Sharp FDD-412A - Page 11

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(5)

(6)

(7)

(8)

(9)

(10)

FDD412A/B

The

rotational

speed

of

the

spindle

motor

is

360

rpm.

Head

load

solenoid

By

sensing

the

presence

and

absence

of

the

HEAD

ENGAGE-N

signal

from

the

controller,

the

head

load

solenoid

engages

the

magnetic

head

(to

enable

reading/writing)

and

disengages

it

(to

disable

reading/writing).

Index

sensor

Two

pairs

of

LEDs

and

phototransistors

are

installed

to

tell

whether

the

recording

medium

is

l-sided

or

2-sided.

The

distinction

is

accomplished

by

detecting

an

index

hole

on

the

medium

for

index

pulse

generation.

QO

track

sensor

With

respect

to

the

carriage

position,

the

O

track

sensor

detects

the

magnetic

head

at

track.0

position

and

causes

the

TRACKOO-N

signal

to

be

generated.

Auto-ejector

mechanism

The

auto-ejector

mechanism

consists

of

a

spring-and-latch

arrange-

ment

capable

of

the

following

functions:

(a)

Upon

insertion

of

floppy

disk

The

floppy

disk,

upon

insertion,

is

not

latched

and

is

rejected

until

it

is

in

place.

This

function

accurately

positions

the

floppy

disk

center

hole

to

the

spindle,

protecting

the

hole

from

damage

and

preventing

track

dislocation.

(b)

Upon

disk

removal

Opening

the

door

allows

part

of

the

floppy

disk

to

pop

out

of

the

FDD.

File

protection

The

file

protection

mechanism

comprises

a

pair

of

LED

and

photo-

transistor,

and

a

logic

circuit.

It

checks

if

the

floppy

disk

jacket

has

an

inhibit

notch.

If

the

notch

is

found

to

be

present,

data

write

operation

is

inhibited.

Spindle

motor

controller

The

spindle

motor

controller

is

an

electronic

control

circuit

that

keeps

the

brushless

direct

drive

motor

turning

at

a

constant

speed

by

accommodating

load

changes.

Electromagnetic

door

lock

mechanism

In

this

mechanism,

an

electromagnetic

door

lock

solenoid

is

driven

by

a

control

signal

from

the

FDC

to

lock/unlock

the

door.

2.2.2

Control

Electronics

(1)

The

control

electronics

consists

of

control

logic

circuitry

com-_

prising

read/write

control

circuits,

and

controls

the

FDD

accord-

ing

to

instructions

from

the

FDC.

With

model

A,

the

VFO

circuit

is

part

of

the

control

electronics.