Shugart SA850 User manual

SA850/851

Bi-CompliantTM g

Double

Sided

Diskette

Storage

Drive

~®Shugart

c:::J

TABLE OF CONTENTS

.1.0 Theory of Operations . . . . .

........

1.1

General Operations.

1.1.1 Head Positioning

1.1.2 Diskette Drive Spindle

.......

1.1.3 Read/Write Heads

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

1.2 Recording

Format.

. .

.....

1.2.1 Bit Cell

..........

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

1.2.2 Byte

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

1.2.3 Recording Format (Double Density) .

1.2.3.1 Rules of Encoding .

1.2.4 Tracks. . . .

.....

1.2.5 Track Format

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

1.2.5.1 Sector Recording Format

1.2.5.2 Soft Sector Recording Format.

1.2.6 Typical Track Index Format

1.2.6.2. . . . . . . . .

.....

1.3.0 Track Accessing

........

1.3.1

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

1.3.2 . . . . . . . . . . .

......

1.3.2.1. .

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

1.3.3 Actuator Control Logic (Figure 21) . . .

........

1.3.3.1 Power

Reset. .

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

1.3.3.2 Forward Seek

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

.....

1.3.3.3 Reverse Seek

.........

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

1.3.4 Track Zero

Indicator.

..........

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

1.4.0 Read/Write Operations

..........

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

.........

1.4.1

. . . . . . . . . . .

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

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

1.4.2 . . . . . . . . . . . . . .

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

1.4.3 . . . . . . . . . . .

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

..........

. 12

........

.....

. . 13

......

........

1.4.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.....

1.4.5 . . . . . . . . . . . . . . . . . .

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

1.5.0 Read/Write Head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.5.1

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

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

....

1.5.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.........

1.5.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..........

1.5.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

........

1.6.0 Write Current Operation (Figure 32)

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

. ·

1.6.1

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

1.6.2 . .

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

1.6.3

.......

1.6.4

...........

1.7.0 Read Circuit Operation (Figure 33)

1.7.1

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

1.7.2

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

1.7.3

..........

1.8.0

Interface.

..........

1.8.1

J1/P1

Connector.

......

1.8.2

Power . . . . . .

......

1.8.3

Power.

......

1.8.4 Output Lines

...

.........

.......

. . . . . . . . . . . . . . . . . . . . . . . . . . . 20

.20

...

. .

....

.22

2.0 Maintenance Section

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

2.1.0 Maintenance Features

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

2.1.1

Alignment Diskette

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

2.1.2 SA809 Exerciser

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

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

2.1.3 Special Tools

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

2.2.0 Diagnostic Techniques

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

'.'

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

2.2.1

Introduction

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

'.'

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

2.2.2

"Solt

Error" Detection and Correction

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

2.2.3 Write Error

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

2.2.4 Read Error

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

2.2.5 Seek Error

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

2.2.6 Test Points SA850/851

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

2.2.7 Connectors

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

2.2.7.1

.........

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

2.2.7.2. . . . . . . . . . . . . . . . . .

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

2.2.7.3 J3/P3

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

2.2.7.4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2.7.5 J5/P5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.7.6 J6/P6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.0 Preventative Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 Preventive Maintenance Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 Cleanliness

....

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

3.4 Cautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.0 Removals, Adjustments

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

;

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

2..4.1

Motor Drive

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

2..4.1.1

Drive Motor Assembly: Removal and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2..4.1.2

Motor Drive Pulley

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

2..4.2

Head Cover Shield Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4.3 Cartridge Guide Access

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

2.4.4 Sectorllndex

LED

Assembly: Removal and Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4.5 Write Protect Detector

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

2.4.5.1 Write Protect Detector: Removal and Installation

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

2.4.5.2 Write Protect DetectorAdjustment

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

2.4.6 Head Load Mechanism Assembly

'.'

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

2.4.6.1 Head Load Mechanism: Removal and Installation

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

2.4.6.2 Head Load Mechanism Adjustment

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

2.4.7 Index/Sector Photo Transistor Assembly

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

2.4.7.1 Index/Sector Photo Transistor Assembly: Removal and Installation

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

2.4.7.2 Index/Sector Adjustment

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

2.4.8 Spindle Assembly

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

2.4.8.1 Clamp Hub Removal

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

2.4.9 Cartridge Guide

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

2.4.9.'1

Cartridge Guide Removal

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

2.4.9.2 Cartridge Guide Adjustment . . . . . . . . . . . . . . .

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

2.4.10 Head Amplitude Check

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

2.4.10.1 Head Actuator Assembly: Removal and Installation

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

'2.4.10.2 Head Penetration Adjustment

.......

..........

.........

..........

, . , . .

2.4.10.3 Head Radial Alignment

........

, ,

...........

.......

.........

, , . . . . . . . . . 43

2.4.10.4 Read/Write Heads Azimuth Check

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

..........

"..

2.4.11 Door Lock Solenoid and

Use

LED

Assembly Removal

..........

........

2.4.12 Track 00 Detector: Removal and Installation

..........

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

, . . . .

2.4.12.1 Track 00/76 Stop Adjustment

..........

...........

...

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

...

2.4.12.2 Track 00 Detector Assembly Adjustment . ,

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

2.4.13 Door Lock Solenoid and

Use

LED

Assembly Removal. . .

...........

Figure

LIST

ILLUSTRATIONS

1. SA850/851 Functional

Diagram

.......

Bi-Compliant Read/Write Head

...........

Data

Pattern

....

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

Bit

Cell.

. . . . . . . . . .

..........

Byte...

. . . . . . .

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

Data

Bytes.

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

.....

FM,

MFM

and M2FM Encoding

.......

SA801

Sector

Recording

Format

Track

Format

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

MFM

Track

Format

Comparison

......

Index Address

Mark

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

Address

Mark

FM . . . . . .

.........

Data

Address

Mark

FM . . . . . .

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

Deleted

Data

Address

Mark

FM .

MFM

Index

Address

Mark

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

MFM

Address

Mark

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

MFM

Data

Address

Mark.

. . . . . . . . .

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

MFM

Deleted

Data Address

Mark.

. .

......

MFM

Index Pre

Address

Mark

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

MFM

Pre

ID/Data

Address

Mark

. . . . . . .

........

Activator

Control Logic

.........

Count 0 . . . . . . . . . . .

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

Count 1

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

Count 2 . . . . . . . . . . .

......

Count 3

......

Byte

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

Basic R/W Head

Recorded Bit

......

Reading a

Bit.

. . .

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

1F and 2F Recording Flux and Pulse Relationship

Read/Write

Heads.

. . . . . . . . .

......

Write

Circuit

Functional

Diagram

........

Read

Circuit

Functional

Diagram

Data Separation Timing

Diagram

......

Interface

Connections.

Interface

Signal

Driver/Receiver.

Head

Load

Mechanism

Adjustment

..........

Head Load Timing .

Head Penetration Tools

.........

Dial

Indicator

. . . .

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

Penetration Plate Installation

Dial

Indicator

Installation

......

Installation

Check

..........

.. ..

.......

· .

.....

.......

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

. . . . . . . .

· . 16

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

......

..........

· . 18

· . 19

.......

....

...

.23

.......

.33

.......

.38

.........

· . 40

...

.......

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

10.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

2·3.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

Correct

Penetration.

Penetration

Adjustment.

Head Radial

Alignment

Motor

Plate . . . . . . . . . . . . . 44

. . . . . . . . . . . . . . 44

III

48. Azimuth Burst Patterns

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

FlowCharts

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

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

logic

Diagrams :

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

.....

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

Physical Locations

...........

: . . . . .

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

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

49.

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

49. (2

...........

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

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

Illustrated Parts Catalog

...........

...

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

50.. "

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

...

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

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

..........

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

" "

.........

Schematic Diagrams

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

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

1.0 THEORY OF OPERATIONS

1.1

GENERAL OPERATIONS

The SA850/851 Diskette Drive consists of read/write and control electronics, drive mechanism, read/write

heads, track positioning mechanism, and removable Diskette. These components perform the following

functions:

• Interpret and generate control signals.

• Move read/write heads to the desired track.

• Read and write data.

The relationship and interface signals for the internal functions of the SA850/851 are shown

Figure

The Head Positioning Actuator positions the read/write heads to the desired track

the Diskette. The Head

Load Actuator loads the read/write heads against the Diskette and data may then be recorded or read from

the Diskette.

The electronics are packaged

the

PCB.

The

PCB

contains:

Index Detector Circuits (Sector/lndex for SA851).

Head Position Actuator Driver

Head Load Solenoid Driver

Read/Write Amplifier and Transition Detector.

Data/Clock Separation Circuits (SA851).

Write Protect

Drive Ready Detector Circuit.

Drive Select Circuits.

Side Select Circuit.

10.

Use and Door Lock Circuits

11. Write Current Switching/Read Compensation

1.1.1

HEAD POSITIONING

The read/write heads are accurately positioned by a Fasflex™ metal band/stepping motor actuator system.

A precision stepping motor

used to precisely position the head/carriage assembly through the use of a uni-

que metal band/capstan concept. Each 3.60 rotation of the stepping motor moves the read/write head one

track

discrete increments.

1.1.2 DISKETTE DRIVE SPINDLE

The Diskette drive motor rotates the spindle at 360 rpm through a belt-drive system. 50 or 60 Hz power

ac-

commodated by changing the drive pulley and belt. A registration hub, centered

the face of the spindle,

pOSitions the Diskette. A clamp that moves

conjunction with the latch handles fixes the Diskette to the

registration hub.

1.1

3 READ/WRITE HEADS

READ

LOGIC

WRITE

LOGIC

SIDE

READ

DATA

SEP DATA (FMI

SEP CLOCK (FMI

WRITE CURRENT

WRITE DATA

WRITE GATE

WRITE PROTECT

SELECT POWER ON RESET

INDEX DETECTOR

INDEX LED

STEPPER

...

STEPPER

-A

,·B

STEPPER

-8

CONTROL

LOGIC

FIGURE 1. SA850/851 FUNCTIONAL DIAGRAM

SIDE SELECT

IN USE LED

HEAD LOAD (OPTIONAL!

STEP

DIRECTION/SIDE SELECT (OPTIONAL!

DRIVE SELECT

TRACK

INDEX

READY

SECTOR (851)

ALTERNATE I/O (3 LINES)

TWO SIDED

(OPTIONAl)

DISK CHANGE

The proprietary heads are a single element

ceramic

read/write head with straddle erase elements to provide

erased areas between data tracks. Thus normal interchange tolerances between media and drives will not

degrade the signal to noise ratio and insures diskette interchangeability.

The read/write heads are mounted on a carriage which is pOSitioned by the Fasflex™ actuator. The head

carriage assembly utilizes a combination flexured/rigid head mounting system. This allows the flexured head

to load the media against its rigidly mounted counterpart (see Figure

2).

The diskette is held in a plane perpendicular to the read/write head by a platen located on the base casting.

This precise registration assures

perfect

compliance

with the read/write heads. The read/write heads are

direct

contact

with the diskette. The head surface has been deSigned to obtain maximum signal trans·fer to

and from the magnetic surface of the diskette.

FIGURE 2. BI-COMPLIANT READ/WRITE HEAD

1.2 RECORDING FORMAT

The

format

of the data recorded on the Diskette is totally a function of the host system. Data is recorded on

the diskette using frequency modulation as the recording mode, i.e., each data bit recorded on the diskette

has an associated

clock

bit recorded with it, this is referred to as FM encoding. Data written on and read

back from the diskettes takes the form as shown

Figure

The binary data pattern shown represents a

101.

1.2.1 BIT CELL

As shown

Figure

the

clock

bits and data bits (if present) are interleaved. By definition, a Bit Cell is the

period between the leading edge

one

clock

bit and the leading edge of the next

clock

bit.

1.2.2 BYTE

CLOCK BITS

~BIT

CELL----1

FIGURE 3. DATA PATIERN

...

B_IT_S

....

DATA BITS

FIGURE 4. BIT CELL

A Byte, when referring to serial data (being written onto or read from the disk drive), is defined as eight

(8)

consecutive bit cells. The most Significant bit cell is defined as bit

celiO

and the least significant bit cell is

defined as bit cell

When reference is made to a

specific

data bit (i.e., data bit

3),

it is with repsect to the

corresponding bit cell (bit cell

3).

During a

write

operation, bit

celiO

of each byte is transferred to the disk drive first with bit cell 7 being

transferred last. Correspondingly, the most significant byte

of.

data is transferred to the disk first and the

least significant byte is transferred last.

When data is being read back from the drive, bit celiO of each byte will be transferred first with bit cell 7 last.

As with reading, the most significant byte will be transferred last from the drive to the user.

Figure 4 illustrates the relationship of the bits within a byte and Figure 6 illustrates the relationship of the

bytes for read and

write

data.

C C o

BITCELL 0

USB

-----------------------B~-----------------------

BINARY REPRESENTATION OF:

DATA BITS

CLOCK BITS

HEXADECIMAL

REPRESENTATION

DATA BITS

CLOCK BITS

BIT CELL 0 OF BYTE 0 IS

FIIRST

DATA TO

SENT

THE DRIVE WHEN

WIfIITING

AND

FROM THE

Df~IVE

WHEN READING

o o

FIGURE 5. BYTE

FIGURE 6. DATA BYTES

1.2.3 RECORDING FORMAT (DOUBLE DENSITy)

CDC

BIT CELL 7 OF BYTE 17 IS

LAST DATA TO

SEIH

THE DRIVE WHEN WAITING

AND

FROM THE

DRIVIE

WHEN READING

Double capacity can be obtained by use

MFM (modified frequency modulation) and

M2FM

(modified,

modified frequency modulation) rather than

(frequency modulation) which is the standard method

en-

coding data on the diskette.

The differences between FM, MFM and

M2FM

encoding are shown

Figure

Note that MFM and

M2FM

result

a 1 to 1 relationship between the

"flux

changes per

inch"

and the bits per inch recorded Oln the

diskette. This also results

a doubling of the data transfer rate, from 250 to 500

KBS,

when compared to

Data error rate performance equal to standard capacity diskettes using

encoding can be achieved by us-

ing:

• The SA850/851 diskette drive with its proprietary ceramic/ferrite read/write head.

• Phase locked loop (VFO) data separator

• Write precompensation.

Provision

the phase locked loop data separator and write precompensation circuitry is the responslibility

of the user of the SA850/851 diskette drive.

Shugart Associates will provide design information, as required, to SA850/851 users who desire to incor-

porate double capacity diskette drives

their products.

The

bit cell for MFM and

M2FM

encoded data is one half the duration of the bit cell for

encoded data.

Also, unlike FM, and MFM and

M2FM

bit cell does not always contain a clock bit at its leading edge. This lack

of clock bit makes data separation more

complex

Also, the window size is half the

window size, which

results

less tolerance to bit shift. The only reliable method to separate MFM and

M2FM

encoded data is

through use of a phase locked loop (VFO) type

data separator. The VFO, once synchronized, tracks the

data and generates clock and data windows, improving the bit shift tolerance over the conventional

"hard"

data separators commonly used

recording, which use windows

fixed timing.

1.2.3.1 RULES OF ENCODING

Encoding:

• Write data bits at the center of the bit cell.

• Write clock bits at the leading edge of the bit cell.

MFM Encoding:

• Write data bits at the center of the bit cell.

• Write clock bits at the leading edge of the bit cell if:

There

data bit written

the previous bit cell, and

There will

data bit written

the present bit cell.

M2FM

Encoding:

• Write data bits at the center of the bit cell.

• Write clock bits at the leading edge of the bit cell

if:

1) There

data bit or clock bit written

the previous bit cell, and

There will be not data bit written

the present bit cell.

NOTE:

M2FM/MFM, the write oscillator frequency

doubled, while maintaining the same flux changes per

inch

FM. Thus, the bit cell

M2FM/MFM

that

FM. Data transfer rate

also doubled, since a

1 to 1 relationship exists between flux changes per inch and bits per inch

to 1

FM).

BIT

CELLS~

______

____

______

____

___

-L

____

121

ID D D

~~LLS

____

....

1_1

....

1_1

.........

.L..I

....

1_°

.....

1_°

..........

....

1---,

D D D D

MFM

D D D D D

4/31

4/51

, ,

FIGURE

FM. MFM AND

M2FM

ENCODING

, , ,

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