Name: Tandy 1000
Brand: Tandy
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Tandy 1000

3-2-2.

Control

Circuit

Technical Reference Manual

The

control

circuit

consists

gates,

detectors,

and

the

stepping

motor

control

circuit.

The

gates

are

drive

select

gate

determine

the

drive

select

condition,

spindle

motor

gate

determine

the

rotational

condition

the

spindle

motor,

write/erase

gate

control

the

actual

write

operation,

etc.

The

detectors

are

index/sector

detector,

track

detector,

file

protect

detector,

and

ready

detector.

The

former

three

detectors

(photo-transistors)

are

mounted

the

front

OPT

Ass'y

and

the

transport

frame.

And

the

other

circuits

are

mounted

the

PCBA

MFD

control

(mostly

packed

control

LSI (CMOS».

Fig.308

shows

the

block

diagram.

Drive

select

gate

classifies

the

external

input

signals

into

several

functions

and

transmits

them

into

the

control

LSI.

The

selection

straps

(short

bars)

determines

the

select

condition

the

drive,

spindle

motor

operating

conditions,

and

turn-on

condition

the

front

bezel

indicator.

Refer

items

1-11

the

Specification

the

detailed

function

each

strap.

The

write/erase

gate

judges

the

FDD

whether

can

execute

write

operation

not

and

issues

write

gate

and

erase

gate

signals

for

the

write

circuit.

For

the

FDD

with

tunnel

erase

head,

specified

delay

time

established

the

erase

gate

signal

internal

counter

(refer

Fig.306).

The

ready

detector

consists

speed

detector

and

ready

latch.

The

output

the

speed

detector

which

constructed

with

re-triggerable

counter

becomes

always

TRUE

(HIGH) when

the

rotational

speed

installed

disk

(soft

sectored)

than

50\,

approx.

the

rated

speed.

The

ready

latch

detects

the

second

index

pulse

after

the

speed

detector

detects

the

50\

the

rated

speed,

then

the

READY

condition

informed

the

host

system

through

the

output

driver,

(pin

'\,

14).

315

Other manuals for Tandy 1000

User Guide337 pages

Programmer's Reference Guide251 pages

Basic Reference Manual411 pages

Owner's Manual46 pages

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Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200