Megatel Quark/100 Specifications download pdf (Page 26)

character.

The

CP/M

operating systems

distributed

with the

QUARK

generaLLy

alLow

the

"TTY:"

or

"AUX:"

input

(the

fuLL-dupLex

port)

to

be

instaLLed as

the

consoLe

input

device.

See

the

Installation

maunuaL

for

more

informatio~

SpeciaL I/O functions

,-----------------------------,---- --------------------------------

Some

of the controL lines

on

the

PIA

are connected internaLly

on

the

QUARK

for speciaL

functions.

Care should

be

taken

when

programming

the

PIA

that

these

functions

are

not

disturbed

by

inadvertently modifying the Control Registers.

The

CA1

control

Line

on

the

PIA

is

connected to the VerticaL

Sync

output for the

Video

Display.

The

CA1

line

can

be

programmed

to generate

an

interrupt

to

the

Z80B

on

either

the

rising

or falL ing

edge

of the VerticaL

Sync

line. This allows the use of a

real-time

clock

function, a feature

which

is

incorporated into

some

of the

QUARK

operating systems.

The

CB1

control line

on

the

PIA

is

connected to the Interrupt Request

(INTRQ)

output

from

the

1793 Floppy Disk ControLler.

The

1793 produces

an

interrupt

request

signal

at

the

completion of

any

command.

The

CB1

input is

initialized

as a

positive-transition

active

input.

When

a

Floppy

Di

sk

Control

Ler

interrupt occurs, the

IRQB

f lag in the

PIA

wi

Ll

be

set.

Thi

s

configuration of the

CB1

Line

must

not

be

aLtered

if

the

Floppy

Disk

Interface

is

to

operate

properly.

The

IRQ

bit

can

be

programmmed

to generate

an

interrupt to the

ZaoB

when

this

occurs,

although

this

interrupt

is

not used under the standard operating system for the

QUARK.

The

CB2

control line

is

the internaL

Boot

Mode

control

Line.

This line

wiLL

be

set

to

act

as

an

input

after

a system reset

has

occured.

When

it

is

configured as

an

input, or as

an

active-high output, a pull-up

resistor

pulls the

Boot

Mode

line high, putting the

QUARK

into

Boot

Mode

operation.

At

the

end

of

the

Bootstrap

routine,

this

line

will

be

cleared

and

configured

to

act

as

an

output, returning the system

to

Normal

mode

operation. There

is

no

need

for the user

to

change

the

state

or configuration of

this

line during normal operation of

the

QUARK.

ALL

of the

PIA

Port B

I/O

lines are

used

for specific output functions.

PBO-3

are the

Floppy

Disk

SELO

to

SEL3

outputs.

PB4

is

the

Floppy

Disk

SIDE

seLect output.

If

floppy disk

drives

re""iring a

''Low

Write-current" input are used,

QUARK

operating systems

can

be

instaLLed

to

aLlow

any

of

the

SELect Lines or

the

SIDE

Line

to

be

used

for

this

purpose. (See

the

Insta L

Lat

i

on

manua

L.)

PBS

is

the

Floppy

Disk

SingLe/DoubLe-density control

Line.

SingLe-density

(FM)

operation

is

selected

when

this

line

is

at a

high

Level.

PB6

is

the ALphanumeric/Graphics

Mode

Line.

A

high level

on

this

output

selects

Alphanumeric

Mode.

PB7

is

the

FulL-dupLex

SeriaL Interface

DTR

output. A

high

LeveL

on

PB7

causes a negative-voLtage output

on

pin

C-3.

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

Floppy

Disk

Interface

The

on-card

Floppy

Disk

Interface is

capabLe

of controLLing up

to

four double-sided floppy

disk

drives.

Both

single-density

(FM)

and doubLe-density

(MFM)

recording

formats

are

supported,

and

either

8-inch or 5.25-inch drives

may

be used.

The

seLection of singLe- or

doubLe-density operation

is

Lnder

software controL, through

bit

5 of

PIA

port B

(PIA

PB5).

This output

is

set

(LogicaL

1)

for singLe-density operation,

and

is

cLeared (Logical

0)

for

double-density.

Jumper 2

(designated

J2),

Located

adjacent

to

the

crystaL,

is

open (not

instaLled)

when

5.25

inch drives are

to

be

used,

and

is

closed (instaLled)

when

8-inch drives

are to

be

used.

The

QUARK

board

is

shipped with

J2

instaLLed

if

the system

was

ordered with

the

distribution

software

on

an

8-inch

diskette,

whi

Le

J2

is

not instaLLed

on

boards ordered

with S.2S-inch

diskettes.

Four

Drive

SeLect

lines

(SEL

0

to

SEL

3)

are provided

to

seLect

one

of four floppy disk

Megatel

Computer

Technologies Toronto,

Canada

Page

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