Sharp MZ-80SFD User Manual download pdf (Page 5)

6)

Write protect detection section

A luminous diode and a photo-transistor are used

to detect write

protect

notch

of

the diskette and

jacket. (Writing

is

not

possible when

the

notch

is

covered with labeL)

Center

hole

Head

window

Label area

Index

hole

Write

protect

notch

3. Interface

1) Interface signal

All

lines are

of

TTL (transistor-transistor logic).

(1) Input signals

For input signals there are 10 kinds

of

input lines,

all

of

which are valid

at

low levels. These signal

lines are terminated

at

a 150-ohm

int~rated

resistor fitted

in

the

IC

socket

of

drive

1.

The

signal voltage levels are

as

follows.

High

level

I

Invalid 2.4

to

5.25V

Low level

I

Valid o

to

OAV

Input impedance

Pull-up

to

5V

at

150-ohm

resistor

Description

of

diskette parts

7)

Index detection section

This section consists

of

a luminous diode and a

phototransistor. An index hole

of

the

diskette

is

detected by this section

to

determine the starting

point

of

a track.

8) Track 00 detection section

A carriage position

is

detected with a limit switch.

When

the

carriage has reached the track

00

point,

track

00

signal

is

emitted.

9)

Control electronics section

The electric circuit

to

control each mechanism

is

composed of 2 sheets

of

PWB.

One

is

to

control

the

DC

motor

control circuit. The

other

is

to

control

other

circuits, say, detection and other

functions with respect

to

read/write, step, head

load, and

other

signals.

10) Diskette protect mechanism

Shutting

the

front door, with the diskette incom-

pletely set in, can give damage

to

the

diskette, thus

shortening its life-time.

To

prevent such a draw-

back, this mechanism has been adopted so

that

the

front door

connot

be closed if

the

diskette

is

improperly in.

-3-

CD

Drive select signals (0

to

3)

MZ-80SFD

is

connectable up

to

4 units.

These signals are used

to

select a desired one of

the

four drive units.

At low levels of drive select signal,

RIW

head

is

loaded

to

cause the operation indicator

to

light up.

Note)

The drive requires

to

be set with a drive select

switch

to

meet the position of use (Drive No. 1

thru 4).

@ Motor

ON

signal

The drive motor starts when

the

signal level be-

comes low. This signal

level

becomes high about

2 seconds after completion

of

all operations,

if

no operation

is

commanded next. It thus inter-

rupts

the

motor, extending the service life

of

motor.

@ Direction select signal

The signal

is

given

to

designate

the

shifting

direction

of

R

IW

head, when the

step

pulse

is

input.

High

level- - .

Out

direction (to diskette

outer

portion)

Low

level

- - -

IN

direction (to diskette center)

@Step

signal

This signal

is

given

to

move the

RNoJ

head

in

the

direction designated by the direction select signal.

The operation

is

done

in

the

course

of

changing

from low levels

to

high levels.

1 2 3 4 5 6 ... 24

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