ACT apricot - Channel B Connections

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SERIAL INTERFACE

Channel B Connections

TxDB

Transmit

Data.

Serial

data

output

to

the

Keyboard

via

a

line

driver. A

mark

is

indicated

by logic

high

on

TxDB

and

a space, by logic

low.

RxDB Receive

Data.

Serial

data

input

from

the

Keyboard

via

a

line

receiver. A

mark

is

indicated

by

logic

high

on

RxDB

and

a space, by

logic low.

RxTxCB

Receiver/Transmitter

Clock. Fixed frequency

clock

input

of

0.25

MHz

(500/0

duty

cycle),

used

to

determine

the

transmit

baud

rate

of

the

data

to

the

keyboard

and

the

receive

baud

rate

of

the

internal

receiver circuitry.

The

clock

frequency

is divided

internally

by

32

to

match

the

Keyboard

baud

rate

of

7.8125

kHz.

RTSB

Request

to

send.

Used

as a general purpose

output

in

conjunction

with

DTRB to

select

the

clock

source

for

the

transmit

and

receive

clock

inputs

of

channel

A (TxCA

and

RxCA).

The

logic

state

on

RTSB is

controlled

by software,

following

the

state

of

an

associated

control

bit

within

an

internal

register.

DTRB

Data

terminal

ready.

Used

as a general

purpose

output

in

conjunction

with

RTSB

to

select

the

clock

source

for

the

transmit

and

receive

clock

inputs

of

channel

A.

The

logic

state

on

DTRB is

controlled

by

software, following

the

state

of

an

associated

control

bit

within

an

internal

register.

continued

....

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Other manuals for ACT apricot

Service Manual305 pages