Atari 850 User manual

TECH

-

NICAL

MANUAL

®

)I~®

ATARI

A Warner Communications Company 0

ATARI

®

8SO

™

INTERFACE

MODULE

TECHNICAL MANUAL

)I\.

ATARI

(i)

a A Warner CommuniCai,IOns

Company

Eve

ry effo

rt

h

as

been made to ensure the acc

ur

acy of the product documen

ta

tion in this manual. However, because Atari, In

c.

iscon-

stantly improving and updating the

co

mput

er software and har

dwa

r

e,

we

are unable

to

guarant

ee

the acc

ur

acy of the printed mate

ri

al after

the date of publi

ca

tion and di

sc

laim

li

a

bilit

y for chan

ges,

errors or

omi

ssion

s.

No

reproduct

io

n of this document or any

por

tion

of

its conten

ts

is

allowed

without specific written permission

of

Ata

ri

, Inc.,

Sunnyval

e,

CA 94086.

Impo

rt

ant Info

rm

a

ti

on:

Li

ke any electri

ca

l appliance, this ATA

RI

Home

Comp

uter equipment u

ses

and produces radio fre

qu

ency

energy. If it's not in

sta

ll

ed and u

sed

prope

rl

y according to the instructions in this guid

e,

the e

qui

pment may

ca

u

se

interference

with

your

radio and television receptio

n.

It

has

been type t

es

ted and found to

co

mply with the l

imi

ts for a Cl

ass

B

comp

uting device. in acco

rd

ance

with

the specificat

io

ns in

Subpart J

of

Part 15

of

the

FCC

ru

les

. Th

ese

rul

es

are designed to provide reasonable protection

aga

inst such interference when

th

e e

qui

p-

ment is u

se

d in a r

es

idential

se

ttin

g.

However, there is no guarant

ee

that interference will not occ

ur

in a particular home or r

es

idence.

If you believe this

eq

u

ip

ment is

ca

using in

te

rference with your

te

levision reception, try turning the e

quipm

ent

off

and o

n.

If the in-

terference

prob

lem stops

wh

en the

eq

uip

ment is turn

ed

off, then the e

qu

ip

ment

is

probably

ca

using the inter

fe

rence.

With

the equ

ip

ment

turned on, you may be able to correct the pr

ob

lem by trying one or more of the fo

ll

ow

ing m

eas

ur

es:

• Reorient the

ra

dio

or

television antenn

a.

• Reposition the

eq

uipment in relation

to

the r

ad

io or television

set.

• Move the e

qui

pment away from the radio or television.

• Pl

ug

the equipment into a different wall outlet

so

the equipment and the radio

or

television are on different

branch

ci

rcuits.

If necessary, consult your ATARI Computer retailer

or

an

experienced radio-television technician for additional suggestions.

LL

RI

GHTS

RESERVED

CONTENTS

HOW

TO

USE

THIS

MANUAL

1

WHAT

IS

RS-232-C? 3

2 ATA

RI

BASIC

AND

THE

AT

A

RI

850

INTERFACE

MODULE

7

How

To Use the Program 8

Improving

the Program 9

Interface

Module

Capabilities

11

3

HOW

THE I

NT

ER

FACE

MODULE

INTERACTS

WITH

THE SYSTEM

13

Turn-On Operation

13

Without

a Disk Drive

13

With

a Disk Drive

13

Using a Printer

14

4

PROGRAMMING

THE SERIAL INTERFACE PORTS

15

'

Input/Output

Control Block

15

Accessing

an

RS-232-C Device

15

Step 1

-Configure

the Serial Interface Port

15

Step 2 - Using the Serial Interface Port 16

Limitations on Port Configurations

18

Restrictions 19

5 SETTING THE

BAUD,

WORD

SIZE, STOP

BITS,

AND

READY

CHECKING

21

6 SETTING THE

TRANSLATION

MODES

AND

PARITY

HANDLING

25

Types

of

Code Translation

26

Parity 27

Short

Word

Conversion 27

7

CONTROLLING

THE

OUTGOING

LINES

29

DTR,

RTS

, and XMT

29

Control Command

29

Contents iii

8 BASIC

1/0

COMMANDS

31

Opening

a Port

31

Closing a Port

31

ATARI BASIC

1/0

Statements

32

GET, INPUT, PUT, and PRINT

33

LIST,

SAVE

, LOAD, and

ENTER

35

9 STARTING

CONCURRENT

MODE

1/0

37

10 THE STATUS

COMMAND

43

Uses

of

STATUS

Command

43

Error STATUS Bits

45

Received Data Framing Error

45

Received Data Byte

Overrun

Error

45

Received Data Parity Error

45

Received Data Buffer

Overflow

Error

46

Illegal

Option

Combination

Attempted

46

External Device

Not

Fully Ready

46

Data Block Error 46

Command

Error

to

Interface

Module

46

11

SAMPLE PROGRAMS

49

Transferring ATARI BASIC Source Programs

49

Baudot Terminal Emulator

53

Programming a Printer 58

Reading a Digitizer 60

12 INTERFACE

MODULE

ELECTRICAL

SPECIFICATIONS

63

RS-232-C Standard

63

RS-232-C Specifications 63

Electrical Specifications

of

the Serial Ports 64

Printer Port Specifications

65

13 PRINCIPLES

OF

OPERATION 67

Software Operation 67

Printer Software

Operation

69

Contents

iv

t

APPENDICES

A Code Tables

B XIO Commands and Tables

C Port Diagrams and Interface

Module

Schematic

D Troubleshooting

E Error Conditions, Causes, and Corrections

F Product Specifications

INDEX

ILLUSTRATIONS

71

81

87

93

97

101

105

1-1

Communications

Hook-Up

Showing Role

of

RS-232-C 4

4-1

Block

Output

Mode

1/0 17

12-1

Timing

of

Printer Ports

66

C-1

Functions

of

Serial Interface Port 1 87

C-2

Functions

of

Serial Interface Ports 2 and 3 88

C-3

Functions

of

Serial Interface Port 4 89

C-4

Hook

Up

of

Serial Interface Port 4 for Use

With

a

20-mA Loop Device 90

C-5

Functions

of

the Printer Port 90

C-6 ATARI 850 Interface

Module

Schematic Diagram

91

TABLES

1-1

4-1

10-1

10-2

12-1

B-1

B-2

B-3

B-4

B-5

B-6

B-7

B-8

B-9

B-1

0

B-11

F-

1

The Most

Common

RS-232-C

Circuits

Available Signals on Ports

1,

2,

3,

and 4

Decimal Representation

of

the Error Bits in Location

746

Sense

Values Added Into Location 747

RS-232

-C Electrical Specifications

Baud

Rate

Specifiers

To

Add

to

Aux1

Word

Size Specifiers

To

Add

to

Aux1

Specifier

for

Two

Stop Bits

To

Add

to

Aux1

Aux2 Specification To

Monitor

,

DSR

,

CTS

,

CRX

Translation

Mode

Options Added

to

Aux1

Input

Parity

Mode

Options

Added

to

Aux1

Output

Parity

Mode

Options

Added

to

Aux1

Append Line

Feed

Options

Added

to

Aux1

Control Values for DTR Added

to

Aux1

Control Values for

RTS

Added

to

Aux1

Control Values for XMT Added to Aux1

Connections

4

18

44

48

63

82

83

84

85

103

Contents v

HOW

TO

USE

THIS

MANUAL

Before reading this manual,

you

should be familiar

with

the

ATARI

®

BSO

™ Interface

Module

()wners

Manual.

It tells

you

how

to

connect

the ATARI 850 Interface

Module,

the ATARI 830™ Acoustic Modem, and the ATARI 825™ 80-

Co

lumn

Printer

to

your

ATARI

Home

Computer.

While

most

of

the

information

in this technical manual covers the use

of

the inter-

face

module

,

you

'll find some instructions here

for

operating the acoustic

modem.

The

modem

cannot

function

without

the interface

modu

l

e.

Sections 1

through

3

of

the manual explain

how

the interface

modu

le

works

and

what

it can

do.

The

beginning

user may

want

to

study these sections after setting

up

·

and using the

equipment.

The advanced user should at least skim this material

before going on

to

Sections 4

through

13

,

which

provide

details

on

the

many

uses

of

the interface

module.

This manual describes

how

to

use

the

ATARI850

Interface

Modu

le

only

with

ATARI

BASIC (often referred

to

in

the

text

simply

as

BASIC). To carry

out

the operations

described,

you

must first insert an ATARI

BAS

IC

cartr

idge in the

appropriate

car-

tridge slot

of

your

computer

console.

How to

Use

This Manual 1

1

WHAT

IS

RS-232-C?

RS-232-C

is

a technical standard

of

the Electronic Industries Association (EIA).

Published in August

of

1969, it

is

titled "Interface Between Data Terminal Equip-

ment

and Data

Communication

Equipment Employing Serial Binary Data Inter-

change."

The standard specifies electrical signal characteristics and names and

defines

the

functions

of

the signal and

control

lines that make

up

a standard inter-

face called RS-232-C.

Figure

1-1

s

how

s,

diagrammatically, the kind

of

hook-up

that RS-232-C was de-

signed to

sta

ndardize. A data terminal

is

at each end

of

the

communication

link

.

The data terminal either generates

or

recei

ves

data (or does both). It

could

be a

keyboard/screen "terminal" in the normal sense

of

the

word;

it

co

uld be a

co

m

~

puter; etc. The idea isthat the data terminal

is

at the end

of

the

communication

link

- hence it is called "terminal."

However

, the data terminal need

not

really be at

the

end-

you

ca

n

think

of

"data

terminal"

as

ju

st

the name

of

one

o(the

two

ends

of

a RS-232-C

connectio

n.

At

the

other

end

of

a RS-232-C

connectio

n

is

the data

set

. In the example

of

Figure

1-1

, each data

set

takes data from the data terminal it

is

connected

to

and

sends/receives the data

over

the

communications

link. The most familiar example

of

a data set

is

the

modem

(such

as

the ATARI 830 Acoustic

Modem)

,

which

takes

data

from

a terminal and converts it for sending and receiving

over

a

telephone

line.

The ATARI

Home

Computer

with

the interface

module

should be

thought

of

as

a

unit

comprising a RS-232-C data terminal.

A

full-duplex

connection

is

one

where

data can be sent and received by both ends

of

the RS-232-C

connection

simultaneously. In a half-duplex

connection

, data can-

not

be sent by both ends at the same

time

. Therefore,

one

terminal must be able

to

tell the

other

terminal, " I' m

through

now

; it's

your

turn

."

The second terminal then

sends a signal saying, "

OK

, here I

come."

This exchange

is

called

"handshaking";

it

is

simply the sending and receiving

of

required signals

to

prepare each end

of

the

connection

for the sending

or

receiving

of

data. Handshaking can be used in full-

duplex

operation

to

tell

the

sending terminal

to

stop sending until the receiving ter-

minal can catch

up

.

What

is

RS-232-C? 3

4

What

is

RS-232-C?

The data-set/data-terminal distinction should be kept in mind because the

RS-232-C

interface

is

directional. That

is

, each line in a

RS-232-C

interface

has

a

direction -one device drives the line (sends information) and the other receives

the information.

Each

line

in

an

RS-232-C interface

is

defined

as

being driven by

either the data-set end

or

the data-terminal end.

DATA

TERMINAL

(TERMINAL)

RS

-

232-C

CONNECTION

DATA

SET

(MODEM)

DATA

SET

(MODEM)

DATA

TERMINAL

(COMPUTER)

DATA

COMMUNICATION

LINK

(

TELEPHONE

)

RS-232-C

~

CONNECTION

Figure

1-1

Communications

Hook-Up

Showing

Role

of

RS-232-C

The

RS-232-C

standard defines some 20 signaling lines,

or

"circuits"

as

the stan-

dard refers

to

them. Most

of

them are optional and rarely used.

Even

with

many

omissions and deviations from the standard, a link may

st

ill be referred

to

as

RS-

232-C. It

is

more

common

to

refer

to

the link loosely

as

"

RS-232

"

or

"

RS-232

compatible."

The most

commonly

used

RS-232-C

lines are listed in Table 1-1. The table shows

the name

of

each line in the

RS-232-C

standard and

commonly

used mnemonics.

Table

1-1

The

Most

Common

RS-232-C Circuits

LINE

(CIRCUIT)

NAME DIRECTION DESCRIPTION ABBREVIA

liON

BA

terminal-+set Transmitted data XMT

BB

terminal+-set Received data

RCV

CA

terminal-set

Request

to

send

RTS

CB

terminal+-set Clear

to

send

CTS

cc terminal+-set Data

set

ready

DSR

AB

(none) Signal ground

CF

terminal+-

set

Signal (carrier) detect

CRX

CD

terminal-set

Data terminal ready DTR

It

is

common practice to

use

common names or abbreviations for the RS-232-C

signals,

and not the two-letter names

in

the official standard.

Transmit (XMT) and receive (RCV),

for

any given device,

is

usually relative to that

device. That

is

, data goes

out

of

a device on XMT and comes in on

RCV.

To connect

two

RS-232-C devices

when

given the

common

names

of

the

signals, you should

connect

XMT

to

RCV

(in one direction) and

RCV

to

XMT (in the

other

direction). If

one

of

the devices

is

wired

as

a data set and the other

as

a data terminal, then you

should

connect

DTR

to

DTR,

DSR

to

DSR

,

RTS

to

RTS,

and

so

on. If,

on

the

other

hand,

they

are each wired

as

data terminals, you should be careful

how

things are

connected.

The Signal Ground

connection

must always be made. RS-232-C requires that the

ground potential

of

the

two

devices be equal. That

is,

their

grounds must be con-

nected together. Devices for

which

this requirement

cannot

be met cannot be con-

nected via a RS-232-C interface.

Data terminal ready

(DTR)

is

used by

RS-232

-C

to

allow

the terminal

to

signal its

readiness

to

send

or

receive data. This

is

a signal

to

automatic answering modems

that

they

have permission

to

answer the ringing

of

the telephone line.

Data

set

ready

(DSR)

is

used by the data set

to

signal its readiness

to

send

or

receive

data. This indicates that communications are established.

Request

to

send

(RTS)

is

used by the data terminal

to

tell the data set

it

wishes

to

send data. Some modems (Bell 202

for

example) require this line

to

switch

directions.

Clear

to

send

(CTS)

allows the data

set

to

signal its readiness

to

pass

data from the

data terminal.

The carrier detect (CRX) line allows the data

set

to

tell the data terminal that the

communication

link

is

established. This often differs little from

DSR

, except that

DSR

usually refers to "telephone

off

the

hook

" (answered), whereas

CRX

means

something like " I hear the

modem

at the

other

end and

we

can talk

now

."

When

CRX

goes OFF, data set ready OFF usually follows a

few

seconds later, indicating

that the other end

has

"hung up."

In normal operation, DTR,

DSR

, and

CRX

are all

ON.

For full-duplex operation

RTS

and

CTS

are also both

ON

.

However

, it

is

often unnecessary

to

have all these lines

ON

-either

one

or

the other devices on the

RS-232

-C connection does not have

all the lines,

or

it

is

all right

to

ignore them (one

of

the

properties

of

the RS-232-C

standard

is

that not all

of

it needs

to

be implemented -it's perfectly all right

to

leave parts out). To operate the ATARI 830 Acoustic

Modem

,

for

instance, none

of

the

control

lines need

to

be used. In fact, the ATARI 830 Acoustic

Modem

ignores

DTR and

RTS,

and it turns

DSR

,

CTS

, and

CRX

on and

off

together (with carrier).

Note

that the

communication

link

shown in Figure

1-1

is

not

defined by RS-232-C.

In particular, this

link

seldom

has

more than

the

"e

quivalent

"

of

XMT and

RCV-

that

is,

only

data lines and

no

control.

However

,

as

often

as

not this

link

is

a full-

duplex

link,

so

data can go both ways simultaneously. ASCII characters are the

most

common

data sent,

so

the data sent each

way

can be either

"co

ntrol" data

or

"data" data.

What

is

RS-232-C?

5

6

What

is

RS-232-C?

•

With

full-duplex

operation,

two

devices can handshake

with

data in various ways.

Common

terminals usually

do

not

have

an

internal

connection

between

the

keyboard and display (or

they

have a switch, usually called

half

/f

ull

duplex

,

to

make

or

break this internal

connection)

so

when

talking

with

a

computer

in full-

duplex

mode

(the most

common

mode),

the

computer

at

the

other

end

"echoes"

(sends back) each character

to

be displayed

as

it

is

typed. This allows

you

to

see

ex-

actly

what

the

computer

at

the

other

end receives. It also allows

the

comp

uter

at

the

other

end

to

decide

NOT

to

let you

see

what

you have

typed,

as

in

"s

up-

pressing" the

echo

of

a password.

In half-duplex

operation,

somew

here along

the

com

muni

cations path data may

pass

in

only

one

direction

at a time.

Not

all parts

of

the

co

mmuni

cations path need

be half

duplex

,

but

if

any part

is

, then the

whole

system

will

probably

have to send

data

only

one

way

at a time. In half-duplex

mode

, the

comp

ut

er at

the

other

end

does

not

echo

back

what

you type. In this case, in

order

to

see

what

you type, the

co

nnecti

on

from

keyboard to screen must be set locally; that

is

, set

your

terminal

to

"half

duplex

."

Note: The ATARI

Telelink

™ I cartridge does

not

have

the

equivalent

of

a half

/f

ull

switch.

However,

the ATARI 830 Acoustic

Modem

does have such a switch, and

when

it

is

placed in

the

half-duplex position, it echoes any data sent

out

over

the

phone

back

to

the

computer

console.

A

common

handshake that requires full

duplex

is

the

XOFF/XON (transmit

off/transmit on) handshak

e.

The receiver

of

data can send XOFF

to

the

sender

to

ask

the

sender

to

pause the data transmission and

XON

to

resume. This allows

the

user

of

a screen terminal

to

stop

the

data

so

he can read

the

screen, and it allows a

computer

that

is

receiving data

from

another

computer

to

effectively

control

the

rate at

which

it can accept data.

2

ATARI

BASIC

AND

THE

ATARI

850

INTERFACE

MODU

LE

This section

will

show you

an

example

of

how

the interface

module

is

pro-

grammed. Using ATARI

BASIC

,

two

ATARI

Home

Computer

Systems

will

be pro-

grammed to let one user talk

to

another user through ATARI 830 Acoustic Modems.

Let's start

simply-

just a program

to

send a message line, then receive a line, and

so

on. The main part

of

such a program might be:

100 INPUT MESSAGE$

110 PRINT #5;

MESSAGE$

120 INPUT #5,

MESSAGE$

130 PRINT MESSAGE$

140

GOTO

100

Here,

unit

#5

is

assumed

to

have been opened to the RS-232-C

port

attached to the

modem

. Thus, line 100 gets a line from

your

keyboard, line 110 sends it

to

the

modem

, line 120 gets a line from the

modem

, and 140 prints that on

your

television

screen.

Here's the

whole

program:

10

DIM

MESSAGE$

(120)

20 OPEN #5,

13

,

0,

"

R1

:"

30 XIO 40, #5,

0, 0,

"

R1

:"

100 INPUT

MESSAGE$

110 PRINT #5;

MESSAGE$

120 INPUT #5,

MESSAGE$

130

PR

INT

MESSAGE$

140

GOTO

100

Line 10 allows space for the variable

MESSAGE$

(used

to

both send and receiv

e).

We've

assumed the

modem

is

attached to

port

1. Line 20 opens the RS-232-C

port

1,

allowing

input

and

output,

and enabling

Concurrent

Mode

1

/0.

Concurrent

Mode

1/0

is

required for

input

(see

Sections 4, 5,

6,

9,

and 10, and

Appendix

B for

more

details about

Concurrent

Mode

1

/0)

. Line 30 turns on the

Concurrent

Mode

1/0.

Once

the

Concurrent

Mod

e 1

/0

is started, you may INPUT

and/or

PRINT at

any

time

to

the

concurrent

RS-232-C

port

;

but

no other 1

/0

to

any peripheral

is

allowed until

Concurrent

Mode

1/0 is stopped by closing the port.

Input

/

output

to

the keyboard and screen

is

allowed

while

RS-232-C

Concurrent

Mode

1

/0

is

active,

and that

is

what

we

'

re

doing

here,

so

there's

no

problem.

BAS

IC

and

the ATARI

850

Interface 7

HOW

TO

USE

THIS

PROGRAM

How

is

this program

used?

The first

thing

to

know

is

that since it

uses

an

RS-232-C

port

, the RS-232-C 1/0 handler for the RS-232-C ports must be loaded

into

the

ATARI

Home

Computer

System. This

is

done

automatically

for you by the

com-

puter

and the interface

module

,

but

you have

to

turn

on

your

equipment

in the

right order. Specifically, the interface

module

must be

turned

on before the

computer

console (or at the same instant),

or

the

computer

will

not

know

the inter-

face

module

is

there. The RS-232-C handler can

only

be loaded

when

the

computer

console

is

turned on.

See

Section 3 for

more

details.

After turning your

comp

ut

er on

correct

l

y,

yo

u

ca

n type in the program.

Or

, the

program can be loaded from tape or diskette. The person on the

other

end does all

these things, too,

but

there's one

sma

ll difference. One

of

you

has

to

write

his pro-

gram

to

listen first, and the

other

to

talk first.

One

way

to

do

this

is

by adding the

statement:

40

GOTO

120

to one

of

the programs. This

way

, the program starts reading from the

modem

instead

of

the keyboard.

You're

ready to go! Get on the

phone

to

each other.

One

of

you

sets

his

modem

to

Answer

mode

, and the

other

sets

his to Originate

mode

(it

doesn't

matter

which).

Both modems should be

set

to Full Duplex.

Note

that

when

the Answer

modem

is

turned

on, it starts

to

squeal. This

is

the same squeal you h

ea

r over

the

phone

when

you call

up

a timesharing service, and it

is

a

sig

nal

to

the

Originate

modem

to

sta

rt

communications.

To avoid the

bother

of

listening

to

this,

don't

turn

the

modem

on

until

yo

u are ready

to

start talking (only the interface

module

needs to be

turned

on

before the

computer

console-

it's.all right

to

turn

on the

modem

later).

Now

put

your

pho

n

es

in the

modem

cradle

s.

The person

with

the send-first program typ

es

a line (up

to

120 characters), e

ndin

g

with

a

i;ljil@l

. Then the

other

can answer...and

so

on.

The listener

will

notice

so

mething

odd

right away:

nothin

g appearson histelevision

sc

reen for a

while,

and then POOF!

ther

e's a message. Here's

why:

The

se

nder's

program gets

to

the INPUT statement, line 100. BASIC waits for

input

from

the

keyboard, and

doesn't

go on

to

PRINT

to

the

modem

(line 110)

until

the l;ljli@j is

typed

by

the sender.

Meanwhile

, the listener's

progr

am is also

doing

INPUT (line

130), and that INPUT

won

't

complete

until an

EOL

(

End

of

Lin

e)

is

re

ceived from

the

sender.

(EOL

is

similar

to

1;11"1;111

, and

is

used inside the

co

mput

er

to

mark the

end

of

a line

.)

EOL

is

the last character sent by PRINT in line 110.

So

the

se

nder's

me

ssage

doesn't start over the

phone

until he pr

esses

l;ljil@j, and the listener

do

es

n

't

see

the message until it's

completely

received!

How

is

the program stopped? (Note that the program is an

infinite

loop

.)

Try the

l1li!D

key. You'll find it doesn't

work

, because the

l1li!D

key

is

turned

off

whenever

Concurrent

Mode

1/0

is

activ

e.

In general,

yo

u s

hould

a

lw

ays

try the

mD

key first

whenever

you

want

to stop a BASIC program, even

if

you

don

't ex-

pect it

to

work.

But,

if

it

do

es

n't

work

,

don't

be

up

set-

just press the

ii1MM1;1}1ji

key (

Note:

On

ea

rly versions

of

the interface

module

, the

l1li!D

key

is

not

disabled

during

Concurre

nt

Mod

e 1

/0

.)

8

BAS

IC and the ATA

RI

850 Inte

rf

ace

IMPROVING

THE PROGRAM You may find the limitation

of

one

line at a

time

bothersome. Also, there

is

no way

to

interrupt

and get the talker's attention

when

you're

the listener. An improved

version

of

the program should

allow

either

of

you

to

talk at any time, and send

characters immediately

as

they'

re

typed. This

improved

program

is

somewhat

more complicated than the simple program

you've

seen, and some background

is

needed

to

understand it.

The basic idea

is

to

use

GET

and PUT instead

of

INPUT and PRINT.

GET

and PUT

work

with

single characte

rs

(rep

res

ented by the character's numeric equivalent in-

side the computer), and characters are immediately available

to

BASIC

without

having

to

wait

for the li!Jill;lli from the keyboard or

EOL

from the modem. (Note

that

when

you u

se

GET

, the l;liiil;lli key produces the code for

EOL

, but this

is

not

the same

as

"e

nding

the

input

line"

which

is

the meaning

of

l;iiii@i

when

using

INPUT.)

GET

shares a problem

with

INPUT: BASIC waits until all the

input

is

available. Ad-

mittedly

GET

is

only

looking

for

one

character

but

until it ar

ri

ves,

BASIC

waits.

So

suppose

your

copy

of

the program

is

executing the

GET

from the

modem

link to

your friend, and he

hasn

't typed anything. This means you

can't

type, because

your

computer

isn

't reading

your

keyboard!

The

trick

is

to avoid actually

doing

the

GET

until you

know

a character

is

there. For-

tunately, there

is

a way to check for a character before

GET

, both for the keyboard

and

for

the

concurrent

RS-232-C port. Thus the

"f

low

"

of

our

improved program

will

be like this:

100

IF

no

chara

cter

from

keyboard

yet THEN 200

110

GET

character from

keyboard

120 PUT

that

character to the

modem

200 get STATUS

of

the

modem

buffer

210

IF

character

not

available THEN 100

220

GET

character

from

modem

230 PUT

that

character

to

television screen

240

GOTO

100

The program

continually

alternates between checking for a character from the

keyboard and one from the

modem

, and in each

case

only

gets and sends along a

character

if

one

is

ready.

(You may

wonder

how

a character can become available even

when

BASIC

has

not

yet tried

to

GET

it. The Operating System

of

the computer, using techniques

of

"in-

terrupts" and "buffering

,"

accepts and

saves

the characters

as

they appear. Then,

when

BASIC

does the

GET

, the saved character

is

handed over

to

BASIC from the

Operating System. The keyboard

has

a one-character buffer, that

is

,

only

one

character

is

saved this way. If you press another key before

BASIC

receives the first

character,

BASIC

will

find the second character you typed and the first

is

lost. The

defauIt buffer for each RS-232-C

port

holds

32

characters; that

is

,

BASIC

can fall

31

characters behind before anything

is

lost. You can

set

up

a buffer larger than

32

if

you need it -

see

Section 9 for more details.)

BASIC

and

the ATARI

850

Int

e

rf

ace 9

INTERFACE

MODULE

CAPABILITIES

This program

ca

n be u

se

d to " talk" with a

co

mputer o

th

er than another ATA

RI

Home

Co

mputer. If

yo

u get double characters w hen

yo

u are entering data in

to

the

other

co

mp

ut

er, then delete PUT #3,

KEY

in line 110.

In effect, th

ese

two

programs have changed

yo

ur

ATA

RI

Home Co

mput

er

int

o a

tel

etypew

ri

ter, using the modem and

int

erface mo

dul

e.

W ith the la

tt

er program,

yo

u can access

co

mput

er ne

tw

orks, such

as

THE

SOURCE, AME

RI

CA'SINFORMA-

TI

ON

UTILITY* and C

OMPU

S

ERV

E*

*.

The program is not

int

ended to r

ep

lace the

Telel i

nk

™ I cartrid

ge

,

as

it

will

prin

t all the

co

ntrol characters to

yo

ur

television

sc

reen and h

as

no pr

ov

ision for using an ATA

RI

Printer.

Both

pr

ograms

ca

n be helpful in l

ea

rning

how

to u

se

, and get

mor

e

out

of, the

ATARI 850

Int

erface

Module.

The

int

erface mo

dul

e h

as

many capabiliti

es

not

me

ntion

ed in the a

bo

ve exampl

es.

The r

es

t

of

this manual c

ont

ains inf

orm

a

tion

abo

ut

the

int

erface

modul

e and how

to take ad

va

ntage of

so

me

of

th

ese

capabiliti

es.

After

you

've r

ea

d

mor

e abo

ut

the

int

erface

modul

e,

l

oo

k at the

Sec

tion 8 exa

mpl

es

of

how

to

u

se

it.

* THE SOUR

CE

and

AMER

ICA'SINFORMATI

ON

UTILITY are

se

rvice marks

of

So

ur

ce Telecomputing Corporation, a

subsidiary

of

The Reader's Digest Associa

ti

on, Inc.

~

**COMPUSERVE INFORMATI

ON

S

ERV

I

CE

is a r

eg

istered tradema

rk

of

CompuSer

ve,

Inc., an H & R Block co

mp

any.

BAS

IC

and

!he A

TAR

/

850

Interface 11

So

much

for the general

idea-

now

for the details. First

of

all, GET does

not

work

from the

Operating

System's screen editor; to use GET you must open the

keyboard (K:). For the PUT commands

to

the television screen, you can use either

the screen device

(S:)

or

the

editor

device

(E:).

(You

might

want

to

experiment

with

E:

and

S:

to

see

which

suits

your

needs

-they

differ in

their

treatment

of

the editing

keys such

as

I

mmm

I and the cursor

movement

keys.

See

the

ATARI

BASIC Reference

Manual

for details.) Here,

we

'

ll

use

the editor.

To check

whether

a key

has

been typed,

PEEK

at the keyboard buffer. It

is

in

memory

at location 764 (decimal), and

has

the value 255

whenever

a key

has

not

yet been pressed. This location

is

reset

to

255

when

you GET

from

the keyboard.

Here's the

improved

program:

10

LET

KB

= 764:

NO

KEY= 255

20

LET

MODEM=

747:

NOCHAR=

0

30 OPEN #5,

4,

0,

"K:"

40 OPEN #2, 13,

0,

"R1

:"

50 OPEN #3,

8,

0,

"E:"

60 XIO 40, #2, 0,

0,

"R1

:"

100

IF

PEEK(KB)

=NO

KEY

THEN 200

110

GET

#5,

KEY:

PUT #3,

KEY

120 PUT #2,

KEY

200 STATUS #2,

XXX

210

IF

PEEK(MODEM)=

NOCHAR

THEN 100

220

GET

#2, CHAR

230 PUT #3, CHAR

240

GOTO

100

Lines 10 and 20

of

this program

set

up

some sy

mboli

c constants. The variables (sym-

bols) are given values

which

will

not be changed

as

the program runs (they're con-

stant)-

but

see

how

much

more

readable these variables make lines 100 and 200.

Lines 30

through

60 open the keyboard (K:),

modem

(attached

to

port

R1

:), and

screen

editor

(E:),

and start

up

the

Concurrent

1/0 through

R1.

The rest

of

the pro-

gram

is

just like the

"f

low

" program shown before, except it's been

turned

into

real

BASIC.

Note

the extra PUT in 110 to place

your

keyboard typing

onto

your

own

television scree

n.

Lines 200 and 210

work

together. First 200 gets the status

of

port

R1:

(which

was

opened through IOCB #2). Part

of

the status

is

the

count

of

characters that have

been received and placed in the receiving buffer, and that

count

is

in location 747

(decimal) after the STATUS check. Line 210 checks 747 to

see

whether

it's zero

or

not

-

if

not

, line 220 gets a character from the buffer.

This program

is

used just like the simpler one. Since either

of

you can talk at any

time

, you can both use the same program -it's

not

necessary

to

modify

one

of

them to listen first. If you both type at the same time, though,

your

two

messages

will

get mixed together.

You'll

have

to

learn to take turns typing,

but

allow

for the

other

to

interrupt

if he wants.

One

character you

might

find useful

is

the bell

(buzzer),

which

is

typed

as

&I

2.

10

BASIC

and

the

ATARIBSO

Interface.

TURN-ON

OPERATION

WITHOUT

A

DISK DRIVE

WITH

A

DISK DRIVE

3

HOW

THE INTERFACE

MODULE

INTERACTS

WITH

THE

SYSTEM

The

Operating

System

(OS)

of

the ATARI

Home

Computer

does

not

contain the in-

formation

necessary to operate the interface

module

SERIAL

INTERFACE ports

or

the ATARI 810™ Disk Drive. This

information

comes from the peripheral itself.

The

computer

asks

for

the data

when

it

is

turned

on.

If

the

peripheral

is

turned on

before

or

at the same

time

as

the

computer,

it

will

answer the

computer's

request

and send the necessary

information

. This

turn-on

and

initialization

procedure

is

called

"automatic

bootstrap

,"

"a

utoboot,"

or

just

"boot."

The term comes from

the expression "

pulling

yourself

up

by

your

bootstraps

,"

indicating that you start

with

nothing

and reach

your

goal by

your

own

efforts.

The bootstrap

information

contained in the interface

module

is

called the RS-232-C

"ha

ndler

."

The disk drive

information

is

called the Disk

Operating

System (DOS).

When

the

power

is

turned on

to

the

computer

console, the

computer

issues a disk

drive

request.

If

there

is

no disk

drive

in the system (or

if

the disk

drive

is

turned

off),

the interface

module

will

respond to the disk

drive

request. The

computer

then

loads the RS-232-C handler bootstrap program from the interface

module

, just

as

though it

were

reading the program from a diskette. The bootstrap program

is

then

run, and it gets the RS-232-C handler from the interface

module

and relocates it in-

to

the

computer's

RAM. The

memory

occupied

by

the bootstrap program

is

then

freed (but the handler remains).

If

the

disk

drive

is

set

for

Drive

1, it

will

respond

to

the disk

drive

request

when

the

compute

r console

is

turned

on. The interface

module

will

not

respond. A special

start-up program

is

loaded from the diskette and this program then loads the

handler from the interface

module.

In the ATARI 810 Master Diskette, CX8104, this

job

is

handled by a file

ca

lled

AUTORUN.SYS that is supplied

with

your

DOS

II

Diskette.

Read

the instructions

supplied for details on

AUTORUN

.

SYS.

Caution: The RS-232-C handler shares RAM space

with

a

portion

of

the DOS

utilities.

When

DOS

is

called (by

typing

DOS and pressing l;ljiii;lll from

BASIC)

,

DOS

will

overwrite

the RS-232-C handler and destroy it. To protect against this, add

MEM.SAV to

your

diskette (item

Non

the DOS

Command

Menu).

Then,

when

you

call DOS, the RS-232-C handler

will

be saved

with

your

program.

Note: ATARI 810 M

as

ter Diskette,

Model

CX8101 , does

not

contain the

AUTORUN

.

SYS

file and

cannot

be used

with

the interface

module

RS-232-C

SERIAL

INTERFACE ports.

H

ow

the Interface

Modul

e Interacts

With

the System 13

USING

A

PR

INT

ER

As

a general rule,

turn

on any peripheral that

you

intend

to

us

e

with

your

ATARI

Home

Computer

before

turning

on

the

computer

. This allows those devices that

need

booting

to

do

so.

There are exceptions

to

this rul

e,

though.

For example, since an ATARI Printer does

not

use the

SERIAL

INTERFACE 1/0 ports

of

the

int

erface

module

, it can be

turned

on at any

time

,

as

can the ATARI 830 Acoustic

Mod

em.

In the case

of

the ATARI Printer,

turning

the

computer

on before

turning

on

the in-

terface

module

saves RAM,

as

the RS-232-C

handler

takes

over

1 1/2 K-bytes

of

memory.

The RS-232-C

handler

is

not needed

to

use

an

ATARI Printer attached

to

the

printer

port

of

the interface

module.

To

see

how

much

memory

can be saved,

boot

your

system with the RS-232-C

handler

and type ?

FRE

(0). This

will

give

you

the

amount

of

free

memory

with

the

RS-232-C handler loaded

into

memory.

Repeat the action without loading the RS-232-C handler. The difference

is

the

amount

of

RAM saved by

not

using the

handler

when

it

is

not

needed.

14

How

the Interface

Modul

e Interacts

With

the

Sys

tem

IN

PUT/OUTPUT

CONTROL

BLOCK

ACCESSING

AN

RS-232-C

DEVICE

4

PROGRAMMING

THE

SERIAL

INTERFACE

PORTS

As

with

any peripheral device attached

to

an

ATARI 400™ or ATARI 800™ Home

Computer, the ATARI 850 Interface

Module

requires a program

to

tell it

what

to

do

. This program may be pre-written

or

you may

want

to

use the

SERIAL

INTER-

FACE

ports from

your

own

BASIC program. In the case

of

pre-written programs,

such

as

the ATARI

Telelink

I cartridge, read the instructions for using that particular

program

with

the interface

modul

e.

Using software instructions to

set

the specific values for the parameters

of

the

port

is

ca

lled

"conf

i

gu

ring the

port."

The

conf

iguration and use

of

the

SERIAL

INTER-

FACE

ports on the ATARI 850 Interface

Module

can be

complex.

Many

details must

be remembered and

comp

licated procedures must be

followed

exactl

y.

This

sec-

tion gives

an

overview

of

the effects

of

commands and their relation to each other.

IOCB

is

an

acronym

for

Input

/O

utput

Control

Block. It

is

that

portion

of

the com-

puter's

Operating

System

(OS)

that

controls the

input

and

output

of

data

within

the

system.

An IOCB allows the

computer

to

keep track

of

the 1

/0

functions, both its

own

and

the user's. Therefore, an IOCB acts

as

an interface between the user and the com-

puter

1

/0

system.

From ATARI BASIC, the user

has

seven IOCBs available

to

use. The

se

are

numbered

1

to

7.

IOCB

#7

is

used by the OS

for

LPRINT and and IOCB

#6

is

used

for GRAPHICS

MODE

functions. These IOCBs should

not

be used

with

the inter-

face

module

if

you have graphics

or

line

printer

commands in

your

BASIC program.

To

be on the safe side, specify IOCB #5.

STEP

1

-CONFIGURE

THE SERIAL INTERFACE PORT

The first

thing

to

be

done

to

access an

RS-2

32-C device

is

to

configure the

SERIAL

INTERFACE

port

to

which

the device

is

connected by using instructions in

your

program. In

configuring

the

port

you may set the

fo

llowin

g:

• Baud rate -bits-per-second sent/received

•

Number

of

bits-per-word sent/received

•

Number

of

stop bits-per-word sent

•

Whether

the

incoming

control

signals

DSR

,

CTS,

and

CRX

are

monitored

•

Whether

input

parity

is

checked

•

Whether

output

parity

is

set

•

Whether

Line Feed

is

added after every Carriage Return sent

• Translation

of

the

word

being sent

or

received (three types

of

translation)

•

How

the

outgoing

contro

l signals DTR and

RTS

are used

These are shown

as

three groups, corresponding

to

the three configuration

com-

mand

s;

otherwise, the division

into

groups

is

arbitrary.

Pr

og

ra

mmin

g

th

e

Se

rial

Int

e

rf

ace

Ports 15

If you

do

not

configure the port, the system

sets

defauIt values

of

the

port

variables,

as

follows:

• 300 Baud

• 8 bits-per-word

• 1 stop

bit-per-word

transmitted

•

Input

parity

is

not

checked

•

Output

parity (bit

7)

is

set

to

zero

• Line feed

is

not

added after every Carriage Return sent

• Light-translation

•

Outgoing

control

signals DTR and

RTS

are set

off

If the defauIt (preset

option)

is

what

you want, then the parameters

of

the

port

con-

figuration

do

not

have

to

be set.

Each

of

these groups

of

conditions

can be changed

with

a configuration

command

and each

port

can be configured

independently.

Configuration

of

one

port

has

no

effect on the configuration

of

any

of

the

other

port

s.

The CONFIGURE

BAUD

RATE

command

is

used

to

set the Baud rate,

number

of

bits per

"wo

rd

,"

and the

number

of

stop bits

to

transmit. This

command

also

establishes the

monitoring

of

DTR,

CTS,

and

CRX.

The CONFIGURE TRANSLA-

TION

MODE

command

will

set

up

the translation

mode

,

input

and

output

parity

modes, and the

automatic

appending

of

LF

(Line Feed) after

CR

(Carriage Return).

The

CONTROL

command

will

let you

turn

the

DSR

and

RTS

control

lines on

or

off.

STEP

2-

USING

THE SERIAL INTERFACE PORT

Once

the

SERIAL

INTERFACE

port

is

configured, you can OPEN the

port

for 1

/0.

There are

two

fundamentally

different ways

of

doing

1

/0

to a

SERIAL

INTERFACE

port: Block

Output

Mode

and

Concurrent

Mode.

As

its name implies, the Block

Output

Mode

can

only

be used for

output

from the

computer

to

your

RS-232-C

compatible

device. The Block

Output

Mode

is

simpler to use,

al

lows use

of

the

DTR,

CTS

, and

CRX

monitoring

, and carries none

of

the

concurrency

restrictions

of

the

Concurrent

Mode.

Concurrent

Mode

1

/0

is

required

for

input

from the

RS-232-

C

compat

ible device and

is

required for

fu

ll-duplex (input and

output

at the same

time) operation.

Block

mode

output

is performed by simply

doing

normal BASIC PRINT

or

PUT

statements

to

the appropriate

SERIAL

INTERFACE

port

(after

opening

it,

of

course).

Your

output

characters

will

be placed in a 32-byte buffer and transmitted to the in-

terface

module

and then

to

your

RS-232-C

compatible

device. This

is

done

when:

• The buffer fills

up

• You close the chann

el

to the

RS-232

port

• A

CR

(decimal

13)

is

placed in the buffer

16

Progr

ammi

ng

th

e

Se

r

ia

l

Int

erface Ports

32-BYTE

BLOCKS

RS-232-C

COMPATIBLE

DEVICE

INTERFACE

MODULE

32-BYTE

BUFFER

PRINT

OR

PUT

Figur

e 4-7. Block

Output

Mode 110

On

occasion, you may

want

to

force the sending

of

the

information

in the buffer.

For example,

if

you have specified the

Append

LF

translate

option,

the

LF

will

be

sent at a different time, later than

the

CR.

You may

want

to

send the

LF

immediately

if the external device

is

a terminal.

As

another example,

if

you are using the DTR,

CTS,

or

CRX

monitoring

feature

to

avoid sending

more

characters

to

a device than

it can handle, you

ca

n use the

FORCE

SHORT BLOCK operation

to

send

your

characters

one

(or a few) at a time. That

way

you can ensure that the device

won

't

lose characters you send it because it became

not

ready in the

middle

of

an

output

block

.

The

FORCE

SHORT BLOCK operation

is

only

valid if you are using Block

Output

Mode.

If you are using

Concurrent

Mode

, you

cannot

use this

command.

If

you issue a

FORCE

SHORT BLOCK

command

when

the buffer

is

empty, no

action

will

be taken.

Doing

this

is

not

an

error

. Since you can alternate

output

to

two

SERIAL

INT

ERFACE

ports

when

using Block

Output

Mode

, you can also alter-

nate

FORCE

SHORT

(?LOCK

commands

from one

port

to

another

. The ports must

be opened

through

different IOCBs,

of

course. The BASIC

command

for

FORCE

SHORT BLOCK

is

listed in

Appendix

B.

Pr

og

r

amming

t

he

Serial

Int

erface

Po

r

ts

17

Atari 850 User manual

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