDE

G924

KEEPER J PLATE

BRAID (ENCAPSULATED)

BRAID BOARD

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

2000-1777

4000-5777

6000-7777

11-32

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, install the G923 assembly in the

sockets furthest to the left, as shown in Figure 11-18.

The G923 will slide into the first slot, the G922

will contact the second slot, and the third slot remains unused.
fourth slot, as shown in Figure 11-19.

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.

The CU main-

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.

The G923 double assembly

‘will require considerable pressure, so be sure not to allow an individual board end to bend under the full

- pressure of insertion.

Continue the installation for Banks 2 through 4, if they are used.

ROM installation.

Figure 11-18

Installing G922/G923 ROM Modules Assembly

11-33

This completes the

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:
1

Mi1gé

M745

M746

and these control cables:

for the PDP-81, 3 - BC@BC-15
for the PDP-8L

or PDP-12, 3 - BCF8A-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.

These cables are slightly different

This flat cable is called "flexprint".

CAUTION

Any computer or other electronic equipment connected
by control cables to the PDP-14 system must share the
same AC neutral and metallic ground potenfial. A
difference in neutrals, such as caused by use of two AC
power sources, could cause large current flows in control cables and permanently 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.

If 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 PDP-14 system, an orderly check should be made of the complete
installation.

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

Proper grounding has been maintained between all units

Output circuits are not shorted and loads will be properly distributed among K614 modules

Control cables are completely seated in their proper slots, and all other modules are firmly

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 NEMA enclosure is to be kept closed at all

1f ROM banks are available for this installation, they are correctly in place.

NEMA enclosure

in their sockets

times.

A lock is suggested

The first powered operation of the PDP-14 system should be to check out electrical operation of all its
components. This initial test is done with the PDP-8/1 or 8/L computer, using these programs:

TEST-14, which checks the CU, and I, O, and S boxes; -(l and O box AC wiring must

VER-14, which checks the ROM contents and operation; and

A BOX-14, which checks all A boxes.

be disconnected for them to be tested with this program);

The computer is connected to the system through its interface, and the test programs are run according to the
instructions provided with them. The result of this testing will be printed on the Teletype printer connected
to the computer, including faults, if any. If module changes are considered necessary, refer to Chapter 12
for further maintenance information.

INITIAL STARTUP

The CU automatically starts the PDP-14 system whenever ac power is applied. The control system then
operates constantly, waiting for commands from the control device. If power is interrupted, the control
sequence simply starts from the beginning whenever power is reapplied.

The CU control panel is 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. This switch is normally left in the ON position,
the NEMA door is closed, and power is applied to the entire control system through the circuit breaker
interlocked fo the door. The CU will then automatically start its control sequence. If the toggle switch
is turned OFF, the control operation stops and all outputs are also turned off. The smaller switches on the
right of the control panel are marked START/STOP and CONTINUE. The START/STOP switch turns the
control sequence on and off, but without turning any outputs off.

11-37

AC POWER SWITCH

START/STOP
CONTINUE

115 VAC
CONVENIENCE
OUTLET

(SEE CAUTIONS)

Figure 11-21

CU Conirol Panel

11-38

CAUTION

The STOP position of the START/STOP switch does not
stop activity of the conirolled device; it merely suspends
control at an indefinite place in the sequence.
use it as an emergency stop switch.

Do not

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

be on to activate its interface, but control operations should not be started.

Figure 11-22 shows the use of

the switches.

Then, while holding the

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.

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

This chapter explains the general maintenance concepts applied when a device controlied by a PDP-14 fails to
perform properly. Modifications to the ROM are described at the end of the chapter.

Only the general method of servicing PDP-14 contolled equipment is described herein, along with some of the

diagnostic aids available. A detailed explanation of troubleshooting for the electrical serviceman and complete
electronic circuit information for repair technicians, to service digital logic equipment, is located in the
maintenance manual.

APPROACH

Every control system is unique; when failure occurs, it can be for countless reasons. Therefore, an orderly
servicing scheme should be employed to reduce downtime. This section discusses some of the general approaches
to servicing 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
suspected of malfunction. 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
as limit switches) are especially prone to failure, since they are usually mechanical and subject to wear and
corrosion.

If the controlled device is totally free of defect, the PDP-14 control system can then be checked. This testing
is divided conveniently between the major elements of the system; the CU, the ROM, and the |- 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:
a.

The mechanical and electrical operation of the controlled device is checked completely in

order to isolate the controlled device faults from the control unit faults. The probability is high that
electrical and mechanical sensors and actuators are responsible for the failure. Testing this equipment
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.
b.

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.
C.

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

~E—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 malfunciion

When a failure of a controlled device occurs, the servicing objectives are to quickly:
qa.

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. To switch one output on or off, a

limited group of conditions is required. Certain inputs and other outputs (and possibly timers) must be on or off.

This situation can be shown in the ladder diagram Figure 12-2.

12-2

Another program list would stafe that:
Y14
X5

A
= SOL
= LSV7

Y143 = | MOT
X37 = PBll

These program lists are an extremely effective diagnostic aid, since they show the control equations affecting
every output circuit in the controlled device. The lists should always be kept convenient to the PDP-14
system for reference.

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, is 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. These lamps are extremely convenient and accurate troubleshooting aids,
since they indicate the actual AC power condition of all circuits.

Checking the CU and ROM

Diagnostic programs run on a PDP-8/1 or PDP-8/L computer provide complete testing of all circuits in the CU.
Similar programs for the ROM will verify that the memory system is working properly and that the contents of
the 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 messages is provided with
the tape. 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 |- and O-box components are last in the testing sequence because it should now be known that both the
controlled device and the CU and ROM are operating properly. By elimination, the indication is that further

malfunction must be in the | and O boxes or their cables.

Since the failure of control has been isolated

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 Approach

The general maintenance approach to PDP=14 controlled equipment implies the following steps:
a.

The controlled device is tested, and is assumed to be the cause of error unless demonstrated

otherwise.

The CU and ROM are checked, and faulty circuit operation serviced by module replacement.

Finally, the I 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 fo be redefined, it is probably easiest
to program for a completely new ROM braid and insert it into the CU. 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.

If necessary, all instructions can be

manually changed.

The ROM change operation has two general stages:

First, the new program, including changes, is determined and the program is converted to a

Wires are then hand-positioned in the ROM assembly according to the pattern determined by the

series of binary numbers.

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

PBII

O—1O0—JC

LSI7

I MOT

SOL A

Figure 12-2

Ladder Diagram Showing Output Controlled
and Inputs and Output Tested

In this example, SOL A is the output controlled, and PB11, LS17 and 1 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:
SOLA

where,

= LS17 AND 1 MOT
OR
PB11

SOL A controls motion of the table to the left;
LS17 senses that the table is in position at the right;
1 MOT is the motor circuit supplying hydraulic power to the table (through SOL A); and
PB11 is the manual operator pushbutton

The PDP-14 program lists later would show all these inputs and outputs in a symbolic relationship, for example:
Y14

X5 (AND) Y143 (OR) X 37

12-5

ation

use one memory location, and its contents are simply changed to correct the error. But if a two-loc

, room

instruction, such as a JMP, or a new one-location instruction must be added to the previous program

must be made for the added location required. In other words, a NOP or other unused instruction in a nearby
location must be deleted. Conversely, a NOP can be inserted in a program change which deletes instructions
and leaves an unused location.

Each of the four possible ROM banks in the Control unit has "1K" or 1024 locations, numbered (in octal) from

gives a
0 to 1777. The first three digits identify a ROM address wire (0 through 177), and the last digit
one
specific row of transformer cores (0 through 7). The ROM reads a specific address by selecting and pulsing
wire and selecting one transformer row. For example (see Figure 12-3):

This allows you to determine the position of an instruction physically in the ROM from its location number.
LOCATION

1346

WIRE NO.

134

and

ROW

L |77

l0
N

TRANSF ORMER

ROWS

\J !

<l |34

= 2

“\I 3
d/l 4

WIRE PIN

AREA

G922 BRAID
BOARD

SIDE

Figure 12-3

COMM

Wire Placement in ROM Transformer Rows

12-6

Each ROM wire runs through all eight transformer rows and makes available eight instructions each time it is
pulsed.

Only one transformer row is selected to be read at a time, and thus only one instruction.

In 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

WIRE NO.

ROW NO.

INSTRUCTION

TXE

]

TXF

2014

JFF

5076

TXN

154

2554

JFN

5477

SYN

JMP

J 3
062

OCTAL
INSTRUCTION CODE

TXN 7

2006
2407

3406

4224

This list 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 consecufive memory location, 063 and is therefore on the next
wire.

If this instruction were changed, two wires would be affected.

The next programming step is to convert the octal instruction code fo 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).

O NO
WL,

octal digits, one af a time.

or,

Convert the four

For example, in location 622, the instruction 5076 is:

101

000
111

110

101

000

111

110

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

WIRE NO.

ROW °
1

T\%‘f

[ d

9 7]

(0O

e
>

.§§;O

o|0O

0|0

167

163

INSTRUCTION
157

BINARY INSTRUCTION NUMBER

NUMBER

153

)

147

2014

MEMORY LOCATION

BITS

REV.

2006

143

REV.

5076

BITS

103

REV.
BITS

REV.

— T~

w
]

N
w

Figure 12-4

ROM Change Sheet - Example

VvIleo ouvos qivim

0,0

COMMON

o¥x o]

(=1

[]

oi |ifi

—_——

011

010

001

000

BINARY

CONVERSION
OCTAL

2407

8-¢l

‘0

123 @ g

bits in each alternate row.

The asterisk (*) indicates the beginning of the binary code.

For example, in

location 620, we have:

OCTAL

2006

BINARY

0lI0

000

TRANSFORMER ROW 0

Oll

000

In location 621, the binary code is simply transferred to the braid board just as read.

Ol0
*

But in location 622

(and all even-numbered locations), the order of bits is reversed, end-fo~end, as in the example.

The

"Rev Bits" remarks (Figure 12-4) remind you to make this reversal when transferring
the number to

the board

drawing.

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 fo ROM wire additions is that a binary 1 (as written on the drawing) corresponds

to a wire placed

through the center of an individual transformer core, and a binary O to a wire
around the outside of the core.

It makes no difference to which side of the core the wire runs to form a 0.

See Figure 12-5 for example.

TRANSFORMER CORES

12 PER ROW

/\
BRAID BOARD G922A
o

°
o

1/0

olo

o/o

0|0

WIRE

oooooooooomm

WIRE

ROW
0

ouT

Figure 12-5

ROM Wire Placement Example For One Transformer ROW

12-9

Preparing the ROM Braid Board

Before removing a ROM bank from the CU, prepare an area which is free from dirt, metal particles and other
contaminants. A clean, flat table should be provided, covered with soft, lint=free cloth or paper. Good
lighting and an ac receptacle for a small soldering iron will also be required.

Locate the proper ROM bank in the CU by its "M" or bank number printed on a sticker on the G922 keeper
plate.

The ROM consists of a double board assembly, G922 and G923, and a separate G924 Sense Board, as described
in Chapter 11. Remove only the G922-923 assembly from the Control Unit. The boards are separated from each
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. Remove the fifteen screws
holding the two boards together and lift the G923 straight up and off the G922. Do not bend the transformer
cores. Lay the G923 down in a protected place, with its cores facing up. Do not disturb the screws holding
the aluminum keeper plate to the G922. The surface now exposed on the table is the "G922 Braid Board,
Side 2". Place this assembly to the left of Figure 12-4, with its pins on the right side.

The example shows wire 062 installed. First, cut 5 feet of no. 36 enameled wire. Tin one end, and solder
it to its proper pin, as shown in Figure 12-6. 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, and is found by counting from the last marked pin (57)

from right to left, bottom to top. Remember to skip 8 and 9 when counting octal numbers. The pins are:

57 - 60 = 61 = 62. Bring the wire to the ST (start) position in the top right row and weave it through the
first 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, until the wire is at the END
position at bottom right. Then, clip the excess wire, fin the end, and solder it to any one of the four

COMMON pins. This completes the wire addition.

12-10

43o

Figure 12-6

Pin Location Example - Pin 62

Removing the Old Braid Wire

Locate the wire pin for the wire just replaced.
under side.
cutters.

This pin extends through the braid board to the braid on the

One braid wire is connected to the pin af 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 exireme pressure.

The board assembly can now be installed in the Control Unit to complete the ROM

modification operation.

12-11

Avoid

KEEPER
PLATE

METAL STAND
OAM BACKING
PAD
PLASTIC SLE

FERRITE CORI
RRITE CORES

SENSE WINDIN

THIS SIDE |
DOWN

FOR ROM
CHANGES

Figure 12-7

ROM Board Assembly - G922-G923

12-12

(Edge View)

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OUTPUT NUMBERS

FOR SIXTEEN OUTPUT BOXES

Box

Box Terminal Number

Box

20|

21|

22|

23 | 24|

25 | 26

40|

41 | 42|

43 | 44)

45 | 46

60|

61|

63 |

65 | 66

| 100 [ 101

62|

64|

| 102 | 103 [ 104{105 | 106

F | 120 | 121 | 122 | 123 | 124]125 | 126

140 | 141 | 142 | 143 [ 144|145 | 146

H | 160 | 161 | 162 | 163 | 164(165 | 166

J | 200 | 201 | 202 | 203 | 204|205 | 206

211

K | 220 | 221 | 222 | 223 | 224|225 | 226
L | 240 | 241 | 242 | 243 | 244|245 | 246
M|

260 | 261 | 262 | 263 | 264|265 | 266

N ] 300 | 301 | 302 | 303 | 304|305 | 306
P | 320 | 321 | 322 | 323 | 324(325 | 326

R | 340 | 341 | 342 | 343 | 344|345 | 346
S | 360 | 361 | 362 | 363 | 364|365 | 366

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 O boxes.

A-2

PDP-14

INPUT

ASSIGNMENT SHEET -P{

(A THROUGH H)

INPUT. BOX

X
X
X
X
X

]
z
2
4
>

X
X
X
X

:
’
:
’

10
y
B!

13
«
14
y
15

=
A-3

PDP-14

INPUT ASSIGNMENT SHEET

INPUT
NUMBER

-P2

(A THROUGH H)

BOX
ASSIGNMENT

COND, | NUMBER

PDP-14 OUTPUT ASSIGNMENT SHEET

(A THROUGH S

OUTPUT BOX

OUTPUT
NUMBER

EXCLUDING I,O & Q)

ASSIGNMENT

PROGRAM

NUMBER

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