Rca 1800 User manual

I

Operator

Manual

for

the

RCA

COSMAC

Development

System

II

CDP18S005

MPM-216 Suggested Price $10.00

RETURN

IU

ARK

L.

LEW

•

' .

.

:

.

~.

Operator

Manual

for

the

RCA

COSMAC

Development

System

II

CDP18S005

nell

Solid IBuenos

Aires'

Hamburg·

Liege'

Madrid'

Mexico

City·

Milan

Stat

Montreal'

Paris'

Sao

Paulo'

Somerville NJ •

Stockholm

e Sunbury·on·

Thames'

Taipei'

Tehran'

Tokyo

"

Information furnished by RCA is believed

to

be

accurate and reliable. However, no responsibility

is assumed

by

RCA for its use;

nor

for any in-

fringements

of

patents or

other

rights

of

third

parties which may result from its use.

No

license

is

granted

by

implication or otherwise

under any patent or patent rights

of

RCA.

Trademark(s) Registered ®

Marca(s) Registrada(s)

by

RCA Corporation

Printed

in

USA/I0-77

•

1

•

________

__________

__

______

____________________________________

3

Foreword

The

COSMAC

Development System CDP18S005 is a

prototyping

aid

for

the

design of

hardware

and

software systems

based

on

the

RCA

CDP1802

microprocessor.

The

COSMAC

Development

System is specially

structured

to provide a testbed

in which

hardware/software

prototypes of systems containing a

microprocessor

may

be designed, built,

and

tested.

In

small-

volume applications it

can

be

used as the

major

building block

for dedicated microcomputers.

This

Manual

is designed as a guide for the COS

MAC

Development System user.

It

includes a detailed description of

each of the available

hardware

modules as well as a complete

explanation of

the

functions available from

the

software sup-

plied with

the

system.

The

COSMAC

Development System (CDS) consists of a

card

nest with self-contained power supply,

an

easy-to-use control

panel,

and

a basic set of plug-in modules.

It

is packaged to

promote easy interfacing with external devices. These interfaces

may be custom-designed

by

the

user or, in

the

case of common

peripheral devices, are available from

RCA

as

standard

op-

tional modules,

and

include a floppy disk interface.

The

COSMAC

Resident

Software

Package

(which

runs

on

the

CDS

in a stand-alone

manner)

provides a means for

rapid

coding

and

debugging of

COSMAC

programs.

Many

of its

features are compatible with those of

the

COSMAC

Software

Development

Package

(CSDP)

timesharing program-

development aids. Additional software

and

firmware packages

are available from

RCA

including packages for floppy disk

hardware

and

multiple precision arithmetic.

4

_____________

___

_ Operator Manual for the

RCA

CDS

11

CDP18S005

,

•

I

•

__________________________________________________________________

5

Table of Contents

Foreword . . . . . . . . .

Operating and Programming the CDS

System Overview

Initial Operation . . . . . .

CDS Hookups

.....

.

CDS

Checkout

Program

Loading and

Outputting

Programs

Paper Tape Systems . . . .

Magnetic Tape Systems

Introduction

to

the Monitor Software UT20

Utility Commands

?M

Commands

!M

Commands

$U Commands

$P Commands

$L

Commands

?R

Commands

Summary

of

UT20 Ope]ating Instructions

Terminal

Interfacing.

. . . . . . .

ASCII Coding . . . . . . . . .

UT20 Read and Type

Routines.

. . .

Examples

of

UT20 Read and Type Usage

Additional Utility Routines

ASCII

to

Hex Conversion Routine .

Initialization Routines

Routine

to

Restart UT20 .

Additional Notes

on

UT20 .

Programming Methods

Machine Language Programming

Programming Interface

to

CSDP

Hardware

Structure

of

the CDS .

System Block Diagram

Module Description and Signal Mnemonics

Card Nest and Backplane . . . . .

CPU Module CDP18S102 . . . . .

Control Module CDP18S103 . . . .

Address

Latch

and Bank Select Module CDP18S206

I/O

Decode Module

CDP18S509.

. .

ROM/RAM Module

CDP18S401.

. .

4-Kilobyte RAM Module CDP18S205 .

Terminal Interface Module CDP18S507

Display Board . . . . . . . . .

Disk Interface Module

Option

CDP18S813

Microterminal

Option

CDP18S021

Power Supply Module . . . . . . .

Page

3

9

9,

10

11

12

13

14

15

18

19

20

22

27

29

30

31

32

33

34

35

36

37

38

6

--'----

--

- -

___

_____

Operator Manual for the RCA CDS

II

CDP18S005

Development System Signals

Memory Addressing

and

Expansion

Memory Organization

RCA Modules . . . .

Custom Memory Modules

Input/Output

Interfacing

.Module Enable Philosophy

Two-Level

I/O

........

.

~

.. Interfacing Signals

and

Custom

I/O

Modules

DMA

Input

DMA

Output.

. . . . .

Byte

I/O

. . . . . .

Interrupt

. .

Bit Serial Interface-The Terminal Interface Module

Interfacing Techniques and Precautions

Use

of

External Clock .

External Flags EF 1

to

EF4

. . . .

Adding I/O Devices

Adding

Remote

Control .

Development System Dynamic Characteristics

Troubleshooting .

...

. . .

Hardware Specifications .

CDS Resident Software Development Aids

CDS

I/O

Terminals .

Memory Space Requirements .

Informal

Introduction

to

the COSMAC Resident Assembler

Flow Chart

to

Operation Mnemonics

Addressing .

Assembly Language Equivalent

COSMAC Resident Assembler

Assembler Operation

The Location

Counter

The Symbol Table

Expression Evaluation

COSMAC Level I Assembly Language

Lines and

Comments

Symbol Definitions

Explicit Constants .

Address Constants .

Operation

Mnemonics

Instructions

and

Operands

Data Lists

CRA Directives .

Additional Notes

Code Examples

and

Review

Error Messages . . . .

CRA Operating Instructions

Summary

of

CRA

Operating Steps

RAM Considerations

Output

Options .

Prompt

Messages

Page

38

40

41

42

43

45

46

47

48

49

51

52

53

54

55

56

57

58

59

63

64

•

Table

of

Contents

____________________________

7

Informal

Introduction

to

the

COSMAC

Resident

Editor

COSMAC

Resident

Editor

CRE

Operating

Considerations

Memory

Space

Requirements

Input

and

Output

Files

Record

Formats

. . .

Buffer

Pointer

CRE

Command

Operation

Command

Strings

Command

Formats.

Punch

Procedure

Correcting

Command

Typing

Errors

Interrupting

CRE

Execution

Filled Work Space Warning

CRE

Command

s .

Single

Commands

.

Pointer

Control

Commands

Reading

the

Input

Tape .

Deletion

Commands

.

Text

Insertion

and Data Manipulation

Output

Commands

Summary

of

CRE

Commands

and

Control

Characters

Composite

Commands

and

Nesting

Horizontal Tabs

Additional

Note

Using

CRE

.

Loading

and

Operating

CRE

.

File

Development

and

Manipulation

Creating a File . .

Adding

to

a File

Deleting a Section in a File .

Moving a

Section

in a File .

Modifying a

Section

in

a File

Some

Command

Examples

Appendices

A.

CDS

18S005

Backplane Wiring

Schedule

B.

Instructions

for Converting a Model

33

Teletype

Terminal

from

Half-to-Full-Duplex

Operation

and

from

60-mA

to

20-mA

Operation

C. Adding

Teletype

Remote

Reader

Control

.

D. Module Logic

and

Circuit Diagrams

and

Layout

Diagrams.

.

E.

Instruction

Summary

for RCA

CDP1802

COSMAC

Microprocessor.

F ASCII -Hex Table

G.

UT20

Listing

H.

System

Checkout

Game

-

DEDUCE.

I. Conversion

to

Different

Operating

Voltages

J.

Connection

List for

Terminal

Interface

Cables

Page

65

66

68

69

70

71

72

74

75

76

77

79

81

82

83

95

99

100

121

123

8

_________________

Operator Manual

for

the RCA

CDS

II

CDP18S005 •

,

.

+

•

--

--------

----------------------------------------

____

__

____

__

9

Operating

and

Programming

the

CDS

System

Overview

The

CDP18S005

COSMAC

Development

System

(CDSl

consists of a power

supply,

control panel,

and

a set of connectors for

printed

circuit

boards.

Many

of

the

25 available positions

are

occupied

by

specific

module types. A

printed

circuit

backplane

distributes

common

signal lines

to

all

connector

positions.

There

are a small

number

of

additional

wire-wrapped

connections.

The

unassigned

connectors are available

for

user

expansion of

memory

and

I/O

function.

Supplied

modules

include

the

CDP1802

CPU

module,

an

address

latch

and

memory

bank

select

module,

a 4-kilobyte

RAM

module,

a

ROM/RAM

module

containing

the

Utility

program,

an

I/O

decode

module,

terminal

interface module,

and

a

control module.

The

position assignments of these

modules

are

given in

Table

III

in the

logic functions are

implemented

in

CMOS

operating

at

+5 V.

The

control

panel

provides a simple

user

interface.

Depressing

the

RESET

switch initializes

the

system.

Depressing

the

RUNU

switch

starts

the

utility

program,

identified

as

UT20.

Depressing

RUNP,

on

the

Dther

hand,

will

start

program

execution from

memory

location 0,

the

normal

starting

location of a

user

program.

A

STEP/CONTINUOUS

switch

allows stepping one

machine

cycle

with

each

depression of

RUNU

or

RUNP.

A 4-digit display

on

the

front

panel

shows

the

current

address

and

a 2-

digit display shows

the

value of

the

data

.bus

or,

by

switch selection,

the

last

I/O

data

byte. Five

ad-

ditional

LED

indicators

monitor

the

State

Code,

WAIT,

CLEAR,

and

Q lines of

the

CPU

while a

sixth

LED

indicates when

the

machine

is

running.

This

RUN

indicator

will be

ON

whenever

the

CPU

is

running

and

not

in

the

IDLE

mode.

The

LOAD

switch is used

to

place

the

CPU

in

the

'load

mode'

in

which

the

DMA

channel

can

be

used

to

load

RAM.

See

The

User

Manual

for

the

CDPl802

COSMAC

Microprocessor,

MPM-201,

for a detailed

discussion of this

mode.

The

LOAD

switch is sup-

plied

as

a convenience for

the

user

designing his own

system interfaces

and

is

not

used

in

normal

CDS

operations.

The

supplied

programs

are

loaded using

the

Monitor

program

as discussed in

the

The

CDS·

is designed

to

work

with

anyone

of

the

following terminals:

Il

An

ASR

33

Teletype'

terminal

(or its

electrical

equivalentl

which

should

include a

remote

reader

control circuit

to

permit

the

CDS

to

control

the

paper

tape

reader.

2l A

TI

"Silent

700"

terminal"',

Model

733

ASR

with

tape

cassettes

and

"Remote

Device

Control"

option.

This

terminal

uses

dual

program-controlled

magnetic

tape

cartridges as

storage

medium

and

prints

at

30

characters

per

seconds.

3l Any

terminal

conforming

to

the

EIA

RS232C

standard

interface

and

having

a

baud

rate

of 110, 300,

or

1200.

The

CDS

is designed

to

automatically

adjust

to

a

variety of

data

terminal

speeds

and

will

accommodate

either

full-

or

half-duplex operation.

Included

with

the

CDS

are

an

assembler

and

editor

program

for software development.

Loading

in-

structions for these

programs

are

given

in

the

Details

on

operation of

the

Assembler

and

Editor

are

given

later

in this

manual.

If

a

Floppy

Disk

system is used

with

the

CDS,

refer

to

the

Floppy

Disk

Manual

for

operation

of

the

Assembler,

Editor,

and

other

programs.

, Registered Trademark, Teletype Corporation.

... Registered Trademark, Texas Instruments Corporation.

L111

("

I \ (

10

_________________

Operator Manual

for

the RCA CDS II CDP18S005

Initial

Operation

,

CDS Hookups

Two

I/O

data

terminal

cables

are

supplied with

the

Development

System -

one

for

terminals

using a 20-

mA

loop interface,

the

other

for

an

EIA

RS232C

data

terminal.

Each

cable

with

it

s

terminal

board

con-

nection is labeled.

To

connect the

data

terminal,

selei':'t

the

proper

cable

and

plug

its receptacle labeled

"fl"

into

the

appropriate

connector

mounted

directly

on

the

accessible

end

of

the

terminal

board,

as shown

in

Fig.

1.

For

a list of

terminal

interface cables

and

their functions, refer

to

Appendix

J.

MOUNTED

I/O

TYPEWRITER

CONNECTORS

CAB

LE

END

RECEPTACLE

CABLE

25-PIN

DELTA

CONNECTOR

LABELED

"

EIA

"

LABELED

tl

TTy

ll

END

CONNE

CTOR

MATING EIA

CONNECTOR

-0

-9

TERMINAL

PLUG

-IN

MODULE

(SLOT"

14) WHITE PLASTIC

MOLEX

CONNECTOR

WHITE

PLASTIC

MOLEX JACK INSIDE

TELETYPE

TERMINAL

IN POSITION "2"

(J2)

92

CS

-

28

210 RI

Fig. 1 - Cable connection

for

I/O

data terminals.

The

two connectors on

the

terminal

board

are

labeled

appropriately.

The

connector

on

the

other

end

of

the

cable plugs

into

the

terminal.

For

a

Teletype

terminal,

remove its cover

and

plug

the

cable into

connector position 2 (J2) in

the

array

of white plastic

Molex

connectors

located

in

the

back

of

the

unit.

For

an

EIA

terminal,

plug

the

EIA

connector

on

the

cable

into

the

receptacle on

the

back

of

the

data

terminal.

Fig. 1 shows these connections.

When

the

Silent 700

terminal

is used,

the

cable

supplied

with

that

device

should

be

connected

to

the

CDS

via

the

EIA

cable.

Put

the

terminal

in

the

Line

mode,

select

the

ap-

pr-;;pa

~

te

baud

rate

and

set for full-duplex operation

before

attempting

to

use any

terminal.

Appendix B gives instructions for converting a

TTY

from half-

to

full-duplex operation.

The

in-

terface

is

a 20-mA

current

loop.

Make

necessary

changes

per Appendix B to convert a

TTY

to 20-mA

operation.

If

a

TTY

is to

be

used

with

the assembler

program,

the

remote

reader

control circuit should

be

installed in accordance with

the

instructions

in

Appendix

C.

Once installed, its switch should

be

set

in the

MANUAL

position before continuing.

Install

the

power cable

and

switch power on.

Press

RESET

followed

by

R

UNU.

This

sequence will

cause

the

RUN

light

to

go

ON

and

the

system is.now

operating

with

UT20

in

control.

This

program

begins by

reading

the

first keyboard

input

character

to define for itself

the

terminal

character

rate

and

whether

it

should

"echo"

typed

information

to

the

data

terminal

printer.

If

th

e

terminal

is

operating

in

the full-duplex mode,

the

user

should begin by pressing the

RETURN

key on

the

keyboard.

For

the

half-duplex

mode,

the

user should

press

the

LINE

FEED

key instead.

The

system

then

responds with the

prompt

character

(*).

It

now

"knows"

the

essential characteristics of

the

I/ O

data

terminal.

Reaching

this stage verifies

that

most

of

th

e

hardware

is

operating

properly.

CDS Checkout Program

Even

with

little

or

no

knowledge of

the

COS

MAC

command

repertoire, the user

can

further

verify

proper

system

operation

by loading, from

the

ter-

minal,

an

elementary

test

program.

For

example, a •

simple time-out loop

can

be

run

in which

the

RUN

~

light goes off

after

a specific elapsed time from

the

initiation of execution.

Each

line of user

keyboard

input

is

terminated

by

a

depression of the

RETURN

key

on

the

keyboard

The

test time-out

program

can

be

loaded

into memory

by

typing

in

!

MO

L'lF8FFB1219191913A0300(CR)

The

system will reply with

the

prompt

character.

One

c

an

verify

proper

loading by

entering

?MOL'l

A(CR)

The

system will

print

the

characters

just

entered

(after the memory location

addressed,

"0000"

in this

case)

and

will

return

the

prompt

character

again.

The

time-out

program

can

then

be

run

either by entering

$PO(CR)

or

by depressing

RESET

followed

by

RUN.

In

either

case, the

RUN

indicator

s

hould

go off after ap-

proximately 2.6 seconds.

This

step

establishes

that

the

read-write

memory

(RAM)

is

operational.

• In this Manual, (CR)

at

th

e e

nd

of an example

of

a user

keyb

o ~rd

input

denotes

the

terminating carriage

RETURN.

Spaces

man

input

line will

be

denoted

by

bl

anks in the

example

or, for add,-

tio

nal

emphasis,

by

the symbol

6.

•

i

I

••

1

•

Operating and Programming

the

CDS _

______

_

______

__________

11

Loading and

Outputting Programs

Programs

may

be

enter

ed

manually

by

use of

the

!M

command,

just

described.

This

and

other

Monitor

commands

are

covered in detail in

the

Ordinarily,

programs

will be loaded from

paper'tape via a

TTY,

from

magnetic

tape

cassettes

via the

TI

terminal,

or

from a floppy diskette via

the

Floppy

Disk

system.

The

latter is covered separately

ill.

:the

RCA

COSMAC

Floppy

Disk

System

CD-

{»18S805

Instruction

Manual

MPM-217.

RCA-

supplied

CDS

programs

are designed to

work

in

the

fllB-duplex mode.

Following

are

the

methods

used with

paper

tape

and

magnetic cartridges:

Paper Tape Systems

To

load a

paper

tape:

UPress

RESET,

followed

by

RUN

U.

21

Press

the

RETURN

key

(C-R)

on the

TTY.

Make

sure it is in

the

LINE

Mode

and

the

installed switch is in the

MANUAL

position.

31

UT20

will

return

the symbol *indicating it

is

ready

to

accept

commands.

41

Position the tape in

the

header

and

tum

on

the tape recorder.

51

When loading

is

complete,

UT20

will issue

another

*.

61

Start

the

program

by typing$UO(CR).

If

preferred, typing

can

be

suppressed

during

paper-tape loading by pressing the

LINE

FEED

key

in

stead of

CR

at

step 2.

In

this case, the user should

re-initialize the system

after

loading by pressing

HESET,

RUN

U,

and

CR

before

attempting

to

start

the loaded

program.

UT20

monitors

the

program

being loaded

and

will

issue a

'!

if a

format

error

is detected.

If

an

error

is

det

ected, stop

and

reload

the

tape

from the begin-

ning.

To

punch reloadable tape:

11

With

the

TTY

in

the

LOCAL

mode,

position

tape

in

the

punch,

tum

the

punch

ON,

and

make

a

header

of nulls (control-shift-

Pl.

.

21

Type

!

Maaaa

6 where

aaaa

is

the hex

address of where the

data

is to be reloaded

(normally location 00001.

31

Turn

the

punch

OFF

and

put

the

TTY

in

the

LINE

mode.

41

Initialize

the

CDS

with a

RESET,

RUNU,

followed by a

RETURN

(CRI.

51

Next, type

?Maaaa

6count,

where the

address

is

the

starting

address of

data

to be

read

from

memory,

and

count

is

the

number

of

hex bytes to

be

punched.

61

Turn

the

punch

ON

and

press

CR.

After

the

tape

is

punched,

some

more

nulls should

be

added

to its

end.

The

assembler

and

editor

programs

automatically

punch

reloadable

tape

as

described in

the Section titled CDS

Resident

Software

Development

Aids.

Magnetic Tape Systems

To

load a

magnetic

tape:

1) Press

RESET,

RUN

U,

then

CR.

2)

UT20

will

return

the

symbol

*.

3)

Mount

the

cassette.

Rewind

it

and

press

LOAD/FF

to

advance

to

the

first record.

Make

sure

the

drive

is

in

the

LINE

and

PLAYBACK

mode.

41

When loading is completed,

UT20

will issue

another

*.

Start

the

program

by typing

$UO(CR).

Typing

during

load

can be

suppressed

by

turning

the

printer

OFF.

If

a ?

is

typed

during

loading,

an

e

rror

has

been detected

and

the

tape should

be

reloaded.

To

record reloadable tape:

11

With

the

terminal in

the

LOCAL

and

RECORD

mode,

mount

a

blank

cartridge.

2)

Type

!Maaaa

6 where

aaaa

is

the

hex

address of where

data

is to

be

reloaded

(normally location 00001.

3) Switch

to

the

LINE

and

PLAYBACK

mode

and

initialize

the

CDS

with a

RESET,

RUN

U,

and

CR.

12

_____________

____

Operator Manual

for

the RCA CDS II CDP18S005

4)

Type

?Maaaa

6count,

where the

address

is

the

starting

address

of

the

data

to be

read

from

memory

and

count

is

the

number

of hex bytes

to

be

recorded.

5)

Tum

the

Record

Control

switch

ON

and

press

CR.

After

the

data

has

been

output,

UT20

will issue

another

*.

For'

another

system

checkout

program

using

the

supplied

"Deduce"

game,

refer

to

Appendix

H.

,

Introduction

to

the

Monitor

Software

UT20

Utility

Commands

The

CDP18S005

COSMAC

Development

System

includes a

Monitor

program,

known

as

UT20,

which

performs

commonly

required

functions

of

running

the

terminal

interface,

providing

a

means

of

reading

and

generating

reload

able

tape,

giving _access

to

all

memory

locations,

and

allows

the

user

to

start

program

at

a given location.

The

following

explains

in

detail

the

?M

and!

M

commands

already

mentioned,

plus

others

not yet discussed.

In

general,

after

the

system

has

been

RESET,

the

user

has

two choices: pressing

RUN

begins execution

of

his

program

at

location 0000, while pressing

RUN

U begins execution of

UT20

(at

8000). After pressing

RUN

U,

the

user

either

a

LF

(line feed)

or

a

CR

(carriage

return)

key,

depending

upon

his

installation. A

CR

initiates

FULL

DUPLEX

operation,

an

LF,

HALF

DUPLEX.

Besides

establishing

the

need

to

echo,

UT20

uses

this

input

to

calculate

the

timing

parameters

necessary

to

run

the

terminal.

Thus,

a single

program

can

operate

with

wide

variations

in clock

speed

or

terminal

speed.

When

UT20

is

ready

to

accept

a

command,

it

types

out

an

asterisk (*)

as

a

prompt

character.

?M

Commands

To

interrogate

memory,

type

a

command

such

as

?M2F53(CR)

UT20

responds

by

printing

out

the

contents

of

memory

beginning

at

location

02F5:

three

bytes

are

printed

out

as

two

hex

digits

each.

Each

line of

output

begins

with

the

address,

and

data

is

grouped

in

2-byte

(4-digit) blocks.

When

necessary,

new

lines

are

begun

every 16

bytes,

with

the

previous lines

ending

in

semicolons.

The

user

may

enter

any

number

of digits

to

specify

the

beginning

location (leading zeroes

are

implied,

if

necessary).

If

more

than

four

digits

are

entered,

only

the

last

four

are

used.

The

number

of

bytes

to

be

typed

out

should

be

in

hex.

Again, if

more

than

four

digits

are

entered,

only

the

last

four

are

used.

This

feature allows

the

correction of a

mistake

simply by

continuing

the

type

and

,terminating

the

..,

~ypedffse~uelnce

OWoi2th4)theIfcorhrect

4-d

b

igit

vfalbues

(2300b

24

~

IS,

e ectlVe y, . t e

num

er

0 ytes

to

e

typed

is

not

specified, one byte is

assumed.

For

example:

?M2F5(CR)

would

result

in the

typeout

of

the

one

byte

at

location

02F5.

When

the

user

wants

to

punch

a reloadable

paper

tape,

he

requests

a

memory

type-out

as

previously

described.

!M

Commands

In

general,

data

is

entered

into

memory,

by

means

of a

command

such

as

!MI2F

434F534D4143(CR)

This

command

enters

six

bytes

(two hex digits

each)

into

memory

beginning

at

location

012F. Once

again,

the

starting

location is

determined

by

the

last

four

digits

entered.

Data

is

entered

into

memory

after

.,

each

two

hex

digits

are

typed.

If

the

user

types

an

odd

.,

number

of digits,

the

last

digit is ignored,

and

the

error

message

('?')

is

typed

out.

It

is therefore only

necessary

to

re-enter

the

last

byte.

1

•

1

•

Operating and Programming the CDS

_________

__

_____________

13

The

!M

command

provides two options

that

facilitate memory loading.

First,

a string of

data

can

be extended from line to line

by

typing in a

comma

just

before

the

normal

CR.

(In this case press

the

CR-

LF

(carriage return-line feed) keys before beginninga

new line.)

For

example,

!M23

56789ABC,(CR) (LF)

DEFOI23456,(CR)

(LF)

3047(CR)

: enters

11

successive bytes beginning

at

location 0023.

Between successive hex pairs while

data

is being

entered,

any

non-hex

character

except the

comma

land

semicolon, as will

be

discussed) is ignored.

This

arrangement

permits

arbitrary

LF's,

spaces (for

readability), nulls (generated by

the

utility

program

or

by a time-share system to give

the

carriage time to

return), etc.

As

a second optional form of

data

entry,

a

string of

input

data

can

be

terminated

by a semicolon

land

a

CR).

The

utility

program

then

expects

more

data

to follow

on

the next line,

but

preceded by a new

beginning address.

The

line

must

have

the

format

of

an

!M

command,

but

with

the

!M omitted.

This

option provides the mechanism

f~r

reading

in a

paper

tape previously

punched

out

as a result of

the

?M

command.

(Recall

the

format

of multiline

?M

out-

puts discussed above.)

The

utility

program

ignores all non-hex

characters

following !

M,

allowing

CR,

LF,

and

nulls

to be inserted in

the

tape

without

disturbing

the

!M

command.

The

semicolon

feature

allows non-

contiguous memory

areas

to

be

loaded.

$U

Commands

The

$U

command

is used to

start

program

execution.

For

example,

$U6C(CR)

starts

program

execution

at

location 006C with

P = X

=0.

This

command

will leave

the

terminal

interface

and

floppy disk interface (if installed) ac-

tive. Consequently, the user

program

should

not

use

I/O

commands

associated with these interfaces.

For

a

further

discussion of

the

terminal

interface

and

the

floppy disk interface, see the material

on

Module

Description

and

Signal

Mnemonics

in the

For

further

details on

the

$U

command,

refer

to "Two-Level

110"

under

Input/Output

Inter-

facing

in the

If

only

$U

(CR) is

typed

with

no

address

specified, execution will

start

at

location 0000.

If

more

than

4

address

digits

are

typed,

only the

last

4

will

be

used.

$P

Commands

The

$P

command

is similar to the $U

command.

~or

example:

$P6C(CR)

would also

start

program

execution

at

location 006C

with

P=X=O

except,

in

this case,

the

temiinal

and

floppy disk interfaces

may

be disabled.

This

feature is

a convenience for

the

user so

that

his

program

can use

I/O

commands

normally associated with these

peripherals.

If

no

address

is specified,

program

execution

starts from location 0000.

The

function

is

equivalent

to

pushing

the

RESET

then

RUN

P

buttons

on

the

control panel.

This

command

also obeys

the

'last-4-

digits' address rule.

For

further

details of this

command,

refer to

"Two-Level

I/O"

under

Input/Output

Interfacing

in the

$L

Commands

The

$L

command

is used in systems having a

floppy disk.

Typing

$L

causes

UT20

to type

READ?

asking for the

unit

and

track

number

of

the

diskette

file to be loaded.

For

a discussion of the disk loader

program,

refer to the

RCA

COSMAC

Floppy

Disk

System

II

CDP18S805

Instruction

Manual

MPM-

217.

If

a floppy disk system is

not

installed

and

this

command

is

accidentally activated, simply do a

CR

after the

READ?

interrogation.

UT20

will type

DRIVE

NOT

ON

and

issue an

*,

waiting for

another

command.

?R

Commands

When

UT20

is activated (via

RESET,

RUN

U),

one of

the

first things

it

Qoes

is save 13-112 of

the

16

'R'

registers of

the

CPU

in its

RAM

stack

located

at

address

8COO

for 32 bytes. Registers

RO,

RI,

and

R4.1 are altered,

but

the

states of the remaining

registers

are

preserved

at

the

time

when

UT20

was

activated.

This

feature provides a means of

examining most

CPU

registers for debugging

pur-

poses.

14

_________________

0perator

Manual

for

the RCA CDS II CDP18S005

The

?R

command

provides for

automatic

readback

of

the

stored register states with

X's

for registers

RO,

RI,

and

R4.I

to

indicate

that

they

have

not

been

preserved.

For

example,

RESET,

RUN

U,

CR

then

?R

gives this format:

XXXX XXXX

18D4 3821, XX33 B760 8A15 0017

t t

RO

R7

5518

tc':

1\8

0717 34AA

8197,

A401 6789 A825 01B9

t

RF

NOTE:

the

?R

must

be

the

first

command

given to

UT20

after

it

is

started,

because

UT20

uses

the

stack

itself

when

other

commands

are

issued.

Thus,

it

may

overwrite

the

preserved registers when executing any

command

other

than

?R.

Summary of UT20

Operating Instructions

In

summary,

after

receiving

the

prompt

character

'*'

the

user

may

type

?M(addressl

f.,

(optional count) (CRI

!M(addressl

f.,(datal

(Optional,

or;)

(CR)

(where

the

data

may

have

non-hex digits between

each hex pair)

$P

(optional

address

I

(CRI

$U (optional address)

(CRI

$L

'?R(CR)

UT20

ignores initial

characters

until

it

detects?,

!,

or

$,

Then

inputs which are

not

compatible with

the

above formats cause

an

error

message (?

I.

A

further

detailed

summary

of these

basic

operating

instructions is given below,

repeating

the

information

just

given in a more concise form.

1.

After pressing

"RUN

U",

the

user should press

CR

(for full-duplex

operation

I,

This

instruction

sets

up

the bit-serial

timing

and

specifies echo

or

not.

2.

UT20

will

return

*as a

prompt.

3. Following

*,

UT20

ignores all characters

until

one of '!,

$,

or

! is

typed

in.

4. Following

'~M

or

!M,

UT20

waits for a hex

character.

It

then

assembles

an

address.

If

more

than

four hex digits

are

typed, only the

last

four

are

used.

Next,

a space

is

required.

Note:

f.,

denotes a

space:

a.

For

'!M

addr

f.,

a hex

count

may

follow (aga\n,

only

the

last

four digits

are

kept),

and

the

command

is

terminated

by

CR.

If

no

count

is

entered,

one byte will

be

typed.

b.

For

!M

addr

f.,

data

must

follow. An even

number

of hex digits is

required,

Before each hex

pair

arbitrary

filler, except for a

CR.

comma,

or

semicolon.

is

allowed.

CR

terminates

the

command,

unless

it

is

immediately preceded by a

comma

or, as is generally

the

case, by a

semicolon.

i.

In

case of

comma

CR

the

user

must

insert

an

LF

for

UT20

to

continue

to

accept

data.

This

procedure is a form of line

continuation.

ii.

In

case of a

semicolon

all following

characters

are

ignored

until

the

CR

is

typed.

Then,

the

user

must

again provide

an

LF,

and

UT20

continues as if it

had

received optional

filler,

then

a

starting

address, then a space,

and

then

data.

iii.

The

!M

command

can

be followed by as

many

continuation

lines as needed, mixed

between

the

two types

if

desired,

and

is

finally

terminated

with a

CR

not

preceded

by

a

comma

or

semicolon.

5.

Commands

$P

or

$U

may

be

followed

by

a

starting

address.

The

last 4 digits are used

if

more

than

4 are

typed

in.

If

no

address

is

given, 0

is

assumed.

Program

execution begins

at

the

specified

location with

RO

as

the

program

counter·

.

The

$P

command

disables

the

terminal

and

floppy disk

interfaces whereas

$U

does

not.

6.

Command

$L

starts

the

floppy disk loader

program

which will issue the

prompt

READ?

A

proper

response is a 4-digit

number

requesting

unit

and

track

number,

followed

by

a

CR.

If

an

error

is detected

during

the

read

operation, a diagnostic message is

printed.

7.

Command

?R causes a

readout

of the 16 R

registers saved when

UT20

is initialized.

X's

are

written

for those registers

not

preserved.

• $P

and

$U

always begin with

RO

as program

counter.

This

arrangement is consistent

with

the fact that

P=O

and

X=O

after

the CPU is RESET. Refer to the CDP1802 data sheet

for

other

actions

of

RESET.

•

Operating and Programming

the

CDS

________________________

15

H.

When

a

!M,

·!M

or

!'R

command

is accepted

and

completed,

UT20

types

another

*

prompt.

9. When

UT20

detects

bad

syntax, it types

out

a ?

and

returns

the

carriage.

If

a

mistake

is

made

when

data

is

entered

(by

typing

in

an

odd

number

of

digitsl, all

data

will

have

been

entered

except

the

last hex digit.

Note

that

the

"only-Iast-four-digits"

tnl

'e in

the

address

field allows

the

user to

correct

an

address

error

without

retyping

the

whole com-

mand.

For

example,

a

mistaken

234

can

be

:corrected by

continuing.

Thus,

2340235 is, ef-

fectively, 0235. A

bad

command

can

be

aborted

by

typing in any illegal

character

except after

!M

or

·-

'!M

or

between

input

hex

data

pairs.

In

these cases,

the

user

should

type any

digit

and

then,

for

example, a period.

Terminal Interfacing

ASCII Coding

The

CDS

is designed

to

interface to a

data

terminal

via a serial

ASCII

code

using

either a 20-mA

current

loop

or

an

EIA

RS232C

standard

electrical

interface.

When

a key is

struck

on a

TTY

terminal,

'

the information

denoting

that

character

is

converted

to

its

ASCII

code

and

appears

On

the

output

ter-

minals as a serial

data-bit

stream.

The

serial

data

originating

at

the

TTY

for the letter

'M'

is shown in

Fig. 2.

The

character

is

framed

by

a

start

bit

Band

LOGIC

I

BFI

DI

~I

DI

D~

FI

F

ACTUAL

-

DATA

BITS

INTELLIGENCE BITS

7

DATA

BITS

PLUS I PARITY BIT

---I

B 1

COMPLETE CHARACTER

"M"

(4DI6)

....

=

ONE

BIT TIME P = PARITY BIT

B =START

BIT

D'

DATA

BIT

F =

STOP

BIT

---

=ASYNCHRONOUS TIME

BETWEEN CHARACTERS

92CS

-28100

Fig.

2 -

Data

terminal

bit

serial

output

for the

character

"M"

.

two stop bits

FF.

By convention two stop bits

are

used for

data

transmission

at

10

characters

per

second

although

1, I

liz,

or

2

are

also acceptable

outputs

from

various different

terminals.

A

parity

bit

P

is

also

shown.

For

even

parity,

the

parity

bit

would

be

a

'I'

only

if

the

7

data

bits

contain

an

odd

number

of '1

'so

Hence,

the total

number

of 1

's

in the eight intelligence

bits

is

always

an

even

number.

Some

data

terminals

may be set

up

to

generate

either

even

or

odd

parity.

UT?O ignores the

parity

bit, so

either

even or

odd

rarity

is acceptable.

Data

from

the

CDS

is

generated

with

the

same

format;

i.e.,

a

start

bit,

7

data

bits, a parity bit,

and

two

stop

bits.

Note

that

the

CDS

does

not

generate

parity -the parity

bit

is always a

'I'

regardless of

the

data

bits. Therefore, terminals interfacing to the

CDS

should ignore

the

parity

bit.

UT20 Read and Type Routines

The

UT20

read

and

type

routines

provide

the

basic software

mechanism

for

communication

be-

tween

the

CDS

and

data

terminal.

Several different

routines

are available to facilitate different types of

110

data

transfers.

These

routines

are

designed

to

allow adoption to

various

terminal

speeds

and

to

determine

whether

or

not

characters

read

in

should

be

"echoed"

(ie., typed

back

immediately

I.

For

these

purposes,

a 'sub-

subroutine'

called

DELA

Y is included which

provides

the

necessary

bit

timing delays to

the

read

and

type routines.

DELAY

uses

RC

as its

program

c

ounter,

which

must

be set-up to

point

to location

80EF.

UT20

does this

automatically

when it is

started.

Any user

program

using a read

or

type

routine

must

not

alter

RC,

or

must

restore it to

80EF

before calling a

read

or

type

routine.

Also,

the

upper

half of register

RE

(RE.I)

contains

a control con-

stant.

The

least significant

bit

specifies echo (0

denotes echo, 1

denotes

no

echol.

For

full-duplex

operation,

then,

this

bit

is a zero. Again, this is

automatically

set when

UT20

is

started

and

the

CR

or

LF

characters

received.

The

remainder

of

RE.l

constitutes a timing

parameter

(TPI.

TP

is calculated

as

follows:

~

.nterval

between two serial

bit~

•

TP=2

x 320 x

(CPU

clock period)

where

the

fraction is

rounded

to

the

nearest

integer.

For

example, because a

Teletype

Model

33 operates

at

10

characters

per

second

and

II

bits

per

character,

for

the

CDS

running

from

the

supplied

2.0-MHz

clock,

-The

factor

of

2 comes from the fact

that

the

input

serial wave-

form is sampled over

two

successive bit times. The factor

of

320

comes from the fact

that

the time between samples

is

20 instruc-

tion

times, with each instruction taking 16 clock periods.

16

_________________

0perator

Manual

for

the

RCA CDS II CDP18S005

1 s 1 char

--

x---

10

char

11

bits

TP

=2

x 320 x 1 s

2.0 x 106

=2 x 56.8 (rounded to

57)

=

11410 =

72

16

Because for

proper

operation

TP

must

be

less

tha.o:

255,

there

is a

bound

on

the

speed

of

terminals

s}:\pported

at

any

given clock

rate.

Faster

terminals

or

slower clocks

can

be

supported

to

the

extent

that

roundoff

errors

do

not

cause

bad

timing.

For

example,

at

2.0

MHz

and

30 lO-bit

characters

per

second,

~

J 1 J

3o

xlo

TP

=2 x =2(20.8) =4210 =2A16

320/2.0 x 106

and

the

round-off

error

is small (2100

instead

of 20.81.

On

the

other

hand,

at

2.0

MHz

with

baud

rates

above

1200, the round-off

error

would be too high.

The

utility

program

UT20

uses a

subroutine

"TIMALC"

to

generate

the

operating

time

constant,

using the first

character

typed

in

by

a user.

This

routine times

the

intervals

between

incoming bits to

calculate

TP

and

reads

one

bit

to

determine

whether

or

not

to echo. Specifically, if a

CR

is entered while

TIMALC

is

running,

then

echoes will be provided;

an

LF

suppresses echoes.

In

either

case,

RE.l

is

loaded

with

the

appropriate

constant.

TIMALC

also

loads

the

subroutine

pointer

for

the

DELAY

routine.

The

user

of

TYPE

and

READ

has

the

option of

calling

TIMALC

or

setting

up

RE.l

and

the

pointer

to

the

DELAY

routine

himself. As a convenience

to

the user,

UT20

leaves

RE.l

and

RC

properly ad-

justed

while

performing

a

$P

or

$U

operation

and

may

be used unless

they

have been altered

by

the

user.

All

read

and

type

routines

and

TIMALC

use

R3

as

their

program

counter,

and

return

to

the

caller

with

SEP

R5.

They

can

be

called directly

from

a

program

that

can

use

R5

as

its

program

counter,

or

they

may

be

called

through

the

Standard

Call

and

Return

Technique

(SCRTI

described

in

the

User

Manual

for

the

CDP1802

COS

MAC

Microprocessor,

MPM-201

in

the

Section

Programming

Techniques

under

"Subroutine

Techniques".

This

programming

technique

is

the

most

general

and

is

recommended.

RE.l

is

reserved for

the

operating

constant

(control

constant

0

or

1

added

to

the

timing

parameter

'1'P

Idiscussed above.

One byte of

RAM

is

needed

by

read

and

type

routines.

These

routines assume

that

R2

points

to

free

RAM

and

M(R(211

is

alt

e

red

by

them.

In

general~

the

user

can

set

R2

to

any

free

RAM

location.

UT20

uses

a

byte

in its

dedicated

RAM

for

this

purpose.

R

F.I

is

used

in

certain

cases

to

pass the byte

being

read

or

typed between

the

calling routine

and

these subroutines.

When

READ

is exited,

it

leaves

the

input

byte in

RF

.1. When

TYPE

is

entered

at

location 81A4,

the

byte

to

be

typed

is

taken

from

RF.l.

All rontines alter

RE.O

and

RF.O.

They

also

alter

D.

DF,

and

X.

The

READ

routine

leaves

the

input

byte

in 0

as

well

as

in

RF.l.

but

the

byte

in

D will be

destroyed if

the

Standard

Call

and

Return

Technique

is

used.

When

TIMALC

exits,

R3.1

is left holding

A.I

(READl

=

A.I

(TYPEI

= 81,

but

R3.0

is

meaningless. When

READ

exits,

R3

is

ready

for

entry

at

READAH

(see

Table

III.

When

TYPE

exits,

R3

is

ready

for

entry

at

TYPE5

(see same tablel. a

When

DELAY

exits,

RC

is

ready

for

another

call

to

~

DE LAY. When

the

Standard

Call

and

Return

Technique

is used,

R3

is

automatically

set

up.

The

READ

routine

has two

entry

points -

READ

and

READAH.

The

former acts as described above

and

has

no

other

side-effects.

The

latter

operates

just

as

READ

does,

but

with

the

following side-effect.

If

the

character

read

in is a hex

character

(0-9, A-FI

then

the

I6-bit

contents

of

RD

are shifted four bits to

the left.

and

the

4-bit

hex

equivalent

of

the

input

character

is entered

at

th

e right.

DF

is

then

set to 1 on

exiting.

If

the

input

character

is

not

a hex

character,

RD

is

not

affected,

but

DF

is

set

to

0 on exiting.

CAUTION:

A

READ

may

immediately

be followed

by

another

READ,

but

not

immediately

by

a

TYPE.

The

caller should

wait

1.5

bit

times

first, which he

can

do by entering

TYPE

at

TYPE5D

or

by calling

DELAY,

with

a

parameter

of 7

or

greater.

The

DELAY

subroutine

assumes

that

the calling

program

counter

is

R3.

It

uses

the

value,

n,

of

the

immediate

byte

at

M(R31 to

generate

a delay

equal

to

(20 +m (2n +

611

instruction

times

where m is

time

constant

in

RE

:I (see previous

discussion

I.

It

then

increments

R3

past

the

calling

parameter

and

returns

via a

SEP

R3.

1

•

Operating and Programming the

CDS

________________________

17

The

TYPE

routine

has

five different

entry

points.

Three

of

them

simply specify different places

to fetch the

character

from:

TYPE

types from

RF.l,

TYPE5

types from M(R51

and

increments

R5,

and

TYPE6

types from M(R61

and

increments

R6.

TYPE5D

is

an

entry which provides a lo5-bit delay

before going to

TYPE5.

The

purpose

of this delay is

to

let"

an

immediately preceding echoed

READ

process to completion before typing.

TYPE2

is

an

eritry which results in

RF.l

being typed

out

in hex

form as two hex digits.

Each

4-bit half

is

converted to

a,

ASCII

hex digit (0-9, A-Fl

and

separately

typed

.out.

Notice

that

the

READ

routines

are

designed to

facilitate

repeated

calls on

READAH,

while

the

TYPE

routines

are

designed for repeated calls

to

TYPE5.

In

order

to

output

a string of variable

data

characters

following a

READ,

given the

timing

restriction

mentioned

earlier.

it

is

most

logical to call

TYPE5D

first.

using

an

immediate

"punctuation"

byte (i.e.,

non-data

such as space, null, etc.Ito

get

the

required initial delay

and

to follow either with

repeated

calls on

TYPE

(with

the

output

variable

data

characters picked

up

from

RF.Il

or

repeated

calls on

TYPE5

using

immediate

data

characters.

This

procedure

permits

a

maximum

output

character

rate.

Another routine,

OSTRNG,

can

be

used

to

output

a string of characters.

OSTRNG

picks

up

the

character

string

pointed

to

by

R6

and

tests each

character

for zero.

The

characters

should

be

already

encoded in

ASCII.

If

a zero is found

(ASCII

'null'l,

the

program

terminates

and

returns

control to

the

user via a

SEP

R5.

If

the

character

is

not

a zero,

it

is

typed

out

to

the

terminal.

The

OSTRNG

routine

includes a delay

on

the

front

end

so

that

it

may

be

called

at

any

time -even following a

read.

Tables

I

and

II

summarize

the

functions

and

calling sequences

just

described.

TABLE

1-

UT20 REGISTER

UTILIZATION

Register

Name

PTER

CL

ST

SUB

PC

DELAY

ASL

AUX

CHAR

Notes

Register

Number

RO

J

R1

R2

R3

R5

RC

RD

RE

RF

Function

and

Comments

Alt.ered

b-y

UT20 while storing registers. R4.1

is

similarly

altered.

Pointer

to

RAM

"work"

byte.

UT20

uses R2 =

8COO.

Program

counter

for

all

routines

except

DE

LA

Y.

Program

counter

for

UT20

which calls

the

routines above.

Program

counter

for

the

DELAY

routine.

Points

to

DELAY1 in

memory.

Assembled

into

by

READAH

(input

hex

digits).

RE.1 holds

time

constant

and

echo

bit.

RE,O

is

used

by

all READ

and

TYPE routines and

by

TIMALC,

OSTRNG,

and CKHEX.

RF.1 holds

input/output

ASCII

character.

RF.O

is

used

by

all READ

and

TYPE routines and

by

TIMALC,

OSTRNG,

and

CKHEX.

TABLE

II -UT20 READ

AND

TYPE

CALLING

SEQUENCE

Entry

Absolute

Name Address

READ

813E

READAH

813B

TYPE5D

819C

TYPE5 81AO

TYPES

81A2

TYPE

81A4

TYPE2

a1AE

TIMALC

80FE

DELAY1

OSTRNG

80EF

83FO

Input

ASCII ~

RF.1,

0 (if non-standard linkage)

Same

as

READ.

If

hex

character,

DIGIT ~ RD (see

text)

1.5-bit delay. Then TYP

E5

function.

Output

ASCII

character

at

M(R5). Then

increment

R5.

Output

ASCII

character

at

M(RS). Then

increment

RS.

Output

ASCII

character

at

RF.1.

Output

hex digit pair in RF.1.

Read

input

character

and set

up

control

byte

in

RE.1.

Initialize RC

to

point

to

DELAY1.

Delay,

as

function

of

M(R3) (see

text).

Then R3 + 1.

Output

ASCII string

at

M(RS). Data

byte

00

ends

typeout

.

(1) All routines,

except

DE LA

Y,

use R3

as

program

counter,

exit

with

SEP5, and

alter

registers

X,D,

OF, RE, RF

and

location M(R2).

exits with

SEP3

after

incrementing

R3, and

alters registers

X,D,

OF,

and

RE.

(3) READ and READAH

exit

with R3 pointing

back

at

READAH.

(4) All five TYPE

routines

exit

with

R3 pointing

(2) DELAY

routine

uses RC as program

counter,

at

TYPE5.

18

__________________

Operator Manual

for

the

RCA

CDS II CDP18S005

Examples of UT20

Read and Type Usage

The

following examples should help clarify how

to use the

UT20

read

and

type subroutines.

Most

examples use

the

standard

subroutine

linkage which

require's

that

R2

point

at

a free

RAM

location.

: Read Routines

.This sample

program

will

read

four

ASCII

hex

characters

into register

RD

translating

them

from

~SCII

to hex in the process.

Reading

will

terminate

-<

when a carriage

return

is entered.

Entry

of a non-hex

digit

other

than

a carriage

return

will cause a

branch

to

an

error

program

which will type

out

a

"?".

This

sample

program

uses

the

standard

subroutine call

and

return

linkage.

READAH=#813B

LOOP:

SEP

R4,A(READAH)

..Call the hex

..

read

program

BDF

LOOP

..

As

long as

ASCII

hex

..digits are entered

..

Read

and

shift in

..Fall

through

if

not

hex

..

character

GHI

RF

..See

what

character

was last

.. entered

XRI

HOD

..

Was

it

carriage

return

BNZ

ERROR

..

If

not,

BR

to error

..

Characters

entered

are

now

..in

RD

The

READ

routine

(at 813E) could be used

similarly to

enter

characters;

however,

READ

only

enters

them

one

at

a time into

RF.I

(and

D)

writing

over the previous entry.

Note

that,

even

though

incoming

data

is

entered

into

D,

the subroutine

return

program

alters

D.

Therefore,

valid

data

will

only be found in

RF.I

(and

RD

when

READAH

is

used) if the

standard

subroutine call

and

return

programs

are

used. An alternative technique is to use

R5 as the main

program

counter

(since all

read

and

type routines

terminate

with a

SEP

RS)

and

call

the

program

with a

SEP

R3 (since

all

read

and

type

routines use

R3

as their

program

counter).

The

following example illustrates this technique.

Type Routines

EXAMPLE

1:

This

program

outputs

a single

c

haracter

using the

TYPES

routine.

It

uses RS as

the

program

counter.

LDI

#81

PHIR3

LDI

#AO

PLOR3

LDI

#FF

PLOR2

LDI

#3F

PHIR2

SEPR3

..Set R3 to

TYPES

routine

..Set

R2

to free

RAM

location

#:~FFF

..Call type

,T'R'

yy

..An

"R"

will be

typed

..

The

TYPESD

routine is used in the

same

way,

EXAMPLE

2:

This

program

outputs

a

chara

cter

using the

TYPE6

routine.

Note

that

R6

should be the

program

counter for

the

program

calling

TYPE6

if

the

character

to

be

typed is

an

immediate byte

because

TYPE6

must

always be from

M(R6).

But,

because

TYPE6

exits with

SEP

S,

TYPE6

must

always be called using

standard

subroutine linkage

for typing

an

immediate

byte. An alternative is to use

RS as the main

program

counter

but

point

R6

at

the

memory location

containing

the byte to be typed.

This

example uses

standard

subroutine

linkage.

SEP

R4

..

Branch

to the call routine

,#8IA2 ..Address of

TYPE6

,

T'?'

..Byte to be typed

out

yy ..Next instruction

EXAMPLE

3:

The

TYPE

and

TYPE2

routines

pick

up

the

byte in

RF.I

for typing.

TYPE

simply

output

s

the

character,

whereas

TYPE2

considers

RF.I

a hex digit

pair

which

it

encodes in

ASCII

before typing.

This

example types

out

the hex digits

'DS',

and

uses

standard

subroutine

linkage.

LDI

#DS

PHIRF

SEP4

,

#8IAE

yy

..

Load

hex digits DS

..

IntoRF.1

..Call

TYPE2

..

Note

that

all type routines, except

TYPE2,

expect the

character

they

pick

up

to be already en-

coded in

ASCII.

EXAMPLE

4: An entire message

can

be

typed

by using

the

OSTRNG

routine.

The

ASCII

bytes

pointed

to

by R6 will

be

typed.

When

a '00' byte

is

detected,

OSTRNG

returns

to the caller.

This

example will

output

the

string

RCACOSMAC

MICROPROCESSOR

The

standard

call

and

return

linkage

is

assumed.

I

r

•

Operating and Programming

the

CDS

______

_

________________

19

.

,:'

"

OSTRNG

= #83FO

SEP

R4,A(OSTRNG

I ..Call

OSTRNG

DC

T'RCA

COSMAC'

..1st Line

,#ODOA

..(CRI (LFI

,T'MICROPROCESSOR'

..

2nd

Line

,#00

..

End

of

Text

Additional

Utility Routines

ASCII to Hex

Conversion Routine

The

ASCII

to hex conversion,

CKHEX,

examines the

ASCII

character

in

RF.l.

If

this

chanl(;ter is

not

a hex digit,

CKHEX

returns

to

the

IIser Ivia

SEP

R:)I with

OF

=

O.

If

the

character

is

IIPx.

CKHEX

returns

with RE.O = hex digit,

OF

=

I

and

with the

digit

shifted into

the

least significant 4

bits of

~egister

RD.

CKHEX

uses the registers

dt's('rihed above

and.

as with

the

other

routines, is

most ft'adily

handled

via the

standard

call

and

return

lI'Chniques.

CKHEX

is located

at

83FC.

Initialization Routines

Two

routines

are

provided,

INITI

and

INIT2,

\\ hil'h initialize

CPU

registers for the

standard

call

and fPturn

technique.

These

routines set

up

registers

as follows:

R2 =

R(X

I - POIntIng to

the

last (highest)

available user

RAM

location

R3

R4

R')

(below 8000),

-will become

the

program

counter

on

return

-

pointing

to the call routine

in

UT20

-

pointing

to

the

return

routine

in

UT20

The

INIT

programs

examine

user

memory

area

(below address 80001

and

determine

how

much

nWlllory

is

present.

They

set

R2

to the highest

available

RAM

address,

which

is

03FF

for the

CDS

as supplied (with one 4-kilobyte

RAM

cardl.

The

only difference between

INITI

and

INIT2

is

the lo(;ation to which they

return.

INITI

returns

to

location 000:) with P =

:1,

while

INIT2

simply

rptllTns by sf'tting P =

:1

and

assumes

that

the user

has already set

R:1

pointing to the correct

return

point.

These

programs

are

intended

as a convenience

to !'n't' the IIser from

generating

the overhead code

n'<Jllin'd by the

standard

subroutine

technique.

They

llW)

also be used as

an

integral

part

of custom

support

programs

running

on

the

CDS.

Their

ab-

,;olllte addresses

are

INITl

=

83F3

and

-INIT2

~

B:W(I. Hefer to Appendix

G,

the

UT20

listing, for

the

absollltt' addresses of

CALL

and

RET,

which will

be

loaded into R4

and

R:) respectively.

Following

are

examples

of

the

use of these

prol-(rams:

EXAMPLE

1:

Using

INITl

= #83F3

Address

Code

Mnemonics

Comment

0000

0001

0002

0003

0004

00U5

71

00

CO

83

F:~

DIS,#OO ..

Disable

interrupts

LBR

INITI

..Initialize registers

USRPGM:--

..User

program

starts

here;

..P = 3

EXAMPLE

2:

Using

INIT2

=

#83F6

Address

Code

1\1fl('moni('s

Comment

0000

71

0001 00

000:2

FH

oom

00

0004

B:3

000:) FS

OOO()

.')0

0007

A3

OOOS

CO

OOOfJ

~n

OOOA

Fe)

OOSU

])IS.#OO ..

Disable

interrupts

LDI

A.I

..Set

R:3

to

return

(STARTI

..

point

PHI

R:3

LDI

A.O

(STARTI

PLOR:1

LBR

INIT2

..Call

INIT2

START:--

..User

program

starts

here

..P

=3

RCA 1800 User manual

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