Sharp mz-800 Instrukcja Obsługi Pobierz pdf (Strona 35)

MZ-800

Pin

name

1/0

Active Signal

name

Function

PAD

IN L RDA

A

low

on

this

line indicates

that

the

printer

data is ready

to

receive.

W

PA,

IN

L STA A low

on

this line informs the personal a paper depletion during

status

check.

u.

PA2

IN

-

GND

~

PA3

IN

-

GND

<{

PA.

IN

H

An

8253

output

used

for

interrupt.

t:

e

PA5

IN H

Horizontal blanking signal used

for

interrupt.

a..

PAs

OUT

H IRT Used

for

printer

initialization.

PA,

OUT

H

RDP

Indicates

the

printer

to

receive data.

PB.

OUT

-

RD.

PB,

OUT

-

RD,

LL

PB2

OUT

-

RD2

U.

~

-

PB3

OUT

RD3

co

PB.

OUT

RD.

Printer data

or

control

code

to

the

printer.

-

t:

PB5

OUT

RD5

e

-

a..

PB.

OUT

RD.

-

PB,

OUT

- RD,

Interfacing timing

CD

@

~

@

RDA

~~~~2~

PBo

-

PB

,

X

Eff~ctive

data

RDP

I

I

I

I

I

,

Personal

Personal

Direct the

After

conforming

computer.

computer

sends

printer

to

high state

of

confirms that data

to

the receive data.

RDA.

it

makes

RDAis

low.

printer.

RDP

forced

low.

After the personal

computer

confirms

that

the

printer

is

ready to receive data

at

(<D),

the

data is

then

sent

to

$FF

port

(PlO

port

B)

at step (ID).

As

reception

of

data is directed

to

the

printer

at step

(@), it makes

RDP

forced

low

at

step (@)

upon

confirm-

ing that the

printer

received

it

(RDA=H).

After

this,

it

awaits until RDA goes

from

high

to

low

before

transfer

of a next data. But,

it

is possible

to

transfer

successive

data by

interrupting

the

CPU

at a falling edge

of

RDA,

since RDA is

inputted

to

the

RSTB

input

of

the

PlO,

when in the

port

B

mode

O.

It

is

also possible to

interrupt

the

CPU

referring

to

Port A

inputs. Though discussed

above

is

the

printer

interface

methlod

for

the

MZ

compatible

printer

types,

there

is

the

Centronics

compatible

method

for

parallel interfacing

of

the printer. Since

this

method

is basically

the

same as

the

MZ mode, except

that

signal

polarity

is opposite.

MZ specification

Centronics specification

c----

-------

-

l

Signal name

Active

Signal

name

Active

'------------------

-----,--,.

RDA

(NOTE)

"L"

BUSY

"H"

RDP

"H"

STB

"L"

IRT

"H"

INPUT PRIME

"L"

34

NOTE:

Though

RDA is active

low,

it

may

be handled

the

same as

high

state

of

BUSY

when

consi-

dered

in

term

of

signal significance.

As

shown

in

the

figure

above,

it

could

be

known

that

RDP

and IRT

should

be

inverted

in

order

to

make

connection

with

the

Centronics

compatible

printer.

It can be attained

by

changing

PRSW

to

high using the

dip

switch.

NOTE:

When

the

MZ-800 dedicated

printer

is used,

there

may

be such a case

that

proper

operation

is

not

attained

due

to

different

printing

charac-

ters

and

control

codes. It

must

be also noted

that

all MZ-800 characters can

not

be printed.

Besides, connection

with

a Centronics

compati-

ble

printer

may

not

be

permitted

hardware-wise,

sometimes.

4-6. Programmable sound generator

The SN76489N is used

for

the

programmable

sound

generator

which

is

controlled

by

the I/O

port

$F2.

It is

write

only. In

order

to

permit

smooth

sound generation,

timer

interrupt

is applied using the 8253. For the

interrupt

timer,

the

count

0

of

the 8253 is used. The

counter

0 is used

for

creation

of

sound steps in the

MZ-700

mode,

but,

it

is used

for

the

timer

interrupt

source

of

the

PSG

in

the

MZ-800 mode. Interrupt is

controlled

by

PA5

of

the

PlO.

it

is, however, possible

to

mask

the

counter

0

output

by

PCO

of

the 8255, in

order

to

prevent

sound

generation

during

interrupt.

l

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