Lear Siegler ADM 3A - Input;Output (I;O) Port 1; ADM 3 A Control Logic; Set-Up Mode; Send;Receive Modes

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__

LEAR SIEGLER, INC.

DATA PRODUCTS DIVISION

1.3.1

Keyboard

The

keyboard

contains

59

keys

from

which

data

entry

and

control

functions

are

initiated.

Each

keystroke

is

encoded

into

a

corresponding

ASCII

character

which

is

immediately

transmitted

to

the

host

computer.

The

character

is

also

routed

back

to

the

CRT

display:

directly

in

half-duplex

operation,

or

echoed

from

the

host

computer

via

the

input/output

(I/O)

interface

in

full-duplex

operation.

1.3.2

Input/Output

(I/O)

Port

The

modem

I/O

portis

the

link,

or

interface,

that

handles

the

flow

of

data

in

both

directions

between

the

ADM

3A

and

the

computer.

It

may

be

configured

for

either

RS-232C

or

optional

20mA

current

loop

operation.

With

the

modenl

DTR

or

X-On/X-Off

handshake

feature,

all

data

transmitted

from

the

host,

even

at

speeds

up

to 19,200

baud,

will

be

received

by

the

ADM

3A

without

data

loss

(9600 for

current

loop.)

1.3.3

ADM

3A

Control

Logic

The

ADM

3A

control

logic

interprets

the

control

codes

that

originate

either

at

the

keyboard

or

host

computer,

and

directs

the

activities

of

the

ADM

3A

accordingly.

These

activities

include

data

handling

and

formatting.

1.3.4

Set-Up

Mode

The

ADM

3A

features

a

non-volatile

set-up

mode

which

allows

the

terminal

parameters

to

be

selected

through

commands

from

the

keyboard.

These

parameters,

including

baud

rates,

word

structures,

cursor

type,

communications

control,

and

operating

modes,

can

then

be

"saved"

in

memlory

and

retained

when

power

is

shut

off.

1.3.5

Send/Receive

Modes

Two

selectable

send/receive

modes

are

available

in

the

ADM

3A

through

the

set-up mode:

half-

duplex

and

full-duplex.

In

the

half-duplex

mode,

each

character

is

transmitted

to

the

computer

as

it

is

entered

on

the

keyboard

and

is

simultaneously

displayed

on

the

CRT

monitor.

In

full-duplex

operation,

the

ADM

3A

can

transmit

and

receive

information

in

both

directions

simultaneously.

Characters

are

transmitted

as

they

are

entered

at

the

keyboard,

1-3

but

are

displayed

only

upon

reception.

In

order

to

display

transmitted

characters,

they

must

be

echoed

back

from

the

host

computer

or

data

set.

1.3.6

Display

Memory

The

display

memory

contains

a

random

access

memory

(RAM), video logic

and

character

generation

circuits

appropriate

for

controlling

the

CRT

display.

The

memory

is

capable

of

holding

1,920

characters,

which

are

stored

in

sequentially

scanned

locations.

The

scanned

data

is

then

sent

to

the

CRT

for

displaying.

Input

to

the

display

memory

consists

of

the

data

character

codes from

the

I 0

port

or

keyboard,

under

the

control

of

signals

from

the

control

logic circuits.

1.3.7

CRT

Display

Monitor

The

CRT

display

monitor

is

a

rectangular

screen

measuring

12

inches

diagonally.

Data

characters

are

displayed

on

24

equally

spaced

rows,

each

consisting

of 80

characters.

The

80-character

lines

are

displayed

clearly

at

a

refresh

rate

of

either

50

or

60 Hz,

corresponding

to

the

AC

line

frequency.

1.4

PHYSICAL

DESCRIPTION

The

ADM

3A

is

a

self-contained

unit

consisting

of

four

major

assemblies:

(1)

base

and

cover

assembly,

(2)

main

logic

board,

(~-))

keyboard

and

(4)

the

CRT

monitor.

The

power

transformer

and

intercomponent

cabling

are

located

on

the

base

portion

of

the

terminal.

The

cover

portion

of

the

terminal

contains

the

CRT

monitor

and

its

associated

subassemblies.

The

cover

is

hinged

to

the

base

at

the

rear,

and

when

swung

open,

all

components

of

the

ADM

3A

are

exposed.

The

main

logic

board

contains

all

other

operating

elements

of

the

ADM

3A

that

are

not

contained

in

the

CRT

monitor,

keyboard

and

the

base

assembly.

The

logic

board

is

connected

to a

metal

plate

which

anchors

to

the

base

supports

of

the

unit.

Two

connectors

on

the

logic

board

provide

the

RS-232C

current

loop

interface

and

the

RS-

232C

extension

interface.

The

keyboard

assembly

is

made

up

of

integrated

key

rows

(or modules).

It

is

connected

to

the

main

logic

board

by

an

eight

pin

connector.

The

CRT

monitor

consists

of

three

subassemblies:

(1)

the

CRT

itself,

(2)

a

printed

circuit

board

that

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