CalComp 142, 140 Technical Manual

CalComp Model 140 & Model 142

Floppy Disk Drives

Technical Manual

MODEL

140

AND MODEL

142

FLOPPY DISK DRIVES

TECHNICAL MANUAL

April

1977

California

Computer

Products,

Inc.

2411

W.

La Palma, Anaheim, CA 92801

Part No. 10150-901-003·2

REVISION

-1

-2

Model 140/142 Technical Manual

PUBLICATIONS RECORD.

NOTES

Expands coverage to include the Model 142 and all versions

of

the Model 140.

Incorporates the intent

of

Technical Bulletin D178 and Field Change Notice

DFOOS.

Incorporates latest changes

as

per Small Disk Operations

Copyright

© 1976, 1977 by

CALIFORNIA

COMPUTER PRODUCTS, INC.

Printed in

the

United States

of

America

CONTENTS

Section

Page

INTRODUCTION
Description

...............................................................

1-1

Physical

and

Electrical Characteristics.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

Special Tools

and

Test

Equipment

................................................

1-3

2 INSTALLATION AND OPERATION

Unpacking

................................................................

2-1

Installation

................................................................

2-1

Ac Power Cable

..........................................................

2-1

Dc and Signal Cabling

......................................................

2-1

Data

Output

Selection

......................................................

2-6

Checkout

........

~

......................................................

2-6

Operation

................................................................

2-6

Floppy

Disk Storage and

Handling.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-6

Write-Protect

Option

......................................................

2-7

Floppy

Disk Loading

and

Unloading

............................................

2-7

3

THEORY

OF

OPERATION

Principles

of

Operation

......................................................

3-1

Recording Medium

........................................................

3-1

Data

Recording

Method

....................................................

3-2

Peak

Shift

Precompensation

..................................................

3-3

Track Accessing

..........................................................

3-3

Read

Data

Timing

........................................................

3-3

Write

Data

Timing

........................................................

3-3

Power-On

to

Data

Transfer

..................................................

3-6

Functional

Areas

...........................................................

3-6

Control

System

..........................................................

3-6

Positioning

System

........................................................

3-8

Read/Write System

........................................................

3-9

Mechanical

System

..........................................................

3-9

Drive Mechanism

..........................................................

3-9

Disk Cen tering Mechanism

..................................................

3-10

Head Load Mechanism

......................................................

3-10

Positioning Mechanism

......................................................

3-10

Logic Symbology and Definitions

................................................

3-11

Detailed Logic Description

....................................................

3-11

Control

Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

Read/Write Head

Positioning Logic

............................................

3-16

Read/Write Logic

........................................................

3-19

+17 vdc Regulator Description

................................................

3-24

Read Decoder

with

PLO

Assembly

..............................................

3-25

Normal

PLO

Operation

....................................................

3-26

Missing-Pulse

PLO

Operation

..................................................

3-27

Sync-Up

PLO

Operation

....................................................

3-27

Data

Decoder

..............................................................

3-27

Read

Sync

..............

'

..................................................

3-29

iii

CONTENTS

(Continued)

Section Page

4

MAINTENANCE
Preven

tive Maintenance

......................................................

4-1

Monthly (covers

on)

......................................................

4-1

Semiannually (covers removed)

................................................

4-1

Disk Drive Exerciser

........................................................

4-1

Controls~

Indicators~

and Test Points

............................................

4-1

Preparation for Offline Checkou t

..............................................

4-1

Disconnecting the Exerciser

..................................................

4-3

Maintenance

Procedures

......................................................

4-3

Tools and Test

Equipment

..................................................

4-3

Plugs and Jacks

..........................................................

4-3

PWB

Assembly ~ Data and Control

..............................................

4-4

PWB

Replacement

........................................................

4-4

Power

................................................................

4-4

Drive System

............................................................

4-5

Spindle System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-9

Position System

..........................................................

4-10

Read/Write System

........................................................

4-12

Data Decoder

with

PLO Board Adjustments

......................................

4-13

5

ILLUSTRATED PARTS BREAKDOWN

Figure

1-1

2-1
2-2

2-3

2-4

2-5

2-6
2-7

3-1

3-2
3-3

3-4

3-5

iv

Group Assembly Parts List

....................................................

5-1

Figure and

Item

Number

.......................................................

5-1

Part

Number

..............................................................

5-1

Description

..............................................................

5-1

Quantity

Per Assembly

......................................................

5-1

Usage Code

..............................................................

5-1

Purchased Parts

............................................................

5-2

Accessories

..............................................................

5-2

ILLUSTRATIONS

Page

Floppy

Disk Drive

..........................................................

1-1

Disk Drive Shipping Configuration

................................................

2-1

Ac Power Cabling Wiring

......................................................

2-2

Twisted Pair Interface

Connector

Board, Schematic Diagram

..............................

2-2

Ribbon Cable Interface

Connector

Board, Schematic Diagram

..............................

2-3

Termination for Disk Drive

Output

Signals

..........................................

2-4

Termination for Disk Drive

Input

Signals

..........................................

2-4

Floppy

Disk

wading

........................................................

2-7

Flexible Disk Construction

....................................................

3-1

Code

Format

Comparisons and MFM Characteristics

....................................

3-2

Peak Shifting and Pre compensation Conditions

......................................

3-4

Track Accessing Timing

......................................................

3-5

Double

Frequency

Raw

Data

Timing

......•.......................................

3-5

Section

3-6
3-7
3-8
3-9
3-10
3-11

3-12
3-13
3-14

3-15
3-16

3-16

3-17

3-18

3-19

3-20

3-21

3-22

3-23

3-24

3-25

3-26

3-27

3-28

3-29

3-30

3-31
3-32
3-33
3-34
3-35

3-36

3-37

3-38

3-39

3-40

3-41

3-42

3-43

3-44

3-45

3-46

3-47
4-1

4-2

4-3
4-4
4-5
4-6
4-7

4-8

ILLUSTRA TIONS

(Continued)

Page

MFM Raw Data Timing

......................................................

3-5

Double

Frequency

Write Data Timing

............................................

3-6

MFM Write Data Timing

......................................................

3-6

Power-On to Write Timing

....................................................

3-7

Power-On

to

Read Timing

....................................................

3-7

Disk Drive General Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Disk Drive Mechanical

System Pictorial View

........................................

3-9
Drive Mechanism

...........................................................

3-10
Disk Centering and Head Load Mechanism

..........................................

3-10
Positioning Mechanism

........................................................

3-11

Logic Symbology

(Sheet 1

of

2)

................................................

3-12

Logic Symbology

(Sheet 2

of

2)

................................................

3-13
Detailed Block Diagram

......................................................

3-14

Index

Pulse Detection

on

Speed Monitor, Simplified Logic Diagram

........................

3-15
Index

Dector

..............................................................

3-15

Ramp Generator

............................................................

3-16
Power-On

to

Ready

Transition Period Waveforms

......................................

3-16

Head

Load

Relay Driver

......................................................

3-16

Single-Track

Positioning Time Waveforms

...........................................

3-17

Multiple-Track Positioning Time Waveforms

..........................................

3-17

Stepper

Motor Position Control Simplified Logic Diagram

................................

3-17

Stepper Motor Direction Sequencing

..............................................

3-18

Decode and

Current Drivers for

00

Code

...........................................

3-18

Track

00

Detector

Circuit

......................................................

3-19

Write

Channel, Simplified Logic Diagram

............................................

3-20

Double-Frequency Write Control and Write Coils Current Flow

............................

3-21

MFM Write

Control and Write Coil Current

Flow

......................................

3-21

Read/Write Matrix Gate for Read

................................................

3-23

Differentiator

Input/Output

Waveforms

............................................

3-23

Raw Data

Output

Gating

......................................................

3-23

MFM Raw Read

Data

Waveforms

................................................

3-24

One-Shot Data Decoders

......................................................

3-24

RAW and

NRZ

Read Data Decoder Waveforms

......................................

3-25

Read Decoder with

PLO Block Diagram

............................................

3-25

PLO, Simplified Logic Diagram

..................................................

3-26

PLO Locked On and Missing Pulse Operation

........................................

3-26

PLO

Sync-Up

..............................................................

3-28

Read/Write Coding Waveforms

..................................................

3-28

Data Decoder. Simplified Logic Diagram

............................................

3-29

Data Decoder Waveforms

......................................................

3-30

Read Data Decoder Sync, Simplified Logic Diagram

....................................

3-30

Composite

MFM

Data

Decoder Waveforms

..........................................

3-31

Composite Double

Frequency

Data Decoder Waveforms

.................................

3·32

Model

2140

Disk Drive Exerciser

................................................

4·1

Exerciser and Disk Drive

Setup

..................................................

4-3

Disk Drive Interconnecting

Cabling Daigram

........................................

4·3

Drive System

Component

Identification

............................................

4·5

Drive Belt Checks and Adjustments

..............................................

4-5

Head Alignment Waveform

....................................................

4·7

Index Pulse Timing Waveform

..................................................

4-7

Index Pulse with Hard-Sector

Option

Timing Waveform,

............

,

...................

, 4-8

v

Figure

4-9
4-10
4-11
4-12
4-13
5-1
5-1
5-2
5-3
5-4
5-4A
5-4B
5-4C
5-4D
5-4E
5-4F
5-5
5-6

ILLUSTRATIONS (Continued)

Page

Spindle System

Component

Identification

.......................................

,

...

4-9

Positioning

System

Component

Identification

........................................

4-10

Track 00 Alignment Waveform

..................................................

4-11

Head Load

Check and Adjustment

................................................

4-12

Data Separator

One-Shot Alignment Waveform

........................................

4-13

Model

140 Series and 142 Disk Drive Unit (Sheet 1

of

2)

................................

5-4

Model

140 and 142 Disk Drive Unit (Sheet 2

of

2)

....................................

5-6

Cone Lift Cover Assembly

.....................................................

5-9

Drive Motor Assembly

........................................................

5-11

Data and

Control Board Assembly, VR49

..........................................

5-13

Data and

Control Board Assembly, VR56

..........................................

5-17

Data and

Control Board Assembly, VR57

..........................................

5-21

Data and

Control Board Assembly, VR58

..........................................

5-25

Data and

Control Board Assembly,

VR60

..........................................

5-29

Data and

Control Board Assembly, VR82

..........................................

5-33

Data and

Control Board Assembly, VR83

..........................................

5·37

Data Decoder with PLO Board Assembly, VR71

......................................

5-41

Data Decoder with

PLO Board Assembly, VR81

......................................

5·43

TABLES

Table

Page

1-1

Physical and Electrical Characteristics

..............................................

1-2

1-2 Tools and Test

Equipment

....................................................

1-3

2-1

Ac

Power Cable

............................................................

2·2

2-2 Twisted-Pair Interface Signal Cable Connections

......................................

2-5

3-1

Binary Code for In-Out Read/Write Head Positioning

..................................

3-18

4-1

Exerciser Switch, Indicator, and Test Point Functions

..................................

4-2

4·2 Initial Exerciser Control Settings

................................................

4-3

4-3

Jack

and Plug Description

....................................................

4-4

4·4

Power Requirements

........................................................

4-4

5-1

Unit Options

..............................................................

5-3

vi

SECTION 1

INTRODUCTION

This manual contains installation and operating instructions,

theory

of

operation, maintenance procedures, and

illustrated parts breakdown for the Model

Model 142 Floppy Disk Drives (Figure 1-1). The Model

140 and

140

and 142 are compact, high-speed, random-access data

storage units

that

use a flexible disk cartridge

as

the storage
medium. Wherever differences between models exist, they
are identified.

Before performing preventive or corrective maintenance

on
the disk drives, maintenance personnel should become
familiar with the electrical characteristics and principles

operation

of

the disk drives.

of

• Installation and Operation

Uncrating
Installation
Operation

• Theory

of

Operation

Principles

of

Operation

Functional Theory

• Maintenance

Preventive Maintenance
Main

tenance Proce

du

• Illustrated Parts Breakdown

DESCRIPTION

The Floppy Disk Drive
memory device

that

is

a high-speed, random.access

is

used for data storage in data pro­cessing systems. The disk drive
power supplies
rack mounted

is

self contained. The disk drive can be

or

used

as

a table top unit.

res

is

compact and except for

Figure 1-1. Floppy Disk Drive

This manual

intended

as

a technical guide for field

is

engineers and other technical personnel who are involved

in maintaining the disk drives. The information in this

manual - other than that contained in this section -

is

divided into four basic sections.

The disk drive uses a removable, flexible disk cartridge
that

is

easily installed or removed through an access slot

on

the front

access to the interior

of

the disk drive. Removable covers allow

of

the disk drive for maintenance

purposes.

PHYSICAL AND ELECTRICAL CHARACTERISTICS

Physical and electrical characteristics for the disk drives
are listed

in

Table 1·1.

1-1

TABLE 1-1. PHYSICAL AND ELECTRICAL CHARACTERISTICS

Physical Characteristics

Height
Width
Depth
Weight

Power Requirements

Ac

Power

Ac

Starting Curren t

Ac

Operating Current

Dc

Power

Operating Environment

Temperature
Relative Humidity
Heat Dissipation

Specifica hons

Disk

Cartridge Capacity

Double Density (Unformatted*)

Per Disk
Per Track

Double Density (Hard

Sector*)

Per

Disk
Per Track
Per Sector

Single

Density (Unformatted)
Per Disk
Per Track

Single Density (Hard Sector)

Per

Disk

Per Track

Single Density

(IBM

3740 Format)

Per Disk

Per Track

Per Sector

Carriage

Positioning Time

*Used

only

with

the

Mode1142

1-2

4.90 inches

8.40 inches

15.00 inches (add 3 inches for connector clearance)
16

pounds;

18

pounds shipping

100 to 240 vac, +10%, -20%,50

±0.5

Hz

or 60 ±0.5

Hz,

single phase

1.7 amperes maximum,

60

Hz;

1.7 amperes maximum, 50

Hz

1.2 amperes maximum, 60

Hz

1.1

amperes maximum,

50

Hz

+24v ±5% at 1.5 amperes maximum, 100 millivolts peak-to-peak ripple
+5v

±5% at 1.0 ampere maximum, 50 millivolts peak-to-peak ripple

600F to

100°F

(20°F

maximum rate

of

change per hour)

20%

to

80%

(no condensation)

275 Btu per hour

6,416,256

bits/802,032 bytes

83,328

bits/l0,416

bytes

6,179,712 bits/772,464 bytes
80,256 bits/l0,032 bytes
2,508 bits

3,208,128

bits/401,016 bytes

41,664 bits/5,208 bytes

3,089,856 bits/386,232 bytes
40,128 bits/5,016 bytes

1,943,552 bits/292,944 bytes
26,644 bits/3,328 bytes
1,024 bits/ 128 bytes
160 milliseconds (average)
6 milliseconds track-to-track slew (minimum)

TABLE 1-1. PHYSICAL AND ELECTRICAL CHARACTERISTICS (Continued)

Specifica tions (con tin ued)

Head

Settling Time
Head Load Time
Recording

Format

Recording

Format

Recording Method

Data Transfer Rate

Data Bit

Cell Time

Rotational

Speed

Rotational Latency

Average

Maximum
Recording Tracks
Track

Spacing

Bit Density

Track Density
Recorded Track Width
Start Time

SPECIAL TOOLS AND TEST EQUIPMENT

10 milliseconds (maximum)
30

milliseconds (maximum)
Fixed or variable length
Fixed

or

variable length
140 or 142: Double frequency, frequency modulated (FM)
142 only: Double frequency (FM) double density, modified

frequency modulation (MFM)

FM:

250,000

bits per second

MFM:

500,000 bits per second
2 microseconds
360

rpm ±2.5%

83.3 milliseconds
167 milliseconds
77

0.0208 inch (nominal)
FM:

3268

bits per inch (inside track)
MFM: 6536 bits per inch (inside track)
48

tracks per inch

0.013 inch (nominal)

2.5 seconds (drive ready)

Tools and test equipmen t recommended for use in
maintaining the floppy disk drives are listed in Table

1·2.

TABLE 1-2. TOOLS AND TEST EQUIPMENT

Tools

Common Hand Tools
Flashlight

Test Equipment

YOM
Oscilloscope
Model

2140

Exerciser

Head Alignmen t Disk

Cartridge

Cleaning Materials

Alcohol (91

% solution)

Lint-free cloth

1-3

SECTION 2

INSTALLATION AND OPERATION

This section contains procedures and descriptive material

to aid trained personnel in unpacking, installing, and

pre-

paring disk drives for online operation. This section

is

divided into three basic parts relating to task-oriented

objectives.

• Unpacking
Unwrapping

Inspection

• Installation
Cable fabrication, connection, and checkout

Preoperational checks

Operational checks

• Operation

The disk drive

is

packaged to ensure adequate protection
for local, long distance, or overseas shipping and handling.
Unpack and remove the unit from the shipping container
as

soon

as

it

is

received (see Figure 2-1).

Figure

2-1,

Disk

Drive

Shipping

Configuration

UNPACKING

The following procedure

is

based on current packing

methods and may be subject

to

minor deviations. After
inspecting the container for obvious shipping damage,
proceed

as

follows:

1.

Cut and discard the fiberglass straps that secure the
shipping container.

Note

Do

not

lift

the

disk drive

by

the

floppy

disk

loading handle,

as

the handle can be damaged.

2. Remove

all

parts from the shipping container.

Re-

move the inner packing material.

3.

Check each part against the packing list.

4. Inspect all items visually for physical damage.

INSTALLATION

Most new installations will normally require that a power
cable and a

dc

and signal cable be fabricated on site.

Ac

Power Cable

The length

of

the

ac

power cable

is

determined at the

installation site.

Cable connectors are supplied with the

disk drive.

CAUTION

Ensure

that

the

power

to

be applied

to

the

disk drive corresponds

to

the requirements

specified

on

the nameplate

of

the disk drive.

Fabricate the

ac

power cable in a phase-to-neutral or

in

a

phase-to-phase configuration in accordance with Table

2-1

and Figure 2·2.

Dc

and Signal Cabling

Dc

and signal cable connections between the controller and

disk drives may be

in either a radial or a daisy-chain

arrangement. Two types

of

interface connector boards are

2-1

available

to

accommodate

both

applications. There are

two

versions

of

each

connector

board - terminated

and

unter-

minated.

Pin

1

2

3

JO

2

3

JO

2

3

TABLE 2-1. AC POWER CABLE

Connector

90606-003

Phase-to-Neutral

115/208

vac

Chassis

Gnd

115/208

vac

PHASE-TO-NEUTRAL

2 AMP SLO-BLOW

PHASE-TO-PHASE

1 AMP S LO-BLOW

1 AMP SLO-BLOW

Phase-to-Phase

208

vac
Chassis Gnd
208

vac

115/208

VAC

(HOT)

CHASSIS

GND

(EARTH)

115/208

(RTN)

230

VAC

(HOT)

CHASSIS

GND

(EARTH)

230

VAC

(HOT>

Figure 2-2. Ac Power Cable Wiring

One type

of

interface

connector

board

is

designed for

twisted-pair wiring, which

must

be soldered

to

the

board.

The

part

number

for this

board

is

12084-001 with terminat-

ing resistors

and 12084-002

without

terminating resistors

(see Figure

2-3).

The

other

type

of

interface

connector

board

is

designed for

ribbon cable, which has press-on connectors

that

plug

into

the interface

connector

board. The

part

number

for

both

the terminated and

unterminated

boards is 16292-001;

however, the terminated

board

must

have terminating net-

work

16557-001 plugged

into

IC socket XA2 (see

Figure 2-4).

Fabricated dc and signal cables may be ordered from the

factory

or

the cables

can

be fabricated

on

site.

2-2

+5V

02

1--_--------...".::--0

+5V

04

HEAD

LOADI

20

1--+------1

.......

----..,;;..--0

SELECT I

18

t---+--~---------o

DIRECTION

06

1--+------1

.....

----

.......

--0

STEP I

08

~+---___4Ir+-----.-::-:=o

ABOVE

TRK 431

24

~+---___4Ir+-~~--.-::-~

WRITE DATAl

Rll

220

R13

220

PWB

EYELETS

WRITE

ENABLEI

34

t--+---___4I

.....

-=-:--:----t":-:::-:-O

+24V

RlS
220

+24V

10

............

--------~:-::-<>

+24V

12

+24V

14

TRACK 001

18

I-----------~:-=O

READYI

22

1-----------

.....

--0

INDEXI

26

I-----------~:-:-O

SECTORI

28

..----------~~

WRITE

ENABLED!

30

..----------._=_::::-=-o

(READ

DATA/)*

361-----------._=_:::_=<>

(READ

CLOCKf)*

RAW

DATAl

()

*USED

WITH SINGLE DENSITY

RECORDING

(FM)

NOTES;

1.

PART NO.

12084-001

SHOWN;

PART NO.

12084-002

DOES

NOT

HAVE TERMINATING

RESISTORS

2.

ALL

ODD-NUMBERED

PINS

ON

PI

ARE

GROUNDED

Figure

2-3.

Twisted

Pair

Interface Connector

Board,

Schematic Diagram

POWER
CONNECTOR

+5

OV

+24

READY

1/

READY

2!

READY

3/

READY

4/

SELECT

11

SELECT

2!

SELECT

3/

SELECT 41

RIBBON

CABLE

CONNECTOR

DIRECTION

OUT

I

STEPI

ATRK

43!

WRT

DATA!

WRT

GATEI

HEAD

LOAD!

TRKOO/

IDXI

SECTOR!

WRTENABLED/

RDATAI

RCLOCKI

J2

,.....-

01
02

~

03

10...-

Jl

,.....-

22
04
02
40
16
14
12

10

06

08

24

32

34

20
18
26
28
30

36

38

10...-

(NOTE 3)

NOTES:

1

2
3

4

5
6
7
8

~

2

~

4

~

6

r

1.

JUMPER

ONE

READY/ SIGNAL

AND

ONE

SELECT/ SIGNAL

2.

INSTALL

TERMINATING

NETWORK

16557-001

IF

REQUIRED

3.

ALL

ODD-NUMBERED

PINS

FOR

Jl

AND

PI

ARE

GROUNDED

XAI

16

L.!.U

'

....

--

---,,'

~

13

(NOTE

1)

12

.......

- - - - -,'"

11

1

10

T

9

1

XA2

~

13

+SV

12

(NOTE

2)

~

~

9

~

PI

~

22

~

02

"-

04
10

12
14

16

24
08
06

20

34

32

18
26
28
30
36
38

L..-,..I

DISI(
DRIVE
CONNECTOR

(NOTE 3)

Figure 2-4. Ribbon Cable Interface Connector Board, Schematic Diagram

• Daisy-Chained Application
Daisy-chaining

of

multiple disk drives requires the use

of

both

terminated and unterminated interface connector

boards. The common

I/O signals are daisy-chained from

drive to drive; the interface connector board for the last

disk drive

in

the chain

is

a terminated board (see Figures

2-5 and 2-6) that provides line terminations for all

inCOming

signals to the disk drive.
The twisted-pair connector board has feedthrough solder

lands with two eyelets in each land. System cabling can be

accomplished by connecting signal and associated ground
leads

to

one eyelet

of

the respective lands. The remaining

eyelet

of

each land can be used to cable signal and associated

ground leads

to

the next disk drive interface connector

board. This technique can be used to interconnect the

remaining disk

drives.

The ribbon-cable interface connector board allows inter­connection

of

disk drives and a controller through a ribbon
cable. The ribbon cable has press-on connectors at various
intervals that plug into ribbon cable interface connector
boards at the disk drives.

Up

to

four disk drives can be

connected

to

the controller through one ribbon cable.

Note

The

SELECT/

signal

and

its associated

ground

and the

READ

Y / signal

and

its associated

ground

should

not

be daisy-chained in multi-

ple disk drive applications. They

should

be

connected

to

the

controller separately. (When

using the ribbon-cable interface

connector

board,

SELECT/

and

READ

Y /

must

be

jumped

[or

the appropriate disk drive.)

OPENCOLLECTO;-

--

--

--

I

R!BBONCAru

INTERFACE

--,

POWER

GATE *

Jl

PI

16292-001

VN45

Jl

......

-+-

...

SIGNAL

DISK DRIVE

I

_

NO~

_____

-.L

____

.......J

OPENCOLLEcTO'R ----

--

T

-;U;B;,;c;B~~C~

POWER

GATE *

Jl

PI

16292-001

VN45

Jl

SIGNAL

DISK DRIVE
NO.2

......

--9-

...

-.L

_____

J

FROM NEXT
DISK DRIVE

r-+S'v----.---

2200

3300

L

__

~~E_R

____

_

PART

OF

RIBBON CABLE

* DRIVE LINE CAPABLE

OF SINKING

36

MA.

Figure 2-5. Termination for Disk Drive

Output

Signals

-

--

--

--

--

--

--

-,-

IUBOONCABLE

INTERFAcE

-,

I

16292-001

VN45

Jl

PI

~J~I~_~

DISK DRIVE

_~1

_____

-L

____

-1

-------T----,

Jl

PI

2200

Jl

+5V

_Af',.J'-~

3300

LAST DISK DRIVE

RIBBON

CABLE INTERFACE J

_

~T~

________

...L

~~1

~~

__

PART

OF
RIBBON
CABLE

I -

QpENCOLLmO;-----

POWER

GATE

*

SIGNAL

L

__

C~R~E~

__

_

PART

OF

RIBBON CABLE

* CONTROLLER DRIVE LINE

MUST

BE

CAPABLE

OF

SINKING

25

MA.

**

RESISTORS

ARE

LOCATED

ON

TERMINATOR

15198-001

PLUG

WHICH

IS INSTALLED

IN

INTERFACE KIT

BOARD

OF LAST DISK DRIVE.

Figure 2-6. Termination for Disk Drive

Input

Signals

2-4

• Radial Application
When

disk drives are connected radially to a con troller,

separate

dc

and signal cables radiate from the controller to

each

disk

drive. A terminated interface connector board

must be used for each disk drive.

• Twisted-Pair

Dc

and Signal Cable Fabrication

The twisted-pair dc and signal cable should consist

of

twisted pairs (approximately

30

twists per foot) whose

wire size

is

either No. 24 or No. 26

AWG

and not

exceeding 25 feet in length.

1.

Fabricate the twisted-pair dc and signal cable in
accordance with Table 2-2.

Use

Cable Terminator

Assembly

12084·001

if

terminations are required;

use Cable Terminator Assembly

12084-002

if

termi-

nations

are not required.

2.

Use a YOM

to check each cable for pin-to-pin shorts.

3.

Use a YOM

to check for continuity between corre-

sponding pins at opposite ends

of

each cable .

4.

Connect the dc and signal cable to the controller.

5. Apply power to the controller, and check each
interface connector board to verify proper pin
assignments. Refer to Table 2-2.

6.

Turn power

off

at the controller, and connect the

cables to the disk drives.

TABLE 2-2.

TWISTED·PAIR INTERFACE SIGNAL CABLE CONNECTIONS

Signal Pin

Ground Pin

Signal

Number Eyelet Connection Eyelet Connection

Number

Eyelet Connection

Eyelet Connection

From Controller

or

To Next Drive

From Controller

or

To Next Drive

Preceding Drive

Preceding

Driv.e

READ CLOCK** or

38 E37

E77

37

E38 E78

RAW

DATA

READDATA**

36 E35

E75

35 E36

E76

PLO SYNC/* 40

E33 E73

39

E34

E74

WRITE DATA/ 34

E31

E71

33

E32 E72

WRITE ENABLE/

32

E29

E69

31

E30

E70

ABOVE TRACK

43/

24

E27 E67

23

E28

E68

WRITE ENABLED/

30

E25

E65

29 E26

E66

SECTOR!

28 E23

E63

27 E24 E64

INDEX/ 26

E21 E61

25 E22

E62

READY!

22

E19

-

21

E20

-

HEAD LOAD!

20

E47 E49

19

E48 E50

TRACK

00/

18

E17 E57

17

E18

E58

+24V

14

E15 E55

13

E16 E56

+24V

12

E13

E53

11

E14

E54

+24V

10

Ell

E51

9

E12 E52

SELECT! 16 E9

-

15

EI0

-

DIRECTION

6

E7 E45

5 E8

E46

STEP/

8

E5

E43

7

E6 E44

+5V

4

E3

E41

3

E4 E42

+5V

2

El

E39

1 E2

E40

*Not Used

·*When unseparated data

is

the

output

of

the disk drive, pin 38 supplies the unseparated data (raw data) and read data

output

(pin 36)

is

not used.

2-5

• Ribbon Signal Cable Fabrication
The ribbon signal cable should consist

of

a 40-conductor
ribbon signal cable (3M part number 3365/40 or equivalent)
and one or more

40-pin connector (3M part number
3417-0000,3417-3000, or equivalent) depending on the
number

of

disk drives to be connected to the controller

through the same cable.

1.

With the use

of

a small arbor press, press the 40-pin
connectors onto the ribbon cable at a predetermined
interval.

2.

3.

4.

Use a VOM

to check each connector for pin-to-pin

shorts.

Use a VOM

to

check for continuity between

corresponding pins

at

each connector.

Connect the cable to the disk drives and to the
controller.

•

Dc

Power Cable Fabrication

When a ribbon cable

is

used to connect the controller to
the disk drives, a separate, 3-wire, dc power cable must be
fabricated for each disk drive.

1.

2.

3.

Crimp contacts (CalComp part number 90441-002)
on

one end

of

each wire.

Insert contacts into the plug housing (CalComp
part number

90605-003). Verify that the contacts

are

inserted into the proper position in the plug

(see

J2

of

Figure 2-4).

Connect a dc power cable

to

each disk drive.

Data

Output Selection

The disk drive can be adapted to either

of

two decode

outputs: separated data

or

unseparated data (raw data).

If

separated data

is

desired, make certain that Floppy Disk

Plug Assembly 14519-001

is

installed

in

IC

socket A6.

Assembly 14519-001 has jumpers between pins 4 and 11,
pins 5 and

10, and pins 3 and 12.

If

unseparated data

is
desired, make certain that Floppy Disk Plug Assembly
14519-002

is

installed

in

IC

socket A6. Assembly 14519-002

has a jumper between pins 4 and

S.

Checkout
The disk drive can

be

checked out operationally by
running the disk drive either offline with the exerciser or
online with the system.

2-6

OPERATION

Floppy disk storage and handling

as

well

as

correct operat-

ing

procedures

are

important for error-free operation.

Floppy Disk

Storage and Handling

Since the recorded disk contains vital information.
reasonable care should be exercised in its handling. Longer
disk life and trouble-free operation will result

if

the

following recommendations

are

followed.

• Floppy disk ID information should be written on an
adhesive-type tape

or

label; then the label should be
affixed to the disk cartridge covering. Writing directly
on the floppy disk covering would damage the surface
of

the disk.

•

Do

not fasten paper clips to the edges

of

the disk

jacket.

•

Do

not

touch the surface

of

the disk exposed by the

jacket slot.

• Do not clean the disk in any manner.

• Keep the disk away from magnetic fields and away
from ferromagnetic materials that may

be

magnetized.

• Return the disk to its protective envelope when removed
from the disk drive.

• Protect each disk from liquids, dust, and metallic
substances at all times.

•

Do

not exceed the following environmental storage

conditions:

Temperature: SooF to

1200F (lOoC to

4B.90C)

Relative Humidity:

B%

to

BO%

Maximum

Wet

Bulb:

BooF

(26.70C)

•

Disks should be stored when not

in

use.

Before using a floppy disk on a disk drive after long-term

storage, the floppy disk should be allowed to stabilize

in

the disk drive environment one hour for each hour

out

of

the disk drive environment (up to 24 hours).

For short-term storage, the floppy disk(s) should be placed
temporarily

in

the same area

as

the disk drive. No more

than

ten floppy disks should

be

stacked in a flat

me.

Write-Protect Option

The data recorded

on

a floppy disk can be stored perma-

nently by using the write-protect option.

If

the floppy

disk

is

intended to be used only for reading, verify that an

opaque tab is

not

affixed over the write-protect hole (see
Figure 3-1) in the floppy disk jacket. To enable data record­ing, the tab must be installed.

Floppy Disk Loading and Unloading

Proper loading

of

the floppy disk

is

vital

to

the operation

of

the disk drive. Figure 2-7 shows the location

of

the

floppy disk opening for loading.

A.

FLOPPY

DISK

IN

LOAD

POSITION

The procedure for loading/unloading the floppy disk

is

as

follows:

1.

2.

3.

4.

5.

Move

the handle to the open position.

Insert the floppy disk in the load aperture as shown

in

Figure 2-7. (Ensure

that

the head aperture

is

to

the rear and that the label faces the handle).

Move

the handle

to

the disk load position; verify

that the cover latches securely in place.
To unload the floppy disk, press the release

button

on
the handle. The load mechanism disengages the floppy
disk from the drive mechanism.

Remove the floppy disk, and close the cover.

B.

FLOPPY

DISK

LOADED

Figure 2-7. Floppy Disk Loading

2-7

SECTION 3

THEORY

OF OPERATION

This section contains descriptions

of

the characteristics and

the basic principles

of

operation

of

the Model 140 and the

Model 142 Floppy Disk Drives.

It

also contains functional

descriptions

of

various operating systems and the digital

logic and analog circuits employed in this device.

Recording Medium

The disk drives use a removable, flexible disk as the

storage medium. Figure

3-1

shows the construction and

dimensions

of

a typical flexible disk and associated jacket.

Only one side

is

used for recording.

PRINCIPLES OF OPERATION

Certain hardware and operational characteristics

of

the

disk drive must be understood

as

a basis for more detailed

study

offunctional

systems and circuits. The following

principles

of

operation provide this necessary background

information.

The recording medium specified for use with the Model

140 and the Model 142

is

a single-side oxide-coated,

flexible disk enclosed within a protective plastic jacket.

(Figure

3-1

B). The protective jacket contains apertures
for spindle loading, head contact, sector/index detection,
and write-protect detection.

SEALED
PROTECTIVE
JACKET

I~------------

BIN.

------------.~I

BIN.

I

\

/

/

I

",--

- -

---

~

.........

,/

/

\

HEAD

SPINDLE/HUB /

\<~:~R~_~:E~//

SEALED

O.06IN.

PROTECTIVE _ I

JACKET

~,

J

LI N ER

ceo

T H .

':'::""'\':'.~::::::.:.:,.,:.

-rl-

SIDES

OF

OISK)/~

f

~

OXIDE-COATED
MYLAR DISK

1.5IN.DIA

LINER

WRITE­PROTECT
HOLE

7.B

IN

'AlDIA

~

REGISTRATION OPTIONAL

SECTOR

1.5iN.

7'---'

OPENING

~~-;<HOLES

O.lOODIA

RADIUS

I

""\

INDEX / /

(('

,/-~'"-\

\

~···O\

INOEX

\.

If

I J

\..

.j

HOLE

rf'

~_/

...

TRACK

00

-

TRACK

76

CD

Figure 3·1. Flexible Disk Construction

The circular opening in

the

center

of

the jacket exposes the
registration opening in the disk. The centering cone enters
this opening

to

cen ter and

to

clu

tch

the disk against the

rotating spindle and causes the disk

to

rotate within

the

jacket (cartridge).

When

the

cartridge

is

loaded, the read/write head is pos-

tioned in

contact

with

the

disk exposed

by

the elongated

opening

(bottom

center

of

Figure

3-1

A). The small circular
opening in the jacket, above the large center circular open­ings, (Figure 3-1A) exposes O.l-inch diameter holes in the

disk (Figure

3-1

C)

that

are detected

as

index and sector. The

index pulse developed from

the

index hole

is

used

to

indicate

the rotational speed

of

the

disk and marks the beginning

of

the recording tracks. Sector pulses

(32

per track) are

developed from the evenly spaced sector holes in the disk

and are used

to

divide each track into equal areas for record-

ing format purposes.

Data is recorded by magnetizing digital bit patterns in

con-

centric circles (tracks)

on

the recording surface

of

the

magnetic-oxide coating.

As

shown in Figure

3-1

C,

the record-

ing surface contains

77

tracks spaced at 0.020-inch intervals.

The tracks are numbered

00

thm

76, beginning with

the

track nearest the

outer

edge

of

the disk.

DATA

NRZ

MANCHESTER

MFM DATA

MFM

FLUX

REVERSALS

o

o

D

Data Recording Method
Modified Frequency Modulation (MFM)

is

the recording

method

recommended for use

in

the Model 142 Disk Drive.

Figure 3-2 provides a comparison between NRZ (non-retum-

to zero), Manchester

Code (used in the Model 140), and

MFM.

MFM

flux reversals

on

the

recording media occur

at
three frequencies: at one-, and one and one-half-, and two­bit cell intervals. This

method

of

recording has three major

advantages.

• Fewer flux reversals (lower recording frequency) for a

given

amount

of

data, which permit a higher packing

density.

• Contains data bit and data clock information,

both

of

which are recoverable.

• Flux change polarity has

no

relationship

to

bit

value,

which simplifies

data

recovery circuit design.

Data cell time for the

6536

bit-per-inch packing density

(MFM)

of

the

Model 142

is

2 microseconds

at

speed, making

the maximum recording frequency

500 kilohertz (all-zeros

or all-ones

bit

pattern). The minimum recording frequency

would be

half

that -250

kilohertz - for an alternate zero

and one bit pattern.

o

o

o

o o

FREQUENCIES--_r

t---2B---1--~--1-1B-1

NOTES~

1.

C = CLOCK PULSE

2.

D = DATA

ONE

PULSE

3.

B = BIT CELL INTERVAL

4.

IB

(BIT

CELL

TIME) = 2

MICROSECONDS

Figure

3-2.

Code Format Comparisons and

MFM

Characteristics

3-2

MFM

coding can be simplified

to

the following three rules:

• A flux change occurring at the midpoint

of

a data cell

is

one data bit, regardless

of

polarity.

• A flux change occurring at a data cell boundry is a data
clock, regardless

of

polarity.

• A data clock flux reversal can only (and will always)
occur between two

zero bit data cells.

MFM data and clock information

is

recovered during

reading

by

establishing bit cell time-related detection

windows.

Peak

Shift Precompensation

To enhance the readback capability, data to be written on

the floppy disk may be precompensated in the controller
for peak shift migration.

High-density, multifrequency recorded signals suffer from
a magnetic effect known

as

peak shifting. Peak shifting

is

the tendency

of

closely spaced flux reversal domains to

migrate away from each

other

into areas

of

lower density.

In effect, unevenly spaced flux reversals

'stress themselves

in an

attempt

to

even

out

the spacing between them. See

Figure 3-3A.

This magnetic interference effect,

if

not

compensated for,
could cause data and clock recovery problems during
reading

if

detection window timing

is

marginal.

To

minimize

the effect, the data

is

written in a prestressed condition.

That is, flux reversals

that

would tend to be shifted late due

to magnetic interference are written early, and vice versa.

Prestress direction

is

determined by looking at the inter-

mediate stream

of

data and clock pulses and making logical

decisions to write the flux reversal early, on time,

or

late.

These decisions are based

upon

the transition intervals

immediately before

(TI)

and immediately after (T2) the

current transition (pulse

8). See Figure 3-3B. The rules are

as

follows:

•

If

nominal

TI

is greater than nominal T2, write pulse 8

late.

•

If

nominal

Tl

is

less than nominal T2, write pulse B

early.

•

If

nominal T 1 and T2 are

both

310

nanoseconds (low

frequency) or 232 nanoseconds (medium frequency),

write

pulse B early.

•

If

nominal T 1 and T2 are

both

155 nanoseconds (high

frequency), write pulse B

on

time.

Figure 3-3C defines the early, on-time, and late timing

con-

ditions relative to the bit cell interval. The amount

of

write

precompensation

is

normally 10 percent

of

the

infonnation

bit cell (about

200

nanoseconds).

Track Accessing

Track accessing

is

accomplished

by

using DIRECTION and

STEPI interface lines. The DIRECTION line must be set

to
the proper level and be stable for 100 nanoseconds, mini­mum, before the leading edge

of

STEP/. Figure 3-4 depicts

track accessing timing requirements.

Head positioning is accomplished by pulsing the

STEP/ line

at 167 pulses

'per second with one head position change per

pulse.

If

stepping occurs without unloading the head, 10

milliseconds

of

head settling time must be allowed after

the last step before proceeding with data transfer.

Note

The disk drives

are

designed to operate at

a step pulse rate

of

167

pulses per second.
Operation at lower step pulse rates may
result in slightly noisy operation.

Should an access position error occur, a reference may be
established either by reading the track header or

by

stepping

the head

out

until the TRACK

00/

line becomes active.

Read

Data Timing

Read data

is

transferred from the disk drive

to

the control
unit in a serial fashion. Figure 3-5 illustrates the various
timing parameters

of

the double frequency raw data signal;

Figure 3-6 illustrates the various timing parameters

of

the

MFM

raw data signal.

Write

Data Timing

Write data

is

transferred between the control

unit

and the

disk drive in

a serial fashion. The interface line WRITE

ENABLE/ signal controls

both

the write-current generators
and the straddle-erase circuits. WRITE ENABLE/ goes low
to write data. Figure 3-7 illustrates the various write timing
parameters

of

the double frequency recording; Figure

3-8

illustrates the various write timing parameters

of

the

MFM

recording.

3-3

,

,.

NORMAL

FLUX

REVERSALS

PEAK

PRESTRESSED

RECOVERED

MFM

DATA

MFM

SHIFTING

<IDEAL)

DATA

0

1

0

1

0

0 0

I

I-

II

II

II

I'

I

I
I

I

11=1

I

II

I

II

I

II

II
II
II

I

d-

II

II

II

I

1l=:J1

II
II
II

1

-I

I'

,I

:1

II
II

II

II
II
II

0

I·

I

II II

I

II

I:

II

II
II

I

-,

I

,I

:,

II
II
II

I~

II II

II

II

II

II

,

I

I--

Tl

A.

--J-I_'

- T 2 ---I

Tl

< T2;

WRITE

B EARLY

EFFECTS

OF

,

PEAK

SHIFTING

I

AND

PRESTRESSING

J-

Tl

-I--

T1

>T2;

WRITE

I

B LATE

T2

--I,

I

I

3-4

.200

NS.=:I

200

NS

---.11

B.

EXAMPLES

OF

PRESTRESS

rBITCELL

Ir-·----L.....

I

Figure

3-3.

__

C. EARLY, ON-TIME,

Peak

Shifting

......;

__

and

DETER

MINATION

NOTE:

EARLYCMFM

ON

_

LATE (MFM

AND

LATE TIMING

Precompensation Conditions

TIME (MFM

CLOCK)

CLOCK)

CLOCK)

MFM
ALSO

DATA

MUST

BE

COMPENSATED

(IN)

~~--------------------~I~I--------------------------------~

DIRECTION

STEP/

I

I I

1--200

NS

TO

2MS

0.1

US

MIN

-I

t--

I

I

I

----l

1

I

I

1

I

I

I

--J

6

MS

MIN

DIRECTION

(OUT)

I I ---t

I I

I I

bMS

~

I

I

I

I

I

~------------~Il~------------------------------------------

STEP/

~~----------------~I

I

I

I

I

I

I

I

HEAD

LOAD/

~I--------------------~I

~l-------------------------------------------

I

I •

30

MS

MIN

• I READY

FOR

HEAD

LOAD

AND

HEAD SETTLING TIME

1/

OAT

A TRANSFER

«

I i

Figure 3-4. Track Accessing Timing

SELECT/

~~

________________________________

__

WRITE

Jill

ENABLE/

I

RAW

DATA

Ie

I

II

1

II

1 I

300

NS

I

4.2

US

MAX

--::-

~

:-

:tlOO

NS

:

I

--I

I

I I

I 1

I

-I

I I

1

'--4US

I

:-2US

I -H).51

US

-0.11

US

1

+0.22

US

-1.02

US

i

Figure

3-5.

Double

Frequency

Raw

Data

Timing

HEAD

LOAD/

--,

AND

SELECT/

~i

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

WRITE JII

ENABLE/

: I 0

RAW

DATA

I

:1

:

30

MS MIN

---'

t-

-t

II

I

I

I I

1

300

N5

1

r-±lOO

NS:

I

--.-j

1

I

1

I

I

I
.---2US

o

1

.-IU5

: +<1.25

US

-0.05

US

I +<1.51

US

-0.11

US

Figure

3·6.

MFM

Raw

Data

Timing

3-5

SELECT/

~~,

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

~\-

WRITE

ENABLE/

WRITE

DATAl

---+-~l

,I--'

--

I

I I

~30

MS

MIN--I

I

I I

I

4US

MAX--l

l-

I I

°

I

I

1

---l2US

1

__

I ±O.l'J. I

I-

I
I

----l

I

0 0

1

I

I

I I

I

I

1

1

__

O.2US

TO

I 4

US

-----I

I

I

1.5

US

,---

±O.l"lo

Figure 3-7. Double Frequency Write Data Timing

SELECT /

~~I

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

I

I

WRITE ENABLE/

----tl

11---

....

II

0 I ° 0 0 I

~I----i·

I~i

U------U------U

Ur----U-

WRITE

DATAl

30

MS

~

1

I-----

3US

--t

I

r--

MIN

I-

2US

--l

±

IS

NS

1

......

.........,..--

4US ±

20

NS

---I

I 1

±lO

NS

I I I

4US

MAX----l

~

I

-l

I--

0.1

US

TO

1

I I 1 I I

0.7

US

1

Figure 3·8.

MFM

Write Data Timing

Power-On

to

Data Transfer

Figures 3-9 and 3-10 are provided

as

references for power-

on to data transfer. Power-on

to

write timing

is

depicted

by Figure 3-9, and power-on

to

read timing

is

depicted by

Figure 3-10.

In

both

cases,

it

is

assumed

that

the controller will step the

head

to

track

00

for a reference before stepping

to

a

specified track.

It is

not

necessary to have a cartridge

loaded

to

step the read/write head.

For

explanatory pur-

poses,

it

is

assumed

that

a cartridge

is

loaded and

that

the

controller will wait for the

READY/

interrupt

before

causing head stepping.

FUNCTIONAL

AREAS

The floppy disk drives contain three main functional areas
(see Figure 3-11):

• Control System

• Positioning System

•

Read/Write System

3-6

Control System

The control system provides the interface circuitry between

the controller and the disk drive. The system continuously

monitors the operating status

of

the disk drive. Status
conditions are summarized in a single READY/signal that
can be checked by the controller at any time.

The controller addresses a disk drive for online operation
by activating a unique select line. Commands are then
received and executed

by

the selected disk drive. This

technique allows multiple disk drive units

to

share com-

mon interface lines while remaining individually selectable.

• Command Execution

Commands are received by the disk drive in the form

of

one

or

more interface signals

that

deSignate one

of

the

following operations:

•

SELECT -Places

the

disk

drive

online

with

the

controller

J

"'"

-----------4;1-------11---11

AC

AND

DC

PWR

ON

I
I

1

READY/il

: 1

:~https://manualmachine.com/-----

-I

r--

2.5

SEC

MAX

SELECT/----!i

~,--------~;~~~-----

I
I

DIRECTION~~rl------4'

-1

:--

0.1

US

I MIN

STEP/~:-ruulJU'

0.1

US_,

.---

I I

200

NS

MIN

1 I

----;

:--

TO

2MS

HEADLOAD/~I~----------~S~~

L..j,

l:r,

-------

1

I

WRITE

ENABLE/~r-1

-----------;j:~i~

I I

30

MS

MIN-

1--

1

WRITE

OATAI~j_1

--------i'~~Tlr

1 I

CD

4US

MAX--;

:-

i

Figure 3-9. Power-On

to

Write Timing

J

~I----------II

~t

--~:

~

I---

AC

AND

DC

PWR

ON

I·

I

1

READV/

T

ll---------i~

~:

------il

~

I---

-:

1-

2.5

SEC

MAX

SELECT I

---;

1'-1

-------11

t-/

----II

t----I

~

I

I

DIRECTION

~

.~)

--+1--,1--

______

--t,

r

~

~

_:

~O.lUS

I

MIN

STEPI

---;ilmlJU~

1 I 0 1

US

I I

200

NS

-I

1--

MiN

-I

t--

TO

2MS

TRACK

001

~

1-/

---------.l~

~--

HEAD

LOADI

~

l""'"""'-------~III-----Til

I

l"-

I

WRITE

ENABLEI

I

C

l~-------""""Ii

.~--~II___t_l

~

I I • I

----.J'---------250

US

MIN------+--·

I

30

MS

MIN-I

I-

I I

READ

DATA

-----t

1-1

---------------11

~l

----t,

~

L I

Figure 3-10. Power-On to Read Timing

REAO/WRITE SYSTEM

FROM
CONTROLLER

SU

BSYSTEMS FUNCTIONS

WRITE

DATA

READ.NJRITE
LOGIC

WRITE -

CONVERTS

WRITE

DATA

TO

MAGNETIC

RECORDINGS

READ

DATA

COMMANDS

.. REAO.NJRITE

HEAD
RECORDING

MEDIA

CONTROL SYSTEM

SUBSYSTEMS

COMMAND
DECODE

STATUS
SENSING

FUNCTIONS

EXECUTE
COMMANDS

MONITOR INTERNAL
CIRCUITS

SEND

STATUS

TO

CONTROLLER

STATUS

POSITION INFORMATION

READ

- CONVERTS

MAGNETIC

RECORDING

TO

DATA OUTPUTS

POSITIONING SYSTEM

SUBSYSTEMS

STEPPER

MOTOR

CONTROL
STEPPER

MOTOR

CARRIAGE ASSEMBLY

FUNCTIONS

POSITION

READ/wRITE

HEAD

OVER

SPECIFIED

TRACK
GENERATE TRACK

00

STATUS

Figure

3-11.

Disk Drive General Block Diagram

TO
CONTROLLER

3·7

• STEP - Moves the read/write head in or

out

from track

to

track depending

on

the logic state

of

DIRECTION.

• DIRECTION

- Determines the direction

of

read/write

head movement when

the

STEP pulse

is

received. Head

moves in when

DIRECTION is high,

out

when

DIRECTION

is

low.

• HEAD LOAD - Places the recording surface

of

the disk

in close

contact

with the read/write head

• WRITE - Enables the write circuit and inhibits

the

read

output

• READ - Enables the read

outputs

and inhibits writing

SELECT and HEAD LOAD instructions

must

precede a

read

or

write operation.

SELECT enables

input/output

gates, while HEAD

LOAD

permits writing

or

reading

on

the floppy disk.

STEP and DIRECTION move the read/write head

to

either

a higher

or

lower track position. Stepping may

occur

at a

6-millisecond

per

track rate

or

slower. Since relative track

positioning

is

employed, the controller maintains current

track position and generates the

number

of

pulses necessary

to reach a new track position.

Once positioned, the con-

troller designates a read operation or a write operation.

In a write operation, the disk drive records the

data

pre-

sented

by

the controller. In a read operation, data

is

decoded

by

the disk drive and

routed

to

the controller.

•

Status

Sensing

Five disk drive status signals

are-

gated immediately

to

the

I/O lines when the controller selects a disk drive.

• WRITE PROTECTED (Optional) - A hardware write­protect

condition exists.

• TRACK

00

- Read/write

head

is positioned at track 00.

• INDEX -

Start

of

a track

• READY -

Not

gated with SELECT and signifies

that

the disk drive

is

operational

• SECTOR (Optional) -

Start

of

a sector

READY and WRITE PROTECTED are steady levels.
READY status indicates

that

the disk

is

up

to

speed, dc

power

is

within limits, and a floppy disk

is

loaded. WRITE

PROTECT signifies

that

write data

cannot

be recorded

on

the floppy disk.

3-8

An INDEX pulse occurs once per disk revolution.

TRACK

00

status

is

available for initializing the controller

track address register. This signal is developed form a

photo­transducer when the carriage is aligned mechanically with
track

00.

When the hard-sector

option

is

installed, 32 sector pulses

are transmitted to the controller for each revolu

tion

of

the

floppy disk.

Positioning System
The positioning system responds

to

stepping pulses (STEP

command)

received from the controller by moving the

read/write head one track position per pulse.

One major

. circuit and two mechanisms accomplish this operation.

• Stepper Motor Control
The stepper

motor

control converts each serial step pulse

to

a 2-bit count-up or count-down sequence. Each decode

energizes one quadature winding

of

the stepper

motor

and

causes two IS-degree rotations

of

the

motor

shaft. One

track position corresponds

to

30 degrees

of

rotation.

•

Stepper

Motor

The variable-reluctance stepper

motor

positions the

readl

write head precisely. The stepper

motor

is

energized

by

+24 vdc and operates in

detent

mode.

An internally generated magnetic field holds the

rotor

in a

flXed

position. To move from

detent,

one

of

four control

lines is grounded. The

rotor

subsequently moves

to

the

next

detent. Sequential grounding

of

the

control

windings

causes the

rotor

to

rotate

through

detent

positions at the

maximum rate

of

167 tracks per second.

A helical groove

on

the exposed

rotor

shaft converts

rotary movement

to

linear movement

to

drive the carriage

assembly.

• Carriage Assembly
The carriage assembly rides between a stationary guide rod

and a helical drive shaft. The guide rod serves

as

a guide,

while the helical drive shaft performs the positioning.

The read/write head, attached

to

the underside

of

the

carriage assembly, penetrates the plane

of

the recording

surface when a floppy disk

is

loaded. This HEAD LOAD

command releases a spring-loaded head load arm

that

moves

the floppy disk

into

contact

with

the read/write head to

allow read/write operations.

Read/Write System

The read/write system records encoded data during a write
operation and retrieves

data

during a read operation. The
WRITE ENABLE signal from the controller designates a
read operation when high

or

a write operation

when

low.

• Read/Write Operation

The read/write head

is

essentially an electromagnet

that
can concentrate a strong magnetizing force over a very
small area

of

the adjacent recording surface. When record-

ing, the flux field is alternated

to

magnetize the disk

with

the desired bit

pattern.

The read/write head also contains a tunnel-erase electro­magnet, the function

of

which

is

to erase the edges

of

the

recorded track

as

data

is

being written. The

width

of

the

track

is narrowed

to

approximately

0.012

inch

by

this

technique

to

minimize interference and crosstalk between

tracks.

When reading, the read/write electromagnet operates as a
sensor. A flux reversal in the recorded track induces a
voltage across the coils

of

the electromagnet. This voltage

is amplified and conditioned

to

recover the recorded infor-

mation.

MECHANICAL

SYSTEM

The disk drive comprises the following mechanisms (see
Figure 3-12):

• Drive Mechanism

• Disk Centering Mechanism

• Head Load Mechanism

• Positioning Mechanism

Drive Mechanism

The drive system (Figure 3-13) rotates the disk

by

using a

single-phase

motor

that

is

selected

to

match the primary

power

of

the controller system. Various drive motors are

available

to

accommodate primary power ranging between

100

and

240

vac

at

50

or

60

Hz.

The disk drive attains ready

status within 2.5 seconds

of

primary power application.

Rotation

of

the disk

is

through a belt and pulley connected

to

the other end

of

the

motor

shaft. The drive pulley and

drive belt are selected for either

50

or

60

Hz

input

power.

Rotational speed

of

the floppy disk is

360

rpm. The disk

is engaged with the drive

by

the centering cone

of

the disk

centering mechanism.

r----

---------,

CENTERING

CONE

READ/WRITE

HEAD

L

___

_

DISK

I

I

VIEW

SHOWING

HELIX

DRIVE.

Figure 3-12.

Di5k

Drive

Mechanical System Pictorial View

3-9

DRIVE
MOTOR

Figure 3-13. Drive Mechanism

Disk Centering Mechanism

SPINDLE

DRIVE

PULLEY

The disk centering mechanism consists

of

a centering cone

and a hollow drive hub. In the unload position, the center-

ing cone

is

moved upward to create an opening through

which the floppy disk

is

inserted. In this position, the

centering cone

is

disengaged from the disk and from the

drive hub.

To load a disk, the operator inserts the floppy disk, then
presses down and latches the load handle. This causes the
centering cone

to

enter the hollow drive hub and

to

ex­pand the centering cone, which centers the disk in the
correct track alignment. Spring pressure

is

applied the

centering cone and drive hub

to

clamp the disk and to

provide rotary motion.

Head Load Mechanism
The head load mechanism (Figure 3-14) consists

of

the
head load arm, the read/write head, and the head load
solenoid

(not

shown). Head loading

is

controlled by a head
load command originating at the controller. This command
actuates the head load solenoid, which causes the head
load pad

to

press the disk against the read/write head so

that the read/write head

is

in constant contact with the re-

cording surface

of

the disk during a read or write operation.

When

the head

is

loaded, a pad on the arm

of

the solenoid

applies pressure to the cartridge, which

is

between the pad

and a raised portion

of

the frame casting, to align the disk

in the proper plane before

it

passes over the read/write

head.

3-10

CENTERING

CONE

SPINDLE

DRIVE:.-.._----..J

PULLEY

A.

CENTERING

CONE

AND

READ/WRITE

.-EAD

UNLOADED

CONE

EXPANDER

HEAD

LOAD

PAD

B.

CENTER I NG

CONE

AND

READ/WR

ITE

HEAD

LOADED

Figure

3-14.

Disk Centering and Head Load Mechanism

Positioning Mechanism
The positioning mechanism (Figure 3-15) comprises a

carriage assembly and a bidirectional stepper motor. The
rotational movements

of

the stepper

motor

are converted

to

linear motion by the helical drive shaft.

The read/write head carriage

is

driven

by

the helical drive

shaft. The carriage movement

is

guided toward and away

from the center

of

the disk by a guide rod. When the

stepper motor

is

pulsed, the helical drive shaft rotates

clockwise

or

counterclockwise

to

move the carriage assem-

bly in or ou

t.

The stepper motor includes four (quadrature) windings. In
detent, current flows in one winding and maintains the
rotor in electromagnetic detent. For positioning, one or
more pulses are applied sequentially to the quadrature
windings and cause an imbalance in the electromagnetic
field. The rotor

of

the stepper motor, consequently,
revolves through detent positions until the step pulses are
halted. The rotor then locks in

that

position. The sequence

in which the quadrature windings

of

the stepper motor are
pulsed dictates rotational direction and, subsequently,
higher or lower track addressing from a relative position.

Track

00 (home) position

is

the disk drive reference track.

This

position

is

sensed

by a phototransducer that generates

TRACK

00

TRANSDUCER

CARRIAGE
ASSEMBLY

HEAD

LOAD

ARM

Figure

3-1S.

Positioning Mechanism

TRACK

00

status. This status is sent

to

the controller for

initial track positioning.

All

track addressing

is

relative. The
controller generates step pulses to position the carriage
from the current track to a new track.

LOGIC SYMBOLOGY AND DEFINITIONS

The disk drives use S-volt TTL logic, where a voltage more

positive than +2.2 volts

(tum-on

theshold) is considered a
logical high, and a voltage more negative than +0.4 volt
(turn-off threshold)

is

considered a logical low .

Figure 3-16 shows the logic symbology and contains a

definition for each element shown.

DETAILED LOGIC DESCRIPTION

Detailed logic descriptions

of

the disk drives are divided

into three major functions:

• Control Logic

• Read/Write Positioning Logic

• Read/Write Logic

The significant interface signals between the major circuits

are

shown

in

Figure

3-17.

Control Logic
The control logic contained in the disk drives perform

three functions:

• Generates and detects index and sector pulses

• Monitors disk speed for disk drive ready

• Actuates the head load/unload solenoid

The first two operations (Figure 3-18) utilize the index
hole that

is

perforated in the disk. The time at which index

occurs

is

directly proportional

to

disk speed. Thus, by
comparing index timing against a known time base, the
percentage

of

full disk rotational speed can be determined.

Also, INDEX

is

routed

to

the controller

to

signify start

of

track. Head load/unload operation

is

initiated by an input

control signal that

is

enabled after disk operational speed

is

reached.

• Index Pulse Transducer
A light-emitting diode (LED) and phototransistor are

physically positioned

in

the disk drive

to

monitor the index

hole.

As

the index hole passes between the two devices,

light passing from the LED

to

the phototransistor (Figure

3-19)

results

in a

2·millisecond,

positive

4.0-volt

pulse.

The

3-11