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Document:	lilgliltlall RTS/8 User’s Manual
Order Number:	DEC-08-ORTMA-C-D
Revision:	0
Pages:	163
Original Filename:	DEC-08-ORTMA-C-D_RTS8_V2B_UsersMan_Feb77.pdf

OCR Text

User’s Manual

Order No, DEC-08-ORTMA-C-D

RTS/8

User’s Manual

Order No, DEC-08-ORTMA-C-D

Version 2B

digital equipment corporation - maynard, massachusetts

First Printing, June
Revised:
September

1975

February

1977

1974

The

information in this document is subject to change
without notice
should not be construed as a commitment by Digital
Equipment
Corporation.
Digital Equipment Corporation assumes no respons
ibility
for any errors that may appear in this document.
and

The

software described

and may be

used

license.

this

document

copied

only

furnished under

accordance with

the

terms

Digital Equipment Corporation assumes no responsibility
or reliability of its software on equipment that is
not

DIGITAL.

(C)

COMMENTS

The

of Digital

are

trademarks

critical

such

for the use
supplied by

form on the last page of this
evaluation to assist us in pre-

Equipment Corporation:

DIGITAL

DECsystem-10

DEC

MASSBUS

DECtape

OMNIBUS

PDP

DIBOL

DECUS

0S/8

EDUSYSTEM

PHA

UNIBUS

FLIP

CHIP

RSTS

COMPUTER LABS
COMTEX

FOCAL
INDAC

DDT

TYPESET-8

LAB-8

DECCOMM

DECsystem-20

TYPESET-10

RTS/8

license
of

1974, 1975, 1977 by Digital Equipment Corporation

The postage prepaid READER'S
document requests the user's
paring future documentation.

following

RSX

TYPESET-11

CONTENTS

Page

vii

PREFACE
CHAPTER

CHAPTER

INTRODUCTION

1-1

1.1
1.2

RTS/8 DESCRIPTION
REAL-TIME SYSTEM OPERATION

1-1
1-2

USING TASKS UNDER RTS/8

2-1

2.1
2,2

THE STRUCTURE OF RTS/8 TASKS
CONCEPTS OF TASK COMMUNICATION

2-1
2-1

2.2,2
2.3

Intertask Messages
EXECUTIVE INTERNAL TASK TABLES

2=2
2-3
2-5

RTS/8 EXECUTIVE REQUESTS

3-1

3.1

COMMUNICATION WITH THE RTS/8 EXECUTIVE

3-1

3.4
3.5

USING INTERRUPTS IN RTS/8
EXECUTIVE REQUEST WAIT STATES

3-9
3-12

2.2.1

CHAPTER

3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.3
3.3.1
3.3.2
3.3.3
3.3.4

CHAPTER

Task Synchronization Through the Use of
Event Flags

ERs USED TO COMMUNICATE BETWEEN TASKS
SEND - Send Messade
WAITE - Wait on Event Flag
SENDW - Send and Wait
RECEIVE - Receive Message
POST - Post Event Flag
Example of ERs for Message and Event Flags
ERs USED TO SET AND CLEAR TASK FLAGS
BLKARG - Block Task for Specified Reason
UNBARG - Unblock Task for Specified Reason
SUSPND - Suspend a Task's Execution
RUN - Run a Task

3-1
3=-2
3-3
3-3
3-3
3-4
3-5
3-6
3-6
3-8
3-8
3-8

RTS/8 SYSTEM TASKS

4-1

4,1
4,1.1
4,2

CLOCK HANDLER
Examples of Clock Handler Calls
TERMINAL HANDLER

4-2
4-4
4-4

Terminal Handler Properties
Useful Equates in the Parameter File
Examples of Terminal Handler Messages
LINE PRINTER HANDLER
MASS STORAGE HANDLERS
Floppy Disk Handler
LINCtape Handler
Example of Mass Storage Handler Call
POWER FAIL TASK
0S/8 SUPPORT TASK

4-7
4-9
4-9
4-10
4-11
4-13
4-16
4-18
4-18
4-19

4,2.1

4,2,2
4.2.3
4.3
4.4
4.4,1
4,4.2
4.4.3
4,5
4.6
4.6.1

Additional Assembly Parameters Affecting

Mapping of Fields with 0S/8 Support Task
iii

4-20

CONTENTS

(Cont,)

Page

4,7
4,7.1
4,7.2

4,8
4,9

0S/8

RTS/S8

Using
Other

the

4,9.2

AI
DI

4.9.5

Digital

Input

4.9.6
4,9,7

Generic

EC
RC

Code

Enable Counter
Read Counter

4.9.10

€S

DCT

4.10
4.10.1
4,10.2
4.11
4.12
4,13

4,13.1
4,13.2
4,13.3
4,13.4

(UDC/ICS)

HANDLER

4-26
4-27

4-27

4-27
4-28
4-29

4-29
4-29

of State
Disable Contacts

4-30
4-30

UDC/ICS Assembly Parameters
Error

4-31

Conditions

CASSETTE HANDLER
Handler Function
Utility Function
CASSETTE FILE SUPPORT HANDLER
PDP-8A NULL TASK
KL8-A SUPPORT
Executive KL8-A Support
TTY Task KL8-A Support
KL8~A Support for the 0S/8 Support

4,14

for

MONITOR

ROUTINE

5.1

MCR COMMAND ARGUMENTS
MCR COMMANDS
DAte [mm/dd/yyyy [,Time-of-day]]

5.2.1
5.2.2
5.2.3

5.2.4
5.2.5

5.2.6

5.2.7

5.2.8
5.2.9

5.2.,10
5.2.11

5.2.12

5.2.13

5.2.,14
5.3

TIme

a User

4-31

4-32
4-32
4-34
4-35
4~37
4-37

4-37

Task

4-38
4-39

5-1

5-1
5=-2

5-2

[Time-of-day
]

NAme Task-ID,Newname
REquest Task-ID [, (@Time-of-day

[,Intervall]
STop Task-ID
DIsable Task-ID

5=2
5-2

Interval)

5-3
5-4
5-4

ENable Task-ID
CAncel Task-ID
SYstat

4-38

4-39

CONSOLE

5-4
5=4

[Task-ID]

OPen Address

4-23
4-24

cChange

UDC/ICS

4-22

4-25

KL8~A Support
EXIT TASK

5.2

CHAPTER

4-21

DC
Disable Counter
ECT
Enable Contacts

4,9.11
4.9,13

CHAPTER

SUBSYSTEM

Analog Qutput
Analog Input
Digital Output

4,9.4

4.,9.12

4-21

FILE SUPPORT TASK
UNIVERSAL DIGITAL CONTROLLER/INDU
STRIAL
CONTROLLER

4,9,.,8
4.9.9

(0Os8COM)

05/8

4.9.1
4,9.3

COMMUNICATION

0S8COM Task
Techniques

5=-4

[,Count)

EXamine Address [,Count]
DEposit Address,Word [,Word]
POst Address

5=5
[,Word]

EXIT

5-6

....

5-6

5.4

MCR ERRORS
NONRESIDENT MCR

ASSEMBLING AND

6.1
6.1.1

PARAMETER FILE STRUCTURE
Executive Specifications

5-6
5-6

TASKS

FOR RTS/8

6-1

6-1
6-2

(Cont.)

6.6.1

6.6.3
6.6.4
6.6.5
6.6.6
6.6.7
6.6.8

B
B
T
T

7.1
7.1.1
7.1.2

OVERVIEW
Writeable Tasks
Checkpointable Tasks

7.1.3
7.2
7.2.1

Interaction Between Tasks
MEMORY PARTITIONS
FREE Command

7.3

NONRESIDENT TASK

7.3.1
7¢3.2
7.3.3
7.4
7.4.1
7.5

Parameters for Nonresident Tasks
Assembling Nonresident Tasks
Creating the SAVE Image File
PARAMETER INITIALIZATION FOR PARTITIONS
General Information
NONRESIDENT TASK IMPLEMENTATION

DEMONSTRATION PROGRAM

8.1
8.2
8.2.1
8.2.2

MODIFIED PARAMETER FILE (PARAM.PA)
NONRESIDENT TASK LISTINGS
Nonresident Task NR20
Nonresident Task NR22

8.3

ASSEMBLY AND

8.4

NONRESIDENT

ADVANCED RTS/8 PROGRAMMING TECHNIQUES

9.1

PERFORMING A RESCHEDULE
Switching

9.2.2
9.2.3

WAITX - Wait for Exactly This Event Flag
DERAIL - Derail a Task's Execution

N
I

Dangers of DERAIL
9.2.3.2
Restrictions Using DERAIL
9.3
STARTING PARTITIONS AT AN ARBITRARY BOUNDARY
9.4
DIRECT REFERENCES TO SYSTEM TABLES

9.2.3.1

EXECUTIVE REQUESTS FOR ADVANCED APPLICATIONS
WAITM - Waiting for Multiple Event Flags

BN B

Inhibiting Task

9.2
9.2.1

Writing Delicate Code

EXECUTION

9.1.2

LOAD PROCEDURE

TASK ASSIGNMENT AND

NNIJUUtd

9.1.1

= O

INITIALIZATION

oo
uTldkd WWWWH

NONRESIDENT TASKS

NN N

NN NN NN NN

EXIT Task

CHAPTER

0S/8 Support Task Parameters
KL8-=A Support Parameters
Line Printer Handler Parameters
DECtape Handler Parameters

6.6.9

CHAPTER

[[

Clock Handler Parameters
Swapper Parameters
Terminal Handler Parameters
Monitor Console Routine Parameters

6.6.2

CHAPTER

Setup

Task

CREATING AN RTS/8 SYSTEM
USING THE 0S/8 BITMAP PROGRAM
SAMPLE RTS/8 TASK PROGRAM
USE OF CONTROL FILES UNDER RTS/8
RTS/8 SYSTEM TASK PARAMETERS

O WOWWYWWWOWWOWYWWYWWYWOW

6.2
6.3
6.4
6.5
6.6

ANTAAN

6.1.5

HEWOINUTESWWN

Task Definitions
System Task Specifications
System Wide Definitions

6.1.2
6.1.3
6.1.4

")
o
Q
®

CONTENTS

(Cont.)

Page

APPENDIX A

RTS/8

DISTRIBUTED

APPENDIX

RTS/8

COMPONENT

APPENDIX

RTS/8

FLOWCHARTS

C-1

APPENDIX

RTS/8

ASSEMBLY

D-1

APPENDIX

EXECUTIVE

SOURCE

FILES

A-1

SIZES

B-1

ERROR MESSAGES

INTERNAL

TASK

TABLES

E-1

GLOSSARY

Glossary-1

INDEX

Index-1

FIGURES

FIGURE

2-1

7-1
B-1

Message Format and Linking of Messages
Nonresident Task Implementation
RTS/8 System Memory Map (Default Memory

2-4

Executive

E-5

7=2

Allocation)
E-1

Internal

Task

B~4
Table

Structure

TABLES

TABLE

1-1

RTS/8

2-1

3-3

Summary of Event Flag States
Summary of Executive Requests
Symbolic Names for Specifying WAITBITS
Summary of Wait States Incurred by Executive

4-1

Summary

9-1

Summary

B-1

RTS/8 Component
MCR Component Size

3-1
3-2

System Tasks

Requests

Terminal

Default Vvalues

B=-2

Task

Handler Assembly

Switching Flag
Sizes

1-2

2-3
3=2
3=-7
3-12

Parameter

(TSWFLG)

States

4-9
9-4

B-1
B-5

PREFACE

ime Operating System (RTS/8) .
This manual describes the PDP-8 Real-T
ge programming (PAL8) is essential
Knowledge of PDP-8 assembly langua
of this manual. In addition, the user
for a complete understanding
should be familiar with real-time

systems in general and with the
The
for the PDP-8, 0S/8.
system
t
opmen
operation and use of the devel
1is
”
iques
Techn
mming
Progra
RTS/8
ced
"Advan
9,
r
Chapte
in
information
has
user
the
after
read
be
should
It
for the experienced RTS/8 user.
gained familiarity with RTS/8.

ed and expanded to
This version of the manual has been enlarg
es include
Major
The
incorporate several new RTS/8 features. EXIT Task,featur
two new
and
the
Task,
Null
KL8-A Support, PDP-8/A
on
entati
implem
ident
the nonres
Executive Requests. Other features are facili
0S/8
the
allows
that
ty
OS8COM
an
t,
of the MCR, UDC/ICS suppor
files that allow the user
system to talk to an RTS/8 task, and controlRTS/8
flowcharts have been
.
copies
to efficiently make multiple task
added to show system operation.

The

following

PDP-8 handbooks

will

helpful

for

review

and

reference:

INTRODUCTION TO PROGRAMMING (DEC-08-XINPA-A-D)

SMALL COMPUTER HANDBOOK (90P45)
0S/8 HANDBOOK (DEC-S8-OSHBA-A-D)

UDC8

UNIVERSAL

DIGITAL

CONTROL

SUBSYSTEM

MAINTENANCE

MANUAL

(46H745)

PDP-8A MINICOMPUTER HANDBOOK (EB0621976)

1CS8 INDUSTRIAL CONTROL SUBSYSTEM MAINTENANCE MANUAL (EKOICS8MM)

vii

CHAPTER 1
INTRODUCTION

1.1

RTS/8 DESCRIPTION

of
RTS/8 is a compact real-time system designed for the PDP-8 family
to
tasks
63
to
up
allows
processors (except the PDP-8/S). This system
basis.
priority
fixed
a
on
s
resource
for
compete
and
ntly
run concurre
It can be used for a wide range of applications in which a number of
e
processes must be monitored and controlled. As with other real-tim
systems, RTS/8 responds to physical or conceptual events to permit the
timely execution and. scheduling of tasks.

The RTS/8 Executive controls execution and interaction among all
The Executive decides which tasks should run (based on the
tasks.

priorities of the runnable tasks), and services the tasks by means

(ERs).

Executive Requests

RTS/8 system tasks
A task is the basic program unit within RTS/8.
(DEC-supplied) and their file names are listed in Table 1-1. The
system supports both resident and nonresident tasks. A resident task

resides permanently in memory; a nonresident task is one in which the
major portion of the task resides on a mass storage device and is
loaded into memory only when that task becomes executable. Using
nonresident tasks permits portions of several tasks to share the
areas of memory, providing economical use of memory.

same

RTS/8 includes system tasks that control most standard DIGITAL 1I/0
devices. A full complement of peripherals is supported, including RKS8
and RK8-E moving-head disks, DF32 and RF08 fixed-head disks, TCO08
DECtape, RX8 floppy disk, LINCtape, DEC cassette, and LE8 and LS8E
The Monitor
line printers (RTS/8 does not support TD8E DECtape).
Console

Routine

(MCR) task provides an interface between the user at

the console terminal and the system. The MCR provides the user with a
series of commands to control, inspect, and, to some extent, debug the
They
system. The MCR commands are straightforward and easy to use.
intervals,
specified
at
tasks
execute
and
schedule
to
allow the user
suspend task execution, and print system status reports.

A system task also is provided that allows a single copy of the 0S/8
operating system to run in the background, creating a real-time
foreground-0S/8 background system. With 0S/8 in the background, the
user has the facilities for program assembly, debugging, and editing.
The minimum RTS/8 hardware configuration required for a foreground
only

system

PDP-8 family processor, 4K words of memory, and a

A system capable of
console terminal capable of papertape input.
running a real-time foreground and 0S/8 in the background reguires a

PDP-8 family processor with KM8-A, KM8-E or TSS-8 Time Sharing
options, a mass storage device (such as an RK8E cartridge disk or RXS8
floppy disk), and two terminals (one must be dedicated to 0S/8 system
execution).

‘

INTRODUCTION

RTS/8 tasks are created by editing the RTS/8
master parameter

produce

Task

parameter

source

files

file

are

that

then

describes

assembled

the

with

user's

the

edited

using the PAL8 assembler.
The assembler can run
the OS/8 support system under RTS/8.
Then using

all

task

binaries

are

joined

into

complete

Table
RTS/8

Task

Name

File

Name

System

RTS8.PA

null

task

0S8

PWRF . PA

CLOCK

blank.

RTS/8

Executive
Console

Support

OS/8

File

Handler

LPT

LPT.PA

DTA

RK8

Task

Driver

Task

DTA.PA

Printer

Driver

Task

TC08

RK8.PA

DECtape

Driver

RK8

Task

RKS8E.PA

Driver

RK8E Disk Driver

RF08.PA

RF08/DF32

Task

Fixed-Head

Disk

Task

CsA

CSA.PA

CSAF

CSAF.PA

UDC/ICS

UDCICS.PA

RX8A

RX01RT.PA

Cassette
Cassette

files.

Routine

Line

Disk

Task

Fail

Clock

inserted
parameter

Support

Power

Terminal

with

0S/8

CLOCK.PA

file

task

TTY.PA

RF08/DF32

file

Appropriate

specific

TTY

RKS8

Function

should

Monitor

PWRF

Task

create

Null

0S8SUP. PA

system.

values

MCR.PA

OS8SUP. PA

RTS/8

parameter

MCR.PA

OS8F

parameter

either under 0S/8, or
ABSLDR
under
0S/8,

Tasks

equates

MCR

system.

1-1

System

PARAM. PA

file

particular

Driver

File

Universal

Task

Support

Digital

Controller

Driver

Task

Controller/Industrial

Subsystem

Floppy

Disk

Handler

Task

(1lst

controller)

RX8B

RXO01RT.PA

RX8C

Floppy

RX01RT.PA

Disk

Handler

(2nd

Floppy

Disk

Handler

controller)

Floppy

(3rd

Disk

Handler

(4th

controller)
controller)

RX8D

RXO01RT.PA

LTA

LTA.PA

SWAPPER

NULLS8A

EXIT.PA

REAL-TIME

SYSTEM

Driver

Nonresident

NULLS8A.PA

EXIT

1.2

LINCtape

SWAP.PA

Null

Task

Exit

Task

for

swapper

PDP-8A

OPERATION

multiprogramming
available resources

(such

convention

since
"subroutine."

overlaps

Multiprogramming

allows

system

software

framework

that

allows

memory, CPU time, and peripheral devices)
to be share
by
d several tasks.
Basically, a
task
is
a
portion
of
machine
code that performs a specific function;
a task is defined by

simultaneously.

because

blocked
switched
system

by
to

waiting

tasks

the

task

cannot

for

completion

some
other
another task

efficiency.

many

with

use

definitions

some

available
of

"program"

state

central
I/0

condition),
the
central
to use the available
time,

execution

processor

operation

(or

time

is
can be
increasing

processor
thus

and

INTRODUCTION

run
Most real-time systems are required to serve a group of tasks that
compute
being
between
e
alternat
and
ies
frequenc
or
at varying times
bound or I/O bound. If machine resources are to be efficiently r used,
these tasks cannot be run in series since the central processo will
In
be poorly utilized during the periods the tasks are I/0O bound.
and
tical
time-cri
lly
essentia
are
tasks
e
addition, most real-tim
should not wait for a slow, less important I/O or compute bound andtaska
Thus, multiprogramming
to finish before being executed.
processor provide maximum
central
the
ng
scheduli
priority scheme for
resource utilization.

1in
Thus, a real-time system is a multiprogramming system that to must,
critical
quickly
respond
,
features
addition to the multiprogramming
to

internal or external events. The real-time system is required
suspend the operation of a less important task and start the task that

deals with the critical event.

A priority scheme establishes the relative importance of various tasks
in the system. This allows a less important task to be interrupted to
For RTS/8, a fixed
permit execution of a critical real-time task.
1is simple and
scheme
a
such
because
chosen
was
scheme
priority
reliable, and requires low scheduling overhead.

CHAPTER

USING TASKS UNDER RTS/8

2.1

THE STRUCTURE OF RTS/8 TASKS

The RTS/8 Executive is the controlling program

RTS/8

System.

The Executive decides which task should run based on the priorities of
the runnable tasks (those tasks not waiting for completion of any 1I/O
It also provides services to the tasks by means of
or other events).
Executive Requests are discussed in Chapter 3.
Reguests.
Executive
The user assigns unique task numbers to each task in an RTS/8 System.
He can assign up to 63 (77 octal) task numbers, and must account for
once
A task number,
system tasks within the total number of tasks.
assigned, cannot change during the execution of the program, since
RTS/8 uses a fixed priority system. Task numbers serve the following
purposes:

The task number is used by the RTS/8 Executive as an index to
system tables which contain information about each
various
task.

other

The task number is used by

tasks

the

system

reference a particular task when performing certain Executive

Requests

(such

sending

a message).

priority - the

lower

The Executive uses five internal tables to maintain information

about

The task number determines the

the tasks in the system.
in

2.2

task's

the task number, the higher the priority of the task.

Section

2.3.

A brief description of these tables is given

CONCEPTS OF TASK COMMUNICATION

RTS/8 is event

driven,

i.e.,

the

highest

priority

runnable

task

executes continuously until it is completed or some event or condition
in the system causes it to be suspended. Another change or condition
can reactivate the task. Tasks can be self-starting if assembled to
run at system startup, started by another task, or started by the user
at the terminal console using the MCR task. RTS/8 performs two main
types of task communication,

as follows:

Task synchronization through the use of Event Flags

Intertask

messages

USING

2.2.1

Task

Whenever

Synchronization

two

wait

until
illustrated

PDP-8,

must

ready

now

first

from

the

occur

RTS/8

Use

independently,

loop

TSF;

that

physical

conceptual

Event

one

Flags

process

may

need

character,

(TLS)

loop

with
the
to signal

alerts

the

instruction.

wishes

terminal

The

PDP-8

further

with

Event

Flags

each

other.

contains the status
processes such as a

a
An

signalling
Event

Flag

exits

mechanism

event.

user-chosen

The events are
either
ticking or a valve closing, or
certain string of characters typed

clock

occurrences

such as
scheduling

as
an

1/0

next
character
until
the
that it is finished printing

the flag is raised, the
PDP-8
then
proceeds to load the next character.

provides

operator

first

JMP.-1

When

and

tasks

the

Sequence

cannot proceed
its ready flag

RTS/8

synchronize

the

generate

character.
wait

location

Through

Teleprinter

wait

Similarly,

Load

immediately.
It
terminal
raises
the

UNDER

the
execution
of
the
other
is finished.
This can be
by using the PDP-8 terminal interface as
an example.
The

when

issuing

processes

TASKS

a
task for execution.
Like device
Flag can signify either a busy or a
completed
state,
defined as PENDING (>0) and FINISHED (=0), respect
ively.
Thus, a task
can direct another task via a message to perform
a
specified
action,
at which time it sets a mutually-agreed upon Event
Flag to the PENDING
value.
When the second task has completed
the
specified
action
it

flags,

sets

the

Event

waiting

then

from
has

Event

Flag.

for

the

Flag

simple

Event

the

Flag

with

/LOAD

EVENT

TAD

Event

SZA

CLA

/IF

JMP

.-2

/KEEP

the

Posting

its

Flag

1loop,

completed

its

FINISHED
example,

EVENT

the

value;

this

the

known

first

task

instructions:

FLAG

Posting

has

been

FINISHED,

SKIP

TRYING

of the Event Flag will
continuing on with the
processing.

cause

the
knowledge

first task
to
that the second

exit

task

Since this loop ties up the PDP-8 processor,
Event Flags
under
RTS/8
have an additional state, WAITING (<0).
Using the example just cited,
the addition of the WAITING state now allows
the first
task
to
tell
the

RTS/8

Executive

signifying

the

saves
the
Wait bit in
WAITING

the

contents

its

state.

that

status
Task
The

taken
set,

WAITING

task's Task
Executive Request
out of Event Flag
the

when

waiting

state

Number.
call,
Wait

task

higher

RTS/8

wants

second

for

When

the

the
by

task

would

look

WAIT

until

Event

The

Event

WAITING

Flag

Flag
for

(If no other
runnable, and will
blocked.) WAITE is the
an

Event

fully

Flag.

octal

Flag

monitor

PC and sets the Event
Event Flag is set
to

RTS/8.

for

the

FINISHED.

again

priority tasks are
Executive Request that Waits

This code

task

of the waiting task's
Flags Table Word.
The

waiting

RTS/8

the

4000

Flag

the
plus

POSTed

via
an
automatically
blocking bits are
is

resume execution
mnemonic for the

follows:

CAL
WAITE

event
All

flag

Executive

Event

Flag

Requests

states

are

shown

described

Table

2-1.

Chapter

summary

USING TASKS UNDER RTS/8
2-1

Table

Summary of Event Flag States

Value

Event Flag State
FINISHED

2.2.2

(posted)

PENDING

WAITING

<0 (4000 + Task No.)

Intertask Messages

to hardware device
Just as Event Flags under RTS/8 are analogous nding
hardware I/0
data-se
to
us
analogo
are
messages
flags,
a task,
start
s
message
is,
That
TLS).
,
example
(for
instructions
time,
same
the
at
and
,
message
a
providing the task 1is WAITING for
by
tted
transmi
are
s
Message
task.
the
to
tion
they pass informa
Executive Reguests.

d by
An RTS/8 message consists of a three-word Message Header followe
between
ed
exchang
be
to
tion
informa
of
any number of contiguous words
The
RTS/8.
two tasks. The Message Header is used exclusively by
.
message
the
for
Flag
Event
the
first word of the Message Header is
to
Flag
Event
the
sets
ve
Executi
RTS/8
the
sent,
When the message is
sent but
the PENDING state. This signifies that the message has beenreceipt
of
upon
Flag
Event
the
to
occurs
action
not yet completed. No
the
that
s
require
RTS/8
,
however
task;
ng
receivi
the
by
message
the
performed the action
receiver POSTs the Event Flag when it has This
posting serves two
.
message
the
by
)
implied
(or
specified
purposes:

1.
2.

It informs the task which sent

the

message

(the

that the requested action has been completed, and

"sender")

It allows the message to be sent again (see Item 2 below).

uses
If multiple messages are waiting to be received by a task,to RTS/8
these
link
Header
Message
the
of
words
third
and
second
the
is a CDF (Change
messages together (see Figure 2-1). The second wordmessage
. The third
next
the
of
field
the
to
tion
instruc
Field)
Data
0 signifies
of
word
second
A
word is the address of the next message.
actively
not
is
task
ng
receivi
the
If
.
message
last
the
is
that this
task's
g
receivin
the
on
placed
waiting for a message, the message is
ing
decreas
of
order
in
queued
then
are
Messages
Queue.
Message
Input
from
sent
s
Message
.
number)
priority of the sender (increasing task
the same task are queued in the order in which they were issued.

USING

TASKS

RTS/8 EXECUTIVE

UNDER

RTS/8

MSGTBL

MESSAGE 1

MESSAGE 2

MESSAGE 3

CDF

Event Flag

PTR

CDF

PTR

Message
Header

Message

Content

Figure

The
a

rest

message

receiving
of

the

should

into

Message

the

message

does

not

task,

first

the

2-1

but

data

word

noted

Data

the

in a
Event

The

same

Event

can contain
physically

provides
of

that

receiver's

the

Linking

any desired
move

the

receiver

information

has

the

Messages

information.

message

with

the

field

message

following

the

cannot

sent

the

first

second
time.

the

It is legal for the receiving
the
body
of
the
message.

message

can

return

task

sends

the

driver

error

returned

message

places

specific

word

occurred.

the

without

back

message

task

the

error

the

to
this

the

not

time

store

way,

disk

For

the

copied

while

before

its

enforces

this

operation

and

the

message

information
"answer" to

complications

sender.

address

sender

RTS/8

by checking the message Event Flag
on a
SEND
putting
the
sender
into
Event Flag Wait if
still PENDING.
3.

and

implications:

not be modified by
message is PENDING.

FINISHED

Sending

information

should

for

message

and

message.

This

message

Flag

the

area.

Flag

Format

example,

the

sending

when

driver task requesting
1/0,
status of the completed operation

message

indicate

whether

USING TASKS UNDER RTS/8

2.3

EXECUTIVE INTERNAL TASK TABLES

maintain information about
The Executive uses five internal tables to ption
of these tables is as
descri
brief
A
the tasks in the system.
follows:

Description

Table

Task State Table (TSTABL)

Contains

the

Task Flags Table (TFTABL)

Contains information about why the

task

information

such

contents of the task's PC, Link and AC
at the time the task stopped running.
is not running, i.e., it indicates for
what conditions (blocking or wait bits)
the task is waiting.

Task Input Message Queue
Header Table (MSGTBL)

Contains messages that have been sent
to this task. This table is referred to

Residency Table (RESTBL)

Used for nonresident tasks,

simply as the Message Table.

this

table

specifies where the task is to reside in

memory, and where it resides on the swap
device.

Partition Table (PARTBL)

Used for nonresident tasks,
contains

information

table

this

about each memory

partition, such as length and location
of the partition. Memory partitions are
shared by nonresident tasks.

The user does not need to know the

RTS/8.

Appendix

However,
E.

format

these

tables

use

detailed explanation of these tables is given in

CHAPTER

RTS/8 EXECUTIVE REQUESTS

3.1

COMMUNICATION WITH THE RTS/8 EXECUTIVE

tasks

RTS/8

Requests

communicate

(ERs).

RTS/8

with

uses

the

RTS/8

1locations

Executive

20-27

communication region for ERs to facilitate Executive

via

Executive

every field as a
Requests

across

any field via a JMS
field boundaries. The Executive can be called in The
Data Field (DF)
CAL).
as
cally
symboli
ated
(design
tion
20 instruc
is given, since
CAL
the
when
value
does not have to be any specific
Field (IF),
tion
Instruc
the
to
DF
the
sets
20
n
locatio
in
the code
sets the IF to 0 and jumps to the RTS/8 Executive.

Most of the
A summary of Executive Requests is given in Table 3-1.
chapter. The
this
in
detail
in
d
explaine
are
Executive Requests
in Chapter
RESCHD, WAITX and DERAIL Executive Requests are described
9.

The RTS/8 Executive will not honor any request to switch tasks arising
was
from an interrupt if the interrupted task's Program Counter (PC)point
entry
e's
Executiv
RTS/8
less than 100(octal). This protects the
(location 20 in each field) from being destroyed. User tasks must be
written so that instructions are never executed below 100 in any
field.

All ER's except DERAIL and SKPINS can relinquish processor control
higher-priority tasks as a result of their action.

3.2

ERs USED TO COMMUNICATE BETWEEN TASKS

The five ERs associated with the

1Intertask

Messages

and

the

Event

Flags are SEND, WAITE, SENDW, RECEIVE and POST. An example of their
WAITX
use is shown in Section 3.2.6. In addition, a sixth ER called(Section
is described in Chapter 9, Advanced Programming Techniques
9.2.2).

RTS/8

Table

Summary

Code|

Symbolic

SEND

RECEIVE

Send

3-1

Executive

message

Look

for

message

WAITE

Wait

and/or

from

for

Event

Run

SUSPND

Suspend

execution

POST

Post

Event

Flag

SKPINS

code

into

Insert

DERAIL

Derail

BLKARG

Block

a
11

SENDW

it
12

UNBARG

WAITX

Wait

for

Flag

Format:

Send

3.2.2

from

task

the

3.3.3

interrupt

3.4

9.2.3

task's

address
running

for

3.3.1

for

3.2.3

task

3.3.2

reason
and

reason

blocked

Force

wait

received

RESCHD

SEND

3.2.4

3.2.5

new

message

3.2.1

task

Remove

force

specific

Send

3.3.4

chain

execution

Reference

3.2.1

task

skip

task

Flag

RUN

Section

receive

Requests

task

posted

REQUESTS

Description

Name

EXECUTIVE

from
RTS/8

that

running
Scheduler

particular

run

9.1.2

Event

9.2.2

posted

Message

CAL

SEND
TSKNUM
MESSAG

The

SEND

sends

CAL

instruction

task

has

message,

this

SEND,
and

higher
the

the
sent.

sender

when

performed.
task

the

first

only

sender

(nonzero),

the

task

priority

1is

only

message

the

sender

case,

message

PENDING

the

than

meaning

put

Flag

Care

should

last

can

taken

sleep

to
in

into
is

Event

Flag

still

Flag

a
a

busy
Wait

field

the

state

location

from

once
a

sent

message
is
permanently.

this

from

runs.

MESSAG

location
will

the

for

receiver

WAIT
busy

receiving

waiting

the

(zero)

message

Event

the

and

Wait

FINISHED

that
send

and

any

Event

TSKNUM.

sender

message

into

MESSAG

suspended

the

becomes

request
to

put
if

the

Event

the

not

However,

will

number

temporarily

the

task

located

whose

the
is

MESSAG,
SEND

only

one

remembered;

RTS/8 EXECUTIVE REQUESTS

WAITE - Wait on Event Flag

3.2.2

Format:

CAL
WAITE
EFLG

it is FINISHED,
The WAITE ER checks the status of location EFLG and if G,
its state is
PENDIN
is
EFLG
If
.
returns control to the <caller

is put into Event Flag Wait.
changed to WAITING and the calling taskr task
or interrupt routine, the
When location EFLG is POSTed by anothe
Event Flag must be
The
again.
le
runnab
s
calling task become
particularly when a
cases,
initialized (set to 1) before use in most
The
completed by another task.

task is initiating an event to be
waiting task must reset the Event Flag before using it again in that
the Event Flag does not reset itself.

NOTE

wuser may
In advanced applications, the
be waiting for multiple Event Flags (see
Section 9.2.1 for description of WAITM).
In this case the task will run whenever
any one of the Event Flags 1is posted,

and not necessarily the one specified in
To insure that a

the WAITE.
Event

particular

is posted, use the WAITX ER

Flag

described in Section 9.2.2.

SENDW - Send and Wait

3.2.3

Format:

CAL
SENDW

TSKNUM

MESSAG

The SENDW ER is exactly equivalent to the sequence:
CAL

SEND

/SEND THE MESSAGE

TSKNUM

MESSAG
CAL

WAITE

/WAIT FOR RECEIVER TO ACKNOWLEDGE

MESSAG

3.2.4

RECEIVE - Receive Message

TAD TSKNUM

Format:

CAL

MADDR,

RECEIVE

/ONLY TO RESTRICT TO ONE
/SENDING TASK

/MESSAGE ADDRESS STORED

CDF TO MESSAGE
/HERE;
/FIELD IN AC ON RETURN

If the AC is zero when the RECEIVE ER is issued, the calling task's
Input Message Queue is examined. If there are messages in the calling
task's Input Message Queue, the first (i.e., highest-priority) message
is dequeued and the address of its first data word is placed in MADDR.
A CDF to the field of the message is stored in the AC.
3-3

RTS/8

there

such
first
the

are

time

examine

state

the

its

nonzero

matches

found,

This

Input

Number

Input

task

1is sent

the

1is

the

contents

removed

placed

bits

for

1-11

field

issued,
the

from

the

queue

message

issuing

task

from

only

given

the
1If

task

until

task may

determine

calling

task's

sender's

such

specified

placed

whose

AC.

Wait

However,

message

found,

one

Message

task.

Header

not

allows

this

RECEIVE

searched

REQUESTS

Message Queue
Message Queue.

when

Queue

the

message

the

Message

message

Input

messages,

EXECUTIVE

Task

message

above;

Message

Wait.

received.

NOTE

The

following

the

advanced

MSGWT,

after

its
PC
as
back to the
Thus, when

user.
just

the

message.

Normally,

task

there

performs

a l in
issued

messages

specified

the

(at

CAL

+3)

for

the

RTS/8

(0f

the

desired

3.2.5

are

POST

with

task

RECEIVE,

and

accepts

normally

user.

harm

One

caused

RECEIVE

Message Queue
Message Wait.

the

Input

put

into

the

equal

Queue

AC),
to

Event

Format:

the

zero.

the

will

task

once

and

the

to inform
pending.

type)

ER,

messages

Executive

Post

the

Message

1-11

the

useful

(i.e., the AC is negative)
the task is not willing to

Input

bits

done

mechanism

that

MSGWT.

0 of the AC
indicates that
in

the

RECEIVE,

bit

a task out of MSGWT because
task
starts
up
again,
it

re-execute

into

RECEIVE

implication

the

having

This

transparent

taking

When

stored in the TSTABL points
location containing the CAL.
a message comes in, the task

re-executes

the

information

(or

none

task

will

The

task

zero

that

Dback

when
a
However,

when the RECEIVE
wait.
Thus, with
sent

then
AC

the

continue

provides

there

were

task

the

no
run

means

messages

Flag
TAD

EFPTR

/POINTER

EFFLD

/FIELD

CAL

EVENT

FLAG

POST

CDF

The

Event

Flag

CDF,

1is

set

WAITING,

Wait.

pointed

the

task

that

This

never

task waiting for the
calling
task,
the
other is run.

FINISHED
was

AC,

(zero)

waiting

sets

Event

the

Flag

calling

the

state.

for

calling
is

task

task
a

EVENT

FLAG

field

specified

1If

the

state

was

its

cleared

higher

temporarily

WAIT

its

Event

state.

Flag

the

priority

than

suspended

the

while

the

RTS/8 EXECUTIVE REQUESTS

3.2.6

Example of ERs for Message and Event Flags

The following example illustrates the RTS/8 ERs dealing with Messages
and Event Flags. Since I/O and interrupts under RTS/8 have not been
discussed yet, this example is elementary.

advantage

There is no

keeping the functions of the two tasks separate, and the entire
send/receive structure is being used here as an elaborate subroutine
call. A description of the execution sequence follows the example.
Task

CAL
SEND

ALOOP,

/SEND TASK B MESSAGE 1

MES1

CAL

/SEND TASK B MESSAGE 2

SEND
B

MES?2

CAL

/WAIT FOR MESSAGE

WAITE
MES1

JMP ALOOP

/LQOP

/RANDOM NUMBERS

/MESSAGE 1

ZBLOCK 3

MES1,

37
23

ZBLOCK
-1

MES?2,

/MESSAGE 2
/RANDOM NUMBERS

Task

CAL
RECEIVE

BLOOP,

MADDR,

0
DCA EFCDF

TAD EFCDF

B4
B5

DCA .+1
HLT
TAD I MADDR

CLA

B8
B9

STA CLL RTL
TAD MADDR

B10

CAL
POST

/GET A MESSAGE

/SAVE MESSAGE CDF FOR POST
/PUT CDF INLINE
/CDF TO MESSAGE FIELD
/GET 1ST DATA WORD OF
/MESSAGE

/=3 IN AC
/AC POINTS TO MESSAGE
/EVENT

B1ll

FLAG

/DECLARE

HLT
JMP BLOOP

EFCDF,

(DO NOTHING WITH

MESSAGE

RECEIVED

/CDF TO MESSAGE FIELD HERE
/LOOP

two
the
of
which
on
The flow of execution in this example depends
Assuming that at some time both A and B
©priority.
higher
has
tasks
of
sequence
the
priority,
higher
A has
become runnable and task
execution

follows:

Sequence
Al
A2
A3
Bl

Reason For

Execution

Task A has higher priority than task B.
Task A has higher priority than task B.
Task A has higher priority than task B.
Task A is now in Event Flag Wait
since
MES1
was PENDING:
MES1 is now in WAITING state.

3-5

IT)

RTS/8

EXECUTIVE

REQUESTS

Sequence

Reason

B2-B1l0

Task A

The

POST

has

continues

tries

B
B1-B10

now

This

has

higher

priority,

that

waits

the

Task

has

Task

are

then

sends

for

Task

A's

stopped

and

Now

task

There

Message

Wait

its

MES2

for

put

task

Wait

input

since

there

queue.

Task

MES1

get

out

another

which

SET

allow

Table

task

entry

entry.

These

3.3.1

BLKARG

ERs

AND

are

Block
TAD

CLEAR TASK
to

BLKARG,

Task

for

TASKNUM

set

and

UNBARG,

and

task

has

put

MES1

run.

"wakes

Wait.

up"

Since

clear

set

SUSPND

Specified
/OR

FLAGS

task,

CAL

message.

and

Message

explicitly

another

Message

FINISHED but

messages,

priority,

the WAITE at A3 has no effect and
task
loops back to Al and sends MES1 again.

the

more,

FINISHED

USED

the

program

B.
task

A's

is:

than

higher

and

Wait;

POSTed.

has

and

Execution

Task

other

sends

returns

and

Format:

tries
no

processes

ERs

Wait

execution

effect.

are

Task A

Message

sets

Flag

re-execute

runs.

B1l0

vet

task

brings

POST at

message

since

other

MES1

priority
in

not

Flag

will

For

messages

higher

MES2.

modified

up"

has

WAITING.

Event

MES]1

placed

Wait;

The

Event

now

sequence

B2-B1l1

Several

POSTs
of

"woke

SEND.

B1l1l

Flags

and

Reason

B2-B10

ERs

into
is

has

and

PENDING.

MES2
out

RECEIVE

than

again;
is

is put

Seguence

3.3

MES2

Executive

now

MES1

priority

MES2

RECEIVes

counter

task

it;

brings

offending
A3

posted

the

executing.

resumed;

RTS/8

B1l0

send

Therefore,

Execution

waiting;

higher

processed

B1l1l

still
MES1

which

received

For

flags

and

its

the

Task

own

table

1is,

not

RUN.

Reason

SELF

task

BLKARG

WAITBITS
TASKNUM

contains

allowed

that
cause
zero,

task's
the
the

the

run).

Task

Flags

specified
issuing

number

WAITBITS

word.

task

will

the

specifies

Assuming
become
be

blocked

WAITBITS

non-runnable.

blocked

3-6

one

the

(that

bits

nonzero,
If

this

TASKNUM

specified

set

will

contains

wait

bits.

RTS/8 EXECUTIVE REQUESTS

the
The TASKNUM=0 form of this ER is the only legal way to specify
the
to
equal
is
TASKNUM
if
;
blocked
be
issuing task as the task to
issuing task number, the action of this ER is undefined.
Example:

Task 14 is placed into User Wait by executing the following code.
TAD

(14

CAL

BLKARG
USERWT

Symbolic names for specifying the condition for blocking or unblocking

a task in the WAITBITS word is given in Table 3-2.
Table

3-2

Symbolic Names for Specifying WAITBITS

Symbolic Name

Meaning

Value

run

cannot

task

Wait - This

NONRWT

4000

Nonresident

EFWT

2000

Event Flag Wait - This task is waiting for

RUNWT

1000

RUN

because it

is not

in memory.

(which contains a WAITING value
Flag
Event
corresponding to this task) to be POSTed.

Run Wait - This task is waiting for a

to be executed with its number in the AC, or
for the operator to type "REQUEST task" to the

Monitor Console Routine

(see Chapter

5).

SWPWT

0400

Swap Wait - This task cannot run because it is

EORMWT

0200

Event or Message Wait - This task

waiting

USERWT

0100

User Wait - This bit is reserved

for

use

Dby

waiting

in the process of being brought into memory.

for an Event Flag to be posted or a message to
arrive, whichever happens first.

user-written

tasks.

RTS/8 does not use this

bit.

ENABWT

0040

Enable

Wait - This

task

and "DISABLE task" commands

MSGWT

0020
0001

(see Chapter

5).

Message Wait - This task is waiting to be sent
a

DNEWT

Use of this bit is restricted to the
Fnabled.
Monitor Console Routine for the "ENABLE task"”

message.

Task does not exist.

This bit should never be

set or cleared by a user task.

RTS/8

3.3.2

UNBARG

Format:

Unblock
TAD

EXECUTIVE

Task

for

REQUESTS

Specified

Reason

TASKNUM

CAL
UNBARG

WAITBITS

TASKNUM

contains

specifies
word.

one

the

operation,

the

number

bits

Task

Flags

word

the

specified

has

task

the

task

cleared

becomes

unblock,

zero

runs.

issuing

no-op

task's

(no

operation)

number.

runnable;

higher priority than the issuing
task and
issuing
task
is temporarily suspended while

This

that

issued

executing

and

task's

WAITBITS

Task

result

the

Flags

this

specified

task

becomes
runnable,
the higher-priority

with

TASKNUM

equal

the
task

the

Example:

Task

taken

TAD

out

User

Wait

the

following

code.

(14

CAL
UNBARG

USERWT

3.3.3

SUSPND

Format:

Suspend
TAD

Task's

TASKNUM

Execution
SELF

CAL
SUSPND

This

SUSPND

identical

TAD

TASKNUM

action

the

following

instructions:

CAL
BLKARG

RUNWT

3.3.4

RUN

Run

Format:

TAD

Task
TASKNUM

CAL
RUN

This

RUN

identical
TAD

action

instructions:

TASKNUM

CAL
UNBARG
RUNWT

The

SUSPND

and

enough

can

used

data

RUN

warrant

collection

without
executed,

ERs
a

task

Report

because

the

their

version.

follows.

task

interrupting
the

exist

shorthand

data

Generation

function

example

that

report

every

1000

collection/reduction
Task

3-8

comes

performed

running,

shows

often

how

data

points

process.
so

they

that

When
the

RTS/8 EXECUTIVE REQUESTS

ied example,
first report occurs on the first data. 1In this simplifbeen
already
have
may
m
progra
report
the data operated on by the
example
full
A
d.
reporte
being
before
cycle
next
the
for
updated
data.
the
protect
to
ng
bufferi
would require a scheme such as double
Data

TAD

DLOOP,

Control

Task

/1000 DECIMAL

(-1750

DCA COUNT
CAL

DATALP,

WAITE

DATAEF
.
.

/WAIT FOR DATA READY
/CODE TO STORE DATA
/POINT IN BUFFER

.
ISZ COUNT

/GET A DATA POINT
/AND PROCESS IT
/COUNT OFF 1000 POINTS

JMP DATALP
TAD

(REPORT

/RUN REPORT TASK

CAL
RUN

/KEEP COLLECTING

JMP DLOOP
0

COUNT,

Report Generation Task

/AC=0, SUSPEND
/UNTIL NEEDED
/HAS BEEN RUN

CAL
SUSPND
JMS TITLE

RLOOP,

/PRINT REPORT

/WITH

TITLE

/REPORT OVER-GO

JMP RLOOP

/BACK

AND WAIT

To eliminate interference with the data collection, REPORT should have
a

lower

3.4

priority than DATA.

USING INTERRUPTS IN RTS/8

The RTS/8 Executive contains code

receive

and

dismiss

hardware

interrupts and to perform interrupt-initiated task switching, but it
does not provide room for an interrupt skip chain. Instead, the skip

1is built up dynamically at system
1is 1literally a <chain and
chain
of the SKPINS ER is as
description
A
ER.
startup time via the SKPINS
follows.

CAL

Format:

SKPINS
MODULE

MODULE

the

address

(in

the

processing module.

3-9

current

field)

interrupt

RTS/8

interrupt processing
MODULE,

EXECUTIVE

module

has

REQUESTS

the

/THIS

/TO

following

format:

WORD

THE

GETS

/MODULE ENTERED HERE - CONTAINS
/CDF CIF TO NEXT MODULE FIELD

SKDR

/SKIP

(SKP)
JMP

/(ONLY

MODULE

DEVICE

READY

SKDR

REALLY

NOT

READY)

/ON

DEVICE

/NOT

READY

/CHAIN

CDF

POINTER

MODULE

CIF

CUR

/THIS

ONE

MINE

/INTERRUPT

CIF

/DISMISS

POSTDS

/AN

See

item

Whenever

the

below

very

usually

SKPINS

the

task

user's

THE

way,

the

end

inserted

them,

since

once-only

code

are

system

The

Data

module

Field

and

must

before

interrupt

any

the

indirect

module

may

interrupt
module
interrupts
are
off.
75us.

task
Flag.

Event

POSTDS

Interrupt

entry

Link,

then

Interrupt
POSTDS
be

any

jumps

than

used

wake

turn

the

interrupt

module,

Data

Field

requiring
before

must

Field

when

JMP

the

use

the

(MQ) .

the
the

instruction.

task

from

because
by

not

AC,

the

Therefore,

save

setting

POSTDS

dismissed

the

second

the

but

MQ should

interrupt
a

Event

interrupt.

issuing

saved,

when
under

needed,

the

and

interrupt

contents

been

dismissing

3-10

performed.

POSTing

destroyed

Quotient

dismiss

described

ERs.

interrupts
will

already

Multiplier

modules
defined

have

skip

the

are

this

RTS/8

computing

task

POSTed

1I/0

request.

those

instruction

restore

Instruction

are

correct

interrupt modules

1its

execution:

perform

the

the
usually

are

compute
excessively
execution time should be

not

(i.e.,

must

that

not

Typical

interrupted

the

and

contents

may

issue

"next

implies

task

interrupt

must

its

interrupts.

time.

scheduled

modules

interrupt.

and

not

Wait.

state

the

1last

This

The

priority

its

addressing

should

considerably

should

ERs

Field

wuser

only.

control

Instruction

module;

is broken
inserted.
This

chain.

POST

UPON

chain

time

start-up

clear

AND

MAYBE

routine
superfluous

SKPINS

receives

above

any

dismiss

skip

restrictions

interrupt

roughly

several

The

interrupt

the

ordered

instruction.

module

avoid

module

l‘

are

start-up
to

MODULE

DEPENDING

POSTDS

interrupt

tries

chain

there

the

skip

interrupt

succeeds),

the

ER, the
interrupt

system

RTS/8

inserts

INTERRUPT,

FLAG

SKPINS

points

the

which
as

the

tasks

this

always

executed

Once

executes
and

skips

definition

task

module

module".

the

end

done

interrupt

for

SET

SKIP

PROCESSING

EVENT

/CONTENTS

/CORRECTLY

MEANS

An
by

it,

the

instruction.

Event
setting

Flag
the

RTS/8 EXECUTIVE REQUESTS

the
Data Field to the field of the Event Flag and placing
g the
issuin
to
prior
AC
the
in
Flag
Event
the
of
n
locatio
POSTDS.

For example:

CDF CUR

TAD (EVFLG
CIF

/DF = THIS FIELD

/EVFLG MAY NOT BE AT LOCATION 0

/DISMISS INTERRUPT AND POST EVFLG

POSTDS

If an Event Flag is not going to be posted by the interrupt
AC must be cleared prior to issuing the POSTDS
the
routine,
instruction.

For example, an RTS/8 Paper Tape Punch handler task might contain

the

runnable

following sections of code:

In the initialization code (contained in a task that

system start-up time):

START,

CAL
SKPINS

GETREQ,

CAL

/LINK THE PUNCH SKIP
/INTO THE SKIP CHAIN

PTPINT

punch subroutine used by the main body of the task:

character

PUNCH,

/WAIT FOR MESSAGE

RECEIVE

/ENTER WITH CHAR IN AC

CAL

/WAIT UNTIL PUNCH READY

DCA TEMP

/SAVE CHAR

WAITE

PTPEF

ISZ PTPEF
TAD

TEMP

PLS

/SET PUNCH EVENT FLAG

/TO THE PENDING STATE
/PUNCH CHAR

CLA

JMP

PUNCH

/RETURN

Interrupt skip chain code:
PTPINT,

ZBLOCK

PSF

JMP
CDF

PTPINT
CIF CUR
I

PCF
TAD

(PTPEF

/USED TO CHAIN SKIPS
/CHECK PUNCH
READY
/SET CORRECT

/NOT

/CLEAR PUNCH

FLAG

DF, IF
FLAG

POSTDS

/DISMISS INTERRUPT,

PTPEF,

/PUNCH INITIALLY READY

TEMP,

/POSTING

PTPEF

RTS/8 does not provide a mechanism for removal
interrupt skip chain.

entries

from

the

RTS/8

3.5
A

EXECUTIVE

summary

Table

REQUEST WAIT

wait

states

3-3.

Summary

Wait

EXECUTIVE

STATES

generated

Table

Wait

REQUESTS

States

Executive

shown

1in

3-3

Incurred

State

Requests

Executive

Condition

Requests

Suspended

SEND

none

EFWT

for

SEND

message

busy

'CAL!
RECEIVE

(No

MSGWT

wait

AC=4000)

WAITE

EFWT

(No

wait

'done')

Input

and

Event

not

messages

'CAL'

Queue

positive
Flag

'CAL'+3

FINISHED

RUN

none

SUSPND

RUNWT

POST

none

SKPINS

none

DERAIL

none

BLKARG

any

(given

task

self

task

message

but

Event

self

argument)

SENDW

EFWT

not
EFWT

'CAL'+2

'"CAL'+3

free

'CAL'+3

Flag

FINISHED
message

busy

'CAL"

UNBARG

none

RESCHD

none

WAITX

EORMWT

specified

Flag
WAITM

any

(given

not

Event

'CAL"

FINISHED

'"CAL'+3

argument)

NOTE:

(a)

(b)

'CAL' denotes the address
Executive Request.
A

message

been

said

POSTED by

its

bus y

3-12

the

CAL

its

user.

instruction

Event

Flag

has

the

not

yet

CHAPTER

RTS/8

The

RTS/8

standard

SYSTEM

TASKS

the
of
most
control
that
tasks
system
I/0 devices.
Also included is one task that

system includes
Digital
PDP-8

interactive system control
from
the
console
terminal
and
to run in the
system
monitor
O0S/8
the
of
copy
single
Foreground tasks are
protected
from
background
tasks;
backgroun d.
the
reverse is not true.
The complete list of system tasks
however,

provides
allows

available

the

RTS/8

system

follows:

Clock
Handler - accepts
requests
in
the
form
of
RTS/8
messages
to
perform
actions
after
a
specified
time has
elapsed.

Console and Non-console Terminal
terminal

Line

either

Printer

line

Handler

Handlers

character

- handle

single

mode.

- supports an LS8,

LS8E,

LP8 or

LV8 line

printer.

Mass Storage Handlers - Control the
passing
of
information
from
these devices to and from memory for the RK08 and RK8-E
moving-head disks, DF32 and RF08 fixed-head disks,
and
TCO08
DECtape unit.
Data is read and written in the standard RTS/8
block

format

Floppy

Disk

floppy

disk.

LINCtape

(400 octal

Handler

contiguous

- provides

supports

words).

support

both

for

the

0s/8

use

and

the

RXS8

DIAL-format

LINCtapes.

0S/8

Files

Support

Task

allows

the

user

look

up,

create,

and
delete files in 0S/8 directories from a foreground task.
This task, when used with the mass storage handlers, provides
the
capability
to
read or write 0S/8 files on mass storage
devices.
0S/8
Support
Task
operating system in
UDC/ICS
types

Handler

Cassette
tape

- supports
the
the background.

- enables

the

user

the

user

execution

control

the

0S/8

wvarious

UDC/ICS modules.

Handler

allows

read

write

data

cassette.

Cassette

enter,

File

and

Support

delete

Handler

files

from

allows

the

DECcassette

user

CAPS-8

1look

up,

format.

RTS/8

)

Power

Fail

provides
Also, it
)

Exit

Task = when used

for
an
allows a

Task

making

PDP-8A

Null

sources
tasks

i.e.,

the

idle

they

handlers

1I/0

I/0 operation,
message

4.1
The

and

CLOCK
Clock

fail

when
when

hardware,

power

perform

in
the

lost.

returns.

special

processing

RTS/8.
the

user

are

supplied

"handlers"

the

1is

count

decimal

are

Message

messages.

Event

Flag

RECEIVE

ER.

with

the

RTS/8

completely

Wait

state.

When

the

systen.

message-driven,

Other

handler

associated

with

any

tasks

send

completes

the

request

HANDLER

the

Task

and

can

The

parameter

PDP-8A,

messages

power

PDP-8A.

request

another

clocks.

for

issues

allows

are

with

user

from

tasks

POSTs

Handler

hardware
CLKTYP

the

system

referred

when

these

the

exit

Task

LED display

The

TASKS

orderly
shutdown
programmed restart

allows

before

The

SYSTEM

file

inserts

the

assembled

user
3

selects
to

0 for
DK8-EP.

for

entries

into

entries

the

handle
clocks

one

setting

of
the

four
symbol

KD8-EA/DK8-EC,
The
an

to 1 for KW12, to
Handler accepts RTS/8

Clock

internal

clock

queue.

the

CLKQLN

become
due, they are removed from the queue, and the request
is decoded and executed.
The user fixes the length of
the
queue
at
assembly
time
by defining the symbol CLKQLN in the parameter file to

the

minimum number

entry

slots.

The

default

20.

The

format

CLKMSG,

clock

ZBLOCK

message

value

for

is:

COMMAND+TASKNO

WORDS

/TASKNO=0

RESERVED
MEANS

FOR

RTS/8

TASKNO=SENDING

TASK

TIMEHI
TIMELO

EXTRA1
EXTRA?2

The

words

TIMEHI

time
in
terms
system ticks in
parameter

specified

SHERTZ.

completely

the
by

reciprocal
exact

and

TIMELO

specify

of
“"system ticks".
a second in the RTS/8
The

hardware

tick

HERTZ.

CLKTYP

parameter
the

the

multiple

wuser's

software
of

line-frequency clock

time

hardware

system

SHERTZ.

might

rate

(in

and

from

ticks

HERTZ

configuration.

clock

For

interval

the

The user specifies
parameter file by

resolution.

example,

the

be:

present

the number of
defining
the
per

second)

are
SHERTZ

HERTZ

determined
equals

must

parameters

the

for

DECIMAL
HERTZ=

120

SHERTZ=

indicating that there will be 10 "system ticks" per second based on
a
60-cycle
clock.
Such
parameters
might be used if only 1/10 second
resolution is necessary in the Clock Handler.
Note that
the
maximum
interval
that can be expressed in TIMEHI and TIMELO is (2**24) /SHERTZ
seconds.

Other

Clock

This

RTS/8

system

Handler.

parameter

file

approximately
tasks

The

use

wuser

equal

three

the

symbol

should

the

days

4-2

CLOCK

define

Clock

SHERTZ=60.
when

this

Handler's

referring

symbol

task

the

number.

the

RTS/8

should

COMMAND

if a Clock Handler is not to be included in the
6 for a description of the parameter file.)

undefined

(See Chapter

system.

SYSTEM TASKS

is the type'of request and has the following meanings:
Description

Symbolic

Octal

0000

MARKTIME

POST the event flag CLKMSG
after
the
TASKNO,
elapses.
interval
specified
EXTRAl, and EXTRA2 are ignored.

1000

SCHEDULE

POST CLKMSG
immediately.
Execute
a
RUN ER on the task specified by TASKNO
after the specified interval
elapses.
EXTRAl and EXTRA2 are ignored.

2000

TIMOUT

POST CLKMSG immediately.
DERAIL
the
task
specified
by
TASKNO
1into
a
subroutine whose address is
specified
in EXTRA]l after the specified interval
elapses.
EXTRA2 is ignored.

3000

SCHEDULE

POST CLKMSG
immediately.
Execute
a
RUN ER on the task specified by TASKNO

PERIODICALLY

after the specified interval
elapses,
and
re-queue
this
command
with the
parameters EXTRAl and EXTRA2 in
place
of
TIMEHI
and
TIMELO.
This has the
effect of running the
specified
task
periodically
with
a period specified
by

7000

CANCEL

EXTRAl

Cancel

all

and

EXTRA2.

the

clock

requests

for

the

task
specified
by
TASKNO.
TIMEHI,
TIMELO,
EXTRA],
and
EXTRA2
are
ignored.
POST
CLKMSG
immediately.
Note

are

not

actually
deleted
and that they
occupy space in the queue
until
time out.

that

the

requests

still
they

—

Command: —_-I
0
1
2
3
7

MARKTIME
SCHEDULE
TIMOUT

SCHEDULE PERIODICALLY
CANCEL

Task number

Command Word Format - Clock Handler

RTS/8

SYSTEM

TASKS

The Clock Handler also maintains the current
ticks

TODL

wuntil

midnight),

(low-order)

Page

symbolic

Field

zero
(i.e., at midnight), it is
(24 hours until midnight) and an
location DATE in Page 0 of Field
Note

that

bits,

order

SHERTZ must

error

will

4.1.1

result

Examples

for

the

less

while

When

TODH

this

Handler

the

SHERTZ

Clock

/JWITH

/THIS

CAUSES

CLOCK

/TO

the

user

2"SHERTZ,

assembly

Calls

CAL

60HZ

"GO

/MESSAGE

0
0;170

Handler.

SENDW

ZBLOCK

and

reaches

contained

larger,

SYSTEM
THE

SLEEP"

TICK

RATE,

CURRENT

FOR

SLEEPM

SLEEPM,

system

quantity - (SHERTZ*86400)
date
word
in
symbolic
incremented by one day.

SHERTZ*86400

192.

(in

(high-order)

time-of-day

reset to the
0S/8-format

assembling

Clock

quantity

than

time-of-day

locations

TASK

SECONDS.

HEADER

/SET EVENT FLAG AFTER INTERVAL
/INTERVAL IS 120 (DECIMAL) SYSTEM
/TICKS

changes

the

the preceding

value

170

the

THE

TASK

assembler

expression

sequence becomes configuration-independent.

CAL

/RUN

SEND

/EVERY

CLOCK

/ASSUMING A

HOUR,

REPORT

ONCE

INDEFINITELY,
60HZ

SYSTEM

TICK

RATE

RUNMSG

RUNMSG,

ZBLOCK

SCHEDULE

REPORT

/MESSAGE
PERIODICALLY

HEADER

/RUN REPORT AFTER SPECIFIED
/INTERVAL AND PERIODICALLY
/THEREAFTER,

0;1
64;5654

4.2

The

TERMINAL

/FIRST RUN IS ALMOST IMMEDIATELY
/(1/60 SECOND)
/PERIOD BETWEEN RUNS IS 216000
/ (DECIMAL) SYSTEM TICKS = 3600
/SECONDS = 1 HOUR.

HANDLER

RTS/8

Terminal Handler handles a single terminal in either line or
mode.
Input in line mode is terminated by a carriage return
or an ALTMODE character and may be edited
using
the
RUBOUT
and
U
characters.
The
RUBOUT
character
deletes the last valid character
typed and prints a backslash;
the “U
character
deletes
the
entire
line and returns the carriage.
Character mode input is not echoed and
is terminated by overflow of a specified character count.
character

If multiple terminals are to
be
handled,
multiple
copies
of
Terminal
Handler
must be assembled.
Assembly parameters in the
of

the

handler

access

1its

handler

specify which

device

terminal.
to

codes

the

handler

will

use

this
body
to

These
parameters
also
specify
whether the
"console" Terminal Handler, that is,
the
terminal

4-4

RTS/8 SYSTEM TASKS

on which the MCR program is going to be run. The console Terminal
Handler invokes the MCR whenever a ~C is typed on the keyboard;
nonconsole terminal handlers treat "C as any other character. For the
console handler, “C wakes up MCR by POSTing an Event Flag.

The parameters edited into the distributed version of the Terminal
Handler assemble the handler to handle the PDP-8 console terminal as a
"console" device. Thus, when the MCR function is required, both the
MCR task and the Terminal Handler task must be assembled and included

to
Modification of the Terminal Handler
as part of the RTS/8 system.
support a VT50 terminal and other features are described in Section
4.2.1.

The format of messages to the Terminal Handler can be

the

either

following:

ZBLOCK

ASSGN+tsknum

command+length
INBUF
OUTTXT

Description:
Types

text

Legal

Commands,

Description:

specified by

ASSGN=200

Assigns Terminal Handler to task specified
Deassigns Terminal Handler if tsknum=0

OUTTXT and command, then
reads text into INBUF.

which can be combined,

are as

follows:

Octal

Symbolic

Action if specified

Action if not specified

4000

NOPACK

Output text is in
unpacked ASCII, one

character per word
terminated by a 0000.

Output text is in
packed 6-bit, two
characters per word
terminated by a 00.
Type a CR/LF after

2000

NOCRLF

Do not type a CR/LF

1000

IND

OUTTXT points to the

after

first word

output

0400

NOLINE

Length

the message.

typing

the message.

OUTTXT is the first

the

word of

the output

text.

Input is

in character

Input is

mode; terminated
after 'length' input
characters read.

in line mode;

terminated by a CR
or ALTMODE (ESC). The
length is still tested.

Is a
seven-bit
field
which
specifies
the
maximum
size of the input buffer if input is
in line mode, or
input
if
input

the
1is

number of characters
in
character mode.

to
If

LENGTH-1
input is in line mode and there are
characters
in
the
input buffer, characters
RUBOUT
ALTMODE,
other than carriage return,
and
"U
will
not
be accepted or echoed the
message Event Flag is Posted.
INBUF

Is a pointer to the input buffer;
if
it
is
zero, no input is taken.
The input buffer is
filled with input characters packed
one
per
word
with
the parity bit (bit 4) forced on.
If

input

line

mode,

the

last

character

the line is followed by a zero word

4-5

(if a

RTS/8

OUTTXT

ASSGN

TASKS

carriage

return

=1(7777)

word

terminated

the

=200

SYSTEM

either

the

terminated
(if

the

1line)

ALTMODE

line).
first

string

(if

IND=0)

word

the

output

same

field

word

pointer

string

the

output

(if

the

text

first

IND=1000)

message.

character

"Assigns"
the
Terminal
Handler
to
the
specified task.
This will cause the terminal
handler to
only
accept
messages
from
the

specified

SEND

the

task.

message

another

task

the

Terminal

Handler

assigned,

tries

while

the message will be placed in
Handler's
Message
Input
Queue
not be removed for processing by the
Handler
until
the
assignment
is

Terminal

but

will
Terminal
released.

The

Handler

assignment
Terminal
operation

task

which

assigned

can

sending a message
Handler to task number
is

performed

the

Terminal

release

the

assigning

the

I/O

the

ASSGN

command

task

assignment

message.

tsknum

6-bit

field

specify

the

used

with

task

number

which the terminal is
to
this
field
is
zero,
deassigned
allowing
the
accept

commands

from

any

the

be
assigned.
the
terminal
terminal
task
task.

Packed ASCII
Unpacked ASCII

}

CR/LF at end of message
No CR/LF at end of message

= e

-—

Command (bits 0-4)

QUTTXT is the first word
OUT
pointsTXT
to first word

Input in line mode

Input in character mode
f

Bit

4 must be a 0

Length (bits 5-11)

If bit 3=1, no. of characters to input
If bit 3=0, maximum size of input buffer]

Command

and

Length

Word

Format

Terminal

Handler

I/0

Mode

If
is
to

RTS/8 SYSTEM TASKS

Unused

Bit 4 must be a 1
Unused

Task Number

Command Word Format - Terminal Handler ASSGN Mode

4.,2.1

Additional

Assembly

Parameters

Affecting

Terminal

Handler

Properties

aid

CTRL/Q

special

this

feature

describes these parameters.
section
This
using
summary of their default values is shown in Table 3-4.
the

VT50

TTY

task.

Do not treat CTRL/S

and

1in

Several assembly parameters are available to the user

characters.

Support CTRL/S and CTRL/Q.

is enabled, typing CTRL/S while data is being

cause
printed/displayed on the terminal will
to stop until the next CTRL/Q is typed.
data
to
terminals
CRT
fast
This can be used on
This
screen.
the
"freeze"
temporarily
user's
the
if
1
to
parameter must be set
is a model VTS50 or VT52 since these
terminal
send
occasionally
will
terminals
host
the
to
characters
synchronization
computer of their own volition.

WIDTH

Where n is an octal number that sets the page

width

characters.

currently set to 120(octal)
example,

width

1is

For

the parameter

setting

WIDTH

TTY

characters.

80 (decimal)
to
changes the TTY page width
n characters are printed
After
characters.
will
handler
the
terminal,
the
on
carriage-return
a
out
type
automatically
to
desirable
1is
it
Sometimes
line-feed.
this CR/LF (for example, when using
suppress
case,
this
In
addressing).
direct cursor
WIDTH should be

SCOPE

set equal

This option is used to determine treatment of
the

RUBOUT key as

follows:

SCOPE=0 provides the normal

support

mode

RUBOUT

(echo rubouts with a backslash).

4-7

RTS/8

SYSTEM

TASKS

©COPE=1 causes
one

position,

character

from

RUBOUT to move
the

screen.

in
column
1, RUBOUT
visible effect.
TAB

This

option

proper

with

Fill

FILL=n

sends

line

1-5.

baud

VTO05s.
=

the

means

not
tabs

does

the

handler

The

shorter.

using

OLDTTY

specifies

3-page

terminal
=

this

and

the

o0ld
with

has
fewer
but it is a
WIDTH,
have

wuse

listing

causes

the

new

both

the

three-page.
only

OLDTTY

the field of the
example, 20 designates
the

starting

task;

for

4-8

supplied

handler
handler

the

Specifies

starting

use
was

handler.

the

new

0O(default)

Specifies

not

handler.

specifies

the

will

VT50,

when

the
2400

typed.

herein

effect

two-page

handler

described

FILL

for

parameters

TAB

new

SCOPE,

and

this

This

the

after

is
being
terminal (default).

which

page

must

recommended

the

(nulls)

specifies
handler

via

follows:

number

that

the

does

simulates

hardware

characters

Handler

characters.

MCR when

selected
listed.

TTLOC

the
TAB

supported

console

version
features
than

for

parameter

fill

the

RTS/8

LSBOT

the

has

This

The

means
for

two-page

LSBOT

tabs

FILL

fill

FILL=4

OLDTTY

feed.

range

CONSOL

hardware

software

are

parameter

provides

wake

but

spaces.

that

<characters

CONSOL

cursor

tabs.

assembled

TTFLD

simulate

the

The

FILL=0

0ld

works,

assembly

that

specifies

assembly

LSBOT

the

tabs.

support

OLDTTY

the

spaces.

TAB=1

CONSOL

the

still

via

specifies

support

left

removing

follows:

TAB=0

FILL

used

number

accomplished

the cursor

physically

location

handler

TTY Handler
field 2.

location

example,

the

parameter

3000.

3000

the

task:

TTY

designates

RTS/8 SYSTEM TASKS
4-1

Table

Summary of Terminal Handler Assembly Parameter
Default Values

Parameter

Meaning

Default Value

VT50

Support “S, "Q

WIDTH

120

Page width of 80 (decimal) characters

SCOPE

Rubouts echo as \

TAB

Simulate tabs

FILL

No fill characters

CONSOL

“C wakes up MCR

OLDTTY

Use 3-page TTY task

LSBOT

List only TTY task selected by OLDTTY

TTFLD

Not

TTLOC

5000

assignments for TTFLD and TTLOC load the
TTY

value, but

a default

example

Handler

location

given

show that the given

5000

field

as an

number

starting

Useful Equates in the Parameter File

4.2.2

e which
Several useful equates (described in Section 4.2) are availabl
are as
They
tasks.
LPT
or
TTY
to
s
message
sending
when
used
be
can
follows:

NOPACK = 4000
NOCRLF = 2000

Used if output message

1is

not

6-bit

Used if output message should not be followed

by carriage return/line feed.

first

IND = 1000

Used if OUTTXT points to the

NOLINE = 400

Used if input is in character mode.

ASSGN = 200
KLSALINE = 100
4.2.3

ASCII

format.

the

output

word

for

use

text.

Used to assign the

only by this task.

device

handler

Used with KL8-A support (see Section 4.13.2).

Examples of Terminal Handler Messages

HIYA,

ZBLOCK 3

/MESSAGE HEADER

0
TEXT /HELLO/

/NO INPUT
/TEXT TO BE OUTPUT

/PACKED TEXT, END WITH CR/LF,

Sending the above message to the Terminal Handler prints HELLO on
terminal.

4-9

the

RTS/8

QUEST,

SYSTEM

ZBLOCK 3

/MESSAGE

NOCRLF+60

Sending

the

ANSWER:

above

/48-CHARACTER

the

carriage.
printed on the
TYPANS,

/POINTER

/TYPE

THE

message

the

terminal

The

answer

terminal
ZBLOCK

the
and

Terminal
inputs

from

sending

the

The

RTS/8

word

present

INPUT

Handler

LIMIT

BUFFER

prints

without

TYPE

first

the
above
message
following message:

/MESSAGE

HEADER

TEXT,

INDIRECT,

INPUT

/POINTER

OUTPUT

could

WITH

Line

Printer

and

outputs

format of messages to
format of messages to the

the

Handler

The

LINE

bit

message).

Packed ASCII

Unpacked ASCII

CR/LF at end of message

are

ignored

LE8,

LS8E,

the

Line
terminal

(the

INBUF

LP8

Printer

OUTTXT is the first word

handler,
word

Input in line mode
Input in character mode f

the

must,

however,

Bit 4 must be a 0

Length (bits 5-11)
If bit 3=1, no. of characters to input
If bit 3=0, maximum size of input bufferj

and

Length

Word

Format

4-10

Line

Printer

Handler

LVS8

but

OUTTXT points to first wordf

Command

CR/LF

Handler

No CR/LF at end of message

TEXT

Command (bits 0-4)

THE

returning

PRINTER HANDLER

line
printer.
identical to the
INBUF

NO CR/LF,

/UNPACKED

/NO

ANSWER

LINE

obtained

ANSWER: /

NOPACK+IND

4.3

HEADER

/PACKED TEXT,

ANSWER
TEXT

TASKS

I/O

Mode

RTS/8

SYSTEM TASKS

Unused
Bit 4 must be a 1
Unused

Task Number

Command

4.4

MASS

Word

STORAGE

Format

Line

Printer

Handler

ASSGN Mode

HANDLERS

Handlers are available for TC08
DECtape,
DF32
and
RF08
fixed-head
disks, RK8 and RK8E moving-head disks, RX01l floppy disks and LINCtape.
All

mass

storage

handlers

the

same

message

write
blocks
on
various
mass storage devices.
Disk Handler and the LINCtape Handler
allow
the
parameters other than the ones described herein.
described in Sections 4.4.1 and 4.4.2.
The

format

MSMESG,

messages
ZBLOCK

to mass

storage

handlers

format

read

However, the Floppy
wuse
of
additional
These parameters are

is:

UNIT
RW

PAGES

FIELD

BUFADD

’

BLOKNO
STATUS

where:
UNIT

the

number

the

logical

unit

which

the

operation

is to be performed.
DF32 and RF08 disks consist of only
one
unit.
TC08
DECtape
has
logical
units
0-7
corresponding
to
its physical units 0-7.
LINCtape has
logical units 0-7 corresponding to
its
physical
units

0-7.
RK8
disk
has logical units 0-3 corresponding to
its physical units 0-3.
RK8E
disk
has
1logical
units
0-7.
Units
0-3
correspond
to the outer (lower track
number) half
of
physical
wunits
0-3,
and
units
4-7
correspond
to
the
inner (higher track number) half of
physical units 0-3, respectively.
RX0l has units 0 or 1
which
corresponds
to
the
1left
and
right
drive,
respectively.
RW

for

PAGES

Specifies

read
the

(times
100
the transfer
PAGES=0,

operation,

number

pages

for

(128-word)

octal).
For
of
20(octal)

40(octal)

4000

write
pages

operation.
to

transfer

example, PAGES=2000 specifies
pages
or
2048
words;
if
4096

words

are

transferred.

RTS/8

FIELD

The

the

PDP-8

field

(times

transfer

takes

RW+PAGES+FIELD word

SYSTEM

which

octal).

TASKS

the

For

place

sometimes

transfer

example,

field

called

the

1if

takes

place

FIELD=30,

function

word

message.

the

Reserved for task use
Unit

Unit Word

Read operation

Write operation

Format

- Mass

Storage

Handlers

No. of pages to transfer

0-7:

Field of transfer

Reserved for task use

Function

Word

Format

BUFADD

BLOKNO

Is the
block
transfer
will

the

starting

Mass

address
number

of
on

begin.

Storage

the

Handlers

buffer

transferred.

the

All

device
from
which
devices are assumed to

256-word blocks.
On DECtape, the
first
128
words
each of an even/odd pair of 129-word DECtape records
considered to be a block.
STATUS

word

that

operation.

the

successful,

handler

contains

otherwise

which
1is
the
Tasks which use

contents
the mass

sets

=zero

completion

the

will

contain

the device

the

have

operation

of
are

the

nonzero

quantity

status

storage
handlers
should
test
this
word
after
the
1I/0 operation has been completed
(that is, after the
Event
Flag
has
been
POSTed)
to
determine
if
any
errors occurred during the transfer.
All RTS/8 mass storage handlers retry
operations
three

Note

that

the

times

STATUS

word

middle

storage

handlers

when

same

the

errors
to

are

three words
are
identical

operation

encountered

before

nonzero.

of
to

performed.

4-12

a
message
to
the
the arguments to an

setting

the

RTS/8
mass
0S/8 handler

RTS/8 SYSTEM TASKS

Floppy Disk Handler

4.4.1

Each copy of the Floppy Handler can control one single or dual RXO0l1
for more than one RX01l, multiple copies of the hapdler are
drive;
required.

The format of messages to the Floppy Disk Handler 1is:

ZBLOCK 3
CODE+DEL+MODE+UNIT
RW+PAGES+FIELD
BUFADD

BLOKNO

STATUS
where:

CODE

BLOKNO is interpreted as an
Reqgular condition.
PAGES 1is
Also,
logical record number.
0S/8
interpreted in the 0S/8 sense to mean the number
The DEL bit is
of pages of data to transfer.
ignored.

PAGES
4000 Special Physical Sector Condition.
It
.
transferred
1is
sector
One
ignored.

specified by BLOKNO which is to be interpreted

is
1is

1is, the high order 7-bits of
That
TTTTTTTSSSSS.
This
BLOKNO represent the physical track number.
1in the range 0-76 decimal (0-114
number must be
represent
The low order 5 bits of BLOKNO
octal).
This number must
the sector number on that track.
be in the range 1-26 decimal (1-32 octal).

DEL

= 0

Deleted data marks should not be considered.

as
CODE=4000)
(if
marks
data
deleted
2000 Handle
If writing a sector, write deleted data
follows:
Do not note this fact in STATUS word.
indication.
If reading a sector, set bit 5 of STATUS word to a
a
such
In
indication.
data
1 if read deleted
STATUS word may be nonzero even though
the
case,
Other STATUS bits
no physical error has occurred.
are relevant and STATUS negative means hard error.
MODE

100

Specifies transfer

12-bit mode.

Specifies transfer

in 8-bit mode.

1In 12-bit mode, the
0S/8 format uses 12-bit mode.
0S/8 floppy
an
comprise
that
words
12-bit
64

the
of
sector are packed into the first 96 bytes
sector, while the last 32 bytes contain random bit
the
on
byte
8-bit
In 8-bit mode, an
patterns.
of
8-bits
order
low
the
to
corresponds
disk
floppy
Data in the high order 4
a 12-bit word in memory.
bits of a word in memory is not transferred to the
floppy disk.

(decimal)
64
contains
sector
In 8-bit mode, a sector
data.
contains 128 8-bit bytes of data.
In 12-bit mode, a
of
words
12-bit

UNIT

Specifies the drive unit number.
It may be
0
or
The number 0 refers to the unit on the left of
1.

a dual drive.

RTS/8 SYSTEM TASKS

Regular condition

Special physical sector condition

Do not handle deleted marks

Handle deleted marks

Transfer in 12-bit mode
Transfer in 8-bit mode

1:
:

Left unit of dual drive

Right unit of dual drive

CODE = 4000 (bit O set to 1) transfers one sector specified by
BLOCKNO as follows:

Physical track no.

(0-114 octal)
Sector no. on track
(1-32 octal)

Unit Word Format - Floppy Disk Handler

Hard error

Deleted data

INIT done
Parity error

CRC error

Status Word Format - Floppy Disk Handler

If
The largest legal 0S/8 block number on a floppy disk is 755 octal.
block 756 is referenced, an error is generated. Use of larger block
Specifying an illegal
numbers may produce unpredictable results.
track or sector may produce an error with STATUS = 4000.
4-15

RTS/8

The

standard 05/8

0S/8

Logical

Track

Block

TASKS

Interleave

Scheme

is as

(octal)

Floppy

Sectors

follows:
(track/sector

1/1,

1/3,

1/5,

1/7

1/9,

1/11,

1/13,

1/15

1/17,

1/19,

1/21,

1/23

1/25,

1l/2,

1/4,

1/6

1/8,

1/10,

1/12,

1/14

1/16,

1/18,

1720,

1/22

1/24,

1/26,

2/1,

2/3

2/5,

2/7,

2/9,

2/11

2/13,

2/15,

2/17,

2/19

2/21,

2/23,

2/25,

2/2

2/4,

2/6,

2/8,

2/10

2/12,

2/14,

2/16,

2/18

2/20,

2/22,

2/24,

2/26

3/1,

3/3,

3/5,

3/7

not

used

mode.

4.4.2

SYSTEM

LINCtape

The

LINCtape

The

format

0S/8,

and

cannot

accessed

decimal)

the

12-bit

Handler

Handler supports
of messages to the

both

0S/8
and
DIAL
LINCtape Handler is:

format

LINCtapes.

ZBLOCK 3
MODE+UNIT

RW+PAGES+FIELD
BUFADD

BLOKNO
STATUS

where:
UNIT=

Specifies

the

7.
MODE=0

Specifies

contain

block.

0S/8

200

LINCtape

Mode.

201

unit

number

LINCtape

(octal)

words

range

presumed

per

physical

RTS/8 SYSTEM TASKS

=4000

Specifies DIAL Mode. A LINCtape is presumed
contain 400 (octal) words per physical block.

The LINCtape used is not checked to see

Note:

it is ©properly formatted for the specified mode.
Use of a LINCtape with improper physical format

will produce unpredictable results.
RW

Read data from LINCtape

=4000

Write data to LINCtape

PAGES

Specifies the number of 128-word pages to transfer
For example, PAGES=2000
octal).
100
(times
if
or 2048 words;
pages
octal
20
s
transfer
octal

pages=0,

pages

are

words

4096

transferred.

transfer
example,
FIELD=30, the transfer takes place in field 3).

FIELD

Specifies the PDP-8 field in which the
(For
(times 10 octal).
takes place

BUFADD

Is the

BLOKNO

address

starting

the

buffer

transferred.

Is the block number on the device from which the
All devices are assumed to
transfer will begin.
two
On O0S/8 LINCtapes,
have 256-word blocks.
consecutive physical blocks comprise one 05/8
logical block. Only the first 128 words in each
physical block contain meaningful data.
When running in DIAL

physical

mode,

BLOKNO

represents

In this case,

LINCtape

block

number.

not

transferred,

PAGES must be even because an even number of pages
PAGES is (incorrectly) odd,
If
is transferred.

the

last

PAGES=1

being
STATUS

page

which

will result in one block

except

1if

(2 pages)

transferred.

(checksum).
is the ones complement of tape check
0 on
always
is
STATUS
error.
no
means
0
value
The

Three software retries are
a Write operation.
Note that the
attempted on a checksum read error.

errors
hardware performs infinite retries on most
bad spot on
not mounted,
tape
(write-lock-out,

tape) and does not return control to
successful.

CAUTION

In the 0S/8 mode, the word following the
temporarily
1is
buffer
the
of
is
destroyed while a LINCtape operation
then
1is
1location
The
progress.
the
of
completion
upon
restored
RTS/8 is a
since
However,
operation.
executing
real-time system, code may be
while the tape operation is in progress.
word
this
The user must make sure that

referenced while the LINCtape
never
circumstances
no
Under
is being used.

should the word following the end of the

buffer belong to another
4-17

task.

RTS/8

until

RTS/8

0S/8 mode

DIAL mode

SYSTEM

TASKS

Unit number

Unit

4.4.3

Example

Word

Mass

Format

Storage

LINCtape

Handler

Call

CAL
SENDW
DTA

/SEND

DTAMSG
TAD

STATUS

SZA

CLA

/AND

JMP ERR

4210

4.5
The

FOR

THE

DECTAPE

COMPLETION

STATUS

CONTINUE

THE

OPERATION

HEADER

/DECTAPE

UNIT

256

/ADDRESS

/INTO

PROCESSING

/MESSAGE

/WRITE

BUFFER
STATUS,

/BAD - GO TO ERROR ROUTINE

/OK

ZBLOCK

MESSAGE

WAIT

/CHECK

DTAMSG,

/HANDLER

4
WORDS

BLOCK

/STATUS

FROM

FIELD

BRUFFER

(RECORDS

OPERATION

132

STORED

1
&

133)

HERE

POWER FAIL TASK
Power

recovers

option

Fail

Task

from

power

provides

the

failure.

mechanism

which

the

power-fail/auto-restart

the

processor

system
hardware

present and if the system parameter
PWRFAL was equated to
a
= value, the SPL (Skip on Power Low)
instruction is included in
the interrupt skip chain.
If
a
power
1low
condition
occurs,
the

nonzero

processor

comes

state

back,

POSTed

the

which

wakes

restores

the

clock,

present,

and

also

the

console

the

contents

this

table,

which

-1

and

state

performs

saved

processor

the

EFWT

the

Task

task

should

Power

Fail

action

internal

nothing

restored

terminal,
an

contains:

table.

should
(Event

Flags
be

and
for

done

Flag

Table
taken out

and

Task.
0S/8

each

halted.

Event

The

Power

Fail

they

terminal
task

Each

task

has

for

this

task

Wait)
of

bit

the

power

Flag

system

one-word

(default

should be
for this task
Event Flag Wait)

entry

When

Task
are
based

entry

value)

cleared

(i.e.,

this

RTS/8 SYSTEM TASKS

If the task should be DERAILed to location ADDR in Fhe
field in which it 1is executing as well as having its

ADDR

EFWT bit

‘

cleared.

Each task in the system may alter its entry in the Power
table

message

by sending a message to the Power Fail Task.
v

is:

Fail

Task's

of the
The format

3
ZBLOCK.

PWRMSG,

WORD

where:

is the new contents of the Power Fail Task's table entry

WORD

4.6

0S/8

_ for

sending

the

task.

SUPPORT TASK

The 0S/8 Support Task supports the execution
system

task

under

0S/8

the

operating

0S/8 is run in the top two or more

RTS/8.

memory fields under control of the KM8-E memory extension and
timeshare option (standard on PDP-8/E, 8/F, or 8/M with 8K or more of
core memory)

or TSS-8 time sharing hardware option.
NOTE

A jumper on the KM8-E module is used
to
The
function.
timeshare
the
select
in
Jjumper
this
module is shipped with
disabled).
function
(timeshare
place
The PDP-8A utilizes the memory extension
and timeshare
option
provided
by the
KM8-A extended option board.
A
switch
on
the
KM8-A
module is used to enable
the timeshare function.

The 0S/8
Support
Task
is
configured
at
system
startup time
to
establish
a
correspondence
between
O0S/8
devices and RTS/8 handler
by
ring-buffered
are
from O0S/8
output
Terminal input and
tasks.
several characters to minimize input loss due to the usurpation of the
CPU by tasks of higher priority.
Because
of
the
1large
number
of
trapped CDF instructions in 0S/8 and its Commonly Used System Programs
(CUSPs), response time is slower than a stand-alone
0S/8
system
but
still
guite reasonable.
The background 0S/8 task must have the same
system device that was used by the.0S/8 system
to
1load
RTS/8.
The
0S/8 Support Task cannot run on a stand-alone PDP-8 without 0S/8.
Several parameters in the system parameter file control
the
assembly
of
the
0S/8
Support Task.
The parameters and their meanings are as
follows:

- OSFLDS

Defined as the number of fields to be dedicated to
Example:
OSFLDS=2
memory for 0OS/8.

OSKBDV:

‘

specifies two fields or
:
_

Set equal to the keyboard IOT
terminal.
Example:

OSKBDV=03

specifies

code
the

‘the

use

05/8
the

console terminal keyboard of 0S/8.
Note:
O0S/8 requires its own dedicated terminal.
4-19

RTS/8

OSTTDV

Set

equal

SYSTEM

the

teleprinter

terminal.
Example:
console

OSFILL

OSTTDV=04
teleprinter

Specifies

how

line-feed

many

allows

high-speed

terminals.

DECwriter
to

null

the

this

the

Specifies

the

system

Example:

device

O0SSYSD=DTA

the

used

should

and

2400

driver

DTAQ0

This

Teletypes!

use

specifies

device.

0S/8

terminal.

parameter

allows

system

the

must

0S/8

OSFILL=4

0S/8

wuse

standard

VTO05.

OSSYSD

the

terminals

For

terminals,

characters

VTO05

code

0S/8.

zero.

Example:

IOT

specifies
for

character

0S/8
set

TASKS

baud

task.

the

0S/8

all

0s/8

NOTE

The

user does
not
need
to
include
a
terminal
driver
for
the 0S/8 terminal
device (it is built into 0S8SUP).

The

0S/8

CUSPs

system

except

FORTRAN

LAB

runtime

teleprinter
teleprinter.
printers
are
parameter

that

runs

BUILD,

under

the

O0S/8

BOOT,

PIP10,

functions.

All

Support

Task

runs
BASIC, and

INDUSTRIAL
references

the

are
diverted
to
the
specified
0S/8
References in 0S/8 to the LES, LS8E,
LP8
diverted to the RTS/8 line printer handler

LPT

Support

Task.

diverted

defined;

otherwise

References

the

corresponding

they

are

the

following

RTS/8

handler

executed

0S/8

and

keyboard

and

keyboard

and
1line

LV8

the

system

directly

device

one

BASIC

names

the

will

defined:

DTAQ0-DTA?7
LTAQ-LTA7

RKA(Q-RKA3
RKB(O-RKB3
RXAQ-RXA7

one

standard

not

defined,

0S/8

handler.

0S/8

will

perform

the

I/0

directly

using

the

In addition, the 0S/8 handlers SYS and DSK are
diverted to the handler
specified
by the parameter 0SSYSD.
Other references to I/0 under the

supported

loop.
Section

4.6.1
The

OS/8

system

References

may

4.7).

Mapping

parameter

Fields

HGHFLD

field
available to the
highest field available
OS8SUP

which
etc.

cause

handler

task

0S/8
are

maps

uses

mapped

0S/8

with
the

the

0S/8

called

0S/8

support

RTS8

Support

parameter

file

are

task

fields

into

real

hang

OS8COM

must

fields

actually

HGHFLD.

consecutive

fields

specify

the

highest

This is usually the
16K
machine).
The
follows.

0S/8

fields

beginning

The

1,
with

!Teletype is a registered trademark of the Teletype Corporation.
4-20

(see

Task

entire RTS/8-0S/8 system.
in memory (e.g., 30 for a

field

diverted

field

RTS/8 SYSTEM TASKS

HGHFLD-OSFLDS+1, proceeding upward. If an 0S/8 program references a
field greater than HGHFLD, unpredictable results will occur, as these

fields are mapped over the lower 0S/8 fields. The software core size
is correctly set to OSFLDS and should be used by multi-field 0S/8
'

programs.

4.7

0S/8 - RTS/8 COMMUNICATION

(OS8COM)

The 0S/8 Support Task contains a mechanism by which 0S/8 can talk to
an RTS/8 task. To perform this communication, the 0S/8 system must be

configured with a handler called RTS8.

This handler can be

dummy ;

In fact, it can be some other handler to
it need not do anything.
traps
Task
Support
The 0S/8
which the name RTS8 has been assigned.
The arguments that are passed to the RTS8
all calls to this handler.
handler by an 0S/8 program will be passed to an RTS8 task «called
The user is responsible for writing this OS8COM task.

OS8COM.

The 0S8COM task performs an

RECEIVE ER.

RTS/8

The

can

then

through

these

task

receive a message any time an 0S/8 program reads or writes to the RTS8
storage
This message looks like any other message to a mass
handler.
Bits 6 through
0S8SUP does make one change to the arguments.
device.
the buffer.
field of
8 of the function word originally contain the
When 0S8COM
field where 0S/8 expects the buffer to be.
the
is
This
the
gets control, these bits identify the actual field that contains
to

information

return

can

0S8COM

buffer.

0S/8

arguments.

4.7.1

Using

the

OS8COM Task

An 0S/8 program that runs an RTS/8 task as specified by the 0S/8
is

shown

the

following

example.

user

Example:

/LOCATION OF 0S/8 USER SERVICE ROUTINE
/PRINT MESSAGE "WHAT TASK WOULD YOU

USR=7700
JMS PRINT

/LIKE TO RUN?" ON THE 0S/8 TERMINAL
/READS RESULT FROM 0S/8 KEYBOARD
/RETURNS TASK NUMBER IN RANGE 1-77

JMS READ
'

DCA TASKNUM
CIF

ADDR

/BE

should

noted

FOUND)

ENTRY

POINT

FOR THIS

HANDLER

JMS I ENTRY
0
0
ZBLOCK 2
JMP I (7605

TASKNUM,

(HANDLER NOT

IS NOT REUSABLE AND THAT LOCATION

SET TO THE
CIF

RESIDENT

/ERROR

/NOTE THAT THIS CODE
IS

IT AWAY

/CALL USR
/TO DO A FETCH
/OF DEVICE 'RTS8'!
/DUMMY ADDRESS (HANDLER WILL ALREADY

HLT
/'ENTRY'

JMS I (USR
1
DEVICE RTS8

ENTRY,

/STORE

that

TASKNUM

/CALL HANDLER
/DUMMY READ
/TASK NUMBER
/DUMMY
/RETURN TO 0S/8

being passed as

the

second

argument

instegd of the first because 0S8SUP automatically modifies bits

the first argument, presuming that a mapped field
4-21

number

6-8 of

1located

RTS/8

there.

TASKS

058COM expects three arguments after

error

return.

These

Where

the

portion

task

that
OS8COM is

what

SYSTEM

0S/8

must

the

specified

program

has

handles

the

RTS/8

side

written

any

other

might

look

the

RTS/8

follows:

TASK=0S8COM

/OS8COM

INIWT=0

/COMES

CUR=40

/SPECIFY

ASSIGNED

PRIORITY

THE

HERE

INTO

RECEIVE

WAIT

FIELD

LEFT

/ADDRESS OF MESSAGE LEFT HERE

MSGFLD

/CDF

ISZ

MADDR

/POINT

FUNCTION

ISZ

MADDR

/POINT

BUFFER

TAD

MESSAGE

HLT
:

example

ADDRESS

/IMMEDIATELY

DCA

0S8COM

written.

RUNNING

/STARTING

RECEIVE

MSGFLD,

the

FILE

FIELD

CAL

MADDR,

CUR%10

*200
START,

user.

been
written,
communication must
user task, and
an

/PARAMETER

FIELD

the handler call plus an

the

/(SECOND

MADDR

0S/8

WORD

ADDRESS

ARGUMENT)

/GET

TASK

NUMBER

/RUN

THIS

TASK

CAL
RUN

/OS8COM WANTS TO BE
/PRIORITY THAN TASK
TAD

MSGFLD

DCA

EFCDF

TAD

(-5

TAD

MADDR

/GET

ADDRESS

HIGHER
IT IS RUNNING

EVENT

FLAG

/FOR MESSAGE
CAL
POST

EFCDF,

/POST

MESSAGE

HLT
JMP

START

/GET

ANOTHER

MESSAGE

In this example, the task number was put in the second argument
of the
0S/8
call.
However,
it
became the third word of the RTS/8 message
because OS8SUP always adds a word to the mass
storage
<call
argument
list,
namely the unit number.
For a description of the 0S/8 standard

handler

call

format,

Manual.

For

storage

devices,

4.7.2

Other

see

Section

description

see

Section

4.4

1If

the

RTS/8

posted

the
2.

the

standard

this

error

Arguments

handler

OS8COM

employed
STATUS

0S/8

Software

message

format

Support
for

mass

manual.

return

may

passed

the

by the

word

nonzero,

list.
3.

4.1

Techniques

techniques which can be
1.

back

(word

then

handler

relocated

before

the

handler

being

<call,

followé:

the

taken

call.

passed

are
5)

return

0S/8

If more than three words
of data need
from
O0S/8,
the
wuser can pass a CDF
where the data resides.
If
the
CDF
argument

user

message

0S/8

:
through

the

argument

to be passed to
O0S8COM
and address of the area

occurs

the

automatically

OS8COM.

first
will

RTS/8

4.8

SYSTEM TASKS

0S/8 FILE SUPPORT TASK

create,

and

allows

(OS8F)

The 0S/8 File Support Task

other

delete files in 0S/8 directories.

tasks

look

up,

This task is included

can
wuser
the
but
in the same source file as the 0S/8 Support Task,
independently of that task (depending on which tasks are
it
assemble
The format of messages to OS8F
defined in the system parameter file).
'

is:

OSFMSG,

ZBLOCK

" 10+UNIT+FUNCT
DEVHND
FILPTR

STATUS

BLOKNO
LENGTH

where:

DEVHND

Is the task number of the handler

for the

desired

Is the unit number on which the operation

is to be

device.

UNIT
’

performed.

FUNCT

Represents the function to
have the following values:

be performed.

can

returns
Looks up the specified filename and
its starting block number in BLOKNO, and its
complement
two's
a
(as
LENGTH
length in

number)
.

2000

Enters the specified filename into the first
space (on the device) whose length is
empty
LENGTH.
in
wvalue
the
equal to or exceeds
Returns
file in

the starting block number
BLOKNO.
If a file of the

previously
deleted.

4000
FILPTR

,
STATUS

existed

a pointer

used

4-word

to generate

Describes the

final

The

>2
-1

filename

unchanged.

status

the

same

filenames.

the

operation

Operation successful.
File not found on Lookup or
No room for file on Enter.

I/0

PAL8 pseudo-op FILENAME

these

follows:

0
1
2

LENGTH

Deletes the specified filename.

field as the message.

can be

device

the

The value of

of the new
same
name

error

occurred.

The

Delete.

wvalue

hardware error status of the device.
Invalid directory on device.

the

RTS/8

SYSTEM

TASKS

Function:

0 Lookup
1 Enter

2 Delete

3 Unused
Unused

Task number
Unit

OS8F

Call

Function

Word

If both OS8F and the 0S/8 Support Task are present
1in
a
interlock
is
set
up
to
prevent simultaneous updating

system,
an
of directory
blocks by both systems.
Because 0S/8 tends to leave directory
blocks
in
memory
for
1long
periods
of
time, this interlock scheme causes
lengthy delays for the OS8F task.
Before a Delete or Enter
operation
is performed, OS8F waits until 0S/8 is in a state in which:

There

active
to

05/8

loaded

Look

1is

corresponding
has

USR

just

into

operations

are

not

The

UNIVERSAL
DIGITAL
(UDC/ICS) HANDLER
UDC/ICS

various
two

types

include

handler

types
of

gives

Keyboard

the

Monitor,

since

they

CONTROLLER/INDUSTRIAL

the

user

the

functional

immediate

and

UDC/ICS

the

file

sending

and

analog

0S/8

device

UNIT.

interlocked

UDC/ICS

action:

reading

and

Command

core.

directory.

4.9

temporary

DEVHND

modify

CONTROLLER

capability

devices.

This

associated.

and

not

digital

Decoder,

the

SUBSYSTEM

control

the

handler

performs

Immediate

actions

values

appropriate

functional devices.
Associated
actions
can
be
1linked
to
specified
events
within
the UDC/ICS (counters overflowing, switches
being thrown).
The associated actions can do the following:
l.

2.
3.

Run

a specified task when the event occurs
Set the' Event Flag when the event occurs
DERAIL a specified task when the event occurs

The

number

determined

assembly

associated

parameter

the

requests

size

RINGBUF.

that

the

can

buffer,

pending

which

simultaneously

specified

the

RTS/8

SYSTEM TASKS

The UDC/ICS handler permits the following operations:

Analog Output

- send a 10-bit value to an analog channel

Analog Input

- accept input from analog subchannel

Digital Output

- send a 12-bit value to a digital channel

Digital

Get Generic Code

- determine

Enable Counter

- permit interrupts from a counter channel

Read Counter

- read

Disable Counter

- disable

Enable Contacts

- permit interrupts from a contact channel

10.

Change Of State

- find the current COS value for a contact

11.

Disable Contacts

- ignore interrupts from a contact channel

- read a digital channel

Input

generic

the

code

for

specified channel

current

value

the

counter

channel

interrupts

from

channel

of
format
Each operation is discussed in detail below, including the
The first three words are
for specifying the operation.
message
the
11
the
of
one
Word 4 specifies
required for use by the Executive.
GC=3;
DI=2;
DO=1;
AO=0;
operations which are as follows:
UDC/ICS
5
Word
AI=12.
DCT=11;
CsS=10;
ECT=7;
DC=6;
RC=5;
EC=4;
Words
the channel being used for the indicated operation.
designates
and
operation,
6 through 8 may be required to completely specify the
The word that
operation.
the
upon
dependent
1is
used
number
the
follows the last word specifying the desired operation is used for the
Word 10 of all UDC/ICS messages
value returned.
the
or
read
value
contains

the

The general
ZBLOCK

error

format

state.

for

UDC/ICS message

is:

OPERATION
CHANNEL

OPWORD1
OPWORD?2

OPWORD3

VALUE
STATUS

4.9.1

Analog

Format:

Output

channel

number
subchannel & wvalue

Channel number is the analog output channel.
The subchannel and value
word
1is formed by the subchannel (0-3) in bits 0 and 1 and the 10-bit
value

in bits

operation:

2-11.

For

example,

message

for

analog

output

RTS/8

AQEX,

4BLOCK

SYSTEM TASKS

/ANALOG

4614
ZBLOCK

AOER,

OUTPUT

/CHANNEL
3

VALUE

614

/ERROR INDICATOR

/SUBCHANNEL

N__

Subchannel *_l
Value

Subchannel

4.9.2

Analog

Format:

and

Value

Word

Format

- UbC/ICS

Handler

Input

channel

subchannel

gain

answer

where
word

channel
need

only

the

analog

specify

9-11

the

input
gain

channel.

bits

for UDC, and 5-11 for ICS.
The
(enable conversion) and read control

The

ICS

analog

(octal)

since

slots

placed

the

converters
all

must

converter

ICS

unit.
After
answer word.

have

The

1-3

subchannel

and

handler

the

automatically

(UDC

addresses

which

modules

must

conversion,

bit

are

located

'the
.

1ICS

less
in

the

digitized

Gain
ICS read control register;

(for UDC, bit 8)
ICS subchannel;

{for UDC, bits 9-11)

and

Gain

Word

Format

UDC/ICS

Handler

gain

sets

Enable conversion

Subchannel

and

subchannel

bits

bit
bit

0
4).

than

first

value

RTS/8 SYSTEM TASKS

An example of a message for an analog input operation is as follows:
3

ZBLOCK

AIEX,

AI
17

/ANALOG INPUT
/CHANNEL 17

AIANS,

AIERR,

/SUBCHANNEL 3, GAIN 1
/RESULT HERE

»
2

ZBLOCK

/ERROR INDICATOR

The user should ensure that for each major channel there is sufficient
. UDC; 5 milliseconds for ICS)
for
time (approximately 250 microseconds
for each subchannel conversion to be completed before anotherfor isa
indicated. In general, it may be helpful if all A/D conversions

major channel are initiated from the same task.

Digital Output

4.9.3

Format:

channel
value

Channel is a legal digital output channel and value is the

be output.

DOEX,

DOER,

Format:

ZBLOCK

Digital

ZBLOCK

DO
20

7777

4.9.4

number

For example:

/DIGITAL OUTPUT
/CHANNEL 20.

/VALUE = 7777
-

/ERROR INDICATOR

Input

DI
channel
result

Channel is the appropriate

digital

input

contain the value of the channel when read.
DIEX,

DIANS,
DIER,

4.9.5

GC
Format:

ZBLOCK

DI
27

channel

/DIGITAL INPUT
/CHANNEL 27

Generic

Code

channel
result

result

will

/VALUE OF CHANNEL 27 WILL BE PUT

/HERE

ZBLOCK

and

For example:

/ERROR INDICATOR

RTS/8

The

generic

code

the

example:

GCEX,

ZBLOCK

SYSTEM

specified

channel

/DETERMINES

27
0
ZBLOCK
GCER,

Generic

2,3

are

Contact

Enable

Format:

/GENERIC

CODE

follows:

Interrupt

GENERIC

/ERROR

result.

For

PUT

CODE

HERE

INDICATOR

interrupt;

Modules;

converter.

4.9.6

put

/CHANNEL
3

codes

error;

GC
GCANS,

TASKS

Counter

Controller

Module;

A/D

the

Counter

channel

initial
reload

wvalue
value

event

action
address

Channel

first

the

value

with

counter

which

channel

loaded

into

enabled,

that

channel,

initial

and

value

reload

value

the

reload the channel
after
every
event.
If
the
0, the counter is not reloaded.
The event action and
address words specify what happens
when the counter interrupts.
There
are
three
mutually exclusive possibilities, indica
ted by setting the
appropriate bit in the event action
word as follows:

reload

value

Bit

Set

Event

Wait

Flag

execution
Address

Bit

Run

a task
specified
Address

Bit

that
by

word

DERAIL the
address
and

Bit

not

specifies

sent

bits

the

4-11

that
only

job;
the

sent

word.

message;

the

task

by the DERAIL operation
address
of
the
DERAIL

subroutine

calling

occurs.

run
action

event

the

continue

event

message;
of

used

the
The

the

this
when

used.

task

word

subroutine.

field

of
this
job
word not used.

task.

must

the

same

Do action just once.
If
bit
3 = 0,
specified
action
1is performed after each interrupt.
Bit 3
indicates whether action
is
to
occur
once
or

repeatedly.

Several

enable

ECEX1,

counter

ZBLOCK

follow:

/ENABLE

/CHANNEL

/INITIAL

VALUE

7700

7710

4000

ECER],

examples

0
0

/RESET

COUNTER

OF 7700
AFTER EACH
FLAG ON EVENT

7710

/POST EVENT
/IT OCCURS

/UNUSED
/ERROR INDICATOR

EVENT

EVERY TIME

RTS/8

ZBLOCK

ECEX2,

SYSTEM TASKS

COUNTER

/ENABLE

4
1205
0
2016

/CHANNEL

/INITIAL VALUE OF

1205

RESET

/DON'T

/RUN TASK 16 ON EVENT EVERY TIME

/OCCURS
/UNUSED

ECER2,

/ERROR

INDICATOR

/ENABLE

COUNTER

5
10

/CHANNEL

7700
1015

/RESET

INDICATOR

0
ZBLOCK

ECEX3,

/INITIAL VALUE OF

7700

5620

/DERAIL TO TASK 15 EVERY TIME
/OCCURS
/AT LOCATION 5620

ECER3,

/ERROR

Read

4.9.7

Counter

Format:

channel
result

where

channel is the counter channel whose
For
That value is placed in result.

read.

ZBLOCK

RCEX,

RCANS,

4.9.8

1is

PUT

HERE

Dbe

COUNTER

/READ

6
0
ZBLOCK

/CHANNEL 6
/VALUE OF CHANNEL

/ERROR

Disable

wvalue

example:

RCER,

current

INDICATOR

Counter

Format:

channel
where channel
ignored.
For
DCEX,

DCER,

is the counter channel from which interrupts are
example:
ZBLOCK

/DISABLE

COUNTER

/CHANNEL

ZBLOCK

/ERROR

4.9.9

ECT
Format:

Enab.

Contacts

ECT

bit

& channel
event action
address

INDICATOR

RTS/8

where

the

from

which

and

the

Event

bit

channel

enable

contact

bit

and address
counter function.

ECTEX1,

2ZBLOCK

word

are

specified
For example:

/ENABLE

5401

/FROM

BIT

/RUN

TASK

ZBLOCK

13(OCTAL)

AFTER AN

CHANNEL

EVENT

/ENABLE

1001
4000

CONTACT

/FROM BIT 2 OF CHANNEL 1
/ON 1ST OCCURRENCE OF EVENT,
/EVENT FLAG

Format:

OCCURS

POST

/ERROR

Change

the

are

1in

CONTACTS

ECT

INDICATOR

messages

4.9.10

manner

/ERROR

ZBLOCK

Twelve

same

ZBLOCK

ECTE2R,

the

ECTEX2,

ECT

2013
ECTE1R,

TASKS

specifies the bit on the contact
channel
interrupts.
Channel is specified in bits 4-11
packed in bits 0-3 as a value from 0-13(o
ctal).

action

enable

SYSTEM

required

CSs

enable

INDICATOR

the

entire

channel.

State

‘

channel
result

where

channel

value

COSEX,

the

contact

placed
ZBLOCK

channel

result.

/RESULT

ZBLOCK

4.9.11

DCT

/ERROR

Disable

0-3

disabled.

INDICATOR

Contacts

channel

For

ZBLOCK

example:

contact.
4-11

/DISABLE

5401

/FROM

ZBLOCK
0

That is,
bits
specify the channel

DCT

CONTACTS

CHANNEL

/13 (OCTAL)
DCTANS,

state

HERE

bit & channel is specified as in enable
specify
the bit (0 - 13 octal) and bits

DCTEX,

DCT

bit
where

change

Format:

current
example:

/READ COS
/CHANNEL 1

COSER,

whose

Cs
COSANS,

For

4
/ERROR

INDICATOR

BIT

RTS/8 SYSTEM TASKS

4.9.12

UDC/ICS Assembly Parameters

The UDC/ICS handler has several assembly parameters that the user must

specify to indicate the UDC/ICS configuration.

The number and address

is required only for those modules that perform interrupts.

follows:

RINGBF

Number of interrupts that can

NCNTR

Number of counter modules.

NCNTC

They

are

the

‘

ring

Number

stored

buffer.

of contact modules.

‘Number of afialog inéut converter modules.

NAD

The modulés

Address of the first counter module.

FCTR

must be at contiguous module addresses.

module.
interrupt
contact
of the first
Address
at contiguous module
be
must
modules
Interrupt

FCT

addresses.

Analog
module

Address of the first A/D converter module.
contiguous
at
must be
modules
input

FAD

addresses.

NMPLX

Number of multiplexer modules per analog converter
(ICS

only).

sizes -of several
the
specify
to
These parameters are used mainly
30(octal) words per
as
allocated
handler,
UDC/ICS
the
in
tables
contact module, 3(octal) words/counter module, and 16 (octal) words per
The UDC/ICS handler currently assumes that the handler
analog module.
(although
field
are entirely within the same data
tables
its
all
and
the

user

could easily reprogram this).

The user must keep in mind when establishing RINGBF size that

the

buffer is full, UDC/ICS interrupts are disabled until there is room in
buffer;
Also, each interrupt requires two entries in the
the buffer.
that

is,

4.9.13

the

actual

buffer

UDC/ICS Error

size

RINGBF.

Conditions

To indicate error conditions, the UDC/ICS handler places
a
value
the tenth word of the task's message.
The values and meanings are:
Value

Meaning

Illega} generic code

1
-

for

specified

Channel or subchannel value not valid

Illegal‘fuhction code

UDC/ICS control not responding

hardware

channel

and

operation

error)

4-31

(power dff or

RTS/8

The

user

should

condition
Only

puts

errors

manner,

are

4.10

device.

Cassette

There

and

this
at

may

the

are
1.

the

noninterrupt
also

Generic

error

codes

are

returned

faulty

UDC/ICS

encountered

Handler

(CSA)

records
functions

allows

on
DEC
(such as

Handler

general

can

categories

the

user

cassettes,
rewind and

operate

eight

cassette

read

Utility

functions

rewind,

backspace

gap,

skip

backspace

block

of
the
message
utility call.

handler

4.10.1

Handler

The

format

call

is:

ZBLOCK

CALL

UNIT

FIELD

error

this

hardware

interrupt

and

read

and

write

Wwrite

file

sequence.

The

units.

write

and

defines

as
well
as to perform
write
end-file).
One

operation:

functions

word

The user should call these functions in a
first

time

indicate

Handler

gap,

word.

HANDLER

Cassette

two

check

TASKS

location.

ignored.

variable-length
various special
copy

they

CASSETTE

The

encountered

thus

functional

time

initialize

SYSTEM

file

gap,

file

gap

meaningful

the

cassette

unit

and

either

the

Function
message
'

the

Cassette

Handler

when

using

handler

NONSTORE

BUFADD

SIZE

STATUS

For

handler

defined

Word

function,

follows:
1

bit

bit
bits

1 =0
9-11

bit

bits
bit

=1
6-8
11

the

words

after

Utility

the

RTS/8

message

header

call

Handler call
Cassette unit
Read

Write

Field of buffer
not store data

(applicable

only)

Word

Buffer

address

Word

Record

size

Word

Status

return

bits

4-11

read

are

RTS/8

Handler call}

Utility call

SYSTEM TASKS

Unit

Unit Word

Format

- Cassette

Handler

Read

Write

—_

Field

Read into memory

1: Check data

Function Word

Format

Handler

Call

Cassette conventions specify a record size of 200 bytes, but the
user
can
use
any
size
up
to
377 (8 bits are transferred).
The buffer
specified by the message cannot cross field boundaries.
For
a
read
operation,
the
buffer
1is optional (although its word in the message
must be included), according to
bit
11
of
word
2.
The nonstore
capability
can
be
used
for
advancing through a long file.
Word 5
contains the contents of status register B, which is
defined
by
the
setting
Bit

follows:

Meaning

O 00~

CRC /block
Timing
EOT/BOT

error

nmwu

EOF

—

bit

Drive empty
Read/write
Write lockout
Ready

RTS/8

SYSTEM

TASKS

Word

Format

CRC/block error
Timing
EOT/BOT
EOF

Drive empty
- Read/write
Write lookout -

Ready

the

check

example

buffer

end

Status

Return

each

cassette

for

errors

of a
starting

MSG1,
:

cassette

operation,

encountered.

not

MSG2,

/HANDLER

v
v

store

ZBLOCK

200

bytes

format

is:
ZBLOCK

CALL+UNIT
FUNCTION

STATUS

100
bytes
follows:

/WRITE

OPERATION

FROM

Word

from

/BUFFER AT 1200
BYTES LONG
/STATUS RETURN
from

unit

the

2 THE
WHICH IS

message is:

0000

0200
0000

/STATUS

UNIT

FIELD

/HANDLER OPERATION
ON
/READ AND DON'T STORE
/UNUSED

Utility

The

examine

0001

call

write

/100

4002

4.10.2

should

message to
to cassette unit 3

0000
and

user

Handler

ZBLOCK 3
4003

1200
0100

read

the

handler

21200

4020

Cassette

/200

UNIT

BYTES
RETURN

Function
message

the

Cassette

Handler

when

using

utility

RTS/8 SYSTEM TASKS

header

For a utility function, the words after the RTS/8 message

defined

are

follows:

Word 1

bit 0 = 0

Utility call

Word 2

(function in bits 6-8):

Handler call
Cassette unit

bit 0 = 1
bits 9-11

Rewind

30 = Backspace file gap

40 = Write file gap
50 = Backspace block gap

70 = Skip to file gap

Word

return

Status

10 | 11

Function:
1 Rewind

3 Backspace file gap
4 Write file gap

5 Backspace block gap
7 Skip to file gap

Function Word Format - Utility Call

For example, to request a rewind on unit 1, the message is:
MSG3,

ZBLOCK

0001

/UTILITY OPERATION ON UNIT 1

/REWIND
/STATUS RETURN

0010
0000

except
times,
If an error is encountered, the operation is retried 3
placed on a write operation or an error
1is
out
1lock
write
a
when
occurs while

reading

CRC.

The CAPS-8 User's Manual

(DEC-8E-OCASA-A-D)

is suggested

reading

for

users who are unsure of cassette conventions.

4.11

CASSETTE

FILE

SUPPORT

HANDLER

The Cassette File Support Handler

(CSAF)

the

DEC

standard

requires

the

cassette

supports

cassette format and allows the calling task to look up and enter files
on cassettes in that

handler

(CSA)

format.

This

to perform the actual

handler

I/O operations involved.

The cassette operations ENTER, LOOKUP and CLOSE are performed
by
the
File Support Handler (CSAF) which in turn calls the cassette
Cassette

ENTER and LOOKUP require the user to put’' appropriate
handler (CSA).
in a record header area with which CSAF performs the file
information

operations.

The header area must be at least 40(octal)

cannot cross

field boundaries.

words long and

Word

CSAF

message

Address
status

TASKS

are

follows:

bit

bit
bit
bits

[

SYSTEM

[

for

definitions

Pl—'ll ([

Word

O No

RTS/8

header

return

for

ENTER

Word

Field

Word

Status

return

for

return

contents

all

cases,

the

status

header

the

for

and

LOOKUP;

ENTER and

ENTER

and
of

(bits

LOOKUP

Status

—

LOOKUP

Function:
1 Close

2 Lookup
4 Enter

Unit

For

ENTER

cassette

format

and

Word

Format

LOOKUP,

standards

the

Cassette

File

format

(and

follows:

of the
therefore is

Support

Handler

header area must conform
compatible with CAPS-8).

Byte

with
This

Use

Filename

Filename
File

12-13

extension

type

ASCII

undefined

File

record length.
Currently word 12 must

14-15

Unused

16-23

Date

(ASCII)

ddmmyy
24-35
is

justified
For

ENTER

area

operation,

found

Unused

Reference

header

specified

the

8-bit

bytes,

file

with

the

specified

-36

unit,

one

name
it

per

word,

specified
deleted.

right

the

RTS/8 SYSTEM TASKS

d file |is
For a LOOKUP operation, the record size of the specifie
returned in location header+13 (byte 13). If the file is not found or
if an error occurs, this location contains 0.

The CLOSE operation is automatically followed by a REWIND.
Examples of messages follow.
3

ZBLOCK

MSG4,

4000

/ENTER ON UNIT 0

/INFORMATION IN HEADER STARTING AT

6400

/6400

/OF FIELD 1

0010

/STATUS RETURN

0000
Z2BLOCK

MSG5,

4.12

1003
0000

/CLOSE ON UNIT 3
/STATUS RETURN

PDP-8A NULL TASK

The PDP-8A Null Task counts from 1 to 9999 in decimal 1in the AC
It also counts from 1 to 7777 in octal in the MQ display.
display.
The source which is called NULL8A, takes up

configure

the

null

task

into

The

page.

user

can

RTS/8 system by inclusion in the

parameter file of its task name and the statement
NULL8A = NTASKS+1

KL8-A SUPPORT

4.13

The KL8-A is a 4-serial line asynchronous multiplexer for the PDP-8/A
that has three lines with partial modem control and one line with full
modem control. KL8-A support is available to the RTS/8 Executive, the
To use KL8-A support, the user
and the 0S/8 Support Task.
TTY task,

should perform the procedures that

are

described

the

following

sections.

4.13.1

Executive

KL8-A Support

The symbol KL8A in the parameter file is set to a value equal

number

being used,

KL8-A

units

being employed by the user.

then KL8A=1 is spr-ified.

If the symbol

'KL8A' is set to 0 or undefined in the

no KL8-A support will be provided by RTS/8.

KL8-A support is provided by the RTS/8

KL8ASR.PA must be assembled as
.PAL

KLB8ASR<PARAM,KL8ASR

follows:

Executive.

the

If one KL8-A is

parameter

file,

source

file

The

RTS/8

The parameters

in the parameter

KL8A

[]

follows:

undefined

SYSTEM

TASKS

file that relate

means

that

means

support

KL8-A
for

desired.
Each
four lines.
KL8ADV

Device

<code

Default

1is

for

1lines

1is

KL8-A provides

the

first

KL8-A.

consecutive

two

device

codes

41).

(e.g.,

and

KL8-A's are used, they
consecutive device codes.

multiple

have

must

page

for

routine.
1).

l-page

KL8-A

physical

uses

KL8A

Task

desired.

KL8-A

Specifies

TTY

Each

connect

4.13.2

service

are

40.

should
KL8ACT

to KL8-A service

The

KL8-A

located

long

for

start

Default

1is

KL8-A
7400

connect

field

(if

routine

one

page

for

every

KL8-A
and
grows
a
three additional KL8-A's

used

(or

part

thereof).

value

KL8-A

support

this

parameter
routine

against

the

location

7577.

end

The

default

such

gets

field

that

Jjammed

ending

the
up

Support

KL8~-A

support in the TTY task is initiated by setting symbol
KL8A
in
parameter
file
+to
nonzero.
Then the KL8-A line to be used is
specified in place of the terminal IOT
device
code
plus
100.
For
example, if the TTY task is to control line 3 of a KL8-A,

the

TTDEV

is
to

KL8ALINE+3

specified
have

the

parameter

value

100

file.

the

(The

parameter

symbol
file.)

KLS8ALINE
If

than

defined
one

KL8-A

interface is used, the lines are numbered consecutively beginning with
0 and continuing across interfaces.
Thus, KL8-A logical line number 5

actually

Physical
KL8-A

support

Support

is physical line number
lines are numbered from

but

included

4.13.3
KL8-A

requires

does

KL8-A

for

the

set

specified

both

the

O0S/8

0ld

for

the

0S/8

similar

using

where

"line"

field

the

TTY

and

that

KL8ALINE+2

interface.

for

(3-page)

Executive

KL8-A

TTY

support

task.

First,
the

for

the

TTY

task.

the

symbol KL8A is
particular KL8-A line

form

100+line in place of the
of the KL8-A that is 0s/8
conveniently defined as being 100

used.
The symbol KL8ALINE is
parameter file.
For 0S/8 support,

OSTTDV

task.

described

Then,

the

being
in the

line

KL8-A

Task

used.

code,

the

new

Support

device

second

size

file.

number

the

memory

procedure

parameter

(2-page)

the

following

nonzero

additional

increase

Support

support

However,

not

number

the parameter

RTS/8

SYSTEM

TASKS

Wben more
specifies that terminal output goes to line 2 of the KL8-A.
KL8-A is used, the lines should be numbered successively as
one
than

described for the TTY task support in Section 4.13.2.

a User

KL8-A Support for

4.13.4

Task

KL8-A

The KL8-A support in the Executive allows a user to program the
in

manner

similar

the

KL8-J.

skip
interrupt
the
First, the user task must insert the KL8-A into
and provide a keyboard and printer interrupt routine to service
chain
the line he wishes to use.
This is
accomplished
via
the
following
code:
CDF

CUR

CIF

IOF

TAD

(LINE"4

JMS

(KLBACT

KEYBD

INTERRUPT

PRINTER

ROUTINE

INTERRUPT

ROUTINE

where LINE is the line
number
of
numbers
are consecutive, begin at
KL8-A line

the

number

KL8-A

specific

actually

(0,1,2...)

KL8-A

and

the
KL8-A
desired.
KL8-A
1line
0, and may span across KL8-As.
The
the form 4a+b where a is
the
number
b
1is the physical line number of the

(0-3).

Second, the user must define the instruction corresponding to the
instruction that will be used when outputting to the KL8-A line.
For example, if the device code for the KL8-A
will probably want an instruction such as

40,

then

the

TLS

user

TLSX=6404

his

task.

Normally,

program would

contain

the

following

code

output

the

KL8-A

to output a character,

the

following

this

character:
TAD

char

TLS

When

using

calling

would

KL8-A,

the

KL8ACT.

task

Then,

would

first

connect

support

code

used:

TAD

line

TAD

char

~400

TLSX

The

4.14

The

not

EXIT

cleared

the

TLSX.

TASK

Task

not

required

for

RTS/8

included
in
task performs

a
system,
it is run
the same functions as

command,

is,

that

it waits

for

operation.

by the MCR EXIT
those performed

any pending

4-39

command.
by
the

operations

task

The
MCR

EXIT
EXIT

completed,

RTS/8

SYSTEM TASKS

then turns off interrupts and returns to the
In

addition,

special
done

EXIT

exit processing

message

(in

the

having
contains

the

same

the
a

the

just

user

single

field

the time
routines
to

Task

allows

prior

task
word.

the

send

0S/8
task

shutting
a

This

message)

user

message
word

operating

request

down

RTS/S8.

to
the

the

EXIT

address

that

will be called
EXIT
command
is
in the order that

of the exit.
When the
MCR
will be called and executed
EXIT Task.

NOTE
Any

message

not

MCR

get

REquest

Task.

sent

posted.

command

the

EXIT

Also,

run

Task

not

use

the

will

the

EXIT

systenm.

additional

This
Task.

(via

1is
This

routine

a JMS) at
typed,
these
they were sent

CHAPTER

MONITOR CONSOLE

ROUTINE

The Monitor Console Routine (MCR) provides functions that the user
request
from
the console terminal to control, inspect, and debug
some extent) his system.
The

MCR

indicates

printing

that

active

the prompting character

MCR command

consists

terminated

by either a carriage

and

> on

command

ready

the

word

commands

system console

terminal.

followed

return or

can
(to

arguments

an ALTMODE.

Only the

and

first

two characters of the command are
significant
except
for
the
EXIT
command.
Commands
can
be
a
maximum
of 40 characters long.
If a
carriage return terminates the command line, the MCR
returns
to
the
terminal
for
another command when it finishes processing the current
command.
If an ALTMODE terminates the
command
1line,
the
MCR
puts
itself
in
a wait state when it finishes processing the command.
The
MCR is brought out of this wait state by typing
“C
(CTRL C)
on
the
console terminal.
When the MCR prompts
RTS/8
task
can use

with its > and
the terminal.

is waiting
Therefore,

for
1input,
no
other
if the terminal is used

for something other than
error logging), type “C,

an
exclusive
MCR
terminal
(for
type the MCR command and terminate

ALTMODE

procedure

character.

This

prevents

the

MCR

from

1instance,
it with an

tying

the

several

MCR

terminal.

5.1

MCR

COMMAND

ARGUMENTS

Certain syntactic constructions are
commands.
The definitions of these
A

single

used

as arguments
arguments follow.

comma

interchangeably
commands.

Task-1ID

Task-ID

name.

either
it

single

space

separate

octal

number,

may

arguments

number

used

represents

MCR

a
the

internal RTS/8 Task Number.
This number also
designates
the priority of a task.
If it is
a name, the first 4 characters
of
the
name
are

looked up in the MCR's
a Task Number.

Task

Name

table

produce

Time-of-day

Address

time-of-day

represents

hours

represents

minutes

Address

digits

that

5-1

the

form

past

octal

hh:mm,

where

and

midnight

hh:00.
number

represents

from

PDP-8

memory

MONITOR

CONSOLE

address.
digits

Word

the

1long

digits

are

Word

ROUTINE

address
is

0.
an

octal

number

long.

5.2
In

MCR
the

MCR

the

square

command

are

not

the

The

choices

points

the

user

[mm/dd/yyyy

mm/dd/yyyy,

portion

others

and

the

are

equal

days

current

five
order

digits

the

system

not

define

date

parentheses,

the

symbol

asterisks

CLOCK

the

clock is not in the system) ,
order to shorten the MCR
code

specified,

becomes
the

The

only

second

printed

the

last

assumed.
midnight,

time-of-day.

preceded

date,

length.

systen

mm/dd/7y.
>DATE

did

embedded

Commands

portion
enclosed

[,Time-of-day]]

ignored since
197
automatically
incremented
at

being

are

().

file (indicating that
MCRCLK is set to 0 (in

symbol

DAte

date

year

([])

present

length).

5.2.1

from

than
high

that follow, the
significant
capitalized.
Optional arguments are

exclamation

parameter

the

descriptions

word

brackets

separated

(*)

1less

COMMANDS

RTS/8

assumed

The
but

the

RTS/8
all

argument,
If

system

digit

For

the
the

system
date
months are treated

specified,

arguments

console

date.

significant;

are

terminal

1is

specified,
in

the

is
as

set
the
form

07/31/76

>DATE

07/31/76

5.2.2

TInme

[Time-of-day]

If
a
Time-of-day
time-of-day.
If

time-of-day
>TIME

command

is
specified,
it
becomes
the
no
argument
is
specified
the
current
printed out on the console terminal in
the form

system

system
hh:mm.

14:00

>TIME

14:00

5.2.3
The

NAme

Task-ID,Newname

character

specified
lost.

Newname

stored.
message

string

Newname

this

command.

can

Newname

any

should

becomes

The

length,
not

but

the

results.

Task

number

REPORT

given

the

name

REPO.

5-2

new

name

only

name

Examples:

>NAME

the

o0ld

name

the
any

that

first
other

the

task
4

(if

task

any)

characters
task

is
are

error

MONITOR CONSOLE ROUTINE

>NAME

REPORT,FOO

Task number 7, which is known as REPO, is now known as FOO.
NOTE

name

MCR

the

initializes

system

The

time to contain the
assembly
at
table
names of any DEC-supplied tasks that are
the parameter file (e.g., if
in
listed
the
1in
defined
1is
CLOCK
symbol
the

parameter file as CLOCK=2, task number 2
the
editing
By
CLCK).
gets the name
MCR.PA after

file

task names can be

by modifying

5.2.4

REquest Task-ID

label

the

NMTBL,

permanently

table.

the MCR name

[, (@Time-of-day !

Interval) [,Interval]]

The REguest Task-ID command requests a task
only

Task-ID

interval,
Interval

or
is

at
of

specified),

a given
the

run

immediately

a given time-of-day,

(if

after a given

interval.

form:

nH
nM

n
n

hours
minutes

seconds

system

Requesting a

user

included

task clears

the

ticks

RUNWT bit

the

Task

Flags

Table

entry

for
that
task.
The interval, given in the third argument, specifies
the period at which the task is rerun.
If the parameter CLOCK in
the
RTS/8 parameter file is not defined, the second and third arguments of
this command are ignored and the given task runs immediately.
In
the

examples given below, three different formats are used for the REquest
command, but only the first two characters are significant except when
using

the

EXIT command.

Examples:

>REQUEST

runs

task

immediately.

>RE

FO0,@2:00

runs

task

FOO at

am).

>RE

2:00 am

(if

after

2 am,

minutes

from

now

clock,

this

command

FOO will

run

tomorrow

five

minutes

5,10M,5M

runs task number

*+en

and

every

thereafter.
>REQ

HIPR,1T,6T

machine

immediately
thereafter).

with

(that

1is,

.016

seconds

from now,

runs

and

the

task

10 times per

HIPR

second

MONITOR

CONSOLE

ROUTINE

NOTE
If,

the

time

the

REquest

command

executed,

(which

after

typed

in)

the

task

does

not

have

the

it is
Task-ID

set

may

several

hours

specified
RUNWT

bit
its Task Flags Table entry,
then
the
REquest
command
1is
a
no-op
(no
operation), that is, the command has
no
effect.
Similarly,
the
task will not
run

5.2.5
The

STop

Task-ID

that
the

DIsable

task

that

task.

command

had

task

other

will

bits

run

are

suspends
RUNWT

has

(in

bit

REquest

set

only

beside

when

the

cleared.

been

this

execution

Task

ENABWT

bit

5.2.8

the

stopped

command).

can
it

the

task

Flags

specified
Table

for

using

the

think

restarted

easier

entry
it

Task-ID

disables
ENABWT bit on

the

future

execution

Task

the

Flags

the

Table

specified
entry

for

Task-ID

Task-~ID

entry

instance

Task-ID command

ENable

the

that

setting

Table

The

blocking

command

MCR

The

other

task

MCR

DIsable

5.2.7

the

turning

task.

5.2.6

RUNWT;

Task-ID

REsume

execution

Task-ID

REquest

upon

command

for

was

command
the

not

CAncel

clears

the ENABWT bit
in
the
task, thus enabling it to
command is a no-op.

Task

specified

set,

the

run.

Flags
If

the

Task-ID

CAncel

Task-ID command cancels any clock queue
entries
involving
task
specified
by Task-ID.
This includes l)any entries made by
MCR (from previous timed Request
commands),
2)entries
involving
the
specified
task
made
by
other tasks (e.g., a timed DERAIL) and
3)entries made by the specified task involving itself (e.g.,
a
timed

the
the

POST) .
and

the

5.2.9
The

the

task

may

SY¥stat

SYstat

case of the

hang

command,

either

greater

detail

SY¥stat

command

prints

blocking

an
the

bits

timed

forever

POST,

the event

waiting

for

whether

flag

is not

it.

POSTed

[Task-ID]

prints

describes

depending

general
a

single

prints

system
task.

system

status
If

status

existent
task

are

argument

report

argument

report.

Each

task in the system.
For each
number/priority, task name (if it

its

Task

Flags

5-4

Table

entry.

a
is

specified,

status

report

specified,

line

the

in
the

report

task
the
report
has one), and what

Each

blocking

bit

MONITOR CONSOLE ROUTINE

printed as a one-letter code, preceded by a space.

The one letter

ZCoonwo=MHTM

codes and their meanings are:
for

Waiting

for
for

Waiting
Waiting

a message
an event flag

to be
to be

Waiting
Waiting

flag

event

REquested or
swapped in

or a message
RUN

Disabled

USERWT bit set
Nonresident wait

In addition, an asterisk printed at the end of the line means the task

has messages waiting

in its

input queue.

1is obtained by
status report on a single task
Task-ID of that task as an argument to the SY¥stat
The detailed report contains all the information 1in the

A more detailed
specifying the

command.

followed by five octal words:

general status report,
WORD 1

WORD 2

The location of the Task State Table
this
entry containing words 2-5;
word

colon

followed by a

Task Link in sign bit, IF in bits 6-8,
DF in bits 9-11 (PDP-8/E and 8/A Flags

WORD
WORD

3
4

WORD

Task

Examples:

A general

the

SYstat command might produce

following

output

sample

line:
CARD

This line means task number 13, named CARD, is in Event Flag Wait
has

input messages pending.
>SYSTAT

and

command:

CARD

might produce
13

The

the

CARD E *

single
1320:

line:
0022

1741

0000

2525

This line indicates that CARD is stopped at location 21741 with its AC
and

Link

zero and

2525

its MQ.

by
MCR assembly
the
of
The user can leave the S¥stat facility out
the system parameter MCRSYS to 0 in the RTS/8 parameter file.
setting
saves one page of code.

Leaving

it out

5.2.10

OPen Address

[,Count]

The OPen
Address
command
displays
the
Count
locations
starting at Address on the console terminal in the form:

octal

11111/ cccc

The range of locations displayed may cross a field boundary.
is

not

specified,

assumed

5-5

If Count

CHAPTER

ASSEMBLING AND LOADING TASKS FOR RTS/8

The user assembles RTS/8 tasks with parameter files,
wusing
the
05/8
PAL8
assembler.
RTS/8
parameter files are all edited versions of a
master parameter file (PARAM.PA) that is included in
the
distributed
sources.
Appendix A lists the RTS/8 source files.
All definitions in
the master file which are to be supplied by the user are left blank in
the file.
For example, a sample line in the file is:
PDP8E=

PDP

8/E

If this parameter is set to
PDP-8/A.
1If either machine

1,
is

PDP

8/A,

the
not

ELSE

specified machine is
used, this parameter

a PDP-8/E or
is set to 0.

Thus, a unique parameter file is
environment,
where
environment
hardware

The

and

the

structure

Other

sections

set

tasks

the parameter
in

this

created
for
the
particular
RTS/8
1is
a
combination
of the available
being run.
file

chapter

discussed

describe

the

the
0S/8

section.

BITMAP program

which allows the user to construct a map showing the memory
1locations
used
by
given
binary
files, 2) a sample RTS/8 program 3) a general
procedure for creating an RTS/8 system, and 4) a listing of parameters
and their functions that affect the individual RTS/8 system tasks.

6.1

PARAMETER FILE

STRUCTURE

The parameter file contains the parameters that the user
must
define
to
specify a particular RTS/8 system configuration.
A parameter file
that has been modified for
the
demonstration
program
1is
shown
in
Section
8.1.
This
file
also
contains
user-defined
symbols
for
DECNET/8.
For further information on DECNET/8,
see
RTS/8
DECNET/8
Programmer's Guide and Reference Manual
(DEC-08-LDPRA-A-D).
The parameter
sections

are

file

labeled

divided
as

into

follows:

Executive

Specifications

Task

System Task

Specifications

System Wide

Definitions

Task

Definitions

Setup

the

following

five

sections.

These

ASSEMBLING

6.1.1
The

AND

TASKS

FOR

RTS/8

Executive Specifications

parameters

assembly

system.

The

the

Executive

Executive,

parameters

Specification

and

this

therefore
section

follows:

and

Symbol

section

are

control

essential
their

meaning

Set

the

be
PDP12

Set

or
EAE

set

being

Set

PDP12

PDP-8F,

used;

PDP-8M

not,

the

an
if

the

machine

PDP-12

system

interrupt
power

not

should

Set

be
HGHFLD

nonzero

loaded

Set

NTASKS

into

KL8-A

Set

octal

value

number

represents

CHECKP

the

highest

contents

task

be assigned

symbol

merely

sets

system.

the

highest

the

all

actual

length

any

field

Set

the

number

system.

Set

partitions

defined

PARTNS

the

indicates

partitions
and

Task

the

have

task

tasks:

this

system

this
the

Definitions

system

The

are

1line

deletion
line,

there

system.

also

assigned

tables.
task

allocated

are

For

that

there

is,

partition

are

memory

example,
two

memory

number

Definitions

tasks.

the

defined, that
partition number 1.

total

possible

partitions

zero

when

nonresident

memory

used;

the

can

the

should

system.

that

Not

the

field

checkpointable.
PARTNS

routines

specifies

number

need

the

that

any

used;

used.

30 specifies
core memory.

tasks

numbers

Set

must

enabled

support

designating

symbol

system.

value

possible

system

switching.

fail/restart

for
example,
HGHFLD
=
using a machine with 16K

The

are

PDP-8/A

being

save

task

hardware.
KL8A

this

undefined,

Set

PWRFAL

PDP-8/E,

machine

MQ during

Task

the
RTS/8

Meaning

PDP8E

6.1.2

the

which

section
names

defined
which

defines
all

here.

defines

inserting
makes

the

Any
it

slash

entire

symbolic

system

tasks

system

deleted

(/)

line

names
which

task
from

character
a

comment.

not
this

for
are

the

various

included

included
section.

the

should
Perform

beginning

Symbolic

definitions

the user's own tasks can be added to this
section.
The
user
is
reminded
that
the assignment of task numbers in octal indicates task
priority, that is, the lower the number, the higher
the
priority
of
the

task.

ASSEMBLING AND LOADING TASKS FOR RTS/8

The Task Definitions section, as it initially appears to the user,
shown

below.

/COMMON TASK NUMBERS - EDITED BY USER

/IT IS ADVISABLE TO DEFINE ALL TASKS HERE. NAMES GIVEN BELOW
/ARE USED BY SOME SYSTEM TASKS AND SHOULD REMAIN COMMENTED OUT
/IF THE CORRESPONDING TASK IS NOT INCLUDED IN THE SYSTEM
/PWRF=

/POWER FAIL HANDLING TASK

/SWAPPER=

/NONRESIDENT TASK SWAPPER TASK

/CLOCK=
/TTY=
/LPT=
/MCR=
/DTA=
/LTA=
/RK8=
/RF08=
/DF32=
/CSA=
/CSAF=

70s8=

/OS8F=
/DDCMP=

/TELETYPE DRIVER TASK
/LINE PRINTER DRIVER TASK
/MONITOR CONSOLE ROUTINE
/DECTAPE DRIVER TASK
/LINCTAPE DRIVER TASK
/RK8 OR RK8E DISK DRIVER TASK
/RF08 DISK DRIVER TASK
/DF32 DISK DRIVER TASK
/CASSETTE DRIVER TASK
/CASSETTE FILE SUPPORT TASK

JUNIVERSAL DIGITAL CONTROLLER TASK

/UDC=

/RX8A=
/RX8B=
/RX8C=
/RX8D=

/CLOCK HANDLER - SHOULD BE HIGH PRIORITY

NTASKS

/FIRST FLOPPY CONTROLLER
/SECOND FLOPPY CONTROLLER
/THIRD FLOPPY CONTROLLER
/FOURTH FLOPPY CONTROLLER

,/0S/8 SUPPORT - NORMALLY LOWEST PRIORITY
/0S/8 FILE SUPPORT
/DDCMP TASK FOR DECNET

/NETWORK SERVICES PROTOCOL TASK

/NSP=

/NETWORK INFORMATION PROGRAM

/NIP=

/TLK=
/LSN=

/NULL8A=
/EXIT=

/NETWORK TERMINAL COMMUNICATIONS TASK TRANSMITTER
/NETWORK TERMINAL COMMUNICATIONS TASK RECEIVER
/NULL JOB FOR PDP-8/A
JEXIT TASK

/AUXILIARY DKC8A HANDLER

/DKC8A=

8.1 after it
This section of the parameter file is shown in Section
shows the
also
It
.
program
n
tratio
demons
nas been modified for the
ration
demonst
the
in
wused
tasks
dent
nonresi
two
the
of
n
additio
program.

6.1.3

System Task Specifications

The parameters in the System Task Specifications section control the
rs
assemblies of the various RTS/8 system tasks. The set of paramete
ed
assembl
and
r
togethe
grouped
controlling a specific task are all
only if that task name 1is defined in the Task
conditionally
The user edits the
Definitions section of the parameter file.
their meanings are
and
ers
paramet
The
.
section
parameters in this
6.4.

listed

in Section

6.1.4

System Wide Definitions

of the
The System Wide Definitions section includes the definitions
Status
Task
and
s
Request
symbols that RTS/8 uses to describe Executive
tion
instruc
as
such
ions
definit
useful
s
Flag bits. It also contain
and
values
nal
functio
UDC/ICS
values,
call
monitor
ences,
equival
section.
this
alter
system locations. The user should not
6-3

ASSEMBLING

6.1.5
The

Task

AND

TASKS

FOR

RTS/8

Setup

body

this

that

task

section
task

the

uses five
initialize

system.

symbols
the

These

five

are:

TASK

Defines

the

that

RTS/8

the

user defines in
the
entries needed to put
and
their
definitions

table

symbols

task

number

form:

the

task

symbolic

statement

name

for

the

RTS/8

parameter

TASK=symbol

where

"symbol"

that

the

file.
CUR

wuser

the

has

Defines

the

field

6-8

(e.g.,

bits

defined

the

task's

the

starting

CUR=10).

task

address

NOTE

The

user

code

must

the

done

pseudo-op

place
field

the

wusing

the

Defines

the

necessarily
INIWT

Defines

the

Table

entry

means

the

up;

INIWT

task's

the

lowest

initial

for

task
=

this

task

Run

Wait

when

another

when

(1000

task

types

INIWT

undefined,

VERS

Defines

the

optional
version

The

wuser

can

and

CUR3,

etc.

define

symbols

for

The

tables

desired,

more than
the
code

task

origining

Task

the

task

RUN

and
or
to

version

number,

convention,

becomes

three

the

other

section

them;

the

that

when

a
the

MCR.

this

task's

runnable

the

starts

becomes

task

Flags

specifies

command

the

(not

INIWT

system

task's

number

setup

into

the

example,

parameter.

value.

corresponding

task)

octal)

Request

runnable.

the

initially

This

issues

operator

address

runnable

the

For

condition.

bits

This

assembler

starting

runnable

starting
CUR.

places

field

task.

RUNWT

not

CUR%10
in

address

wait

this

PALS

FIELD.

For
example,
FIELD
task's starting code

START

task's

specified

the

being

task's

initial

tasks

one

tasks

are

TASK2

and

TASK3,

CUR2

data

into

the

RTS/8

places

its

executable

code

assembly.

The

generated.

If
tasks can
be
created
1in
one
assembly
by
adding
for any additional tasks at the end
of the PARAM.PA
file.
It should be noted
that
only
one
task
is
defined
in
the
demonstration program in Chapter 8.

three

ASSEMBLING AND LOADING TASKS FOR RTS/8
6.2

CREATING AN RTS/8 SYSTEM

procedure that is
An RTS/8 System can be created by using the general user
has physically
the
that
assumed
is
It
described in this section.
apped the
bootstr
has
and
medium,
ution
distrib
the
of
copy
a
mounted
in this
treated
are
tasks
ent
nonresid
Although
development system.
in
given
is
tasks
ent
nonresid
g
employin
on
detail
greater
e,
procedur
Chapter

The general procedure for creating an RTS/8 System is as follows:

Layout on paper the system and user tasks required for the
particular RTS/8 configuration to be employed. Utilize the
tables and memory map given in Appendix B that show the RTS/8
components,

their

sizes,

and

their

default

origins

determine where the tasks are to be loaded into memory.

Assign task names and task priorities.

If nonresident

tasks

are used, assign the Swapper Task a higher priority than any
of the nonresident tasks. Remember that the lower the value
assigned to a task, the higher its priority.

When large programs are involved, a documentation file should
be created as a user convenience to maintain a directory of
the system configuration. This file can contain information
such as the tasks employed in the system, task names, task
priorities, and control files.

Obtain a listing of the
Use the 0S/8 command
.LIST

master

parameter

file

(PARAM.PA).

PARAM.PA

to get a listing from a line printer, or
.TYPE

PARAM.PA

to get a listing from a terminal.

Use an editor (EDIT or TECO

values

the

under

0S/8)

establish

the

parameters in the parameter file (PARAM.PA).

The structure of the parameter file is described

Section

6.1, and the parameters affecting the individual RTS/8 system

tasks are described in Section 6.6.

PARAM.PA should be read in as an input file, edited, and then
This procedure maintains the
renamed as an output file.
integrity of DIGITAL-supplied sources.

Section

Create and edit any control files that are used (See

Assemble the tasks with the parameter file after all the
required parameters are defined. This can be accomplished by
individually assembling each task with the parameter file as

6'5).

follows:

.PAL RTS8<PARAM,RTSS8
or

.PAL PARAM-NB,

RTS8

ASSEMBLING

The

CCL

option

AND

-NB

indicates

Ccreated.

Shown

has

done

for

every

file

used

Each

control

file

with

file
between
follows:
-PAL

the

for

Batch

the

and

task
must

parameter

RTS/8

binary

RTS/8

included

should

the

system.

the

required

This

Assemble

placing

and

not

Executive.

assembled.

tfile,

file

the

that
also

parameter

efficient

also

are

used

can

the

control

module

assembly,

inputs

for

that

The

generated

then

commands

system.

method

streanm.

system

command

job

can

Batch

the

SUBMIT

method

that

assembly

FOR

TTY1<PARAM,TTYCF1,TTY

use

commands

05/8

the

alternate

the

TASKS

run

and

Batch

BATCH

and

save

job.

which

execute

installing

employed

load

The

will

them.

nonresident

use

This

tasks

into

The

assembly of each task, prece
ded by the parameter file,
is
required
because
there
1is
no linking loader function with

RTS/8.

The

sources

System

task

loading
assemble
system

tasks

Obtain

bitmap

tasks

are

same

page

Load

the

required

. LOAD

RTS/8

Save

11.

the

When

using

(nonresident

file

. LOAD

Then

save

the

same

two

memory

are

and

control

time

follows:

area

tasks

tasks,

by
into

registers

required

user

for

can

editing

the

all

tasks,

Task
are

after

the

more
or

use

assembled.

files

can

always

included

and

saved,
needed.

the

nonresident
disk

must
in

this

executive
loaded

loaded
step

table

first.

order

Also,
to

entries.

using

the

load

following

filename

user

tasks,

image)

for

follows:

does

not

have

rebuild

create
each

a
SAVE
image
file
nonresident task from its

TASKX

the

device:
.SAVE

determine

user
used

autoindex

redefined

after

portions

SYS

system

time

binary

the
RTS/8

6.3).

tasks

system

.SAVE

and

also

not

for

section

command:

each

memory
tasks

(See

Executive

resident
the

locations
can

The

locations

system

one

Each

assembles

memory.

system

from

run.

RTSS,CLOCK,TTY,MCR,UTl,UT2

nonresident

their

system

loaded

The

files

and

that

core

areas

of RTS/8 tasks to
erroneously loaded into

All

the

tasks

binary

loaded

code

area

into

edit

Page

tasks.

assembler

load

system

creates

specific
or

areas.

process

ready

contains

1into

affected

the

10.

are

tasks,

specific
used

assembly

that

DSK

nonresident

TASKX

portion

the

task

the

swap

N1-N2

where DSK is the swap device,
N1
partition, and N2 is the highe
st

6-6

the

address

lowest
in

the

address

in the
partition.

ASSEMBLING AND LOADING TASKS FOR RTS/8

12.

Start the system by using the following command:
.R filename

The following is applicable when using nonresident tasks.
When the system starts, it calls the 0S/8 command decoder,
At this
which types an asterisk on the console terminal.
1initialize the block address of each nonresident task
time,
core

image

follows:

*DSK: TASKX=N

In this command line, DSK is the swap device and TASKX is the
core image file containing the nonresident portion of task N.
Repeat this procedure for each nonresident task, one task per
This
line, and terminate the 1last 1line with an ALTMODE.
procedure automatically initializes and starts the real time
system.

An RTS/8 system created with the procedure just described has
If an RTS/8 system was not
00200.
of
address
starting
a
it halts
PDP-12,
specifically confiqured for a PDP-8/E or

initially to allow the operator to clear any stray device
by
switches or
nonstandard hardware
flags by operating
Press START to resume operation on a PDP-8,
START.
pressing
8/1 or

6.3

8/L.

USING THE 0S/8 BITMAP PROGRAM

The 0S/8 BITMAP program can be extremely useful in determining that no
RTS/8 tasks are loading into the same area or using the same Page
two

0S/8 BITMAP accepts a list of binary files as input and
0 locations.
Each location of core
its output a map of core memory.
as
produces
which has the
digit
single
a
by
map
this
in
represented
is
memory
following

meaning:

Nothing has been loaded into this location

Information has been loaded into this location

Information has been loaded into this location twice

ipformation has been loaded into this location three or more
imes

to
allowed
are
2's
memory where
There are certain places in core
These areas are the RTS/8 Executive Tables
bit map.
the
in
appear
(starting at location 01200), the MCR name table in the MCR, the power

fail action table, and nonresident task partitions (which may contain
these
than
Appearance of a 3 or a 2 in an area other
2's and 3's).
just mentioned in the bit map indicates that two or more
areas
three
tasks are being loading into the same location.

6.4

SAMPLE RTS/8 TASK PROGRAM

for
selected
The task that is used as an example in this section was
and to show the basic concepts of RTS/8 operation.
its simplicity,
The user requires
The purpose of the task is simply to print "HELLO".
an RTS/8 system configuration that includes a console Terminal Handler
the
that
It is assumed
(TTY) and the Monitor Console Routine (MCR).
6-7

ASSEMBLING

task

will

standard

The

program

with

the

system.

The

wuser

the

reqguested

PDP-8

FOR

E/F/M/A with

terminal.

task

the
by

initially

through

the

console

the

/SAMPLE

terminal,

user,

RTS/8

START,

the

same

the

Run

RTS/8

8K of core memory and

Wait

Console

and

then

seguence

/GIVEN

CUR=0

/IN

FIELD

INIWT=RUNWT

/SET

FIELD

/PLACED

will

the

task

prints

itself.

again

requested

occur.

PRIORITY
RUN

WAIT

FIELD

/ANY AVAILABLE
BE

DEFINED

/SEND

AND

WAIT

MSG1

/THE

START

ZBLOCK

/RESUMES

/RTS/8

0;0

"START"

/TYPE

BLOCK

TASK

HERE

REQUESTED

LINKAGE

/TERMINAL
/HELLO/

STATE

TERMINAL

MESSAGE
/SUSPEND THE

SUSPND

PAGE

/MUST

CAL

SENDW

TEXT

When

suspends

TTY

JMP

state.

Routine,

PROGRAM

TASK=5

CAL

MSGl,

Monitor

*3000

TASKS

(SAMPLE.PA) listed below is complete,
and
when
assembled
parameter file, will run as task 5 in
a properly-configured

"HELLO"

running on

console

AND

OPTIONS

HELLO

edited

version of PARAM.PA now is required for this
confiquration,
it
1is
named PARAMS.PA.
To produce PARAMS.PA from PARAM.PA, the
following definitions are edited into the paramet
er file:

and

PDP8E=1

HGHFLD=10
NTASKS=10
TTY=4
MCR=3

NTASKS

assigned
sample

the

largest

any

number

task

task,

and

which

SAMPLE,

MCR

and

TTY

zero

less

The

and

program
.R

than

then

number

greater
is

were

used

than

smaller

than

arbitrarily

with

the
100

system.

for

octal.

chosen

NTASKS.

assembled

this

values

the

The

MCR,
task

range

TTY and

the

values

greater

for

than

follows:

PALS

*SAMPLE .BN<PARAMS.PA,SAMPLE.PA

The

system

the

TTY

following

for
and

Batch

the

sample

MCR

Task

task
run.

stream:

$JOB
.PAL

PARAMS-NB,RTSS8

. PAL

PARAMS-NB,MCR

. PAL

PARAMS-NB,TTY

. PAL.,

PARAMS-NB,SAMPLE

. LOAD

RTS8,MCR,TTY,SAMPLE

.SAVE

SYS:SAMP

SEND

requires
This

the

can

Executive

Task
RTS8
plus
accomplished by using the

ASSEMBLING AND LOADING TASKS FOR RTS/8

1is
Assembly and loading of the tasks, including saving the program, be
to
not
is
PARAM
that
es
indicat
-NB
option
CCL
The
e.
now complet
used as the name of the binary file being created.

The system now can be run as follows (user input is underlined):
.R _SAMP

/0S/8 RUN COMMAND

HELLO

/TASK EXECUTES AND SAYS 'HELLO'

/REQUEST SAMPLE FROM MCR

>RE 5($)

/RETURNS CONTROL TO MCR
/SYSTEM STATUS COMMAND

el
>SYSTAT
03
04

MCR
TTY

>RE 5(8$)
HELLO

/MCR TASK
/TERMINAL TASK

/TASK 5 WAITING TO BE RUN
/RUN TASK AGAIN
/TASK SAYS 'HELLO'

AGAIN
/RETURN CONTROL TO MCR
/RETURN TO 0S/8

°c
>EXIT

/0S/8 MONITOR

NOTE

all other
($) is the ALTMODE character;
input lines are terminated by a Carriage
Return.

USE OF CONTROL FILES UNDER RTS/8

6.5

There are times when a user may want to assemble a given source module
in more than one way and use the results under RTS/8. For example,
suppose there are three terminals that a user wants to service under
Each terminal has its own characteristics, and each copy of
RTS/8.
the TTY task needs to have its own set of parameters. The wuser must
load three copies of the TTY task into memory at different locations,
This cannot be accomplished
and possibly in different fields.

With a single
efficiently when wusing a single parameter file.
made and each
be
must
TTY.PA
file
the
of
copies
three
file,
parameter
one edited to produce three individual tailored copies of the TTY
This procedure is not convenient or modular.

task.

A better way to do this is to use a control file that contains all the
equates necessary to define the parameters needed by a particular TTY
task. The control file then is assembled together with and placed
between the parameter file and the TTY module.
.PAL TTY1l

For example,

<PARAM,TTYCF1l,TTY

control

creates a binary file called TTYl from TTY.PA

using

To facilitate using this procedure, a skeleton

TTY

control

called

file

TTYCF1l.

file

|is

It contains all the parameters
supplied with the RTS/8 task sources.
Thus, a user
that the user normally defines in the parameter file.
the parameters
editing
of
instead
terminals,
multiple
who wants to use

in the parameter file, can create a control file for each terminal
that is used, and then edit the control file to make multiple copies
as

necessary.

An example of a TTY Control file after it has been edited by a user is
shown

below.

ASSEMBLING

AND

TASKS

FOR

RTS/8

TASK=TTY1l

TTDEV=

KBDEV=

VT50=

SCOPE=1

FILL=

WIDTH=

DEVICE

/KEYBOARD

CONSOL=1

/DEFAULT
/PRINTER

/NUMBER

LINE

FILL

TAB=

LSBOT=

LISTS

TTFLD=20

DEFAULT
-

AND

DEFAULT

TTDEV-1

CTRL/Q

CHARACTERS,

WIDTH

TTY

CODE

CTRL/S

/120

OLDTTY=0

CODE

DEVICE

ENABLES

/TTY

'TTY'

MEANS

I.E.

INFINITE),

HAS

HARDWARE

TARBRS

BOTH

HANDLERS

(DEFAULT

that

been

DEFAULT

TTLOC=3000

This

example

TTY1.

shows

This

TTY control

terminal

terminal.

file

handler

task

will

has
be

edited

for

task

assembled

for

the

console

the

floppy.

Users

Setting SCOPE=1 causes RUBOUT to
move the cursor
left
one
physically removing the character from
the screen.
The new
three-page handler is specified.
It is placed in field 2, starting at
location 3000.

position,

skeleton

can

easily

6.6

RTS/8

control

file

generate

and

use

SYSTEM

TASK

also

supplied

control

for

files

for

the

section
the

parameter,
or

text

6.6.1

its

chapter

Clock

this

function

where

manual

Handler

a
is

and

where

detailed
noted

Parameters

Specifies

=
=

description

after

the

(Section

selection

PDP-8/A

DK8-EP

Specifies

Specifies
are

minimum

queue

HERTZ

each

the

system

which
task

example.
task

The

appears

subhead.

4.1)

hardware

number

and

Specifies

OCTAL,
octal

SHERTZ

preceded

This

number

(default

1in

pseudo-operator

SHERTZ

task

parameters

for

clocks

follows:

DK8-EA/DK8-EC
KW12

clock

HERT?Z

those

Given

MEANING

0
1

CLKQLN

applicable,

PARAMETER

CLKTYP

purposes.

PARAMETERS

This section provides a convenient groupi
ng
affect
the individual RTS/8 system tasks.

RX01

other

the

which
base.

entry

slots

decimal

the

ticks

per

values

parameter

file

DECIMAL.

resets

20).

hardware
are

number

parameter

system

followed
the

radix

ticks

the
to

per

the

second.
that

they

the

second.

pseudo-operator
its

original

ASSEMBLING AND LOADING TASKS FOR RTS/8
Swapper

6.6.2

Parameters

(Section 7.4)

SYS

for
task;
swap driver
Specifies the
SYS = RK8 specifies the RK8 driver task.

SUNIT

Specifies the swap
SUNIT

selects

MEANING

PARAMETER

value

KBDEV

set

default value

proper

the

is TTDEV-1.

the

TTY

VT50

code;

device

Kkeyboard

The following parameters are available to the user to
of

default

Is set to the proper printer device code;

TTDEV

use

unit;

drive

RKAO.

(Section 4.2)

Terminal Handler Parameters

6.6.3

physical

device

example,

facilitate

the

task.

CTRL/Q
Is set to 1 (default) to enable CTRL/S and
set to 0, CTRL/S and CTRL/Q are
When
functions.
CTRL/S
Typing
not treated as special characters.
the
on
printed/displayed
being
1is
data
while
next
screen stops the data presentation until the
This parameter must be set to 1
1is typed.
CTRL/Q
Both
VT52.
or
if the user's terminal is a VT50
CTRL/S and CTRL/Q turn off the echo flag.

CONSOL

WIDTH

Is set to 1 to specify that the handler
assembled for the console TTY (default).
not
to specify that this handler should
the MCR when "C is typed.

TTY
the
Is set to an octal number that specifies
1is currently set to 120
width
TTY
width.
page
decimal
80
of
width
page
a
(octal), that is,
WIDTH = 60 sets the TTY page width to
characters.
characters.

48 decimal
SCOPE

being
1is
Set to O
up
wake

This option
the

RUBOUT

SCOPE=0
RUBOUT

is used to determine
key

(default)

the treatment

follows:

provides

the

normal

mode

support.

SCOPE=1 causes RUBOUT to move the cursor left
one
position,
physically
removing the character from
RUBOUT
If the cursor is in column 1,
the screen.
still

TAB

works,

but has

visible

effect.

This option simulates tabs by the proper number of
spaces.
This
1s
accomplished
via the assembly
parameter

TABR=0

not

TAB

follows:

(default) specifies that the
hardware
does
support tabs.
The software simulates tabs by

spaces.

TAB=1

specifies

that

tabs.

6-11

the

hardware

does

support

ASSEMBLING

FILL

Fill

AND

characters

parameter

FILL=0

FILL

TASKS

are
as

(default)

FILL=n

OLDTTY

sends

feed;

does

specify

handler.

fewer

Set

3-page

shorter.

and

set

specify

listed

TTY

LPT

Used

the

output

ASSGN=200

TTY

They

OUTTXT

points

the

Used

assign

this

task.

Used

with

output
the

KL8-~A

not

Parameters

for

Task;

for

character

first

handler

(see

useful

for

ASCII.

followed

word

the

mode.
for

Section

(Chapter

location

are

not

device

the

Task;

6-bit

the

support

PARAMETER

new

follow:

text.

Routine

starting

equates

message

TTY

message should
return/line feed.

Console

file.

These

if the
carriage

Used

and

location

parameter

output

the

field

specifies

the

Used

the

Tasks.

The
have

to 0(default) when only
OLDTTY is to be listed.

specifies

3000

2-page

the

has

FILL

Set

use

page
TAB

o01ld

Used

use

only

4.13.2).

MEANING

set

printing

the

system

SYSTAT

status

tasks.

MCRFLD

the

NOLINE=400

MCRCLK

SCOPE,

both

output

MCRSYS

list

selected

2-page

handler

old

o0ld

set

Monitor

The

3000.

6.6.4

the

handler.

KL8ALINE=100

(default)

old

example,

IND=1000

use

the

NOCRLF=2000

the

using

example,

NOPACK=4000

after

FILL=4

when

handler.

fill

VT5's.

WIDTH,

any

1-5.,

effect
to

assembly

(nulls)

range

handler

equates are
messages to

baud

but

VT50,

the

provide

the

handler.

features,

3-page

Several
sending

not

set

via

characters

2400

barameters

TTLOC

fill

must

for

standard

TTFLD

supported

recommended

TTY

LSBOT

RTS/8

follows:

characters.

line

FOR

set

the

user.

set

locate

the

MCR.

the

field

clock

in
MCRFLD =

facility

reports

functions

which
30

desired

for

existent

system

are

wanted

places

the

not

desired
MCR

field

ASSEMBLING AND LOADING TASKS FOR RTS/8
MCRPRT

Is set to the number of the partition into which
nonresident portion of the MCR will be
the
MCR
the
makes
parameter
This
swapped.
MCR
the
of
page
first
the
r,
howeve
nonresident;
is always resident.

MCRORG

Is set to specify the starting location of the
Default causes the MCR to load against the
MCR.
end of the field.

MCRCDV

Set to task name of task which is to

console device.

0S/8 Support Task

6.6.5

Parameters

Default is TTY.

OSTTDV

MCR

MEANING

Is set to the number of fields allocated for 0S/8.
specifies

OSFLDS = 2
for

OSKBDV

the

(Section 4.6)

PARAMETER

OSFLDS

two

fields or 8K of memory

0S/8.

Is set to the device code that selects desired
OSKBDV = 03 specifies the
0S/8 keyboard terminal.
keyboard for 05/8.
terminal
use of the console
O0S/8 requires its own dedicated terminal.
Note:
Is set to the device code which selects desired
OSTTDV = 04 specifies the use
0S/8 teleprinter.
of the console teleprinter for 0S/8.

OSSYSD

Is set to select the
0SSYSD = DTA
task.

0S/8 system device driver
specifies DTAO0 as the 0S/8

system device.

OSFILL

Is set to the number of null characters that

hard-copy

terminals.

A terminal device handler does not have
Note:
be included for the 0S/8 terminal device.

6.6.6

must

follow a line feed character on the 0S/8 terminal.
2400-baud
a
OSFILL = 4 is specified when wusing
0 when using standard
Set to
VT05 terminal.

KL8-A Support Parameters

(Section 4.13)

PARAMETER

MEANING

KL8ADV

KL8-A.
first
the
for
Specifies the device code
If multiple KL8-A's are used, they
Default is 40.
should have consecutive device codes.

KL8ACT

Specifies the page for the KL8-A connect

routine.

The KL8-A connect
(if KL8A=1l).
7400
is
Default
routine must be located in field 0.

ASSEMBLING

6.6.7

Line Printer

Handler

AND

Parameters

TASKS

(Section

PARAMETER

Specifies

Printer
LPTFLD

Handler

the

starting

Handler

Specifies

DECtape

DTALOC

the

Parameters

Specifies

DTAFLD

field

the

(Section

4.4)

Line

the

Printer

(Section

the

starting

1location

Task.

Specifies

Task

location

Line

Task.

MEANING

Handler

EXIT

4.3)

Task.

PARAMETER

6.6.9

RTS/8

MEANING

LPTLOC

6.6.8

FOR

the

field

the

DECtape

the

Handler

DECtape

Task.

4.14)

PARAMETER

MEANING

EXITFLD

Specifies

the

field

EXITLOC

Specifies

the

starting

the

EXIT

location

Task.
of

the

EXIT

Task.

CHAPTER

NONRESIDENT

7.1

TASKS

OVERVIEW

A nonresident task is a task or a portion of a task that resides on
a
mass
sStorage
device
during
the time the task is not runnable.
The
mass

storage

device

medium

(e.g.,

called

the

swap device.

can

any

mass

an RK8 cartridge disk or an RX8 floppy disk).

When a nonresident task becomes
executable,
residency
request.
The Executive then runs

the
Executive
posts
a
a special task called the
Swapper to load the nonresident or portion
of
the
nonresident
task
into
memory.
The loading process is called a swap.
The memory area
into which or out of which the nonresident task is swapped is called a
partition.
A
partition is a contiguous block of memory that is used
for task execution;
it is readable in a
single
mass
storage
call.
The
use
of nonresident tasks permits several tasks to share the same
areas of memory, optimizing the use of available memory.
Tasks can be either totally or partially nonresident.
are
totally
nonresident;
in
most
applications,

Very few
tasks
the
nonresident
portion includes all, or nearly all, of the active locations.
Active
locations
are those that contain executable instructions or data that
are never accessed by other tasks.
The resident
portion
of
a
task
includes
messages, event flags, buffers and similar passive registers
that

may

needed

other

tasks.

NONRESIDENT

TASKS

PDP-8 MEMORY

SWAP DEVICE

(Disk, DECcassette, etc.)
REAL TIME PROGRAM AREA
Contains

Contains:

nonresident

Resident tasks

Resident portions of

portion of a

task

non resident tasks

pK
PARTITION AREA

SWAPPER TASK
1.

Contains non resident portion

(SWAP.PA)

’

2. Allows multiple tasks of same
.

relative size to run in the

Swap Device.

3. The characteristic of a partition
as

3. Also pads and

follows-

Swaps out non-

.
resident task onto

same memory area.

portion of task into
memory.

swaps

writeable and

checkpointable tasks.

Has a starting address

Resides completely within a
single memory field

Length has to be an integral
number of pages

Cannot overlap another partition

Figure

The

process

that

similar

and

task

onto

is
the

another

are
made

the

Implementation

portion

capability
swapping

nonresident

Task

nonresident

overlay

swapped

task

into

found

1is

much

has

two

out

task

0S/8
more

"checkpointability".

"writeable"

its

nonresident

task.

i.e.,

whenever
writeable

the

task

task's

portion

swapped
is

code

memory

IV and

powerful

than
that establish
memory.
These
two

and

device

into

FORTRAN

properties

"writeability"

swap

self-modifying

Nonresident

However,

Every

how

properties
A

swaps

the

programs.

overlaying.

when

7-1

any

must

out

make

task

written
room

that

changeable

during

execution, and any task that must initialize before it
can start.
writeability feature guarantees that the nonresident portion
of a
is always up to date by
refreshing
the
swap
device
image
of
nonresident portion whenever the task is swapped out of memory.
A

task is made
automatically,
task.
swapped

task
back

"checkpointable"

without
that

was

its

if it may be
swapped
consent, to make room for a

checkpointed

automatically

relinquished the
the
point where
was interrupted.

soon

and
as

necessary memory space.
it was interrupted, and

swapped
all

task

The
task
the

of
memory
higher priority
of

priority

Execution
the

is
task

out

higher

for

then
not

memory
tasks

is
have

continues

aware

that

NONRESIDENT TASKS

checkpointable
Some nonresident tasks have Dboth writeabedle whenanda task
must modify
utiliz
are
tasks
ble
Writea
characteristics.
temporary
or
tions
instruc
itself (for example, it includes JMS
that are
those
are
inting
checkpo
for
e
suitabl
Tasks
locations).
1) fairly long-running, and 2) are required only occasionally.
Writeable Tasks

7.1.1

difying, or
A writeable task is one that includes code that is self-mo
execution
Before
on.
executi
code that must be initialized before
>n the
files
image
core
as
reside
must
tasks
dent
begins, all nonresi
ent
swap device. The core images are created by loading each nciresid
can
this
command;
SAVE
monitor
0S/8
an
g
task separately, and executin
portion
ent
nonresid
its
,
executed
is
task
a
When
BATCH.
under
done
be
If a task 1is
is read from this core image file by the swapper.
the same file
into
written
be
will
portion
ent
nonresid
its
e,
writeabl
writeable
task,
a
that
when it is swapped from memory. It is likely
later
some
at
e
writeabl
not
itself
flag
would
,
at execution start-up
time when all initialization is completed. The nonresident portion of
a task is writeable if it must be saved on a mass storage device (swap
device) before overwriting it in memory with another task.

Checkpointable Tasks

7.1.2

Checkpointing is ideally suited for long-running

can

short

run

tasks

tasks.

The

system

1in the same area, swap them out of memory, and

swap the long running task back again.

Interaction Between Tasks

7.1.3

any
Resident tasks can interact with the resident portion of
ng
overlappi
occupy
that
tasks
nt
nonreside
Two
task.
nt
nonreside
memory regions can interact with each other through their resident
partitions. For example, if a nonresident task is executing, it sends
The message recipient can
a message and is then checkpointed.
the sender is not totally
though
even
message
acknowledge the sender's
resident.

7.2

However, the message sent must be resident.

MEMORY PARTITIONS

The swappable portion of a nonresident
This partition is simply
partition.

task resides in a memory
a contiguous block of memory

locations that is readable in one mass storage call.

has the following characteristics:

Every

partition

It is wholly contained in one memory field.

It has a starting address.

It has a length (size) that must divide evenly by 200 (octal)
since 0S/8 file structured devices read and write in one-half

block

(one page)

increments.

It normally begins at an address which is a multiple of 400.

NONRESIDENT

The

user

can

the

parameter

procedure

are

Only

one

task

are
being

task

owns

(described
long

parameters

Any

for

the

establishing

source

Section

mutually

another.

partitions
number

the

file
described in

Partitions
overlap

set

the

partition

Swapper

7.4.

distinct,
number

TASKS

that

is,

one

partitions

can

partition
be

numbered in any order, from 0 to
n-1,
the first partition.
They need not be
can

the

occupy

partition

the
higher

nonexecutable.

until

that

section), or
(if
priority
tasks
that

any given
task

the

cannot

defined.

time.
is

This

The

with
partition
adjacent.

executes

task

either

Task.

The

occupying

"free"

command
checkpointable) as
partition
remain

is most convenient if every partition begins on
the first
1location
even-numbered pages, that is, the starting address
is a multiple of
400 octal.

7.2.1
A

FREE

free

(for

Command

request

example,

can

SEND,

appended

RECEIVE,

CAL

COMMAND+FREE

CALL

the

function

etc.)

follows:

/REQUEST.

THE

/ISSUING
/MEMORY
/BECOMES

/CANCELS
free

the

request

must

some

ER's

EXECUTIVE
ANY

RTS/8

EXECUTIVE

TASK IS TO BE SWAPPED OUT OF
SOME OTHER TASK
EXECUTABLE AND REQUIRES THE

/PARTITION

THE

~ /"COMMAND"

argument

BEFORE

THE

combined

FREE
with

seguence:

THE

FREEING TASK
REQUEST.

some

other

executive

request.

CAL
FREE

issued,

will

interpreted

as:

CAL

SEND+FREE

Only
are

nonresident tasks may issue free requests;
other
free
1ignored.
A
task
may
free
1its
own
partition, but

partition
A

task

swapped

pending

in
In

any

into

compete

1is
partition.

task

its
task

the

The

the

has

whenever

pending

partition
partition,

partition

freeing

request

cancelled,

and

No read or
this
case.
(which may or may
is

assured

the

freeing

task

along

with

executable

partition.

wait
for
partition,

an
it

there

continues

requests

any

this

freeing task retains
operation is
necessary

the

executable

the

write
By

must
for

immediately.
the

task may become

residency

programmer

partition

free

for

requests

command

swap

frees

partition until some other
occupant
case,
once
the freeing task becomes

occupants.
task

task.

other

request

the free
either

must

another

normally

event.

requests
never

other

before

1is
to

wait

residency.
again,

executable

any other

case,

the
free
possession of the

to
effect
this
the partition whenever the occupying
writeable) must wait for an
event,
the

freeing

not

that

the

partition

7-4

contains

running

(i.e.,

NONRESIDENT TASKS

nonwaiting) task whenever possible. If there are no writeable_ tasks
in the partition, no swap device I/0 1is involved in freeing the

partition.

7.3

NONRESIDENT TASK INITIALIZATION

RTS/8

system

resident

task.

The following procedure is recommended to implement any

containing nonresident tasks.

task

Code and debug each nonresident

During the debugging, load the task being debugged and only
the tasks required for execution of the task to be debugged.
Once the task executes correctly while resident, make it
1in the
Making a task nonresident is described
nonresident.
sections

that

follow.

each
of
portion
On a 1listing, mark the nonresident
task's
size of each
the
Determine
task.
nonresident
Then design the partitioning scheme and
nonresident portion.
allocate nonresident tasks to memory partitions by modifying

the parameter file as described

Re-origin each

nonresident

in Section 7.4.

task

that

its

nonresident

If necessary, ensure that
portion lies within its partition.
into
resident portions of nonresident tasks do not overlap
an O0S/8 utility program, is
BITMAP,
another partition.
two
useful for this since it allows the user to determine if
being loaded into the same
erroneously
are
tasks
more
or
Section
in
The use of BITMAP is described
memory section.
2
Chapter
in
given
is
BITMAP
of
description
detailed
A
6.3.
task
resident
a
Execute the task as
of the 0S/8 Handbook.
once more to make sure it does not contain location dependent
odd
an
on
begins
any memory partition
if
Also,
code.
numbered page, temporarily relocate each task that resides in
An example of starting a nonresident task at
that partition.
an arbitrary boundary is given in Section 9.3.

7.3.1

Parameters for Nonresident Tasks

employing
initialized when
Several .assembly parameters must be
the
in
located
are
the parameters
Five of
tasks.
nonresident
the
in
included
three must be
and
(PARAM.PA)
file
parameter
task

nonresident

itself.

contains
(PARAM.PA)
file
parameter
The
which
SUNIT)
and
SYS
SWAPPER,
CHECKP,

employing

nonresident

tasking.

These

(PARTNS,
parameters
five
1initialized when
be
must
as
defined
are
parameters

follows:

PARTNS

defined.
of memory partitions
number
is set to the
PARTNS is set to zero in the parameter file to indicate
that no memory partitions are defined in the system.

CHECKP

is set to 1 if any nonresident task is checkpointable.

SWAPPER

is the nonresident
task
swapper
task;
it
must
be
a task number that is of higher priority than
assigned
value
in
lower
number
the task it swaps, that is, a
than that of any nonresident task

in the system.

NONRESIDENT

SYS

set

designate

example,

SUNIT

set

SYS

RK8

specify

for
example,
drive.
Every

nonresident

task

the

SUNIT

source

PARTNO=

where

the

WRITE=

the

task

Failure

execute

task
not

initialize

used

except

nonresident

However,

the

buffers

executed.

will

is
executing.

always
It

nonresident

portions

Each

checkpointable

not

writeable

presence

Hence,

not

out

present

1in

tasks

that

Assembling
nonresident

must

include

safe

TASK3

(see

clearly

intermixed.

task

the

when

name

program

identifies

the

PARTNO

from

portions

that

task

should

while
to

resident

task.

task

since

not

being

restrictions.

The

nonresident

assume

that

the

task
is
nonresident

is not executing.
There
resident and nonresident

defined

assembled

6.1.5,

resident

and

is
a
tasks;

nonresident

Tasks

parameter

Section

different

memory

Nonresident

three

(starting

PARTNO

variable

coding

have

cannot

causes

parameter

nonresident

memory

generally

unit;

cartridge

tasks.

special

correctly
of

the

appreciably

not

drive

disk

writeable

parameters

The

number

for

task.

following

checkpointable

is never present when the task
structural
difference between

slight

7.3.2

task

the

partition

task;

driver

physical

include

task

task's

nonresident

1is

specifies

not

task.

are

device

driver

disk

swap

must

the

should

There

portion

task

buffers

device

these

nonresident

swap

task

unpredictably.

as
be

the

specifies

parameters:

CPABLE=

TASKS

separately.

TASK,

Task

but

never

The
the

nonresident

parameters

Setup).

TASK2

task
and

The

swap device file that contains
the
nonresident
portion
of
the
nonresident
task
requires special treatment.
This file must contain
the first word of the nonresident portion in
the
first
location
of
relative
block
1,
the second word of the nonresident portion in the
second

location,

and

on.

This

file

must

core

image;

however,

the
O0S/8
monitor
requires that the first location of any core image
section load into a memory address that divides evenly
by
400(octal).
If
the
1lowest
address
in
the
partition
also
divides
evenly by
400 (octal), this condition is met.
There is no problem because
every
task can be assembled in the partition directly.
Modify- the

parameter

parameters.

Then

file

assemble

the

together.

7.3.3

(PARAM.PA)

nonresident

establish

task

and

the

desired

parameter

file

Creating the SAVE Image File

Create

image

file
.R

SAVE

image

file

follows:

(nonresident

ABSLDR

*TASKX.BNS

.SAVE

DEV TASKX.SV N1-N2

7-6

disk

image)

from

the

binary

NONRESIDENT TASKS

For each task, where DEV is the swap device, Nl is the lowest address
The
in the partition, and N2 is the highest address in the partition.
of each

s
resulting core images contain only the nonresident portion
, the
However
d.
outline
sly
previou
ments
require
the
all
task and meet
control
core
the
is
0)
first block of the core image (relative block
it is
block, which is not used by the swapper. As stated previously,
strongly recommended that the partitions begin at a location that is a
multiple

400(octal)

starting at 400(octal)

since the 0S/8 SAVE command only saves areas

boundaries.

NOTE

can be constructed
files
image
SAVE
Also, the 0S/8 CCL
under 0S/8 BATCH.
command LOAD may be used to create the
SAVE

7.4

image.

PARAMETER INITIALIZATION FOR PARTITIONS

The user must initialize certain parameters to define the partitioning
scheme. They can be set in either PARAM.PA or SWAP.PA. The following
three variables are required for each of the partitions:
MFLDnn=
ADDRnn=

SIZEnn=

MEMORY FIELD OF PARTITION N
MEMORY ADDRESS OF PARTITION N

SIZE OF PARTITION N, SPECIFIED IN PAGES

The user can set up the parameter file to accept eight sets of
When more than eight partitions are defined,
partition parameters.
be extended according to instructions
must
the parameter table
contained in source. Since adding extra partitions does not increase
system overhead, it is best to have as many partitions as possible.
This minimizes the number of tasks that must share a partition. Each
partition should have at least two occupants; otherwise, there is no
making the task nonresident.

reason

for

swapper

source.

also be defined by initializing the

7.4.1

General

The partitioning scheme can

required

parameters

within

the

Information

The entire partition table appears on the swapper PAL or CREF output
The user should check it carefully to ensure that all
listing.
partition parameters (MFLDnn, ADDRnn and SIZEnn for each partition)
The parameter file generates the residency
were defined correctly.
table entry for each nonresident task and it appears

the

PAL

CREF output listing for that task. The user should examine word 1 of
this entry to verify that the nonresident task parameters PARTNO,
CPABLE, and WRITE were initialized correctly. Word 2 of the residency
table entry will be zero because the task's block address on the swap
device is unknown at assembly time. This location is initialized by
the 0S/8 command decoder shortly after program startup, and it can be

examined anytime thereafter. 1In the usual case, where the file is a
core image, this location should contain M+l, where M is the Dblock
address returned by the following command:
.DIR DEV:TASKX.SV/B

NONRESIDENT

TASKX.SV

nonresident

7.5

the

core

portion

NONRESIDENT

Perform

the

TASK

image

the

TASKS

the

swap

device

task.

containing

the

IMPLEMENTATION

following

procedure

implement

nonresident

tasks.

Assemble every task that will
be included in the
program
as
described
1in Section 7.3.2.
Obtain PAL or CREF listings and
bitmaps.
Finally, obtain a bitmap of the
entire
system
and
verify that memory is allocated
correctly.
On the bitmap, 3s
are

legal

Create
Load

only

the

within

SAVE

partitions.

image

binaries

file

the

RTS/8

described

start

load

their

Either

save

from

the

resident

the

Section

executive

including
nonresident
tasks.
Always
first.
Nonresident tasks are included

order
to
entries.

and

1load
in this

portions and
program as a

loaded

keyboard.

7.3.3.
each

task,

the
executive
operation
in
Executive

core

table

image

file

Start

the real-time program
using
the
monitor
R
command.
calls the 0S/8 command decoder,
which types an asterisk
on the console terminal.
At this time, initialize the
block
address of each nonresident
task core image as follows:
This

*DEV:TASKX.SV=N
In

this

command

line,

DEV is the swap device and TASKX
.SV
is
file containing the nonresiden
t portion of
task N.
Repeat this procedure for each
nonresident task, one
task
per
1line, and terminate the last
line with an ALTMODE.
This
procedure
automatically
1initializes
and
starts
the
real-time program.
the

core

This

initialization

under

image

0S/8

BATCH

procedure

may

control.

executed

automatically

Example:

$JOB

SYSTEM
"SYSTEM" AND INSTALL
/NONRESIDENT TASKS.
/RUN
-RUN

SYS

SYSTEM

*TASK1=35

/TASK

*TASK2=36%

/TASK

"TASKI"

SAVE

IMAGE

"TASK2"

SAVE

IMAGE

SEND
Submitting

SYSTEM.BI

installing

its

Debug the
placing

entire

two

HLT

appropriate)

and

examining

executed.

Use

remove

permanently

MCR

output

undetermined

MCR

has

the

MCR

HLT

resident

user

system

tasks.

point

the

and/or

memory
the

When

snapshot

time that
terminal.

once

console

instructions
areas.

represents

output

RTS/8

program.
Accomplish
this
instructions
(preceded
by

place

and

runs

nonresident

and
using

of
long

SYSTEM. SV,

selectively

IOF,

the

HLT

switch

NOP,
has

modify

MCR,

remember

memory
past

if
been

at
the

time

all
that

some
the

CHAPTER

DEMONSTRATION PROGRAM

This chapter contains a demonstration of RTS/8 with nonresident tasks
1Included is a listing of the modified
executing in the foreground.
1is an example of
there
In addition,
parameter file (PARAM.PA).
NR20

(Tasks

tasks

nonresident

NR22) and the assembly and load

and

instructions required for implementing the demonstration program.

8.1
/2,8

MODIFIED PARAMETER FILE
PARAMETERS

LSTFLGaQ

RTS/8

TASKS

VEB+DECNET

JCHANGE @ TU 1 TO PREVENT LISTING PARAM

N N NN NN NNN

YN,

XLIST

FOR

LSTFLG

(PARAM.PA)

(C)

1974,1975,1976 BY DIGITAL EQUIPMENT CORPORATION

NN NN N NN N

/THE INFORMATIOM IN THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE
/AND SHQULD NOT BE CONSTRUED AS A COMMITMENT BY ODIGITAL EQUIPMENT

/CORPORATION,
/FOR

ANY

ERRORS

OIGITAL EQUIPMENT CORPORATION ASSUMES NO RESPONSIBILITY
THAT

MAY

APPEAR

THIS

DOCUMENT,

/THE SOFTwWARE DESCRIBED IN THIS DOCUMENT I8 FURNISHED TO THE PURCHASER
/UNDER A LICENSE FOKR USE ON A SINGLE COMPUTER SYSTEM AND CAN BE COPIED
/(WITH INCLUSION OF DIGITAL’S COPYRIGHT NOTICE) ONLY FOR USE IN SUCH
/SYSTEM, EXCEPT AS MAY OTHERWISE BE PROVIDED IN WRITING BY DIGITAL,
/

/DIGITAL EQUIPMENY CORPORATION ASSUMES NO RESPONSIBILITY FOR THE USE
/O0R RELIABILITY

/DIGITAL,

ITS SOFTWARE ON EQUIPMENT

THAT

NOT SUPPLIED BY

DEMONSTRATION

/RTS8

EXEC

PDP8E=]

PARAMETERS

EDITED

USER

/NUMBER

KL8A’S

USE

ONE

KL8A

(UP

PROGRAM

PDP1e=D
EAE=Q
PWRFAL=D

KLL8ARD

/L.t

HGHFLD=3Q

IFDEF
IFNZRO

LINES)

CUR

HGHWFLD~CURB 42020 €CURBIG, _ERROR_ »>

NTASKS=23

/FLAG WARNING

IF UNDEFINED FIELD SEEN

CHECKP®]
PARTNS
=1

/(THE

PARTITIONS

ARE

NUMSERED

FROM @

N=1)

/COMMON TASK NUMBERS = EDITED BY USER

/1T

/ARE

/1F

ADVISABLE

TO DEFINE ALL TASKS HERE ,
NAMES GIVEN BELOW
BY SOME SYSTEM TASKS AND SHOULD REMAIN
COMMENTED OUT
CORRESPONUING TASK IS NOT INCLUDED IN THE
SYSTEM

USED

THE

/PWRFs

CLOCK={
SWAPPER=]s
TTy=se

/POWER FAIL HANDLING

TASK

LPTe3
MCRsd4

/DTAm
/LTAs

/OECTAPE DRIVER TASK
/LINCTAPE DRIVER TASK

/RFQ8s

/RF28 DISK URIVER TASK
/0F32 DISK DRIVER TASK
/CASSETTE ORIVER TASK
/CASSETYE FILE SUPPORY TASK
/UNIVERSAL DIGITAL CONTROLLER

RK8=7

/DF32s
/CSAx

/CSAF=
/UDCx
/RX8Ax
/RX8B=
/RX8Cs
/RX80Ds
DS8=NTASKS
0S8F=15
NR20=20

/FIRST FLOPPY CONTROLLER
/SECOND FLOPPY CONTROLLER

TASK

/THIRD FLOPPY CONTROLLER
/FOURTH FLOPPY COUNTROLLER

NR22s22

/DDCMPs
/NSP=

/UDCMP

/NIP®

/TLKs=
/LSNs
/NULLL8AS

/EXIT=
/DKC8An

TASK

/NETWORK
/NETWORK
/NETWORK

INFORMATION PROGRAM
TERMINAL COMMUNICATIONS
TERMINAL COMMUNICATIONS

/NULL

JOB

/EXIT

TASK

PARAMETERS

XLIST

DECNET

SERVICES

FOR

/AUXILIARY

/SOFTWARE

FOR

/NETWORK

TASK

PDP=8/4A

UKCBA

EDITED

PROTOCOL

TASK
TASK

TRANSMITTER
RECEIVER

HANDLER

USER

IFDEF

0S8

XLIST

LSTFLG

0SFLDSsE2
0STTOVa3]
0SKBDV#3D
0SSYSDeKKS
OSFILLwO

/DEFAULT

IS OSTTOV=}

/(EG 4 FOR 24@@ BAUD
/QRIGIN (IN FIELD @)

/0S80RGa
XLIST
1FDEF

MCR

XLISY

LSTFLG

K=
/MCRCL

MCRSYSs{

/MCRFLD=
/MCRORGs
/MCRPRTs
/MCRCDvVs

MCR

DESIRED

/FIELD

/LOCATION

700

/CONSOLE TO
/DEFAULT
1§

XLIST

IFDEF

cLock

XLIST

LSTFLG

FACILITIES

MCR

NUMBER
BE

TTY

CLKQLN®=2Q

DECIMAL

HERTZsiooo

/MAY

CHANGED

OMITTED

(DEFAULT

(DEFAULT)

MCR

/PARTITION

CLKTYP®Q

VT@S)

USER

(DEFAULT

USED

MCR
BY

IS
(IF

MCR,

END

OF FIELD)
NONeRESIDENT)

E,G,

TTY

§)

DEMONSTRATION PROGRAM

SHERTZu1{

IFNIZRO

OCTAL
XLIST

/LPTLOCs
/LPTFLOs

IFDEF

CLKTYP&{ <HERTZ®175@>
1>

LPT

DTa

IFDEF

/FORCE DKBEP,KWwi{2 TO { KHZ

/DTALQOCS
D=
/DTAFL
>

/SET TO *LSTFLG® 1F YOU DON’T DESIRE

TBLLST® 0@

/70 SEE TABLES WHEN PARAMETER FILE 18
/NOT

LISTED,

/SYSTEM LOCATIONS:

MSGTBLS 1200-2
TSTABLS NTASKS+2"2+MSGTBL=4

/TASK MESSAGE TABLE
/TASK STATE TABLE = HOLDS

TFTABLS NTASKS+2"4+TSTABL=!

/TASK FLAGS TABLE = HOLDS

XLIST

/TASK STATUS FLAGS

IFDEF
XL1IS8T

SWAPPER «
LSTFLG

IFNDEF

SUNIT

SYSERKS
SUNIT=Q

/TASK LINK,UM,DF,I1F,PC,AC,MQ

/DEFAULT SWAP UNITY IS 0

@
FIELD
/

(PARTBL) ENTRIES?H

/PARTITION TABLE

/MUST BE INITIALIZED 8Y USER AS EXPLAINED IN THE COMMENTS
/DON*T FORGET TO REMOVE LEADING "/" FROM LINES USED
/

RESTBL® TFTABL+NTASKS+2
PARTBL® NTASKS=SWAPPERTM2¢RESTBL*347774

/RESIDENCY TABLE
/PARTITION TABLE

*PARTBL
XLIST

IFNZRO

MFL.D2O=}

XLIST

PARTNS

TBLLSY

ADDROQO=4Q0

S1ZEQ0Qn}

SIZEQQ*10+*MFLDO0Q"10+4000
ADOROD

MFLOD]=
ADDROQLs=

SIZEQ)s

IBLOCK
XL18Y
IFNZRQ
XLI8T

PARTNS»=}

TBLLST

/MEMORY FIELD OF PARTITION »}
/LOWEST ADDRESS IN PARTITION #}

/8S12E OF PARTITION #1 (CORE PAGES)

SIZEQ1TM1@+MFLDBL1TM10+400Y

ADDROY
I8LOCK

XLIST

MFLDOes
ADDROZ=
SIZER2TM=

IFNZRQ
XL187

PARTNS=2
TBLLST

/MEMORY FIELD OF PARTITION #2
/LOWEST ADDRESS IN PARTITION #2
/S81ZE OF PARTITION w2

SIZEQ2"10+*MFLDO2"10+4000
ADDRQ2

ZBLOCK
XLISY

XLIST

THLLST
/PARTITION #3

IFNZRO

MFLDR3s

PARTNS=3

ADDRO3s

SIZEQ3s

SI2EQ3~10+MFLDO3"10+4000
ADDRE3

Z8LOCK
XLIST

IFNZRQ
XL1ST

MFLDO4s

2
PARTNS=4
TOLLST
/PARTITION

<
#4

ADORO4s

S1lEQ4s

SIZEG4"1O+*MFLDO4TM10+4000
ADORQ4

DEMONSTRATION

ZBLOCHK

PROGRAM

XLIST

IFNZRO

PARTNS=5

XLIST

TBLLST

MFLDRS®

/PARTITION

ADDROSH

SIZEQSs
SIZE@5TM10+MFLDRSTM18+4000

ADDROS

ZBLOCK

XLIST

IFNZROD

PARTNS=8

XLIST

TBLLST

MFLDO6=

/PARTITION

ADDRO6®=

S1ZEd6s

SIZEQ6"1 2+MFLDR6"10+4000
ADDRQS&
ZBLOCK
2
XLIST
IFNZRO
XLIST
THLLST
/PARTITION #7

PARTNS®=7

MFLLBT=

ADDRO7=

SIZEQTs
SIZEQTTM) Q*MFLLRT"10+400Y
ADDROY

ZBLOCK
XLIST

/
/ADDITIONAL

2
{>>»>>»>>

PARTITIONS

/FURTHERMORE,
/

THE

NN NN,

PRTEND=,
1>

IFDEF

TTy

XLIST

L3TFLG

NNN

SCOPEs=
FILL»

OLDTTYn

LSBOTs
TTFLD»
TTLOC=

PARTITION

SHOWN
IN

IFNZRO

KL8A

XLIST

LSTFLG

XLIST

IFDEF

EXIT

ABQOVE

FIELD

ZERO

TABLE

DEVICE

CODE

DEVICE

DEFAULT

LINE

/1
/1

1IF
TO

LISTS

WIDTH

TTY
USE

HAS
OLD

BOTH

(©

MEANS

TTDEVel

INFINITE),

DEFAULT

HARDWARE TABS
2=-PAGE TTY NANDLER

HANDLERS

(DEFAULT

/FLIELD OF TTY TASK (TIMES
/LOCATION OF TTY TASK

XLIST

10)

/KL8A
/KLBA

/KLBACT=

DEVICE CODE = DEFAULT IS 40
CONNECT ROUTINE PAGE = DEFAULT

74002

XLIST
/EXITFLODs

LSTFLG

/EXITLOCs

/LOCATION
i >

/FIELD OF

EXIT TASK
OF

EXIT

(TIMES

TASK

12)

LSTFLG
PUPBE

<PDPBEE{>
<PDP12e0>

PUP12
EAE

<EAEED>

PWRFAL

<PWRFAL®D>

KL8A

<kLB8A=D>

IFDEF

i
NSP

XLISTY

LITFLG

MAXCCBs

USER

ANYWHERE

CODE = DEFAULT
MEANS CONSOLE TTY (DEFAULT)
ENABLES CTRL/S AND CTRL/Q

/TTY

TABs

XLISTY

THE

RESIDE

/1 MEANS TTY CAN 00 A BACKSPACE
/NUMBER OF FILL CHARACTERS, 1,E,

WIDTHS®

IFNDEF
IFNDEF
1FNDEF
IFNDEF
IFNDEF

MAY

/1
/1

VTSo=

XLIST

END

/KEYBUARDO

CONSOL
=

XLIST

DEFINED

TABLE

/PRINTER

KBDEVsS

/KL8ADYS

/NOTE

XLIST

TYDEVS=

MAY

PARTITION

/NUMBER
/EsG, 3

OF LOGICAL CHANNELS
FOR 3 CHANNELS

(CCB*S)

BEING

USED

/THESE ARE NUMBERED {,2,3

MAXNOD=

/NUMBER

NODE

NAMES

NODE

TABLE

NSPFLDw®

/PIELD

NSPLOCe

/(TABLES INCLUDE CCBTAB, LNKTAB, NODTAB AND
NETTAB)

NODNUMS

2600

NSP

TASK

AND

MOST

NETWORK

/URIGIN OF NSP TASK,
MuST BE ,LE,
/THE DEFAULT 1S CURRENTLY 3200

/NODE

NUMBER

THIS

NOOE

TABLES

3200

(E,G.

32)

120

DEMONSTRATION PROGRAM

/IMPORTANT RELATIVE ORIGINS WITHWIN NETWORKS TASKS
DRLXITs N3PLOC+4400
CCBTABs DRLXIT+200

/ADDRESS OF AST DE~QUEUER
/ADDRESS OF CCB TABLE

NETTAB=® NODTAB+60

/ADORESS OF NETWORK *INFORMATION® TABLE

/ADDRESS OF NODE TABLE

NODTABs CCBTAB+1R0

/THE DEFAULT NETWURKS TASKS USt CORE AS FOLLOWS:

(1 LINE, @ PAGE NODE POOL)

/DDCMPE PAGE 0, 0200=~3577

3200~7517

PAGE ©,

/N8P

/NETWORK TASKS USE PAGE @ AS FOLLOWS:
10=12,
15=17,

/DDCFLD:
/NSPFLO
/NCDE

TABLE

ENTRIES

/EACH ENTRY

HAS THE

/WORDS 1=3

32=77
77177

FQORM

©@=PADDED)

(é=BIT,

NODE NAME

LINE NUMBER
BlT 2=1 IF ADJACENT NODE
BITS 4»11 CONTAIN NODE NUMBER

/WORD 4
/WORD 5
/

IFOEF

TASK

FIELD

NSPFLOX10

IFZERO

TASK=NSP

*NODTAB

NOOTAB,

TEXT
/NAME/
0
)
*NETTAB+4

/LINE
/NODE
/0UKk

NODE

NUMBER

TEXT

/NAME/

/0UR

NODE

NAME

i
DUCMP

NODNUM
FIELD

NUMBER
NUMBER

>»>

>»

XLIST
IFDEF

MAXLINS

XLIST

MAXPKTs 24

/KG8E®m
ODCFLD=
DDCLOCs Q200

LCBSIZs 32
PKSIZE=

LSTFLG

/NUMBER OF PHYSICAL LINES BEING USED
/t,6, 3 FOR 3 LINES
/THESE

ARE

NUMBERED

/SET TO 10T SKELETON IF KGBE IS PRESENT (E.G, 6118)
/FIELD OF DDCMP TASK,LCBTAB AND *NODE POOL* (E,G, 20)
/THIS FIELD MUST BE DIFFERENT FROM NSPFLD
/O0RIGIN OF

DDCMP TASK

/THE ABOVE MUST BE BELOW S000~SIZE OF NODE POQL AND LCBTAB
/THE DEFAULT IS CURRENTLY 200
/GLOBAL DEFINITION OF LCB SIZE
/6L0BAL

DEFINITION OF PACKEY

ODCFNCs DOCLOC
HEAQPKs

9,1,2

/8ET TO NUMBER OF NODE POUL PACKETS TO ALLOW
/THE NODE POOL EXISTS AT THE END OF DODCMP
/JUST BEFORE THE LCB TABLE (SIMILAR TO THE CLOCK QUEUE)
/EACH PACKET REQUIRES 14 WORDS OCTAL, (ABOUT 10, PER PAGE)
/(THE DEFAULT REQUIRES 2 PAGES CORE)

/ADORESS OF

LCBTABs MAXPKT"PKSIZE+HEADPK

DDCEF=
FREWDs

DOCTL=e
DDCHD=

NETWORKS PAGE @

46
47

50
S}

ATNINPS S¢2
OHORs
5%
QCRCLs

ODCRCL®

OUTCOFs 67
DDCUSKRS®

N3P

XLI8T

XLIST

IFDEF

XLIST

/NIPFLDs

/NIPLOCs

/NIPARTs
/SKIMPu

NIP
LSTFLG

(OO0 NOY ALTER)

/ADDRESS OF DDCMP

DUCLOC+3@2e9?

/IMPORTANT

(DO NOT ALTER)

SIZE

fFUNCTION CALL" ROUTINE

START OF PACKET

FREELIST

/ADDRESS OF LINE CONTROL BLOCK TABLE

GLOBALS

/DOCMP 1/0 EVENT
/LOCATION OF I/0

FLAG
PACKET

/POINTS TO TAIL OF
/POINTS TO HEAD OF

DDCMP
DDCMP

FREELIST HEAD
INPUT QUEUE

INPUT QUEUE

/POINTS TO TRANSMIT COMPLETE RING BUFFER
/LOCATION OF HEADER BUFFER FOR TRANSMITS
/HEADER CRC FOR TRANSMITS
/DATA

CRC

FOR

TRANSMITS

/DATA DESCRIPTOR FOR TRANSMITS
/DEFAULT

USER

DDCMP

TASK

/FIELD OF NIP
/LOCATION

(TIMES

NIP

10)

/PAKTITION FOR NIP
/SET

TO GET SHORT NIP

8-5

DEMONSTRATION

/NIPLOGE

PROGRAM

/DEVICE NIP QUTPUTS TO

/DEFAULT

/NIPRESs

LPT IF IT EXISTS (OTHERWISE
FOR RESIDENY PORTION OF NIP

/LOCATION

/REGUIRED

/TLKF| Dn

/DEFAULT

XLIST

IFDEF
XLIST

TLK

LSTFLG

ONLY
IS

/FIELD OF

/TLKLOCs
TLKCHNS
XLIST
IFDEF
XLIST

1
LSN

NIPART

TLK

TASK

TLK
ASSIGN

TASK
TO

TASK

/START
CHANNL TO

/CCB

DEFINED

NIPLOCe2p0

TLK

TASK

>
<

LSTFLG

/LSNFL D=

/FIELD

/LSNLOC=

/START

LSNCHNsz

LSN

TLK

(TIMES

TASK

10)

/QCB CHANNL TO ASSIGN TO LSN TASK
1
>

XLIST

LSTFLG

/EQUIVALENCES:
ACTT776s3

CLL

STA

AC7775=

RAL

CLL

STA

RTL

AC4D0Os

CLA

STL

RAR

AC3T777Ts

CLL

STA

RAR

AC20002®

CLA

STL

RTR

ACQo0o2m

CLA

STL

RTL

/MONITOR

CALs=
POSTDS=
WAITM®

SENDs
RECEIvs

CALL

VALUVES:

JMS

JMP

JMS

/CALL

THE EXECUTIVE

/DISMISS
/WALT

FOR

INTERRUPT

MULTIPLE

EVENTS

/NOTE:
"we® MEANS CRITICAL VALUE MAY NOT
/BE CHANGED WITHOUT MODIFYING SYSTEM CODE}}
/SEND MESSAGE

")
|

/RECEIVE

MESSAGE

WAITE=

/WALIT

RUN®

/CONTINUE

SUSPNDs

/SUSPEND

FOR

EVENT
TASK

TASK

FLAG
EXECUTION

EXECUTION

POSTs

SKPINS®
DERAILs

/POST

6
7

BLKARG®

/INSERT CODE INTO INTERRUPT
/INITIATE ENU=ACTION

/BLOCK

SENDWs

TASK

UNBARGS®
RESCHDs
WAITXs
FREE=

/SEND

12
13
14
4000

MESSAGE

/UNBLOCK TASK FOR REASON SPECIFIED
/FORCE A RESCHEDULE
/JWALT FOR EXACTLY THIS EVENT FLAG
/*«FREE PARTITION

XLIST

IFDEF

uoC

XLIST

EVENT

FLAG

FOR

REASON

AND

SKIP

SPECIFIED

CHAIN
IN

ARG

WAIY

ARG

LSTFLG

AD=2)D0%1}D1s2)GCa3JECu4RCES

DCs6JECTS7)CSs1pjDCTa
AT
11

/TASK

XLIST

XLIS8T

LSTFLG

STATUS

NCNRWTs
EFWTs

4200
2000

RUNWT=s

{p0o@

SWPWTe
EORMWTS

2400
22080

FLAGS:
/*«NONRESIDENT

TASK

JEVENT FLAG WAIT
/SCHEDULE WAIT
/*%SWAPPER

WALT

/EVENT FLAG OR MESSAGE

USERWTs=s

2100

/USER

ENABWTs
MSGWT=

Qp40

/ENABLE

NETWTs

Q0202
Qp1i@

/NETWORK

.DNEWTs

Qp01%

/*%DOES NOT EXIST

IFNZIRO

WAIT

SPECIFIED

/MESSAGE

KL8A

WAIT

WALT
WAIT

_
(RESERVED

<IFNDEF

FOR

POSSIBLE

WAIY

KL8ACT

KLUD=
KLBACT=

KL8A=1/3"200

TSWFLG®

TODL»
TOOHs
DATEs
MCREFs

/TASK

L1
37
40
41

/LOW ORDER TIME OF DAY

IN FIELD @

/OATE IN 088 FORMAT

IN FIELD @

7420=KLUD>>

INHIBIT

/HIGH ORDER

/MCR

START

FLAG

TIME OF DAY

EVENT

FLAG

FIELD @

IN FIELD @

FIELD

8-6

FUTURE

USE)

TTY)

DEMONSTRATION PROGRAM

/SOME USEFUL EQUATES FOR TTY AND LPT MESSAGES!

IND®1000

/TEXT IS NOT PACKED IN 6=BI7
/OUTPUT SHOULD NOT BE FOLLOWED BY CR/LF
/OUTTXT PTS TO FIRST WORD OF TEXT

ASSGN=200

/ASSIGNS DEVICE

NOPACKS400D

NOCRLF=2000

/INPUT IS IN CHARACTER MODE

NOL INE= 42V
KLBALINE®100
XLIST

IFDEF
XLIST

/USED TO SPECIFY A LINE OF A KLBA

CLOCK

LSTFLG

SOME USEFUL EQUATES FOR STANDARD CLOCK MESSAGES!
MARKTIME=
SCHEOULE=
TIMOUT=

XLIST

IFDEF
XLIST

/POST EVENT FLAG AFTER SPECIFIED INTERVAL

200e
200v

/DERAIL TASK AFTER SPECIFIED INTERVAL
/USED AS MODIFIER TO °SCHEDULE’

Te0u

/DELETE ALL REQUESTS FROM SPECIFIED TASK FROM GUEUE

IFNDEF
IFNDEF

TASK

INIWT

INIWT2
INIWT3S

*TASK*2+MSGTBL

8L.0CKk

/RE=QUEVES RUN REQUEST AFTER SPECIFIED INTERVAL
*SCHEDULE FOO PERIOQODICALLY’
/E .G,

/FORCE LISTING OFF
<

/TASK TABLE SETUP = "TASK",
/MUST BE DEFINED BY TASK1
IFNDEF

/RUN TASK AFTER SPECIFIED INTERVAL

1000

PERIQODICALLYs
CANCELs
XLISY

"CUR","INIWT",

AND "STARTY

/MESSAGE BUFFER

INITIALLY CLEAR

*TASKTM4+TSYABL

CUR%12+CUR

/INITIAL

/INITIAL AC
<
VERS

STARY

XLIST}

IFDEF

FLAGS
@

XLIST

JINITIAL

VERS

XLIST
XLISTY

*TASKeTFTABL

INIWT
XLIST
>

1FDEF

TASK?

XLIST
*TASK2"2+MSGTBL

/MESSAGE BUFFER
2
"4+ TSTABL
wTASK2
/INITIAL FLAGSZ
CUR2%10+CUR2

ZBLOCK

START2
Q

XLIST}
XLIST

VERS2
XLIST
XLIST

1IFDEF

/ZINITIAL AC
<
VERS2

/INITIAL

INITIALLY CLEAR

"TASK2+TFTABL

INIWT?2
XLIST
4

IFDEF

TASK3

XLIST

*TASK3I“2+MSGTBL
¢
ZBLOCK

/MESSAGE BUFFER INITIALLY CLEAR

CUR3X10@+CURS

/INITIAL FLAGS3

*TASK3I~4¢TSTABL

STARTS
]

XL1ST)

IFDEF

/INITIAL

VERSJ

XLIST

VERS3

>
XLIST
XLIST
*TASK3I+TFTABL

INIWT3

XLIST
>

/INITIAL

DEMONSTRATION

1FDEF
1FDEF

TASK
PARTND

PROGRAM

«
«

XLIST

/RESIDENCY

TABLE

(RESTBL)

ENTRY:

/INITIALIZED FOR NONRESIDENT

TASKS ONLY

"TASKeSWAPPER=1%2+RESTBL
PARTNOTM4+PARTBL+CPABLE+CPABLE+WRITE
XL187

IFNDEF
IFNZRO

SWAPPER SNOSWAP, ERROR, >
/SNAPPER MISSING
TASK=SWAPPERL4DOD
<SWPRIO, ERROR_>»/NONRESIDENT
/HAS

»>

IFDEF
IFNDEF
IFNOEF

The

«
SNOTASK, _ERROR_ >
<NOSWAP, ERROR, >

/PARTITION

TASK

are

Nonresident

LISTINGS

listings

Task

nonresident

tasks

NR20

TASK=20
002@

TASKS20Q

20e0

TASK=2p
START=4002

2400

1173}

WRITEal

0ol

CPABLEs=]

Qoo
5000
200
0ol

CUR®=1Q
INIWTSRUNWT*NONRWT
PARTNQ=Q
FIELD CURX1Q

2400

12614

TASK

8.2.1

10605
12606
10611
10612
10618

XLIST

following

10600
10603
10604

BUT

TASK
THAN SWAPPER

NONRESIDENT

104020
106401
10402
10403
10404
10405
10406
10407
10410

HIGHER

/PARTITION BUT NO SWAPPER
PARTNS
<NOPART, _ERRQR_»
/MISSING PARTITIONS
PARTNO=PARTNSE4000
<PRTERR,_ERROR,>»
/PARTNO,GE,PARTNS

IFNDEF
IFZERO

8.2

PARTND
TASK
SWAPPER

PRIORITY

4020
4011
Q001
0622
420
40141
Q003
0606
5200
2600
0QQ@2
o000
2000
02001
QQQ0
Q000
Q02
2421
2313

10615

4pee

10616
10617

6042
2225

10622
10621
10622

1616
1116
0702

»d00

SLPMSG,

LPTMSG,

CAL
SENDWeFREE
CLOCK
SLPMSG
CAL
SENDW+FREE
LPT
LPTMSG
JMP START
%600
ZBLOCK 3
2
D7SHERTZ

ZBLOCK 3
2
2
TEXT /TASK

RUNNING/

(NR20

and

NR22):

DEMONSTRATION PROGRAM

8.2.2

Nonresident Task NR22

TASKs22
ooee

10400
10401
10402
104023
12404
10405
10406

10407
10410

106302
10633

10634
10635
10636
10641
10642

10643
10644
10645

TASKs22
START=4090

ooeo

PARTNO=Q

Y0}
@400

FIELD
x40

4020

CAL

4011

SENDW+FREE
CLOCK
SLPMSG
CAL
SENDw+FREE
LPT
LPTMSG
JMP START

WRITE=]

CPABLEs=]
CUR=10

INIWTRRUNWT+NONRWT

eapl
2639

4020

4211
0003
636
5200
Q000

0000
veeo
2001
2000
2000
2000
4ol
e313
4062

6249

10647

2ees
1616

1116
9709

CUR%i®

%630

P630

10646

10650
12651
10652

TASKE=2¢

goee
0400
Qoo
oR01
0010
5000

SLPMSG,

ZBLOCK

@) SHERTZ
LPTMSG,

ZBLOCK

2
0

TEXT

/TASK

RUNNING/

DEMONSTRATION

8.3

ASSEMBLY AND

The

assembly
follows:

JFAL

and

LOAD

load

PROGRAM

PROCEDURE

procedure

for

the

demonstration

program

RTS8CFARAMYRTSSE

ERRORS

DETECTED:

LINKS

GENERATED:

+FAL

CLOCK<FARAMy CLLOCK

ERRORS

DETECTERD

LINKS

GENERATED:

MCREPARGMy
MCR

ERRORS

DETECTEDRS

LINKS

GENERATED:

058SUPCFARAM
y 0S8SURF

ERRORS

DETECTED:

LINKS

GENERATED:

JPAL

TTYSFARA
TTY
M

ERRORS

DETECTED:

LINKS

GENERATED:

cFAL

LPTSPARAM
LT

ERRORS

DETECTED:

LINKS

GENERATED:

RKBECPFARAMy
RKBE

ERRORS

DETECTED:

LINKS

GENERATED:

FAL

NRZOCPFARAMy
NR2O

ERRORS

DETECTEDG

LINKS

GENERATED:

fFAL

NR2Z2CPARAMy
NR22

ERRORS

DETECTED:

LINKS

GENERATEDD

+FAL

SWAFCFARAMy
SWAF

ERRORS

DETECTED:

LINKS

GENERATED:

+ROABSLIDR

KNR20%
+9A

BYS

NR20

1040010577

+ROARSLIR

KNRZ224%
+ 58

BYS

ARSLIR

NR22

1040010577

XRTS8yMCRy CLOCKsRKBE s TTY v LLFT» QSRBSUF
XSWA
s NR20O» NR22%
F
+85A

8YS

RTS8BV2

This

example shows the assembly of the parameter file and
the
source
task
itself.
The
binaries of each nonresident task are then loaded
into memory, and their nonresident portions saved on the swap
device.

All

tasks

being
memory

are

loaded
is

then

first.

saved

using

loaded

using

the

Finally,

the

core

the

0S/8

SAVE

ABSLDR with

image

command.

8-10

the

RTS/8

all

the

Executive

tasks

PROGRAM

DEMONSTRATION

NONRESIDENT TASK ASSIGNMENT AND EXECUTION

8.4

The following is the execution of

tasks NR20 and NR22 to the system.

RTS/8

showing

the

assignment

+R RTHBV2
ANR20=20
ANRZE2=22
X$:6Y
CLOCK 0O
01
M
M

02
03

TTY
LPT

MCRK

07
15

RK8
088F

M
M

SWAF

22
23 088
RE 20
FREO22
FEXTT

RN
E

In
the
above
example,
the
user
nonresident
tasks
with an ALTMODE,

terminates
the
installation
of
and returns to the MCR.
A SY¥Ystat

command is executed which prints a system status report
(see
Section
6.2.9).
The REquest command is then used to run tasks NR20 and NR22.
Shown below is output from tasks NR20 and NR22 on the line printer.
TASKR 20
TASK 280
TASK 20
TASK 20
TASK 22
TASK 20
TASK 22

TASK
The
the

RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING

20 RUNNING

EXIT command is
0S/8 monitor.

typed

terminate

RTS/8

execution

and

return

CHAPTER

ADVANCED RTS/8 PROGRAMMING TECHNIQUES

9.1

9.1.1

PERFORMING A RESCHEDULE

Writing Delicate Code

data

Frequently, a task needs to manipulate

another

task

common area. Since tasks are running ‘'simultaneously', problems will
arise if two tasks want to access the same data at the same time.
Consequently,

delicate

while accessing data

code

in another

wants

task.

run with interrupts disabled

NOTE

temporarily
disabled
Interrupts may be
on
or,
pair
IOF/ION
a
either
using
CIF
a
extension,
machines with memory
interrupts
inhibits
which
instruction
until the execution of
JMS instruction.

the

JMP

For example, suppose Task A increments location COUNT occasionally and
from time to time during program
COUNT
location
B decrements
Task
following:
the
like
look
might
code
The
execution.
/TASK

LOOPA,

ISZ

COUNT

JMP

LOOPA

COUNT,
/TASK

LOOPB,

STA

TAD

COUNT

DCA

COUNT

ADVANCED

RTS/8

JMP

LOOPB

If Task A increments
decrements COUNT, it

the

program.

condition
Suppose

that

waiting

Task

for

Task

ready

has

store

that

and
then
containing a 5

This

higher

with

COUNT.
executed.
into COUNT.

event

Task

resumes

goes

back

and

situation
the

employed:

Solution

/JTASK

LOOPB,

The

an
contains

interrupt

for

has

Task

now

bumps

sleep.

happening

Either

the

Solution

/TASK

Task

and

just

occurs

Task

routine,

occurred,

COUNT

two

from

now

the

AC
proper

interrupts

solutions

can

CIF

CUR

STA

TAD

COQUNT

DCA

COUNT

TAD

COUNT

DCA

COUNT

ION

JMP

LOOPBRB

Solution

CIF

2 (only
instruction

JMP

JMS

JMP

usable

since

machines

Task

with
temporarily

instruction

Inhibiting
the

race

containing

disabling

following

Although

and

B
end

LOOPB,

I0F

9.1.2

since

Task B then resumes with
COUNT which is incorrect for

into

the

service

waiting
A

Task

interrupt

STA

was

fronm

code.

Task

currently

prevented

delicate

than

COUNT

that
be

Task

stores

times
would

However,

been

and

COUNT

necessarily

priority

occur

TECHNIQUES

number
that

not

execution.

around

back

the

Task

this

decrement

program

same
assumed

has

location

suspends

the
be

event

after

noting

COUNT
would

However,
occur.

can

PROGRAMMING

LOOPB

memory

extension)

inhibits

executed.

interrupts

uses

the

until

the

Switching

procedure

the

section

can

used,

at
times
can
be very inefficient.
If it is desired to perform a lot
of
manipulation on data which could
be accessed by other tasks, it
may be
inappropriate
to turn off interrupts.
Inhibiting interrupts for long
periods of time could affect other
portions of the system where
timed

events

are

example,

significant
For

this

RTS/8

case,

inhibiting

important.

interrupts)

amount

Also,

time.

another

solution

that

wants

interrupt

interrupts

are

can

turned

lost

off

(for

for

possible.
A task
can
inform
the
continue to run, and that while
it is
a certain piece of code, no other
task should run even if
a
higher
priority becomes runnable.
This process is known as

Executive

executing

task

very

clock

task

switching.

ADVANCED RTS/8 PROGRAMMING TECHNIQUES

Task switching should be inhibited only

under

unusual

circumstances

While task switching is inhibited,
with care.
per formed
and
interrupts may still occur and the interrupt service routine will get

However, if task switching 1is inhibited, the interrupt
control.
service routine will always return control to the interrupted task
after the interrupt has been serviced even if higher priority tasks
are

now

runnable.

NOTE

data
manipulate
to
If the user wishes
1is accessed by an interrupt-level
which
inhibited
be
must
routine, interrupts
switching alone
task
1inhibiting
since
will not be sufficient in this case.

There are two methods

inhibiting

task

switching

which

are

follows:

Method 1:

Task switching is automatically inhibited whenever a task's

1less

1is

bottom of page

than

Thus,

100.

0 of any field.

delicate code could be placed in the

A task may inhibit task switching by zeroing location 35 in
Method 2:
This location is symbolically referred to as TSWFLG (task
O.
field
In
file.
switching flag) and is defined as such in the parameter
either case, after the task is through with its delicate code, it may
not be sufficient for the task to reset TSWFLG to its original
fact that there may be some other
to the
is due
This
value (1) .
run because
to run but did not
entitled
is
that
task
y
higher-priorit
this out by
find
can
user
The
inhibited.
switching was
task
If another task became runnable while
interrogating location TSWFLG.
the RTS/8 executive sets the task
inhibited,
task switching was
When a task is ready to allow task switching
switching flag to -1.
1If it was
it must examine this flag before resetting it to 1.
again,
1is
This
-1, the task returns control to the RTS/8 scheduler.
performed by using the RESCHD ER as

follows:

CAL
RESCHD

This ER causes RTS/8 to perform a reschedule that allows the runnable
1If a user does not perform a
task of highest priority to be executed.
task
priority
RESCHD after re-enabling task switching, then a higher

run until the next interrupt
not
run might
to
entitled
is
which
too
The interrupt may never occur, or if it does, it may be
occurs.
late

for proper program execution.

The preferred code for inhibiting task switching for Task B which
described previously
/TASK

LOOPB,

CDF

DCA

shown below:

(TSWFLG

/INHIBIT TASK SWITCHING

STA

TAD

COUNT

DCA

COUNT

ISZ

(TSWFLG

/ALLOW TASK SWITCHING

9-3

was

ADVANCED

JMP

RTS/8

.+3

PROGRAMMING

/SHOULD WE

CAL

/YES

TECHNIQUES

RESCHEDULE?

RESCHD

CDF

CUR

/NO

JMP LOOPB
NOTE

summary

Interrupt

level

the

TSWFLG

set

states

Summary

TSWFLG

not

shown

Table

9-1

Switching

Table

Flag

(TSWFLG)

State

Task

switching

inhibited

Task

switching

inhibited;

soon

EXECUTIVE

REQUESTS

WAITM

Waiting

Sometimes
of

quite

Flags.

simple.

The

possible

-1

FOR ADVANCED APPLICATIONS

for

desirable

Event

States

Value

allowed

look

9-1.

switching

9.2.1

OR)

should

Task

reschedule

9.2

Task

routines

TSWFLG.

Multiple

wait

Waiting

for

Event

for
the

Flags

logical

AND

sequence:

combination

(AND

Flags

two

Event

CAL
WAITE

CAL

/WAIT

FOR

EVENT

/AND

THEN

WAIT

been

POSTed.

FLAG

WAITE
B

waits

until

both

A and

Waiting

the

logical

since

the

for
there

interrupts

involved.
successfully

testing

state

none

the
of

have

EVENT

FLAG

OR of several event flags
is
more
possible race condition between the various

(or

The

FOR

task

key
not

to allow

first
the

executions)

waiting

Event
flags

any

Flag
were

for

which

and

the

POSTed.

POST

the

several

interrupts

difficult
tests and
Event
Flags

placing

occur

the

Event

Flags

between

task

the

Wait

ADVANCED RTS/8 PROGRAMMING TECHNIQUES

This is accomplished by using a special sequence of instructions and a
It
special RTS/8 call named WAITM. WAITM is defined as JMS I 25.

must be executed with interrupts off, the Instruction Field set to 0
and the Data Field set to the current field, and it must be followed

by a word containing the blocking bit(s) to be set in the Task Flags
The action of WAITM is equivalent to the action of the RTS/8
Table.
except that a fast path through the RTS/8 Executive is taken
ER
BLKARG
and interrupts remain off until the blocking bits are on in the Task
Flags

Table.

For an example of the use of WAITM, assume that a task "TASK" wants to

If A is POSTed, control should go to
test two Event Flags A and B.
if B is POSTed control should go to 1location BDONE.
location ADONE;
If neither is POSTed, the task must wait until one of them is POSTed.
The code to perform this function

is:

/INTERRUPTS OFF - DELICATE CODE

TESTAB, IOF
TAD

SNA

CLA

TAD

(4000+TASK

/ADONE MUST TURN INTERRUPTS ON

JMP ADONE

/SET A TO "WAITING"

/THAT THIS TASK IS WAITING ON IT

DCA A
TAD

SNA

CLA

TAD

(4000+TASK

/BDONE MUST TURN INTERRUPTS ON

JMP BDONE

/SET B TO "WAITING"

CDF

CUR

STATE

/INDICATING

/THAT THIS TASK IS WAITING ON IT

DCA B
CIF

STATE

/INDICATING

WAITM

/BLOCK TASK ON EVENT FLAG WAIT
/WE'RE BACK - ONE OF THE TWO

EFWT
JMP TESTAB

/EVENT

FLAGS

HAS

BEEN

POSTED.

/GO BACK TO FIND OUT WHICH ONE

9.2.2

WAITX - Wait for Exactly This Event Flag

The exception is that if the
The WAITX ER is similar to the WAITE ER.
the task goes into EORMWT (instead of
FINISHED,
is not
Flag
Event
location
EFWT), and the task's PC in the TSTBL points back to the

Thus, when the task resumes execution,

containing the CAL of this ER.

some
If the EORMWT bit was cleared for
it will re-execute the WAITX.
reason other than the Posting of the Event Flag in question, the task

will

immediately go back

into

EORMWT.

Consequently, control will never

flow past this ER

wunless

the

Event

1is actually posted (see discussion of DERAIL, Section
specified
Flag
on
task was waiting
the
if
If a WAITE had been used and
9.2.3).
(which can happen using WAITM), then control
Flags
Event
multiple
conceivably could start up after the WAITE ER because some other Event
This
about, was posted.
cared
longer
is no
that
and one
Flag,
situation can not occur with a WAITX.

9.2.3

DERAIL - Derail a Task's Execution

The DERAIL ER modifies the execution of a specified task and transfers
some
process
to
task
the
of
subroutine
special
a
to
control

exceptional condition.

It does not cause any wait bits to get set

cleared.
9-5

ADVANCED

Format:

TAD

RTS/8

PROGRAMMING

TECHNIQUES

TASKNUM

CAL
DERAIL

ADDR

This ER simulates
in
TASKNUM
(the
field

(from

which

1its

the

Task

a "JMS ADDR" for the task whose number 1is
"derailed" task).
ADDR is assumed to be
derailed

State

task

Table

entry)

executing.

stored

The

derailed

ADDR;

the

its Task State Table entry is
then
set
to
ADDR+1.
points concerning the operation of the DERAIL
ER are as
1.

The

derailed

saved

restored

subroutine

contents
affected
by
runnable,

DERAIL

all

operations

can

seconds.

"watchdog

solution

1is

task

can

The

RTS/8

for

provide

in
Power-Fail

facility
to

used

1In

task's

ER.

a
it

will

not

temperature

all

unmodular

machinery

location

order

task

uses

on power-fail recovery
reinitialize a task.

shut

down

the

(see

its

DERAIL

Section

derail

level.

until

signal

an
be

abort

critical

wvalue.

necessary

some

not

would

temperature

code

better

equipment-controlling

own

4.5),

piece

equipment.

provide

which

can

similar

used

Example:

example

DENTRY,

DERAIL

routine

DCA

follows:
/DERAIL

ROUTINE

SAVAC

/SAVE

SAVLNK

/SAVE

LINK

/SAVE

DATA

ENTRY

POINT

RAR

DCA
RDF

RESUME,

DFRESET,
NORESUME,

TAD

(CDF

DCA

DFRESET

CDF

CUR

FIELD

/HANDLE

EMERGENCY

/BRANCH

/TO

/BRANCH

TAD

SAVLNK

CLL

RAL

TAD

SAVAC

HLT

JMP

CLA

CLL

DENTRY

CDF

CUR

JMP

RESTART

SAVAC,

SAVLNK,

RESUME
TO

every

shutdown

controlled.

each

not
and

task

exanple

include

being
which

are

saved

executed

task

room

the

exceeds

measures

Flags word
are
derailed task is

sometimes

which

priority
tasks.

room

and

sense,

the

entry

settings

this

Task

task's

Two
1important
follows:

must

high

priority

where

Field

contained
the same

they

interrupt

task

DERAILED

subroutine

lower

the

derailed

inefficient

task"

Data

runnable.

environment

checked

and

therefore

subroutine.

DERAIL

derail

generally

This

the

condition

Link,
ER;

much

the

becomes

process-control

this

task

emergency

derail

very

the

AC,

DERAIL

the

The

the
The

task's

the

CONDITION

'RESUME'

WHERE

YOU

'NORESUME'

/RESTORE

LINK

/RESTORE

/RESUME

(SAME

/RESTART

TASK

/RESTORE DF

FIELD)

YOU

LEFT
IF

WANT

OFF
NOT

ADVANCED RTS/8

PROGRAMMING TECHNIQUES

if
9.2.3.1 Dangers of DERAIL - A task can get into serious trouble
If this happens,
is derailed while already in a derail routine.
it
is no simple
There
the original PC, AC, link, etc., will be lost.
in the derail routine may be too
interrupts
Turning off
solution.

already
late to prevent this - the second derail could have
before the derail routine was even entered the first time.
Consequently,

than

a user doing a DERAIL should make

done

DERAL

one

sure

that

not

Alternatively, before doing a

a time.

occurred

DERAIL, a task can check an interlock flag (which it must maintain) to
see
whether
the
target task has been derailed or not.
The test and

set of such a flag should be performed with interrupts inhibited.

runnable,
not
1is
task
a
If
Restrictions Using DERAIL 9.2.3.2
If the task is in Event Flag
it will not make it runnable.
derailing
When
Wait, it will remain in Event Flag Wait until the event occurs.
1is POSTed, the task will wake up and begin to run in
Flag
Event
the
its derail
routine
rather
than
in
the
mainline
routine.
Thus,
derailing
a
task to get it to perform some important job immediately
and
The task might be in one of the Wait states
may not always work.
For example, if the task were
be able to run for some time.
not
may
a
in Receive Wait at the time, the derail routine would not run until
message

came

A partial

for

that

task.

solution around

this

restriction

is to code

the

task

derailed
so
WAITE.
Then,

that
it
always
waits on events using WAITX instead of
if the user wants to derail this task, the task is first

An example

the

taken out of MSGWT or

TAD

code

EORMWT and
for

this

then derailed.

situation

follows:

TASKNUM

CAL

UNBARG
MSGWT ! EORMWT
TAD

/UNBLOCK THE TASK
/FROM MESSAGE-RELATED WAITS

TASKNUM

CAL
DERAIL
DENTRY

This will work because
both
the
RECEIVE
and
the
WAITX
Executive
Requests
bump
the PC back to the CAL before going into a Wait state.
Thus, no harm is done if the task is taken out of that wait state
for
an
1incorrect reason.
When the task resumes running at that point, it
will re-execute the CAL (RECEIVE or WAITX) and go back into
the
Wait
state as necessary.
This method will not work if the task was in EFWT
due to a WAITE ER because the task would resume running
thinking
the
Event

Flag

had

been

posted

when

1in

fact

had

not.

A way

circumvent this (other than WAITX) is for the task to do WAITM instead
of a WAITE, and poll the Event Flag upon waking up.

9.3

STARTING PARTITIONS AT AN ARBITRARY BOUNDARY

The advanced user can start a partition at an
arbitrary
boundary
by
using the following assembly and loading procedure.
The example given
assumes that the partition in which the user
writes
the
nonresident
portion
of
the
task
to run is three pages long
PAL8 pseudo-operators FIELD and
RELOC
are
used,
detail in the 0S/8 handbook.

(11200-11777).
The
and
described
in

ADVANCED

RTS/8

PROGRAMMING

TECHNIQUES

/TASKX

FIELD

/SET

*1000

FIELD

/LOAD

RELOC

1200

/BUT

THIS

CODE

ASSEMBLE

procedures

for

11000-11577

RUN

11200-11777

<CODE>

PAGE

<CODE>

RELOC

The

assembly,
.R

load

and

save

code

are:

TASK)

PALS

*TASKX<PARAM.PA,TASKX.PA
.R

the

(ASSEMBLY

ABSLDR

*TASKXS
-SAVE

(LOADING

DEV

TASKX

11000-11577

(SAVING

OF
OF

TASK

INTO

TASK-THREE

CODE)

The

swapper,

11200,

9.4
A

upon

which

DIRECT

where

REFERENCES

task

may

directly

tables

obtain

the

following

task

For

may

immediately
to

symbolic
symbolic

entries

task, places it
assembled to run.

SYSTEM

into

the

partition

TABLES

Due to the interrupt-driven nature of the
system, these table
entries may change at any time;
therefore, interrupts should
be inhibited between the time these entries
are
tested
and
the
time
that
processing
which
depends on the testing is

Symbols

this

was

PAGES

interrogate
1locations
in
the
RTS/8
Executive
information about itself or any other task,
as long
two restrictions are observed:

completed.

11000)

run.

example,

show

after
This

result

turned

off

the

and

table
entries
Executive Requests.

testing

messages,

the

but

test might

task

test.

during

System

might

I/0

allow a

send

prevent

Message

an
a

Queue

higher

message,

this,

the

test.

may

changed

for

occurring

priority

task

invalidating

interrupts

after

Header

interrupt

only

the

should

through

RTS/8

have

been defined in the system parameter
table
that
permit
references
to
be made into these tables symbolically.
The
expressions which yield
the
address
of
the
system
table

for

task

N+TFTABL

N are:

Task

N~ 2+MSGTBL

Flags

1if

Table

zero,

Input Message
task

N;
messages

if
in

entry

task

Queue
zero,

its

for

task

runnable.

Header
task

queue.

has

for
no

ADVANCED RTS/8

PROGRAMMING TECHNIQUES

N"4+TSTABL

First word of Task

Entry

N~ 2+RESTBL

for

task

First word

State

Table

Residency

Table

entry for nonresident

task N.

For example, for a task to determine whether it had
messages
1in
input queue without issuing a RECEIVE request, the code would be:
CDF

The

/EXEC TABLES

IN FIELD 0

IOF

/TURN

TAD I (TASK”~2+MSGTBL
SNA CLA
JMP NONE
ION

/ANY MESSAGES?
/NO
/YES

code

NONE must

eventually

turn

INTERRUPTS

interrupts

OFF

back

on.

its

APPENDIX

RTS/8 DISTRIBUTED SOURCE FILES

The

RTS/8

source

File

Name

Task

files

included

the distributed

Task

Name

MCR

MCR.PA

null

0S8SUP.PA

0S8

0S8SUP.PA

OS8F

PWRF.PA

PWRF

CLOCK.PA

CLOCK

TTY.PA

TTY

file with all

Appropriate values should
specific parameter files.
RTS/8 Executive
Monitor Console Routine

RTS8.PA
MCR.PA

task

LPT.PA

LPT

DTA.PA

bTA

RK8.PA

RK8

RKBE. PA

RK8

RF08.PA

RF08/DF32

Null

are:

Function

System parameter

PARAM.PA

tape

equates

inserted

task

0S/8 Support Task
0S/8 File Support
Power Fail Task

Task

Clock Handler Task
Terminal Driver Task

Line
TC08

Printer
DECtape

Driver
Driver

Task
Task

RK8 Disk Driver Task
RK8E Disk Driver Task
RF08/DF32 Fixed-Head Disk

Driver

Task

Cassette Driver Task
Cassette File Support Task
Universal Digital Controller/
Industrial Controller Subsystem

CSA.PA

CSA

CSAF.PA

CSAF

UDCICS.PA

UDC/ICS

RX01RT.PA

RX8A

Floppy

Disk

Handler

(lst

controller)

RX01RT.PA

RX8B

Floppy

Disk

Handler

(2nd

controller)

RX(01RT.PA

RX8C

RX01RT.PA

RX8D

controller)
controller)

LTA.PA

Handler

Task

LTA

Floppy Disk Handler (3rd
Floppy Disk Handler (4th
LINCtape Driver Task

SWAP.PA

SWAPPER

Nonresident

NULL8A.PA

NULLS8A

Null

Task

EXIT.PA

EXIT

Exit

Task

for

Swapper

PDP-8A

blank.
create

APPENDIX

RTS/8

COMPONENT

SIZES

of
RTS/8 memory map showing
The modules may
be
default memory allocation is shown in Figure B-1.
in
memory at the user's discretion except for RTS8,
placed
anywhere
Also, certain modules must be placed in field 0 where
CLOCK and SWAP.
indicated in the tables.

The

following table gives the approximate size and default origins

each

The

component

following

RTS/8

the

parameters,

system.

which are used

in Table B-1,

are defined

follows:

Any

NTASKS

Number

CLKQLN
MCRSYS
MCRCLK

=
=
=

Number of entries in clock queue
1 if MCR SYSTAT function desired,
1 if MCR CLOCK functions desired,

KLINES

Number

fractions

tasks

physical

from divides

system

0
0

KL8-A lines

should

Table
RTS/8

else
else

dropped.

B-1

Component

Sizes

Software

Default

Number

of Pages
Required (1 page

Component

Origin

=128

RTS/8
Executive

00200

5+NTASKS/18

words)

Comments

Must
be
locations

in
00200~

Uses

01200.

0
1locations
and
20-47
auto-index
register 17.
Clock

Module

1st

page

3+CLKQLN/22

after end of
RTS/8 Executive
(or SWAPPER)
New

Must

page

0-3
and

field

0.
Uses
auto-index
register 10.

03400

Terminal
Module,

0ld

Terminal
Module,

(Continued

page)

RTS/8

COMPONENT

Table B-1
RTS/8

SIZES

(Cont.)

Component

Number

Sizes

Pages

Software

Default

Component

Required

Origin

=128

Line

14400

14600

04200

04400

LINCtape

15000

RK8

04200

Fail

10200

1+NTASKS/32

Module

10600

Printer

Module
TC08

DECtape

Module

RK8E

Disk

page

words)

Comments

Module

DF32/RF08
Module

Disk

Module

Power
Module

UDC

7-11

depending

table

space

Uses

page
0

locations

130-144

Requires

cassette

desired.
Cassette

13600

Label | 13000

Module

Cassette
Support

0S/8

Module

File

Support

handler.

04600

Module | support

0S/8

Requires

present,

storage

otherwise 06200!

Must run

mass

handler.

in field

0S/8

Support

06200*

Task

Must run in field
0 - requires
8K
for

0S/8

mass

Monitor
Routine

Console|
Task

17600 minus
(15200
with all
options and
length

KL8A

support)

5+3xMCRCLK+
MCRSYS

+
(NTASKS+40) /64.

plus

storage

handler.

Uses

page
0
164-177.

locations

Requires "console"
terminal handler
and page 0
locations 100-117.
See

Table

B-2

for

details.

!Moves down by length of KL8A support code if KL8A support present.
(Continued on next page)

RTS/8

COMPONENT

Table

B-1

SIZES

(Cont.)

RTS/8 Component

Number

Software

Sizes

Component

Default

Origin

Required

RX01

13200

SWAPPER

lst page after
end of RTS/8

Pages

(1 page

=128 words)

Comments

Must
be
field 0

1in

May relocate

executive

EXIT

15000

1/2

NULLS8A

13600

17600 minus

1+KLINES+1

KL8A

Support

length

within

Must

page

field

RTS/8

COMPONENT

SIZES

RTS/8 SYSTEM MEMORY MAP (Default Memory Allocation)
PAGES
0

FIELD 0

200 -

400 -

FIELD
1

(
RTS8

600 ~

TPWRF

—

{20 tasks)

—

1000

n
-

uDCICS

y
2000

SWAP

CLOCK

3000

‘
CSAF

|
—
RX01RT

TTY V2

4000

TTY, V1

INULLSA

TCSA

J_
—

]E?KS

RKSE

:[FPT

:[%FOS

—

‘]jjTA

5000
IEXIT

—

CTA

ossH

6000

-F

0S8suUP

)

|—

Large

MCR

Small

MCR

7000

[

iKLSASR

_j_

KEY:

RTS/8 modules may vary in size and placement in memory depending upon

The following symbology has been chosen to show component

Fixed

Expandable

the chosen system configuration,

default allocation in memory.

Relocatable

Relocatable
and Expandable

Figure

B-1

RTS/8

System

Memory

Map

(Default

Memory

Allocation)

RTS/8 COMPONENT SIZES

Table

B-2

MCR Component

than

less

34(octal)

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APPENDIX

RTS/8

FLOWCHARTS

This appendix contains RTS/8 flowcharts that
system operation.

graphically

show

RTS/8

FLOWCHARTS

Calling Sequence:

SAVE AC IN
ACARG

p-1

TAD VAL

CAL

p+i

FUNCTION CODE

pt2

ARG1

p+3

AGR2 (or return)

pt4

RETURN

CAL = JMS 20
Thru Current Field:

TASK-

SWITCHING
ALLOWED
>

)

TSWF:‘E )
-

CDF CUR

CIFO

CMP CALIOF (field 0}

DSPOST

XWAITM

Rescan

ASAP

INHIBIT TASK-

SWITCHING.
CLEAR RESCAN

EXECUTE

FLAG

DISPATCH JUMP
THRU COMMAND

ION

Function

TABLE. IGNORE

FREE BIT

Code

]

JMP | +FUNC+1

XSEND

Pg.

XRECEIV

Pg. C-11

XWAITE

Pg. C-7

SAVE RETURN

XRUN

Pg. C-20

XSUSPND

Pg. C-20

XPOST

Pg. C-14

XSKPINS

Pg. C-15

XDERAL

Pg. C-16

XBLKARG

Pg. C-13

XUNBARG

Pg. C-12

XTSTOP

Pg. C-8

XWAITX

Pg. C.7

SAVE CALLING
FIELD

ADDRESS

GET FUNCTION

C-

9. C-4

CODE

)

COMMAND

SW designates an operation that is performed
only when using nonresident operations.

EAE designates an operation that is performed
only when the Extended Arithmetic Element
is used.

FLOWCHARTS

RTS/8

SET UP
RETURN FIELD

Yes

TSWFLG=1

TSWFLG = -1

KEEP TASK-

Cannot

TASKSWITCHING

SWITCHING

Happen

NEEDS RESCAN

INHIBITED

TSWFLG=0
No

ALLOW TASK-

SWITCHING
JMP 1 20
RETURN TO
CALLING TASK

Pg. C-8

RTS/8

FLOWCHARTS

SEND
SENDW

Calling Sequence:
SET

CLEAR

WAIT FLAG

p
p+1

CAL
SEND (W)

[

p+2

p+3

TASK # (Sending to)

l
‘

P+4

MSGADR
RETURN

GET TASK
NUMBER TO

SEND MSG TO
Initial Values
p

MSGADR, 0000

Becqmes
Sending Task =

p+1

0000

ADDRESS

CDF to next
msg, if any

GET MESSAGE

p+2

0000 | Addr of next

msg (0 if none)

p+3

Start of Message

MESSAGE
Yes

ALREADY IN QUEUE

(FIRST WORD OF MESSAGE
=0)

-4

BACKUP RETURN

MSGFRE

TO CAL

ADDRESS

BUMP RETURN
TO
MSEFWT

CAL+4

Y
y

AC=
MESSAGE

FIND

ADDRESS

RECEIV-

ING TASK ='s

ENTRY IN

MSGTBL

i
Pg. C-7

GET DATA

FIELD OF
MESSAGE

ADDTOQ

Pg. C-8

RTS/8

FLOWCHARTS

ADDTOOQ

GET FIRST
QUEUE WORD

(CDF TO NEXT)

CDF INTO
NEXT

MESSAGE

SENDING TASK

FIND NEXT

NUMBER LESS THAN TASK

MESSAGE IN

NUMBER IN THIS

QUEUE

QUEUE MSG

ENDOFQ

PUT CDF TO

MSG AND PC OF
MSG INTO
QUEUE WORDS

10F

GET TASK #

TO SEND
MESSAGE TO

|
to page C-6

ADDTOQ

Pg. C-5

RTS/8

FLOWCHARTS

from page C-5

’

|
FREE MSG WAIT

AND/OR EVENT
WAIT BITS IN

Via call to FREEJ

STATUS TABLE

i
L=1IF RECEIV-

ING TASK 1S
RUNNABLE & OF

HIGHER PRIORITY
[eRw)

THAN SENDER;
L=01F NOT

IOCo-

-0z

MSGCDF
i

STORE SENDING
TASK NUMBER

IN MSG HEADER

Link indicates whether
a new task should be
run or not,.

The link status will be
checked later on in

STORE CDF TO
NEXT MSG IN

MSGHDR

=0 if none

POSTEX.

not a SENDW.

STORE PC OF
NEXT MSG IN
MSGHDR

=0 if none

Message is now
linked into the
message queue.

mooon

w—-—T4

This will be tested if

this CAL was a SEND and

CAL WAS
SENDW

Pg. C-12

RTS/8

FLOWCHARTS

WAITE
WAITX

Calling Sequence:
CLEAR

SET ACARG

TO -1

ACARG

]

Enter Here From

GET ADDRESS

SEND or SENDW

OF EVENT

CAL

p+1

WAITE

p+2

EVENT FLAG ADDR

p+3

RETURN

FLAG

WAITS

SAVE ADDRESS

ACARG # —1

OF EVENT FLAG

IOF

Yes

Restart caller if

TASKSW allows

Pg. C-3

EVTFLG =
4000 + TASK

Give it waiting status

PUSH PC BACK

TO POINT

TO CAL

‘

AC=EFWT

Store Event Flag Wait

in Flag Table

AC=EORMWT

Jump with link clear

Y
TSWAIT

(tested at TSTOP)
Pg. C-8

Pg. C-8

RTS/8

FLOWCHARTS

Wait for message.

Enter here from RECEIVE,

BACKUP

CALLING PC
TO DO CALX

AGAIN

SET LINK
AC = MSGWT

Message Wait Status

TSWAIT

SAVE AC
IN MASK

TSWATX
|

STORE IN

TASK #'s
FLAG TABLE

ENTRY

ION

CLEAR TASK AC

TSTOP

SAVE AC IN

ACARG

-l

|
GET TASK
NUMBER’S
ENTRY IN

STATUS TABLE

to page C-9

Interrupts were off here
if we came from XWAITE.

RTS/8

‘

FLOWCHARTS

from page C-8

)

Y
SAVE RESTART

FLAGS, PC, AC

SAVE MQ

EAE

Y
FREE PARTITION
IN FREE BIT

WAS SET IN
COMMAND
SW

FINDJ

RTS/8 Scheduler

Schedule next
runnable task

TASK #=1

(start scan
from top)

ENABLE

TASKSWITCHING

|
SET ‘MACHINE

STATUS UNIMPORTANT’
FLAG

FINDJL

GET TASK #'s
ENTRY IN
FLAG TABLE

Interrupts temporarily
inhibited here.

FLAGS=0

Pg. C-10

(RUNNABLE)
?

Note no end of table
check - there must be

a runnable task.

BUMP TASK
NUMBER

(Null

task is always runnable.}

RTS/8

FLOWCHARTS

Here from FINDJ (Scheduler)
Found a runnable task

ION

|
GET TASK #'s
ENTRY IN

STATUS TABLE

I0F

SAVE OLD
STATUS IN TEMP

LOCS OF INTERRUPT ROUTINE
Interrupt

Dismiss

DISMIS

Code

This is tested on an

8/E or 8/A only

PENDING

INTERRUPTS

SWEEP OLD
STATUS INTO
DF, IF, AC, PC,

ETC.

RESTORE MQ

EAE

iON

JMPIO
RETURN FROM

INTERRUPT

Pg. C-17

RTS/8

FLOWCHARTS

RECEIV

Calling Sequence:
p-1

TAD ARG

CAL

p+1

RECEIV

p+2

MADDR, 0

p+3

RETURN

GET ENTRY
IN MESSAGE

QUEUE

Y
GET FIRST

WORD OF
QUEUE ENTRY

EMPTY

Pg. C-8

(NO MSGS)
?

UNLINK THIS

[)

MESSAGE FROM

THE QUEUE

Y
STORE ADDR OF
ADVANCE TO
NEXT MESSAGE
ON THE QUEUE

SENDING

Yes

MESSAGE IN
2
CAL

TASK OF MSG

= ARG
?

i
AC = CDF
TO MESSAGE

Pg. C-3

C-11

RTS/8

FLOWCHARTS

UNBARG

XUNBARG

GET BIT MASK
FROM ARG.

LIST

UNBLOK

I0F

CLEAR MASK
BITS IN FLAG

Call FREEJ

TABLE
L=1if clearing mask

bits makes task

runnable and it is
higher priority;

ION

L=0

otherwise.

POSTEX

Pg. C-3

RTS/8

FLOWCHARTS

BLKARG

XBLKARG

GET WAIT BITS
FROM ARG.
LIST

BLOK

—>

CALLING
TASK TO BE BLOCKED

(TASK #=10)

SET MASK BITS

IN FLAG TABLE
ENTRY OF SPEC-

IFIED TASK

Pg. C-3

p—1

TAD TASK#

CAL

p+1

BLKARG

pt2

WAITBITS

pt3

RETURN

RTS/8

FLOWCHARTS

POST

Calling Sequence:
p—1

SAVE ORIGINAL
EVENT FLAG

TAD EFPTR

CAL

p+1

POST

pt2

ECDF, CDF EFFLD

p+3

RETURN

CLEAR EVENT
FLAG

WAS

SOMEONE
WAITING FOR THIS TO

HAPPEN (OLD FLAG
NEGATIVE)

GET WAITING
TASK'S £ FROM

LOW ORDER BITS

OF THE OLD
FLAG

CLEAR BOTH
EVENT FLAG
WAIT AND
EVENT OR MSG

WAIT

Pg. C-12

Pg. C-3

RTS/8

FLOWCHARTS

SKPINS

Calling Sequence:
p

CAL

p+1

SKPINS

pt+2
p+3

MODULE ADDR
RETURN

GET FIRST
MODULE WORD

ALREADY IN

THE SKIP

CHAINI!

PUT DISMIS

ROUTINE ADDR

Pg. C-3

IN 1st WORD

Y
PUT CDF, CIF

OF DISMIS IN

2nd WORD

]
PUT MODULE

ADDRESS AND

CDF, CIF IN
LAST MODULE

OF INTERRUPT

SKIP CHAIN

Pg. C-3

RTS/8

FLOWCHARTS

DERAIL

Calling Sequence:

GET TASK #'s
STATUS TABLE

p—1

TAD TASK#

POINTER

CAL

p+1
pt+2

SUBROUTINE

p+3

STORE
RESTART
PC
IN SUBR

|
STORE SUBR+1
IN RESTART

Pg. C-3

DERAIL
RETURN

RTS/8

FLOWCHARTS

INTERRUPT
ROUTINE

TIME-

SHARING

INTERRUPT

GO TO

0S/8

SUPPORT

If present

SAVE THE
MACHINE
STATUS

USERSK

\
USER-INSERTED

SKIPS FOR ANY

APPROPRIATE

A
|NTE;fiUPT

HALT

MODULE

;

CRUCIAL DEVICES

GO TO

INTERRUPT

FAIL RESTART

POWER-UP

RESTART

POWER

FAILURE

AC = POWER-UP

EVENT FLAG

ADDRESS

GO TO

CLOCK
HANDLER

Pg. C-18

If present

GO TO FIRST
USER INTERRUPT MODULE

RTS/8

FLOWCHARTS

POSTDS

Come here from user
issuing POSTDS

p—3

CDF EFFLD

p—2

TAD EFPTR

p—1

CIFO

POSTDS

SAVE THE OLD

EVENT FLAG
VALUE

i
ZERO EVENT
FLAG

WAS A

TASK WAITING

ON THIS FLAG? (OLD

Pg. C-10

VALUE NEGATIVE?)

CLEAR EVENT
FLAG AND EVENT

OR MESSAGE
WAIT BITS IN

Call FREEJ

TABLE ENTRY

OF WAIT TASK

Run the waiting task if

its flag word is now zero
and it is higher priority
than the current user.

RUN

WAITING

TASK

to page C-19

Pg.

C-10

RTS/8 FLOWCHARTS

from page C-18

TASK

SET RESCAN

INHIBITED

CTSWFLG
= —1

SWITCHING

FLAG

Pg. C-10

SAVE STATE
FLAG-1
?

SAVE CURRENT
TASK'S PC, AC

IN ITS STATUS
TABLE ENTRY

SAVE
TASK'S MQ

EAE

ION

Yy
PREPARE TO

START NEW
TASK

Start Swapper

ISIT

RESIDENT

STARTJ

Pg. C-10

FINDJ

Pg. C-9

RTS/8

FLOWCHARTS

)

RUN

Calling Sequence:

AC = RUNWT

p—1

TAD TASK=

CAL

p+2

RETURN

p+1

Run Wait

RUN

Pg. C-12

Go and set
the flag bits

SUSPND

Calling Sequence:

AC = RUNWT

‘ Pg. C-13

p—1

TAD TASK=

CAL

p+1
p+2

SUSPND
RETURN

RTS/8

FLOWCHARTS

WAITM

XWAITM

SAVE AC
IN ‘COMMAND’

SwW

CLEARAC, L

FAKE A CAL

DISABLE
TASK

SWITCHING

\
PUT WAIT

BITS IN AC

TSWAIT

Pg. C-8

RTS/8

FLOWCHARTS

RTS/8 SCHEDULER

FINDJ

ENABLE
TASK
SWITCHING

GET SETTO
EXAMINE
FIRST TASK

!
ZERO SAVE

STATE FLAG

ION

j
BUMP TO
NEXT TASK

IOF

GET
TASK FLAGS

BLOCKING

BITS OTHER THAN
NRWT
?

CONTINUE
NEXT PAGE

FIND
A TASK TO RUN

RTS/8

FLOWCHARTS

FROM
PREVIOUS PAGE

IS
TASK

RESIDENT

STARTS

Start task

PUT TASK
INTO SWPWT

TAKE SWAPPER
OUT OF RUNWT

SwW

FINDJ

APPENDIX

RTS/8

Certain

user

standard

PAL8

errors
error

are

ASSEMBLY

caught

diagnostics

ERROR MESSAGES

assembly

the

terminal

time.
of

They

the

produce

form

tag

where

the

tag

specified

indicates

the

type

error

described

below.

Tag

Module

MCRBLK

MCR. PA

Possible

MCR

was

declared

Error

nonresident

(MCRPRT

defined)
and MCR origin was incorrectly
a multiple of 400.
Nonresident
portion
of
MCR
1is second page which must start
on

block

Fix:
SYSERR

several

Redefine

System

user

boundary.

error;

See

RTS8.PA

Internal

RTS/8

Executive

RATERR

PARAM. PA

CLOCK.PA

See

task

was

Fix:

Redefine

CUR.

HERTZ

multiple

Fix:

specified

Redefine

CLOCK.PA

SHERTZ

less

than

too

large.

192

(decimal).
SHERTZ

parameter

D-1

wvalue

for

CUR

SHERTZ.

Redefine

generated

SHERTZ

must

file.

than

Fix:

were

HGHFLD.

HERTZ

parameter
TODERR

tables

line

error.

source.

User

not

unless

source

the

which

larger

occur

generated

incorrectly.
CURBIG

not

sources.

comments

which
TBLERR

should

modified

Fix:

MCRORG.

file.

SHERTZ

RTS/8

Tag

NOKLS8A

ASSEMBLY

ERROR MESSAGES

Module

KL8ASR.
PA

Possible

The

symbol

KL8A
file.

Fix:

symbol

Set

equal

KL8~-A's

KLOERR.

KL8ASR.
PA

The

symbol

the

file

Fix:

HITMON.

KL8ASR.PA

The

PARAM.PA

KL8A

was

the

not

service

preserve

task

Fix:

this

Change

error

PARAM.
PA

Some

task

form

parameter

file.

assembled

Fix:

parameter
in

was

user

PARAM.
PA

Correct

One

the

was

not

Fix:

file

task.

given

higher

swapper

user

representing

value

parameter

file.

symbols
the

Correct

times

a
field
was not in the correct
HGHFLD, MCRFLD, etc.)

parameter

CURERR

swapper.

priority

times

(e.g.

code.

PARTNO

the

parameter

number

7600

you

resident

task.
FLDERR

KL8-A

redefine

0S/8

was

SWAPPER

undefine

than

yet

swapper.

nonresident

priority

KL8ASR.PA
desired

KL8ACT

location

nonresident

overlaid

want

Redefine

equal

assembled.

file.

not

Define

file

parameter

1Ignore

set

assemble

KL8A

with

the

present.

Fix:

PARAM.PA

parameter
physical

system

SWPRIO

support

KL8-A

KL8ASR.PA was

not

defined

KL8A

field

not

number

Fix:
NOSWAP

was

parameter

Error

CUR,

proper

CUR2,

CUR3

form.

value in user
field of task.

task

APPENDIX

EXECUTIVE

INTERNAL

TASK TABLES

The Executive uses five internal tables to maintain information
about
the
tasks in the system.
Each task's task number is used as an index
into the first four tables to retrieve and update information for that
task.

The

internal

tables

are

follows:

The
Task
State
Table
(TSTABL) - contains
4-word
holding
the
most
recent contents of CPU registers
task

entries
for each

follows:

Word

contains

the

link

(bit

the Greater Than Flag (bit 1) -if
exists on machine being used
the User Mode Flag (bit
5)
=-if
exists on machine being used
the Instruction Field (bits 6-8)
the Data Field (bits 9-11)
Word

contains

the

contents

the

Program

the

Accumulator

the

Multiplier

flag
flag

Counter

(PC)
Word

- contains

the

contents

Word

contains

the

contents

Quotient

(MQ)

assembled

the

system

(AC)

has

been

MQ.

Whenever

the
CPU

the system executes a task, it loads the contents of
task's
Task
State Table entries into the corresponding
registers.
Whenever a task
stops
executing,
its
Task

State

Table

registers.
Table, that

entries

The
is,

are

set

the

new

contents

these

Task State Table is located after the Message
at location NTASKS+2" 2+MSGTBL-4 in field O.

Example:

Consider

the

following

TSTABL

entries

for

task.

4012
3376
1234
0211
The task is interrupted just as it is
instruction
at
location 3376 (entry
of entry
1).
At
this
point,
the

registers
1234

set

for

(entry

(bit

entry

1).

this

task

are

and

the

entry

1),

and

3),

entered
is

0211

the

about
to
execute
2) of field 1 (bits
contents
of
the

the

(entry

data

field

TSTABL.
4).

The

(bits

1link

9-11

the
6-8
CPU

is
1is

EXECUTIVE

The

Task

holding
whether

Task

set

Flags

Table

(TFTABL)

flags

(bits)

the

task

Table

runnable.

entry

nonzero

run.

meanings

The

are

Octa 1

Symbolic

4000

NONRWT

word

SWPWT

each

task

zero.

1l-word

task

runnable

Each

defined

Wait

Flag

Wait

Flag

entries

determine

only

flag

reason
flags,

(bit)

its

which

why

the

task

set,

and

their

This

cannot

run

This

(which

task

this

be executed with its
the operator to type

the

Monitor
Wait

task

task)

Wait

Console

This

the

contains

to
for

This

task

in memory.

Run

Swap

not

corresponding

0400

contains

Meaning

Event

RUNWT

for

follows:

Event

1000

TABLES

indicates

currently

Nonresident

EFWT

contains

because
2000

TASK

various

Flags

cannot

INTERNAL

task

for

(see

RUN

run

the AC,
task"

Chapter

brought

or
to

6).

because

being

value

POSTed.

number in
"REquest

cannot

for

WAITING

waiting

Routine

process

waiting

into

memory.

0200

EORMWT

Event

for

Event

arrive,
0100

USERWT

Message

Wait

Flag

whichever

This

happens

User Wait - This bit
user-written
tasks.

task

set

waiting

message

first.

is reserved
RTS/8 does

for
not

use
by
use this

bit.
0040

ENABWT

Enable

Wait

Enabled.

the Monitor
task”TM
and
Chapter 6).
MSGWT

0020

Message
sent

0010

NETWT

0001

DNEWT

Does

The

Task

that

is,

Flags

task

1is

this

bit

Console Routine
"DIsable
task"

Wait

This

task

future

use.

Not

for

Exist

Wait

because

Task

runnable.

located

Table

location

TIf

the

TFTABL

for

after

task

run.

1000

the

task

waiting

for
the
"ENable
commands.
(See

1is

This

the

NTASKS+2"4+4TSTABL-1

entry

restricted

waiting

task

cannot

run

is nonexistent.

Examples:

waiting

message.

Reserved

0000

This

Use

Task

State

field

Table,

EXECUTIVE

TIf

the

TFTABRL

INTERNAL

entry

for

TASK

TABLES

task

0440
the

task

MCR

was

disabled

from

while

the

terminal

waiting

the

TFTABL

swapped

for

task

running

the

nonresident

operator

portion

the

the
task

in.

0000

the task is runnable.
However, this task
task of higher priority has precedence.

may

not

run

a
The

Task

Input

2-word

entries

message

gueue

Word

Message

that

Queue

Header

represent

for

each

task:

zero,

there

non-zero,

the

first

word

the

are

the

message

was

not

address

Table

"head"

messages

word
in

(MSGTBL)

(start)

the

zero,
of

CDF

contains

the

input

queue;

field

queue.
this

the

word

first

pointer

message

the

queue.

The

Message

Executive

Table

field

1is

located

the

end

the

RTS/8

Example:

Consider

the

following

MSGTBL entries

for

task.

6211
2044

Since
input

the first entry is a nonzero, there are messages in the
queue waiting for this task to receive them.
The first

entry

pointer
2044
The
each

CDF

instruction

indicating
field

Residency

the

field

Table

(RESTBL)

contains

The

that

Residency

is,

contains

pointer

entry

task

bits

second

begins

2-word

the

entry

location

entries

task's

through

checkpointable,

if
a
task
1is
writeable tasks
2

The

for

task.

Table

Word

first message

nonresident
Word

that

writeable.
are defined

and

Bit

bit

Partition

Checkpointable
in Section 5.1.

set

set
and

contains

the absolute block address (plus 1
to
allow for the core control block) of the task's
core image on the swap device.

Table

location

located

after

TFTABL+NTASKS+2

the

Task

field

Flags

Table,

EXECUTIVE

INTERNAL

TASK

TABLES

Example:

Consider

the

following

RESTBL entries

for

task.

1611
0124

This

task

table

has

entry

task is not
is writeable

nonresident

used

by this
checkpointable

(bit

The
the

disk-resident
swap device.

The

Partition

each

(bit
entry 1

The
4-word
at location

begins

10
is

portion of this
(The save image

Table
partition.
It

Word

portion.
task

of entry
a 1).

contains

0),

task begins at block 124
begins at block 123.)

- contains
indexed into via

the

but

(PARTBL)

partition
1610.
The

length

a
a

(size)

4-word
entry
for
partition number.

bits

field

1-5

and

(bits
6-8) argument of the mass storage
device driver call that reads an occupant
into
the partition with the "WRITE" bit set.
Bit 11
of this word is the partition busy flag.
Word

contains

the

Word

contains

RESTBL

Word

The

Partition

multiple
i.e., at

memory

pointer

address

word

the

1 of

partition.

the

occupant's

entry.

unused

Table

must

begin

address

that

1is

of
four.
It is located after the Residency Table,
location NTASKS-SWAPPERTM2+RESTBL+3&7774 in field O.

Example:

Consider
the
partition.

following

PARTBL

entries

for

particular

5421
1400
1553
0000
This partition is
by
a
task whose

(entry 3).
of
field
(octal)
Figure E-1
Executive.

currently in use (bit 11 of entry 1 is
2-word RESTBL entry begins at location

The partition
(bits
6-8

pages

long

summarizes
the
The
Residency

(bits

begins at
of
entry
1-5 of

internal
Table and

a 1)
1553

location 1400
(entry
1).
The partition is

entry

2)
14

1).

task
table
structure
of
the
Partition Table are optional in

that they are used only when
nonresident
tasks
are
employed.
The
exact
location
of
these
tables
in memory depends on the number of
tasks and other parameters in the parameter file.
They can
be
found
for a particular assembly under the "System Locations:" heading at the
end of the parameter file assembly listing.

TASK INPUT MESSAGE

RESIDENCY

PARTITION

QUEUE HEADER (MSGTBL)

TABLE (RESTBL)

TABLE (PARTBL)

Contains pointer to task PARTBL
bit 10 check-

Contains the Length (size) and

Instruction

Data

Bits determine if task is

If zero, no messages in queue, if

Field

runnable

nonzero, word is CDF to the fieid

entry in bits 0-9;

of first message

pointable;

If nonzero, this word is pointer

Block address plus 1 of the task’s

Contains starting address of

to the first message in the queue

core image on swap device

the partition

e Represents the “‘head’’ of the

e Bit 10 of word 1 is set if task

input message queue for each

checkpointable

the occupant’s RESTBL entry

Link

(IF)

(DF)

9-11

Field argument (bits 1-8) of the
mass storage device driver call

that reads occupant into partition
with ‘write’ bit set (bit 0).

Contents of Program

Counter (PC)

bit 11 - writeable

e Task runnable if entry

contains zero

Word 3

Contents of Accumulator

(AC)

Contains pointer to word 1 of

task

o Bit 11 of word 1 is set if task
writable
Word 4

Unused

Contents of Multiplier

Quotient (MQ)

e Bit 0 is always set (write)

e Upon task execution, TSTABL

loaded into corresponding CPU

e Bit 11 of word 1 is the

registers

partition memory flag

e Upon task interruption, TSTABL
entry set to new contents of CPU
registers

Figure

E-1

Executive

Internal

Task Table

Structure

JAILNDIXH

Word 2

TASK FLAGS

TABLE (TFTABL)

SHTAVL MSVLI TUVNJILNI

Word 1

TASK STATE
TABLE (TSTABL)

GLOSSARY

arithmetic
the
which
in
register
The
operations are performed (abbreviated AC).

Accumulator

Representation of

Analog

information

continuous

variables.
Analog

Channel

UDC/ICS

functional

device.

the
A variable or constant which is given in
a
call of a subroutine as information to it;
a
of
value
the
value
whose
upon
variable

Argument

the known reference factor
function depends;
necessary to find an item in a table or array
the

(i.e.

index).

A program which translates symbolic
op-codes
menory
assigns
and
1language
machine
into
locations for variables and constants.

Assembler

Auto-index

Auto-restart

from
1locations
Whenever one of the absolute
memory field is
any
in
0017
through
0010
that
of
contents
addressed indirectly, the
1is incremented by one, rewritten in
location
the same location, and used as the
effective
address of the current instruction.
The ability to start the CPU automatically on
power-up.

A unit of measure of data

Baud

flow

(one

bit

per

second)
.

A binary digit
of 12 bits).

Bit

(each

PDP-8

word

1is

composed

A method of keeping track of used and
unused
assigning one bit in a table to
by
entities

Map

entity.

each

Block

set

consecutive

machine

words,

unit,
a
as
handled
digits
or
characters
and
input
to
reference
with
varticularly

octal
400
is
block
0s/8
an
output;
process
also to inhibit a
contiguous words;
from continuing.

Block

The blank space between blocks on a

Gap

recording

medium.
Blocking

Bits

Bits
why

in an
a

given

Byte

2 group
upon as

Cassette

A magnetic
data

RTS/8 Monitor
task

1is

of
binary
a unit.
tape

storage.

Glossary-1

Table which

specify

blocked.

digits

device

used

usually

for

operated

program

and

Central

Processing

Unit

The

unit

the

computing

circuits

and execution
CPO)
.

Checkpointable

Task

task

out

instructions

includes

interpretation
(abbreviated

if it may be swapped
automatically,
without
its

make

room

tasks.
Clear

that

the

checkpointable
memory

consent,

system

controlling

for

higher

priority

erase

the contents of a
storage
location
replacing
the
contents,
normally
with

zeros.

Clock

time

keeping

computer

interrupts.
Communication

Compute

Region

Bound

measuring

Locations
20-27
simplify
passing
field boundaries.

every
executive

Requiring

extensive
to

The

number

other

and

(or

types

Channel

Contiguous

UDC/ICS

Code

which

adjacent
Controller
Core

Image

The
File

functional

circuitry
file

'picture'
Core

Storage

The

other

main

to
across

the

CPU

(such

present

memory

image

core);

CPU

Channel

Registers

UDC/ICS

device.

known

storage

functional

High-speed

(i.e.,

as
a

SAVE

CPU
Data

(e.g.,

computer

general

facts,
can

Data

Field

IF,

term

used

numbers,

connotes

basic

processed

3-bit

(abbreviated
To

detect,

the

denote

and

which

DF).

Glossary-2

and

any

store

correct

the

all

It
which

computer.

determines

operands
addressed

locate

the

symbols.

information

produced

which

program.

1letters
or

operation of

DF).

elements

field
from
indirectly

Debug

used

affecting
PC,

a
file.

device.

circuitry

information

immediately

which
binary
data
is
represented
switching polarity of magnetic cores.
Counter

code.

format

also

high-speed

use

elements

controls

core

sections

that

used

request

hardware

the

periodic

device.

resides

within

field,

total)

hardware

system.

Contact

device

provides

relative

I/0 devices).
Configuration

system;

the

memory

are

taken
in
instructions

mistakes

Deferred

Actions

Actions
are

which

not

actions
Deferred

Requests

are

Requests
and

are

considered

performed

low-priority

until

and

higher-priority

serviced.

which

are

considered

serviced

after

1low-priority
high-priority

requests.

Derail

transfer
control
or
execution
specified task to a subroutine.

Device

Codes

assigned

Numbers

each

device

the

system.

Device

Status

of
Digital

Digital

Representation
units.

Channel

Driver

UDC/ICS

See

Dynamic

Flag

The

location
be

The

location

Executive

Requests

Field

Devices

program

Codes

which

Executive.

and

of
to

fixed

length

recording

the

size

devices

Bound

increase
used

routine

I/O

and

which

by
1is
also

control

begun.

status
result

of
of

an
some

occurrence).

controls

the

execution

routines.
between

tasks

PDP-8

section

memory.

blank

tape

and

the

computer

separating
generally

files

several

block gap.

available

in
to

for

signal

power.

identify

which

condition

much

affected

use

under

the

handler.

operation
I/0

discrete

time)

the

either

medium;

contains

memory
a

execution

communication

Codes

routine

functional
device caused
direct program control to
Handler

status

the
condition;
system run-time.

physical

RTS/8

Generic

Means

The

to
at

being

programs

UDC/ICS

Gain

other

times
Functional

that

(such

which

A division

Gap

(event

referring

File

current

device.

quantity

transferred

operation,
The

relative
features

can

event

Executive

the

information

condition

therefore
refers to

Event

functional

Pertaining

Point

contains

Handler.

some

Entry

which

device.

but

a
in

UDC/ICS

designed

control

the

device.
which

using

Glossary-3

type

an interrupt and to
service routines.

process

performing

very

little

CPU

time.

Indirect

Address

address

computer

instruction

which

indicates a location where the address of the

referenced

Initialization

Code

operand

which

sets

found.

counters,

switches,

and

addresses to zero or other starting values at
the beginning of or at prescribed points in a
computer routine.
Input

Buffer

section

memory

used

for

storage

input

data.

Instruction

Field

which

holds

the

determining from which field the
directly
addressed
instruction
taken (abbreviated 1IF).

Interactive

Highly

Interface

The

responsive

common

between
Interlock

Scheme

hardware

two

Interrupt

break

execution

Processing

Module
A routine which
which caused an

software

caused

1is

acts upon the
interrupt.

1list
of
actions
to
accompanied
by the interval
to elapse from the
previous
current

Line-frequency Clock

that

external

resumed

external

event

perform,
each
of time which is
action
to
the

whose ticking occurs
power line frequency.

multiple

A one-bit register in the PDP-8;
an
pointer
generated
automatically by
assembler to indirectly address
an

Link

boundary

one.

A clock

the

some

usually

Queue

a
be

systems.

the
control
of
devices
operation is interdependent.

event;
execution
later time.

Interval

and/or

devices

inputs.

Arranging

their

Interrupt

real-world

contents

operand
should

address
the PALS
off-page

symbol.

Logical

A logical function
of
which is true whenever

Loop

sequence

repeatedly
prevails.

Mass

Storage

Master

Device

Parameter

File

two
or
more
either input is

instructions

until

1is

executed

condition

A device

such as disk or DECtape which stores
large
amounts
of data readily accessible to
the central processing unit.

file
RTS/8

included in
which
the

the

distributed

user

can

parameters
specific
configuration.
Memory Address

that

terminal

1inputs
true.

A
by

memory

which

holds

reference

Glossary-4

the

edit

sources of
to indicate

his

address

instruction.

system

specified

A contiguous

Message

information
Message~driven

RTS/8

only

task

from

Alphabetic

octal
Module

memory
which
contains
execution of tasks.
called

executes

received
Mnemonic

area
about

other

message-driven

response

routine

1if

messaqges

tasks.

representation

machine

function

instruction.
which

handles

particular

function.

Monitor

Console

Multiplier

Routine

Quotient

The Monitor routine which provides
the
user
with
functions
which
allow him to control,

inspect,

and

used

accumulator

12-bit

the

operations
Multi-programming

Two

same
on
Nonresident

Task

the

current

task

task
1is

conjunction

perform

MQ).

(tasks)

memory

alternately

the

task

with

mathematical

swapped

the

depending

system.
or

into

portion

memory

when

proceeds

the

executable.

operation

system.

execute
state

that

becomes
No-op

programs

which

nonresident

his

(abbreviated

time

debug

occurs;

instruction

control

sequence.
/

Null

Characters

Overflow

Charécters with ASCII code 000.
A condition that occurs when
a
operation
yields a result whose
greater

than

storing.

Pack

conserve

Page

128-word

the

data

memory

presentation

(decimal)

combining

section

memory
beginning
at
an
multiple of 200(octal).
Parameter

Parity

Bit

file

bit

number
or

Pointer

Post

capable

information.

PDP-8

address

A file used to record arguments
assigned different values.
A

mathematical
magnitude is

core

which

may

which
indicates
whether
the
total
binary one digits in a word is even

odd.

word

containing
memory.

post

FINISHED

Event

state

the

address

Flag

means

via

another

set

RTS/8

word

Executive

Request.

Posted

One

the

indicating
as

states

that

"FINISHED".

Glossary-5

the

event

flag,

event

complete;

same

Power-fail

Priority

Program

Scheme

Counter

interruption
scheme

power

the

computer.

which

execution

preference

over

certain operations
set of instructions
other operations.

or
is

the
given

Prompting

Character

Queue

character
terminal
and
action.

which

prints

cues

the

waiting list (e.g.,
waiting for processing

Ready

Flag

Real-time

System

bit

which

ready

system

while
so

device

queue
time).

commands

which

computation

the

physical

results

gquiding

controller

the
console
perform some

that

used

user

sets

when

the

CPU.

from

process

the

programs

performed

occurring

computation

measuring

can be
physical

the

process.

Receiver

The

task

another
Record

Record

which

task

A collection

Header

Ring-buffer

Area

area

has

least

contains

perform

cassette

storage

first-in,
but

message

items

data

unit.

which

received

from

(sender).

40(octal)

words

information

length

necessary

operations.

area

for

data

accessed

first-out

basis.
Similar
involves
storage
of

usually

treated

to Queue,
character

codes.

Scheduling

The

operation

computing
Sender

The

Bit

Simulate

sharing

task

Sign

The

which has
(receiver).

bit

resources

among

tasks.

which

sent

contains

represent

the

program

with

message

the

sign

function

another

number.

device,

system

program.

Skip

Chain

instruction

source

- of

sequence which determines
the
interrupt request on a PDP-8;
or more tests for each
possible

contains one
(hardware) interrupt
State

Status

condition.

A complete description of
piece of hardware or of a
That

portion

tasks

might

Glossary-6

the

the condition
task.

state which other
interested in.

devices

Subchannel

One of the
functional

Suspend

To temporarily halt execution of a task
another task of higher priority runs.

while

Symbols

Names

which

can
a

4 channels
device.

which

can

used

assigned

indicate

A means of coordinating
flags) so that one task
wait.

System

RTS/8

tasks

Task

UDC/ICS

values

specific

analog

locations

program.

Synchronization

Ticks

convention

the

freqguency

A task is
function.

tasks (through
executes while

designed

system

the

event
others

obviate

the

from

knowing

the

clock.

routine which performs a specific
A
task
may
be
"resident"
or

"nonresident".
A
resident
task
is
permanently located in memory.
A nonresident
task is loaded into memory as
it
1s
needed

and
Task

Flags

Table

can

table

overlaid
of

after

1-word

Input

Header

Message

Table

completion.

entries

Executive whose contents
not a task is runnable.
Task

its

1in

determine

the

RTS/8

whether

Queue
A

table

head

2-word

the

entries

1input

which

message

represent

queue

for

the

each

task.
Task

Task

unique
assigned

Number

State

Table

Switching

Terminal

Word

between

each

task

and

63
(decimal)
RTS/8 system.
contains
registers

the
for

The act of
ontinuing

stopping execution of one task
execution
of
another
from

and
the

point

task.

that

A peripheral
data

Utilities

table of 4-word entries which
ost
recent
contents
of
CPU

.ach
Task

number

can

was

device

enter

Routines
to
functions.
In

the

stored

leave

perform

PDP-8,

last

one

Glossary-7

12-bit

stopped.
a

system
the

through

non-Monitor

unit

addressable

which

computer.

data

which

location.

may

INDEX

4-4,

ALTMODE,

Digital output UDC/ICS operation,

5-1

Analog input UDC/ICS operation,

4-27

Disable contacts UDC/ICS operation,

Analog output UDC/ICS operation,

4-30

4-25

Disable counter UDC/ICS operation,

Arbitrary boundaries, 9-7
Assembling nonresident tasks,

4-29

Distributed source files,

7-6

Assembling tasks,

6-5,

8-11

Editing parameter file,
ENable command, 5-4

Assembly,

nonresident tasks, 7-8
Assembly error messages,

Assembly parameters,

5-4

DIsable command,

4-26

A-1

6-5,

6-8

Enable contacts UDC/ICS operation,

D-1

UDC/ICS,

4-29

Enable counter UDC/ICS operation,

4-31

4-28

Error conditions,
UDC/ICS, 4-31

Batch control,

nonresident tasks, 7-8
Batch stream, 6-6, 6-8

Event flag states
Event

BLKARG ER, 3-6
Buffers, 7-6

flags,

2-5,

Cassette handler,

E-1

Executive KL8-A support, 4-37
Executive request wait states,
3-12
Executive

4-35

Cassette file support
tasks, 4-35

system
‘

requests,

BLKARG,

3-6
DERAIL, 9-5
POST, 3-4
RECEIVE, 3-3

4-32

Change of state UDC/ICS operation, 4-30
Character mode, 4-4
Checkpointable tasks, 7-3

RUN, 3-8
SEND, 3-2

Clock handler, 4-2
Clock handler system parameters,
6-10

SENDW, 3-3
SKPINS, 3-9

CTRL/C, 4-5, 5-1
Communication region, 3-1
Component sizes, B-1
Control files,
use of, 6-9
Core image, 7-6, 7-7
Creating an RTS/8 system,
Creating SAVE image file,

UNBARG, 3-8
WAITE, 3-3
WAITX, 9-5

SUSPND,

EXIT task system parameters,
6-5
6-6 [4

Field mapping,
FINISHED

DECtape

5-2

task,

file,

4-13

DEposit
DERAIL

system

program,

command,
ER,

‘Digital

6-10

C-1

command,

7-4

7-8
parameters,

Generic code UDC/ICS operation,

6-14
Demonstration

2-2

Floppy disk handler,
Flowcharts,

6-14

4-20

state,

Floppy disk control

FREE

handler

3-8

EXIT command, 5-6
EXIT task, 4-39

7-6

command,
Debugging,
nonresident

2-3

EXamine command, 5-6
Executive internal task tables,

CAL instruction, 3-1
CAncel command, 5-4
Cassette file support handler,

DAte

summary,

2-2

5-6

Inhibiting task
Instructions,

9-5

input UDC/ICS

4-27

8-1

operation,

CAL,

4=27

3-1

POSTDS,

Index-1

3-10

switching,

9-2

INDEX

Instructions
WAITM,

(CONT.)

(cont.),

9-4

Interrupt module

restrictions,

3-10
skip

Intertask

messages,

support

chain,

3-9

TTY

2-3

system parameters,

support task,
task,

User

LINCtape

4-38

4-39

handler,

4-16

Line mode, 4-4
Line printer handler,

Mass

MCR

tasks,

7-8

6-6,

8-11

tasks,

storage

command

address,

handlers,

space,

time-of-day,

5-1

CAncel,
DAte,

5-4

DEposit

address,

5-6

DIsable, 5-4
ENable, 5-4
EXamine address,

5-6

EXIT,

5-6

NAme,

5-2

OPen

address,

5-5

POst

address,

5-6

REquest,
STop,

definitions,

task

setup,

task

specifications,

component

size,

B-5

MCR

error messages,

5-6

MCR

system parameters,

Message

table,

file

Partition

parameter

6-3

structure,

6-1
initializa-

7-7
takle,

null

E-4

task,

state,

POst

address

POST

ER,

4-37

2-2

reschedule,
command,

9-1

5-6

3-4

instruction,

Power

fail

Read

counter

task,

3-10
4-18

UDC/ICS

command,

task

operation,

5-3

structure,

RUBOUT,

4-4

RUN

3-8

ER,

Sample
6-~12

task

program,

2-1

6-7

SAVE image file,
creating, 6-6, 7-6
nonresident tasks, 7-8
Saving the system, 6-6, 8-11

7-3

2-3
E-3

SEND

5-2

Nonresident MCR, 5-6
Nonresident task debugging, 7-8
Nonresident task implementation,
7-8

Nonresident task
7-5

€-2

6-4

Parameter

REquest

MCR

header,

4-21

file,

task

RTS/8

Message

6-13

communication,

Residency table, E-3
RTS/8 description, 1-1

5-3

Memory partitions,

4-19
system param-

Real-time system operation,
RECEIVE ER, 3-3

5-4

command,

task

4-29

SYstat, 5-4
TIme, 5-2

NAme

task,

support

POSTDS

5-2

5-5

support

Performing

MCR commands,

6-5

file support task, 4-23
operating system, 4-19

PENDING

5-1

7-8

0S/8
0S/8

PDP-8A

5-1

file,

7-8

listings,

Partition

5-1

7-8

command,

tion,

single

7-5

7-1

OPen

5-1

task-ID,

image

eters,

4-11

parameters,

7-8

starting,

0S/8~RTS/8

arguments,

comma,

word,

SAVE

Parameter

nonresident

tasks,

0S/8
0S/8

4-10
system parameters,

Line printer
6-14
Loading,

Nonresident

Obtaining

4-38

task,

tasks,

batch control,
loading, 7-8

6~13

0S/8

task

Nonresident
assembly,

Interrupt

KL8~-A

Nonresident

SKPINS

ER,

3-3
3-9

nonresident

tasks,

command,

SUSPND

Swap

Index-2

3-2

Starting,
STop

initialization,

ER,

SENDW ER,

ER,

5-4

3-8

device,

7-1,

7-6

7-8

1-2

INDEX

Swapper

system parameters,

Syntactic constructions,
SY¥stat

command,

6-11

Terminal handler, 4-4
Terminal handler system param-

5-1

5-4

eters, 6-11
~ Terminal parameter default values,

System parameters,

clock handler, 6-10
DECtape handler, 6-14
EXIT task, 6-14
KL8-A support, 6-13
line

printer,

MCR,

6-12

0S/8

support task,

swapper,

4-9

TIme

6-14

6-13

6-11

task

summary,

4-1

cassette file support,
cassette handler, 4-32

LINCtape

handler,

4-13

Line printer handler,

4-10

mass

storage

4-11

0Ss/8
0S/8

file support,
support, 4-18

PDP-8A null,

read counter,

4-23

UNBARG ER,

power fail, 4-18
terminal handler, 4-2
UDC/ICS handler, 4-24

WAITBITS
Task

flags

table,

Task number,

Task
Task
Task

4-29

3-8

Use of control files, 6-9
User task KL8-A support, 4-39
Using BITMAP program, 6-7, 7-5
Using interrupts, 3-9

4-37

Task communication,

4-19

change of state, 4-30
digital input, 4-27
digital output, 4-27
disable contacts, 4-30
disable counter, 4-29
enable contacts, 4-29
enable counter, 4-28
generic code, 4-27

4-35

4-16

handler,

5=~2

UDC/ICS assembly parameters, 4-31
UDC/ICS error conditions, 4-31
UDC/ICS handler, 4-24
UDC/ICS handler system tasks, 4-24
UDC/ICS operation,
analog input, 4-26
analog output, 4-25

System tasks,

clock handler, 4-2
EXIT, 4-39
floppy disk handler,

command,

Timeshare function disabled,
TTY control file, 6-9
TTY task KL8-A support, 4-38

terminal handler, 6-11
System status report code, 5-5
System tables direct references,
9-8
System

(CONT.)

2-1

WAITE

E-2

symbolic

ER,

WAITING

names,

state,

2-2

2-1

WAITM

instruction,

state table, E-1
status report, 5-5

WAITX

ER,

synchronization,

Writing delicate

Writeable

2-2

Index-3

3-7

3-3

9-4

9-5

tasks,

7-3

code,

9-1

RTS/8 User's Manual
DEC-08-0ORTMA~-C=D

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RTS/8

Read

data

4000 Write
PAGES

SYSTEM

from

data

TASKS

floppy disk.
floppy disk.

Specifies

the number of pages to
transfer
(times
100
octal).
Pages = 0 transfers 40 pages (a full
field).
This value takes the range 0-37
in
bits
1-5
of
this
word.
PAGES
1is ignored if CODE =
4000.
In that case,
either
100
(octal)
12-bit

words

200

transferred

8-bit

bytes

depending

(from

FIELD

Specifies the field of buffer
Bits 6-8 of this word have the

BUFADD

the address of the
containing
data.
determined by FIELD.
Length
PAGES if CODE = 0 or on MODE

Specifies

Represents

first

logical

CODE

Each

Track

ignored

'employed.

physical

0S/8

track

sector

STATUS

Receives
the
completion.
occurred.

may

The

meaning

buffer

depends

CODE

4000.

block

positive

nonzero

the

only

STATUS

Bit

"Meaning

0
1-3
4

Not
Not

Hard

has

DEL

INIT

done

(can

occur

Parity

CRC

error

NOTE

po wer

might
the

fail

¢ alling

message

restart,

occur.

task

again.

When

the
this

should

word

2000.

follows:

INIT
error

send

error
occurs,

the

1/0

after

failure

controller)

has

This

power

upon

error

temporary

format

operation

controller

scheme

contains

the

hard

sectors.

word

used by controller
used by RTS/8
Deleted data indication
Not used by controller
Reserved for future use

5
6-7

occurred.

bits

transfer

interleave

numbers

error

this

of
the
negative,
a

consists

status

the

buffer

2-to-~l

TTTTTTTSSSSS.

CODE
= 4000,

and

are

octal).

word

Field

0S/8

block

and

words)

(times
10
range 0-7.
first

buffer

BLOKNO

200

MODE.