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· HARDWARE

High speed

DMA

data

transfers,

from

a

selected

source

(memory

or

peripheral)

toa

selected

destination

(memory

or

peripheral), are

performed

by

the

lOP.

The

lOP

is

able

to

transfer

data

whilst

the

central

processing

unit

is

engaged

in

executing

tasks

which

do

not

require

use

of

the

buses.

The

8087

numeric

data

processor

extends

the

processing

capabilities of

the

Apricot

computer,

by

performing

arithmetic

and

comparison

operations

on

numeric

types

which

can

vary

from

16

to

80 bits.

It

is also able

to

execute

numerous

transcendental

functions

(e.g.tangent

and

logari

thmic

functions).

-

The

Apricot

computer

uses

3.5

inch

Sony

disk

drives

and

employs

the

IBM

system

34

format

in

the

double

density

mode,

with

512

bytes

per

sector

(and 9

sectors

per

track).

The

total

storage

capacity

of

each

disk

is

315 Kbytes of

formatted

data.

The

floppy

disk

controller

incorporates

the

necessary

capability

to

control

a

second

floppy

disk

drive

without

any

modification

to

the

hardware.

The

serial

interface

provides

two

separate

channels;

one

channel

for

communication

between

the

System

Board

and

the

Keyboard

Unit;

the

second

channel

for

communication

between

the

System

Board

and

data

communications

equipment.

The

serial

link

to

the

keyboard

is

a full

duplex

asynchronous

communications

channel,

which

transmits

and

receives

data

at

a fixed

baud

rate.

The

RS232C

channel

can

be

programmed

to

operate

in

both

asynchronous

and

synchronous

modes,

with

the

programmer

having

independent

control

over

transmit

and

receive baud rates.

The

rates

can

be generated

by

either

an

internal

programmable

timer

or

determined

by

the

external

data

communications

equipment.

Both

byte

and

bit

oriented

synchronous

modes

are available.

These

include

the

byte

oriented

modes,

Monosync

and

Bisync,

and

the

bit

oriented

modes, SDLC

ana

HDLC.

The

two

expansion

slots

are

identical

and

allow

the

basic

configuration of

the

computer

to

be expanded

by

the

addition

of

optional

expansion

cards.

The

expansion

bus

consists

of

the

processing

system

buses (address,

control

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Other manuals for ACT apricot

Service Manual305 pages