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Preliminary Service Manual November 1983 PIN 39259-0

Shugart 300 Flexible Disk Storage Drive

ShUI(BIt

Shugart 300 Flexible Disk Storage Drive

Preliminary Service Manual

For Single-Sided

3.5 Inch Microfloppy Applications

First Edition November, 1983

Copyright 1983 Copyright 1984 All Rights Reserved

First Edition First Printing, 11/83 Second Printing, 2/84

Third Printing, 6/84

Printed in U.S.A.

Written and Published by

Shugart Corporation 475 Oakmead Parkway Sunnyvale, CA 94086

(408) 737-7900 TWX: 910-339-9355

SHUGART SUVL

TABLE OF CONTENTS

Page

TABLE OF CONTENTS . . . iii

LIST OF FIGURES. . . . .. vi

LIST OF TABLES . . . . . . .. vii

ABBREVIATIONS/MNEMONICS . . . ; . . . , viii

NOTICE TO USERS . . . viii SECTION I INTRODUCTION . . . 1-1

1.1 Purpose . . . 1-1 1.1.1 General Description . . . 1-1 1.2 Specifications Summary . . . 1-1 1. 2.1 Performance Specifications. . . . 1-1 1.2.2 Functional Specifications . . . 1-2 1.2.3 Physical Specifications . . . 1-2 1.2.4 Reliability Specifications . . . 1-2 1.3 Functional Characteristics . . . 1-3 1.3.1 Read/Write and Control Electronics . . . 1-4 1.3.2 Drive Mechanism . . . 1-4 1.3.3 Precision Track Positioning Mechanism ... 1-4 1.3.4 Read/Write Head . . . 1-4 1.3.5 Recording Format . . . 1-4 1.4 Recommended Receiving Inspection . . . 1-4 1.4.1 Unpacking the Drive . . . , . . . 1-4 1.4.2 Physical Checkout . . . 1-5 1.5 FunctionalOperations . . . 1-5 1. 5. 1 Power Sequencing . . . 1-5 1.5.2 Drive Selection . . . 1-5 1.5.3 Motor On . . . " . . . 1-5 1.5.4 Track Accessing . . . 1-5 1.5.5 Step Line . . . 1-6 1.5.6 Normal Step Mode ... , . . . 1-6 1.5.7 Buffered Step Mode . . . 1-7 1.5.8 Read Operation . . . 1-7 1.5.9 Write Operation . . . 1-9 1.5.10 Sequence of Events . . . 1-10 1. 5.11 Microcartridge Handling . . . 1-11 1.5.12 Microcartridge Loading . . . 1-11 1.6 Mounting . . . 1-12 SijCTION II ELECTRICALINTERFACE . . . 2-1

2.1 Introduction . . . 2-1 2.2 Signal Interface ... , . . . 2-1 2.2.1 Input Lines . . . 2-1 2.2.2 Input Line Terminations . . . , ... 2-3 2.2.3 Drive Select 1-4 ... 2-3 2.2.4 Motor-On . . . 2-3 2.2.5 Direction Select ... , . . . 2-4 2.2.6 Step . . . , . . . 2-4 2.2.7 Write Gate . . . 2-4 2.2.8 Write Data . . . 2-4 2.2.9 In Use Input . . . 2-4 2.2.10 Output Lines . . . 2-4 2.2.11 Track 00 . . . 2-4 2.2.12 Index Signal . . . 2-4 2.2.13 Sector . . . 2-5 2.2.14 Read Data . . . 2-5 2.2.15 Write Protect . . . 2-5

iii

TABLE OF CONTENTS (CONT.)

Page 2.3 Power Interface . . . 2-5 2.4 Frame Ground . . . 2-6 SECTION III PHYSICALINTERFACE . . . 3-1 3.1 Introduction . . . 3-1 3.2 Jl/P1 Connector . . . 3-2 3.2.1 J2/P2 Connector ... 3-2 3.3 Frame Grounding . . . 3-2 SECTION IV THEORY OF OPERATION . . . 4-1 4.1 Introduction . . . 4-1 4.2 Microprocessor Logic ... 4-1 4.3 Read/Write Operations ... 4-2 4.4 Read/Write Head . . . 4-4 4.5 Write Circuit Operation ... 4-4 4.6 Read Circuit Operation . . . 4-5 4.7 Drive Motor Control . . . 4-6 4.8 Index Detector . . . 4-6 4.9 Track Zero Indication ... 4-6 4.10 Track Accessing . . . 4-6 4.11 Drive Select . . . 4-9 4.12 Write Protect . . . 4-9 4.13 Drive Status . . . 4-9 4.14 Auto Shutter Opening/Cartridge Eject Mechanism ... 4-10 4.15 Elevator Operation . . . 4-10 4.16 Drive Status . . . 4-10 SECTION V MAINTENANCE . . . 5-1

5.1 Maintenance Equipment ... 5-1 5.1.1 Alignment Diskette ... 5-1 5.1.2 Exerciser PCB ... 5-1 5. 1. 3 Special Tools . . . 5-1 5.2 Diagnostic Techniques ... 5-2 5.2.1 Basic Diagnosis Techniques ... _ ... 5-2 5.2.2 "Soft Error" Detection and Correction ... 5-2 5.2.3 Write Error ... 5-2 5.2.4 Read Error ... " ... 5-2 5.2.5 Seek Error ... 5-2 5.2.6 Trouble-Shooting ... 5-2 5.2.7 Self-Test ... 5-7 5.2.8 Test Point Usage ... 5-8 5.3 Adjustments . . . 5-9 5.3.1 Head Radial Alignment ... 5-9 5.3.2 Track Zero Adjustment ... 5-11 5.3.3 Head Amplitude Check ... 5-11 5.3.4 Index Adjustment ... ' ... 5-12 5.4 Motor Speed Adjustment ... 5-12 5.4.1 Motor Speed Adjustment (Using Fluorescent Lighting) ." ... 5-12 5.4.2 Motor Speed Adjustment (Using a Frequency Counter) ... 5-12 SECTION VI REMOVAL AND REPLACEMENT PROCEDURE ... 6-1

6.1 Face Plate Removal and Replacement ... 6-1 6.2 Drive PCB Removal and Replacement ... 6-1 6.3 Elevator Removal and Replacement ... 6-1 6.4 Write Protect Switch Assembly and Disassembly ... 6-2

iv

TABLE OF CONTENTS (CONT.)

Page 6.5 Cartridge Eject Parts Removal and Replacement ... 6-2 6.6 Actuator Plate Assembly ... 6-2 6.7 Head and Carriage Assembly ... 6-2 6.8 Stepper Motor Removal and Replacement ... 6-3 6.9 Drive Motor and Spindle Assembly Removal and Replacement ... 6-3 6.10 Track Zero and Elevator Detector Assemblies Removal and Replacement ... 6-4 6.11 Load Pad Removal and Replacement ... 6-4 SECTION VII ILLUSTRATED PARTS CATALOG ... 7-1 7. 1 Description... 7-1 7.2 Quantities Per Assembly ... 7-1 7.3 Recommended Spare Parts Stocking Guide ... 7-1 SECTION VIII SPARE PARTS ORDERING INFORMATION ... 8-1 8.1 Routine Order Entry ... 8-1 8.2 Emergency Order Entry ... 8-1 SECTION IX PACKAGING INFORMATION ... 9-1 SECTION X SCHEMATIC DIAGRAMS ... 10-1

v

LIST OF FIGURES

Figure Title Page

1-1 1-2 1-3 ' 1-4 1-5 1-6 1-7 1-8 1-9 1-10 1-11 1-12 1-13 2-1 2-2 2-3 2-4 3-1 3-2 3-3 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12 4-13 4-14 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 6-1 7-1 7-2 7-3 7-4 7-5 7-6 7-7 10-1 10-2 10-3 10-4 10-5

SA300 Single-Sided 3,5-lnch Microfloppy Disk Drive .... , ... , , , , .... , .. , , , , , . , , , , , ,. 1-0 Functional Diagram .... , . , , . , . , , , . , . , , ... , .. , ... , , . , , .... , , , , , , , , . , , , , . .. 1-3 Track Access Timing ., ... " ... ,., ... , .. , .. , " ' , " , . , . , " " , ... ,.... 1-6 Normal Step Mode .. , . . . . . . . . . . . . . . . . . . .. 1-6 Buffered Step Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-7 Read Initiate Timing . . . '.' . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-8 Read Data Timing (FM) . , . . . 1-8 FM and MFM Code Comparisons . . . . . . . . . . . . . . . . .. 1-8 Write Initiate Timing . . . . . . . . . . . . . . . . . . . . .. 1-9 Write Data Timing (FM) . . . 1-9 General Control and Data Timing Requirements. . . . . . . . . . . . . .. 1-10 SA130 Microcartridge Nomenclature . . . 1-11 Recommended Mounting Positions . . . . . . . . . . . . . . . . . . .. 1-12 Interface Connections . . . 2-2 Interface Signal Driver/Receiver . . . 2-3 Track Zero Circuit . . . 2-5 Track Zero Timing . . . 2-5 Interface Connectors - Physical Locations . . . 3-1 J1 Connector Dimensions . . . , . . . 3-2 J2/P2 Connector . . . 3-2 Byte . . . 4-2 Basic Read/Write Head . . . 4-2 Recording A Bit . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 Reading A Bit . . . 4-3 IF and 2F Recording Aux and Pulse Relationships . . . . . . . . . . . . . . . . . . . .. 4-3 Read/Write Heads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-4 Write Circuit Functional Diagram. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . 4-5 Read Circuit . . . 4-6 Stepper Logic . . . . . . .. 4-7 Power On Reset. . . . . . . . . . . . . . . . . .. 4-8 Stepper Timing . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-8 Drive Select, Motor On and In Use . . . 4-9 Cartridge Shutter Opening/Cartridge Eject Mechanism . . . . . . . . . . . . . . . . . . . . . 4-11 Drive Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4-13 Write Protect Inoperative . . . 5-3 Diskette Not Rotating . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-4 Track 00 Indicator Inoperative . . . 5-5 Drive Not Coming On Line . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6 Index Pulse Inoperative . . . ; . . . 5-7 Test Point Locations and Probe Positioning . . . 5-8 Head Radial Alignment . . . 5-9 Head Radial Alignment . . . 5-10 Index Burst Timing. . . . . . . . . . . . . . . . . . .. 5-10 Brushless Spindle Motor Assembly . . . 5-12 Load Pad Assembly . . . . . . . . .. . . . . . . . . . . .. . . . . . .. 6-4 Drive PCB and Face Plate Assembly . . . 7-2 Platform Ejector/Elevator Assembly . . . 7-3 Ejector Head and Carriage Assembly . . . . . . . . . . . . . . . . . . . . . . . . .. 7-5 Stepper Motor Assembly . . . ; . . . . . . .. 7-6 Brushless Spindle Motor, TK 0 and Elevator Detector Assembly . . . . . . . . . . . . .. 7-7 Drive PCB Component Locations. P /N 25281-03 (Component Side) . . . . . . . . . . . . . . . . . .. 7-8 Drive PCB Component Locations. PIN 25281-03 (Solder Side) . . . . . . . . .. 7-9 Write Protect - Track 00 - Elevator Down Sensor Connections. . . . . . . . . . . .. 10-2 Spindle Motor Harness Connections . . . 10-2 Stepper Motor Harness Connections . . . . . . . . . . . . .. 10-3 Read/Write Head Connection . . . 10-3 Control PCB Schematic (2 Sheets) . . . 10-5

vi

LIST OF TABLES

Table Title Page

3-1 Recommended J1 Connectors ... 3-2 7 -1 SA300 Spare Parts Stocking Guide . . . .. 7-12

vii

ABBREVIATIONS /MNEMONICS

bpi Bits Per Inch

NHA

Next Higher Assembly

fei Aux Changes Per Inch

NRZI

Non Return to Zero

FM Frequency Modulation

PCB

Printed Circuit Board

ID

Identification

PM

Preventive Maintenance

I/O

Input/Output ^tp Test Point

IPC

Illustrated Parts Catalog tpi Tracks Per Inch

LED

Light Emitting Diode Vin Voltage In

MFM

Modified FM Vout Voltage Out

MTBF

Mean Time Between Failures

2F

Double Frequency

MTTR

Mean Time To Repair

NOTICE TO USERS

While every effort has been made to ensure that the information provided herein is correct, please notify us in the event of an error or inconsistency. Direct any comments to:

Shugart Corporation

Technical Publications, MS 3-14 475 Oakmead Parkway

Sunnyvale, CA 94086 (U.S.A.) (408) 737-7900

Shugart makes no representations or warranties with respect to the contents hereof and specifically disclaims any implied warranties of merchantability or fitness for any purpose.

Further, Shugart reserves the right to revise this publication and to make changes from time to time in the contents hereof without obligation to notify any person of such revisions or changes.

The information contained herein has been copyrighted by the Shugart Corporation. No portion of this document can be duplicated in any form, or sold, without the express written consent of Shugart Corporation. Failure to com- ply could entail legal action to remedy such violation.

viii

FIGURE 1·1. SA300 SINGLE-SIDED 3.5-INCH MICROFLOPPY DISK DRIVE

1-0

1.1 PURPOSE

SECTION I INTRODUCTION

This document is intended to satisfy the information needs of field Engineers. maintenance and test technicians. A separate OEM manual (P /N 39254-2) is available which describes the installation. power requirements and related information for the applications of this product.

1.1.1 General Description

The single-sided SA300 3.5-inch microfloppy disk drive is designed for new generations of desktop and portable systems. It offers the same performance as any Minifloppy disk drive but in a much smaller package.

The SA300 features 500 k bytes of unformatted storage capacity. a fast six msec track-to-track access time.

microprocessor-controlled electronics. and internal write-protect circuitry. In addition. the SA300 is interface com- patible with Minifloppy disk drives.

The SA300 also uses the proposed industry standard 3.5-inch media. engineered specifically for consumer oriented applications. At 3.5 inches. the new media also fits conveniently into a shirt pocket. Typical applications for the SA300 include personal and portable computers. intelligent typewriters. terminals. word processors. and computerized office equipment.

Key Features

• 135 tracks per inch

• Microprocessor-controlled electronics

• Cartridge load/true ready

• One-touch cartridge load and eject

• Automatic cartridge shutter

• Compact size - one-fourth the volume of standard Minifloppy

• Fast six msec track-to-track access time

• Direct drive brush less dc motor

• Internal write-protect circuitry

• Removable faceplate

• Buffered Seek

1.2 SPECIFICATIONS SUMMARY 1.2.1 Performance Specifications

Capacity Unformatted

Per Disk Per Surface Per Track

Formatted (10 Sectors/Track) Per Disk

Per Surface Per Track Transfer Rate Latency (average)

Single Density (FM) 250 k bytes 250 k bytes 3.125 k bytes 204.8 k bytes 204.8 k bytes 2.56 k bytes 125 k bits/sec

100 msec

1·1

Double Density (MFM) 500 k bytes 500 k bytes 6.25 k bytes 409.6 k bytes 409.6 k bytes 5.12 k bytes 250 k bits/sec

100 msec

Single Density (FM) Access Time

Track-to-Track (without settling) Average (with settling)

Settling Time Motor Start Time

1.2.2 Functional Specifications Rotational Speed

Recording Density (inside track) Flux Density

Track Density . Tracks

Index

Encoding Method Media Requirements

SA130 Microfloppy Cartridge Soft Sectored

1.2.3 Physical Specifications Environmental Limits

Ambient Temperature Relative Humidity Maximum Wet Bulb DC Voltage Requirements

Operating 50° to 115° F (10.0° to 46.1 0c)

20 to 80%

85° F (29.4°C)

+

12 V ± 5% @ 0.4 A operating, 1.5 A max

+

5 V ± 5% @ 0.6 A operating, 0.7 A max Mechanical Dimensions (exclusive of front panel)

Width

=

4.0 in. (101.6 mm) Height

=

1.625 in. (41.275 mm) Depth

=

6.0 in. max (152.4 mm) Weight

=

1.3 Ibs. (0.59 kg) Power Dissipation

8 Watts (27 BTU/hr) Operating 4 Watts (13.5 BTU/hr) Standby 1.2.4 Reliability Specifications

6 msec 158 msec 15 msec 500 msec

300 rpm 4093 bpi 8187 fd

135 tpi 80

1

FM

Shipping -40° to 144° F (-40° to 62.2°C)

1 to 95%

No Condensation

MTBF: 10,000 power on hours under typical usage·

• Assumes the duty cycle of the drive spindle motor to be 25%

PM: Not Required MTTR: 30 minutes Component Life: 5 years Error Rates:

Soft Read Errors:

Hard Read Errors:

Seek Errors:

Media Life:

1 per 10⁹ bits read 1 per 10¹² bits read 1 per 10⁶ seeks Passes per Track: 3.0 x 10⁶

Insertions: 30,000 +

1·2

Double Density (MFM)

6 msec 158 msec 15 msec 500 msec

300 rpm 8187 bpi 8187 fd

135 tpi 80

1 MFM

Storage -8° to 117° F (- 22.2° to 47.2°C)

1 to 95%

No Condensation

1.3 FUNCTIONAL CHARACTERISTICS The SA300 drive consists of:

a. Read/Write and Control Electronics b. Drive Mechanism

c. Precision Track Positioning Mechanism d. Read/Write Head

The interface signals and their relationship to the internal functions are shown in figure 1-2.

WRITE PROTECT

FIGURE 1·2. FUNCTIONAL DIAGRAM

1-3

39254·02·A

1.3.1 Read/Write and Control Electronics The electronics are packaged on a PCB which contains:

a. Index Detector Circuits b. Head Position Actuator Driver

c. Read/Write Amplifier and Transition Detector d. Write Protect Circuit

e. Drive Select Circuits f. Spindle Motor Control

The Head Positioning Actuator moves the read/write head to the desired track on the diskette. The media car- tridge is loaded onto the read/write head by an elevator mechanism when the cartridge is inserted.

1.3.2 Drive Mechanism

The dc drive motor under servo speed control (using an integral tachometer) rotates the spindle at 300 rpm through a direct-drive system. A magnetic chucking device in conjunction with a metallic hub on the media pro- vides precision media positioning to ensure data interchange. A mechanical interlock ensures proper media inser- tion. thus eliminating media damage.

1.3.3 Precision Track Positioning Mechanism

The read/write head assembly is accurately positioned through the use of a precision lead screw with rack follower which is attached to the head carriage assembly. Precise track location is accomplished as the lead screw is rotated in discrete increments by a stepping motor.

1.3.4 Read/Write Head

The glass bonded ceramic and ferrite read/write head contains straddle erase elements to provide erased areas be- tween data tracks. Thus. normal interchange tolerances between media and drives will not degrade the signal-to- noise ratio and diskette interchangeability is ensured.

The read/write head is mounted on a carriage assembly which is located on a precision carriage way. The diskette is held in a plane perpendicular to the read/write head by a pin located on the base casting. This precise registration assures perfect compliance with the read/write head. The read/write head is in direct contact with the diskette. The head surfaces have been designed to obtain maximum signal transfer

to

and from the magnetic surface of the diskette with minimum head/diskette wear.

1.3.5 Recording Format

The format of the data recorded on the diskette is totally a function of the host system. This format can be designed according to the user's needs to take maximum advantage of the total available bits that can be written on anyone track.

1.4 RECOMMENDED RECEIVING INSPECTION

All Shugart drives are 100 percent adjusted and tested before leaving the factory. Therefore. it is necessary to in- spect only for shipping damage on receipt of drives.

1.4.1 Unpacking the Drive

All drives are shipped in sturdy boxes and are secured properly with protective materials. We recommend the following procedure for unpacking the drive.

a. Place the container on a clean and dry surface in the proper position.

b. Open the top portion of the container.

1·4

c. Remove the drive from the inner container.

d. Make sure that all the items match the packing slip.

NOTE

If anything is found damaged. notify the carrier immediately indicating the nature of damage. If anything is missing (that is included in the packing slip). contact the office where you placed the order.

1.4.2 Physical Checkout

a. Ensure that the front latch opens and closes without any difficulty.

b. Ensure that the drive hub rotates freely.

c. Check to see that the PCB is secured properly and no pins are bent.

d. Make sure that there is no contamination at all between the arm and the head.

1.5 FUNCTIONAL OPERATIONS 1.5.1 Power Sequendng

Applying dc power to the SA300 can be done in any sequence. However. during power up. the WRITE GATE line must be held inactive or at a high level. After application of dc power: a 500 msec delay should be introduced before any operation is performed. After powering on. initial position of the read/write head is at track 00. aecause of this. a recalibrate operation should not be required.

1.5.2 Drive Selection

Drive selection occurs when the DRIVE SELECT line is activated. Only the drive with this line active will respond to input lines or gate output lines. Under normal operation. the DRIVE SELECT line enables the input and output lines and lights the activity LED on the front of the drive.

1.5.3 Motor On

In order for the host system to read or write data. the dc drive motor must be turned on. This may be accomplished by activating the MOTOR ON line. A 500 msec delay must be introduced after activating this line to allow the motor to come up to speed before reading or writing can be accomplished.

The motor must be turned off by the host system by deactivating the MOTOR ON line. This should be done if the drive has not received a new command within two seconds (ten revolutions of diskette) after completing the execu- tion of a command. This ensures maximum motor and media life. An option is available to activate MOTOR ON with DRIVE SELECT. Refer to paragraph 2.2.3.

NOTE

All motors in a daisy chain configuration are activated by MOTOR ON (refer to paragraphs 2.2.3 and 2.2.4).

1.5.4 Track Accessing

Seeking the read/write head from one track to another is accomplished by:

a. Activating the DRIVE SELECT line.

b. Selecting the desired direction using the DIRECTION SELECT line.

l

c. WRITE GATE being inactive.

d. PulSing the STEP line.

1·5

Multiple track accessing is accomplished by repeated pulsing of the STEP line until thede$il:et:ltrack has been reached. Each pulse on the STEP line will cause the read/write head to move one track either in or out. depending on the DIRECTION SELECT line. Head movement is initiated on the trailing edge of the step.pulse. See figure 1-3.

1.5.5 Step Line

. The STEP line causes the read/write heads to move in the direction defined by the DIRECTION SELECT line. Any change in the DIRECTION SELECT line must occur at least one p.sec before the leading edge of the step pulse.

With the DIRECTION SELECT line at a plus logic level (2.5 to 5.25 V). a pulse on the STEP line will cause the read/write head to move one track away from the center of the disk. The pulse(s) applied to the STEP line must have the timing characteristics shown in figure 1-3.

With the DIRECTION SELECT line at a minus logic level (0 to 0.4 V). a pulse on the STEP line will cause the read/write head to move one track closer to the center of the disk. The pu)se(s) applied to the STEP line must have the timing characteristics shown in figure 1-3.

Stepping can be performed in either a normal or buffered mode:

DRIVE SELECT

I

DIRECTION SELECT

---"'!"--... I _I

^REVERSE

FORWARD

L

1 /Lsee MIN

500 nsee MIN STEP

1 /Lsec MIN

--.f ^j..-

6mseeMIN~ L

^{1/Lsee MIN~ 39233-07}

. FIGURE 1·3. TRACK ACCESS TIMING

1.5.6 Normal Step Mode

In normal step mode, the read/write heads will move at the rate of the incoming step pulses. Motion is initiated at each true to false transition. The minimum. time between successive steps is six msec. with a minimum pulse width of one "sec. See figure 1-4.

-1 J.---

1.0/Lsee MIN - DIRECTION IN

i

!~III!~

.

-STEP

1.0/Lsee MIN ~ , ...

~6.0

^msee

MIN---I"~I

r - - - t j ~~

U ^LJ

21 msee -READY

50 /Lsec MAX

---.I ^{j.- I I"}

• " " - - - i

____________

~---~'r I~

__________ _

(TR JUMPER OPEN) ^39254-27

FIGURE 1·4. NORMAL STEP MODE

1·6

1.5.7 Buffered St~ Mode

In buffered step mode. the step pulses are received at a high rate and buffered into a counter. After the first step pulse. the read/write heads begin stepping the desired number of cylinders. READY goes true after the read/write heads settle on the cylinder if the TR jumper is open. The buffered mode of operation is automatically selected when the time between step pulses is less than six msec. See figure 1-5 for timing requirements.

DRIVE SELECT may be dropped and a different DRIVE SELECT may be performed one p.sec after the last step pulse has been sent to the drive.

The maximum time between steps in buffered mode is 5.9 p.sec with a minimum pulse width of 1.0 p.sec (see figure 1-5). Step pulses with periods less than 50 p.sec are not permitted. Seek accuracy is not guaranteed if this timing requirement is violated.

READY may not go false until 50 p.sec after the true to false transition of STEP. The TR jumper must be open for READY to go false in response to step pulses.

- DIRECTION IN

r

1.0."sec MIN

1 "sec MIN---.I

~

(.-10 "sec MIN

-STEP

U U U U ^\\

50 "sec MAX

--+I J.-

495 msec MAX

-I ^{I ..}

I ^\\ I

-READY

'.0'''CMIN~

(TR JUMPER OPEN)

j=i~

- DRIVE SELECT X

39254-26

FIGURE 1·5. BUFFERED STEP MODE·

1.5.8 Read Operation

Reading data from the SA300 is accomplished by:

a. Activating DRIVE SELECT line.

b. WRITE GATE being inactive.

The timing relationships required to initiate a read sequence are shown in figure 1-6. These timing specifications are required in order to guarantee that the read/write head position has stabilized prior to reading.

The timing of read data (FM) is shown in figure 1-7.

The encoding scheme of the recorded data can be either FM or MFM. FM encoding rules specify a clock bit at the start of every bit cell (see figure 1-7). MFM encoding rules allow clock bits to be omitted from some bit cells if the preceding bit cell or the current bit cell contains a data or clock bit. See figure 1-8.

In the above mentioned encoding schemes, clock bits are written at the start of their respective bit cell. and data bits at the centers of their bit cells.

1·7

DC POWER MOTOR ON

DRIVE SELECT

STEP

WRITE GATE

VALID READ DATA

1500

^{msec MIN}

I

U I

-.j I--

^{21 msec MAX}

I l.--

^{2 IlSec MAX----.,}

!..-=

^{500 msee}

^MIN~

FIGURE 1·6. READ INITIATE TIMING

150 TO 250 nsec

----.I L

(200 nsec ^NOM) ~

I L

^8.0 Ilsec - ' 4.0 IlHC /4.0 Ilsecl---

,--- NOM

I

^{NOM N O M ,}

READ DATA

BIT

I

CELLS

C 0 C D

FM

I ..

1

^4.00

j.-

- - - . Ilsee

---.

A

I

B A A B A

FIGURE 1·7. READ DATA TIMING (FM)

0 _{0 0} 0

C 0 C C 0 C C C

-18.00 ^{,sec ~}

ss

, / , / , / , / , / , / BIT

1

I

¹

¹

¹

I ⁰ I

¹

^{1 o 1}

^{. .0}

^{1 01}

¹

I

^{, /}

CELLS , /

, / , / , /

D D D 0 C C 0 ^{, /}

, / MFM

FIGURE 1-8. FM AND MFM CODE COMPARISONS

1-8

I

C 0

, / , / , / , /

39211-(16

1.5.9 Write Operation

Writing data to the SA300 is accomplished by:

a. Activating the DRIVE SELECT line.

b. Activating the WRITE GATE line.

c. Pulsing the WRITE DATA line with the data to be written.

The timing relationships required to initiate a write data sequence are shown in figure 1-9. These timing specifica- tions are required in order to guarantee that the position of the read/write head has stabilized prior to writing. The timing specifications for the write data pulses are shown in figure 1-10.

MOTOR ON - - - -..

1

DRIVE SELECT

----...;I~-_I

I ..

^{500 nsec MIN _\}

STEP

----...;.1-.. ^{--U . ~ \\}

--..I .

^{21 msec MIN}

500 msec MIN---.

ss ss

WRITE GATE

I .. ______ ^-\~---- ...

- \\

8.00 jtsec MAX

----'1 r- ^~ , ^r--

^8.00

^"sec

^MAX

WRITE DATA

---~~~---

FIGURE 1·9. WRITE INITIATE TIMING

WRITE DATA

U U U U U Lf

~I r

^{200 2100 nsec nsec MIN MAX}

^r----

^{8.00 "sec}

_{-I r}

^4•OO

^"sec

3!l211.

FIGURE 1·10. WRITE DATA TIMING (FM)

Write data encoding can be FM or MFM. The write data should be precompensated 125 to 175 nsec starting at tracks 40-43 to counter the effects of predicable bit shift. The direction of compensation required for any given bit in the data stream depends on the pattern it forms with nearby bits. Write current is automatically switched at track 50.

1·9

The timing diagram shown in figure 1-11 shows the necessary sequence of events with associated timing restric- tions for proper operation.

POWER ON MOTOR ON

I~---~S\---

-..." ... , j..-

500 msec MIN

I I

~1~1-· ---~\~,---

DRIVE SELECT

VALID TRK 00

I ~ ^1-

500 ""'" MAX AND WRT

PROT_--~I~

^..

"':"I-ili _I

OUTPUT

S~---

VALID INDEX

DIRECTION SELECT

STEP

WRITE GATE

WRITE DATA

VALID READ DATA

' ...

..

l 1

---~S~\---

SOO msec MAX

~

I

500 nsec MAX

1~1l'sec MIN

I

---~\~--- ---~\\~---

~ ~, ^,.ec MIN~~

_...,....,,...21 msec MIN 11'sec MIN

j.-

LrlSU

~I

^{6 msec} MIN

1'- I

21 msec

~ MIN

~

u~

⁵⁰⁰ 500 msec MIN---=+I-. ^{"sec MIN}

----;'~I

..

^.... -r-8-~~-~c~\JI

~\~---

I.. --..1 ^I~

100 I'se.c MIN

---~---~ I ^L

21 msec MIN -III-

lIU----"po...o-UlJ

^SS

~

^•

21'secMAX~

.. 500 msec MAX-_'I

FIGURE 1·11. GENERAL CONTROL AND DATA TIMING REQUIREMENTS

1·10

39254·05·A

1.5.11 Microcartridge Handling

To protect the cartridge, the same care and handling procedures specified for computer magnetic tapes apply.

These precautionary procedures are as follows: .

a. Cartridges not intended for immediate use should be stored in the box.

b. Keep cartridges away from magnetic fields and from ferromagnetic materials which might become magnetized. Strong magnetic fields can distort recorded data on disk.

c. Place 1.0. labels in correct location, never use in layers.

d. Do not use erasers.

e. Heat and contamination from carelessly dropped ash could damage disk.

f. Do not expose cartridge to heat or sunlight.

g. Do not touch exposed portion of disk with your fingers.

1.5.12 Microcartridge Loading

To load the microcartridge, insert the cartridge. auto shutter first, with the label facing up. Push in the cartridge. A mechanical interlock ensures proper media insertion. See figure 1-12. Figure 1-12 provides nomenclature descrip- tion.

If the cartridge fails to load. press the eject button. then reinsert cartridge.

To remove the cartridge. push the eject button. The cartridge will automatically eject.

AUTO SHUTTER

MIDDLE

EDGE OF MEDIA

~

... _ _ _ _ _ _ _ _ _ 3.54 IN.

---I ..

~I 90.0 mm

FIGURE 1·12. SA130 MICROCARTRIDGE NOMENCLATURE

1.11

0.13 IN.

-..I I . -

3.3 mm -

I 1-

3.7 IN.

94.0 mm

39254·20

1.6 MOUNTING

NOTE

Do not mount the drive in horizontal position with PCB down.

As shipped from the factory, the drive is capable of being mounted in either of the following positions (see figure 1-13):

1. Top Loading - mounted upright.

2. Front Loading - mounted vertical with door opening left or right.

- mounted horizontal with PCB up.

o

~ ~ _{II II} ? ^o

HORIZONTAL VERTICAL UPRIGHT

FIGURE 1·13. RECOMMENDED MOUNTING POSITIONS ^39254·14

1-12

SECTION II

ELECTRICAL INTERFACE

2.1 INTRODUCTION

The interface of the SA300 can be divided into two categories:

a. Signal Lines b. Power Lines

The following paragraphs provide the electrical definition for each line. See figure 2-1 for all interface connections.

2.2 SIGNAL INTERFACE

The signal interface consists of two categories:

a. Control Lines b. Data Transfer Lines

All lines in the signal interface are digital in nature and provide signals to the drive (input), or to the host (output) via interface connector Pl! J1.

2.2.1 Input Lines

The input signals are of three types: those intended to be multiplexed in a multiple drive system, those which will perform the multiplexing. and those which are not multiplexed and affect all the drives in a daisy chain system.

The input signals to be multiplexed are:

a. DIRECTION SELECT b. STEP

c. WRITE DATA d. WRITE GATE

The input signals which are intended to do the multiplexing are:

a. DRIVE SELECT 1 b. DRIVE SELECT 2 c. DRIVE SELECT 3 d. DRIVE SELECT 4

The signals which are not multiplexed are IN USE and MOTOR ON.

2-1

HOST SYSTEM

"TRUE READY IS A

CUSTOMER JUMPER OPTION

SA300

FIGURE 2·1. INTERFACE CONNECTIONS

The input lines have the following electrical specifications. See figure 2-2 for the recommended circuit.

True

=

Logical 0

=

V1N + 0.0 to + 0.4 V @ 40 rnA (max) False

=

Logical 1

=

V1N + 2.5 to + 5.25 V @ 250/LA (open) Input impedence

=

^{150 ohms}

2·2

39254·06

MAX 10 FEET ... RIBBON OR

TWISTED PAIR

-

^{- 39254-07}

FIGURE 2·2. INTERFACE SIGNAL DRIVER/RECEIVER 2.2.2 Input Line Terminations

The SA300 has been provided with the capability of terminating the following seven input lines:

a. MOTOR ON

b. DIRECTION SELECT

c. STEP

d. WRITE DATA

e. WRITE GATE

f. DOOR LOCK

g. IN USE

These lines are terminated through a 150 ohm resistor pack installed in a DIP socket. In a single drive system. this resistor pack should be kept in place to provide proper terminations.

In a multiple drive system, only the last drive on the interface is to be terminated. All other drives on the interface must have the resistor pack removed. External terminations may also be used, but the user must provide the ter- minations beyond the last drive and each of the seven lines must be terminated to + 5 Vdc through a 150 ohm.

1/4-watt resistor.

2.2.3 Drive Select 1-4

The SA300 is configured to operate with up to four drives in a multiplexed multiple drive system.

SINGLE DRIVE SYSTEM (MX shorting plug installed)

With the MS shorting plug installed, DRIVE SELECT, when activated to a logical 0 level. will turn the motor on.

With MX shorted, the I/O lines are always enabled.

MULTIPLE DRIVE SYSTEM (MS shorting plug not installed)

Four separate input lines (DRIVE SELECT 1. DRIVE SELECT 2, DRIVE SELECT 3, and DRIVE SELECT 4) are provided so that up to four drives in a multiplexed system may have separate input pins. Only the drive with its unique DRIVE SELECT line active will turn on its motor, allow the drive to respond to multiplexed input lines, and enable the outputs to drive their respective signal lines. A logical 0 on the interface selects a unique drive select line for a drive.

2.2.4 Motor-On

This input, when activated to a logical 0 level. will turn on the drive motor to allow reading or writing on the drive.

After activating this line, a 0.5 second delay must be allowed before reading or writing. For maximum motor life, this line should be deactivated if no commands have been issued to the drive within two seconds nominal (ten revolutions of the media) after completion of a previous command. Depending on the application, this time may be varied by the host system to maximize system through-put and motor life.

2·3

2.2.5 Direction Select

This interface line defines the direction of motion the read/write heads will take when the STEP line is pulsed. An open circuit. or logical 1. defines the direction as "out" and if a pulse is applied to the STEP line, the read/write heads will move away from the center of the disk. Conversely, if this input is shorted to ground, or a logical 0 level, the direction of motion is defined as "in," and if a pulse is applied to the STEP line, the read/write heads will move towards the center of the disk.

2.2.6 Step

This interface line is a control signal which causes the read/write heads to move in the direction of motion defined by the DIRECTION SELECT line. This signal must be a logical 0 pulse with a minimum pulse width of one ^p.sec and a logical 1 for 5.9 msec minimum between adjacent pulses. Each subsequent pulse must be delayed by six msec minimum from the preceding pulse.

The access motion is initiated on each logical 0 to logical 1 transition. or the trailing edge of the signal pulse. Any change in the DIRECTION SELECT line must be made at least one p.sec before the trailing edge of the STEP pulse.

The DIRECTION SELECT logic level must be maintained one p.sec after the trailing edge of STEP pulse.

2.2.7 Write Gate

The active state of this signal. or logical 0, enables WRITE DATA to be written on the diskette. The inactive state or logical 1, enables the READ DATA logic and stepper logic. Refer to figure 1-7 for timings.

2.2.8 Write Data

This interface line provides the data to be written on the diskette. Each transition from a logical 1 level to a logical 0 level will cause the current through the read/write heads to be reversed, thereby writing a data bit. This line is enabled by WRITE GATE being active. WRITE GATE must be inactive during a read operation. See figure 1-7 for timings.

2.2.9 IN USE Input

Normally. the activity LED on the selected drive will activate when the corresponding DRIVE SELECT signal is active. The IN USE input can alternately activate the LED on all the drives in a daisy chain or separately in a radial configuration.

2.2.10 Output Lines

The output control lines have the folloWing electrical specifications:

True

=

Logical 0

=

VOliT + 0.0 to + 0.04 V ^@ 40 rnA (max) False = Logical 1 = VOliT + 5.25 V (open collector @ 250 ^p.A max) See figure 2-2 for the recommended circuit.

2.2.11 Track 00

The active or logical 0 state of this interface signal indicates when the read/write head of the drive are pOSitioned at track 00 (the outermost track) and the stepper is locked on track. This signal is at a logical 1 level or inactive state.

when the read/ write heads of the drive are not at track 00. When the heads are at track 00 and an additional step out pulse is issued to the drive. a mechanical stop will keep the read/write heads at track 00. See figures 2-3 and 2-4 for track 00 circuit and timing.

2.2.12 Index Signal

This interface signal is provided by the drive on each revolution of the drive motor or every 200 msec. The media has no physical hole, so the pulse is generated by a detector which picks up an output from a magnetic device on the motor hub. This pulse is required to generate READY and indicates the physical beginning of a track.

When using the INDEX signal, look for an edge or transition rather than a level for determining its status. With no diskette inserted, this signal remains active or at a logical 0 level which is an erroneous status.

2-4

+5V

TP8

-SELECT

FIGURE 2·3. TRACK ZERO CIRCUIT

DRIVE SELECT

STEP---~

ON TRACK

DIRECTION - - - -

TRACK 00 (TP8)

39211·13

FIGURE 2·4. TRACK ZERO TIMING

2.2.13 Sector

Drive has no provisions for sector pulses.

2.2.14 Read Data

This interface line provides the "raw data" (clock and data together) as detected by the drive electronics. Normally, this signal is a logical 1 level and becomes a logical 0 level for the active state.

2.2.15 Write Protect

This interface signal is provided by the drive to give the user an indication when a write protected diskette is in- stalled. The logical signal at 0 inhibts writing when the diskette is write protected. The logic disables the write elec- tronics and supplies the status signal to the interface.

2.3 POWER INTERFACE

The SA300 requires only dc power for operation. DC power to the drive is provided via P2/ J210cated on the com- ponent side the PCB near the spindle drive motor.

"'"

2.4 FRAME GROUND

CAUTION

It is important that the drive be frame grounded to the host system ac or frame ground.

Failure to do so may result in drive noise susceptibility. Refer to paragraph 3.3 for grounding procedures.

2-6

3.1 INTRODUCTION

SECTION III

PHYSICAL INTERFACE

The electrical interface between the SA300 and the host system is via two connectors J1 and J2.

a. J1 provides the signal interface.

b. J2 provides the dc power.

This section describes the location of connectors used on the drive and the recommended connectors to be used with them. See figure 3-1 for connector locations.

FRAME GROUND CONNECTOR AMP PIN 60972·1

SHORTING PLUG MOLEX PIN 15·24-1024 AMP 530153·2 SA 156480

P1 CONNECTOR AMP PIN 499566·9 MOLEX

PIN 15·29·8342

39254·11·A

FIGURE 3·1. INTERFACE CONNECTORS - PHYSICAL LOCATIONS

3·1

3.2 Jl/Pl CONNECTOR

Connection to J 1 is through a PCB pin type connector. The dimensions and location of pin 1 for the connector are shown in figure 3-2. Pins are numbered 1 through 34 with the even numbered pins on the top row. Pins 1, 2, and 34 are numbered on the PCB. Keying is not available with this connector. The recommended connectors for PI are shown in table 3-1.

TABLE 3·1. RECOMMENDED J1 CONNECTORS

39259-24

0.200

(42.773) 0.069 (1.752)

~ ^..

^1.684

^~

0.069111(5.588)

0.042

1__

^(1.752)

(1.067)

---.t

0.06 (1.524) TH'K

ok ^IiI

^:+1

=='::':--:':'-===':-"::--=--~-=QI ii _ _ f. _ _ Q~---

^{/ PCB}

(6:045) ^....L--

"71 . _{u u}

. : ^'+' ~-1 I

=--=--=--=--=-=---.:..:--.,.-=

^{I .}

_U ^{1m - - -}

~o

~

_(28.194) 0.100 (2.540) ^{---r---Q T}

U --- _{11 U}

PIN 1

-l

\'-0.100 (2.540)

t I I

^0.100

TYP 0.318

--!

~ ^(2.540)

NOTE: Measurements in parenthesis (8.077)

are in milimeters. Measurements

outside parenthesis are in inches. 39254·25

FIGURE 3·2. J1 CONNECTOR DIMENSIONS 3.2.1 J2/P2 Connector

The dc power connector, J2, is mounted on the component side of the PCB and is located near the stepper motor.

J2 is a 4-pin AMP data connector P/N OD/-013003-0. The recommended mating connector (P2) is AMP P/N 22-26-9043 . J2, pin 1, is labeled on the component side of the PCB. Figure 3-3 illustrates the J2 connector.

P2 CONNECTOR PIN 1 + 12 V DC 2 + 12 RETURN 3 +5 RETURN 4 +5V DC

39254·13-A

FIGURE 3·3. J2JP2 CONNECTOR 3.3 FRAME GROUNDING

The drive must be frame grounded to the host system to ensure proper operation. If the frame of the drive is not fastened directly to the frame of the host system with a good ac ground, a wire from the system ac frame ground must be connected to the drive. For this purpose, a faston tab is proVided on the drive where a faston connector can be attached or soldered. The tab is AMP P/N 61664-1 and its mating connector is AMP P/N 60972-1.

3-2

SECTION IV

THEORY OF OPERATION

4.1 INTRODUCTION

This section describes the basic principles of operation of SA300. The drive has all the necessary components to perform different functions. A dc power of

+

12 volts and

+

5 volts is required to operate this drive.

The drive electronics are packaged on one PCB which contains:

a. Read/Write Amplifier and Transition Detector b. Spindle Motor Control

c. Drive Select Circuits d. Index Detector Circuits e. Track Zero Circuits f. Track Accessing Circuits g. Power On Reset Control h. Write Protect Circuits

i. Drive Status Circuits (optional) j. Microprocessor Control Electronics

The head positioning actuator moves the read/write head(s) to the desired track on the diskette. The head(s) is loaded onto the diskette when the door is closed.

4.2 MICROPROCESSOR LOGIC

Much of the logic for the SA300 is implemented with an internal microprocessor. The microprocessor has its own internal firmware ROM, RAM memory and I/O ports. This approach provides many advanced features in a physically small package. The microprocessor monitors the interface lines for commands from the host system and monitors the drive's internal status information to the host system via the DRIVE STATUS, TRACK 00. and WRITE PROTECT interface lines. The stepper motor positioner, activity LED, spindle motor on/off state. and write enable functions are all controlled by the microprocessor. By appropriate software. the microprocessor makes available buffered step. True Ready and Disk Change status options, and Self-Test with no additional hardware.

4·1

4.3 READ jWRITE OPERATIONS

a. The SA300 uses double frequency non return to zero (NRZI) recording method.

b. The read/write head. in general. is a ring with a gap and a coil wound at some point on the ring.

c. During a write operation. a bit is recorded when the flux direction in the ring is reversed by rapidly reversing the current in the coil.

d. During a read operation. a bit is read when the flux direction in the ring is reversed as a result of a flux reversal on the diskette surface.

SA300 drives use the double-frequency (2F) longitudinal (NRZI) method of recording. Double frequency is the term given to the recording system that inserts a clock bit at the beginning of each bit cell thereby doubling the fre- quency of recorded bits. This clock bit. as well as the data bit. is provided by the using system. See figure 4-1.

The read/write head is a ring with a gap and a coil wound at some point on the ring. When current flows through the coil. the flux induced in the ring fringes at the gap. As the diskette recording surface passes by the gap. the fr- inge flux magnetizes the surface in a longitudinal direction. See figure 4-2.

BINARY

REPRESENTATION

BITCELLO

1

BIT CELL 1

1

BITCELL2 BITCELL3

0 0

.. .. .. ..

BITCELL4 BITCELL5 BITCELL6 BIT CELL 7

1 0 1 0

HEX

REPRESENTATION

~,---- .... ^~ _¥ .... ----~/ ,~---- .. ^--~ _¥ .... - - - ' /

MYLAR BASE

FRINGE FLUX

C A

FIGURE 4-1. BYTE

CURRENT

...--

FIGURE 4-2. BASIC READ/WRITE HEAD

DISKETTE MOTION

39211·17

39211·18

The drive writes two frequencies: IF 62.5 k Hz and 2F 125 k Hz. DUring a write operation, a bit is recorded when the flux direction in the ring is reversed by rapidly reversing the current in the coil. The fringe flux is reversed in the gap and hence the portion of the flux flowing through the oxide recording surface is reversed. If the flux reversal is instantaneous as compared to the diskette motion, the diskette surface is magnetized. The diskette surface that just passed under the gap is magnetized in one direction. The portion still under the gap is magnetized in opposite direc- tion. The flux reversal represents a recorded bit. See figure 4-3.

4-2

CURRENT 'II

DISKETTE· MOTION

'II RECORDED BIT

39211-19

FIGURE 4·3. RECORDING A BIT

During a read operation. a bit is read when the flux direction in the ring is reversed as a result of a flux reversal on the diskette surface. The gap first passes over an area that is magnetized in one direction. and a constant flux flows through the ring and coil. The coil registers no output voltage at this point. When a recorded bit passes under the gap. the flux flowing through the ring and coil make a 180⁰ reversal. This means that the flux reversal in the coil causes a voltage output pulse. See figure 4-4.

These flux reversals produce an FM waveform which transmits data to and from the diskette. See figure 4-5.

BINARY EQUIVALENT WRITE DATA WRITE DRIVER 1 WRITE DRIVER 2 DISKETTE SURFACE

READ SIGNAL READ DATA

r

VOLTAGE PULSE

~----(FLUX REVERSAL IN GAP)

RECORDED BIT

39211·20

FIGURE 4·4. READING A BIT·

" r o " r 'r

81'sec

", 1

Ie D Ic Ic D i e D

"

~_----~n~---~r~---~r~----~n_----r~----~n~--~

I I , r I ~ ^{, I}

I "

r

I I I I

Ie·

_{.. 41}

;Yry~411 ~

~~:::::::::::y S> ~ ~

<11'"

¹¹⁼ V

'II:: x:

i> ^'II i>

"'r-.~ ~~i=: :C~j

~ < 4 -=w;: Iii:

!:

^{4 '} j !

;t

I I I l ^I

I

^FLUX

I I I

I

I . REVE~~ :::::0

^I

I

v-~~ ~ ..r~~

I~I I~I~

I

I I I I

, n n n n n ... _ _ nL. __

39211·21

FIGURE 4·5. 1F AND 2F RECORDING FLUX AND PULSE RELATIONSHIP

4·3

4.4 READ/WRITE HEAP

a. The ceramic read/write head contains three coils.

b. When writing, the head erases the outer edges of the track to ensure that the data recorded will not exceed the .0045 inch track width.

The read/write head contains three coils. Two read/write coils are wound on a single core. center tapped and, one erase coil is wound on a yoke that spans the track being written. The read/write and erase coils are connected as shown in figure 4-6.

39259·02

FIGURE 4·6. READ/WRITE HEADS

During a write operation. the erase coil is energized. This causes the outer edges of the track to be trim erased so that the track being recorded will not exceed the .0045 inch track width. Trim erasing allows for minor deviations in read/write head current so that when one track is recorded, it will not "splash over" to adjacent tracks.

Each bit written will be directed to alternate read/write coils. thus causing a change in the direction of current flow through-the read/write head. This will cause a change in the flux pattern for each bit. The current through either of the read/write coils will cause the old data to be erased as new data is recorded.

During a read operation, the direction of flux changes on the diskette surface as it passes under the gap and current is induced into one of the windings of the read/write head. This results in a voltage output pulse. When the next data bit passes under the gap, another flux change takes placein the recording surface. This causes current to be in- duced in the other coil, producing another voltage output pulse of the opposite polarity.

4.5 WRITE ~IRCUIT OPERATION

a. The WRITE DATA trigger flips with each pulse on the WRITE DATA line.

b. The WRITE DATA trigger alternately drives one or the other of the WRITE DRIVERS.

c. WRITE GATE allows WRITE CURRENT to flow to the WRITE DRIVER circuits if a diskette is not write protected.

d. WRITE CURRENT sensor allows ERASE COIL CURRENT.

e., Heads are selected by grounding the appropriate center tap.

WRITE DATA pulses (clock and data bits) are supplied by the using system. The WRITE TRIGGER "flips" with each pulse. The outputs are fed to alternate WRITE DRIVERS.

WRITE GATE and NOT WRITE PROTECT are ANDed together and will cause WRITE CURRENT to flow to the WRITE DRIVER circuits, which in tum causes the center tap switch to close and ERASE CURRENT to flow after the tum on delay of 400 ^p.sec.

4·4

The output of one of the WRITE DRIVERS allows WRITE CURRENT to flow through one half of the read/write coil. When the WRITE TRIGGER "flips," the other WRITE DRIVER provides WRITE CURRENT to the other half of the read/write coil.

The removal of WRITE GATE causes the turn off delay circuit to time out for 1.1 milliseconds. At the end of the delay, the center tap switch opens and the ERASE CURRENT source is turned off. See figure 4- 7.

WRITE DATA - - - - -

WRITE GATE - -... ---... - - - .

TRACK 40 ---;_~

ERASE

39259·03

FIGURE 4·7. WRITE CIRCUIT FUNCTIONAL DIAGRAM

4.6 READ CIRCUIT OPERATION

a. Duration of all read operations is under control of the using system,

b. As long as the drive is selected and WRITE GATE is not active. the READ signal is amplified and shaped, and the square wave signals are sent to the interface as READ DATA.

When the using system requires data from the diskette drive, the using system must select the head and DISABLE WRITE GATE. The READ signal is then fed to the amplifier section of the read circuit. After amplification. the READ signal is fed to a filter where the out-of-band noise is removed. The READ signal is then fed to the differen- tiator amplifier.

Since a clock pulse occurs at least once every eight /Lsec, and data bits are present once every four /Lsec, the fre-

quen~y of the READ DATA varies (FM encoding only). The READ signal amplitude decreases as the frequency in- creases. Note the signals in figure 4-8. The differential amplifier will amplify, differentiate. limit. and digitize the READ signals (sine waves).

The drive has no data separator, only a pulse standardizer for the READ DATA signal.

4·5

ERASEO---~

I

I I I

L

4.7 DRIVE MOTOR CONTROL a. Speed Control

b. Speed Adjust c. Index Adjust

+ 12 V

+5 V REG

- READ DATA

39259·04

FIGURE 4·8. READ CIRCUIT

The spindle motor on the SA3QO is a direct drive brushless. dc type with associated control electronics.

When the host system commands the motor on through the interface. the internal drive microprocessor applies power to the spindle motor control electronics. The control electronics start the motor. apply current to the proper motor windings in sequence and regulate the motor speed using an integral tachometer signal. Motor speed adjust- ment is accomplished through a potentiometer on the motor/electronics module.

4.8 INDEX DETECTOR

Each time a magnetic output device located on the motor hub is moved past the index sensor, a pulse is formed.

This pulse is present on the interface as index pin eight. Without a diskette in the drive. the interface line will be high and the using system must look for a transition to be a valid signal. The detector output is fed into a schmidt trigger with a level trigger latch-back to maintain pulse stability while shaping the pulse. With output enable true, this pulse will be on the interface as a negative going pulse.

4.9 TRACK ZERO INDICATION

Track 00 signal (pin 26) is provided to the using system to indicate when the read/write head is positioned on track 00. Figures 2-3 and 2-4 show the logic and timing for track 00 indication. The track 00 indication is provided when the flag attached to the head carriage passes between the photo transistor and the photo detector. On track, DRIVE SELECT is ANDed with the photo detector output. These conditions will cause a track 00 indication to the interface.

4.10 TRACK ACCESSING

a. Stepper Motor (Four Phase) b. Stepper Control Logic

4-6

c. Reverse Seek d. Forward Seek

Seeking the read/write head from one track to another is accomplished by selecting the desired direction utilizing the DIRECTION IN interface line and pulsing the STEP line. Multiple track mov!'!mentis accomplished by repeated pulsing of the STEP line.

The four phase stepper motor turns the actuator leadscrew in two step increments per tracK. Two increments will move the head one track via a follower which is attached to the carriage assembly. The follower rides in the helical grove in the leadscrew.

The stepper motor has four windings: two windings are energized for each phase. Phases A and C occur when the head is on track. Phases Band D are transient states.

The microprocessor provides control of the stepper motor, sequencing the phases with the proper time delays to perform the seek specified on the interface. The microprocessor additionally controls two current modes for the stepper motor. When stepping and settling, the high current mode is used. The low current mode is used while the head is stable on track. Within 21 msec after the last step pulse is issued, stepper motor current is reduced.

At power on reset time. the drive microprocessor automatically recalls the head to track 00. If the track 0 sensor is inactive at power on reset. the head is stepped until the track 0 sensor and phase A are both active. If the track 0 sensor is already active at power on reset. the head is first stepped in to make sure it clears the rear stop and then is

stepped back out. Figure 4-9 illustrates the Stepper Logic. See figure 4-10 for Power On Reset and figure 4-11 for Stepper Timing.

-STEP

J4 PHASE A1

PHASE A2 PHASE A3 PHASE A4 STEPINT

RESET STEP

+5V

39211-27

FIGURE 4·9. STEPPER LOGIC

4·7

ERASE CURRENT ENABLE

+5V +5V

+5V

FIGURE 4·10. POWER ON RESET

- DIRECTION IN - - - ' - STEP

---u---u

+ HIGH CURRENT

---1

- WRITE ENABLE - - - - , ... _ _ _ _ _ _ _ _ _ _ _ -'

- TRUE READY

---1

PHASE A - - - ' ... _ _ _ ~

-POR

ERO ER1

WRITE CURRENT ENABLE

39211-29

u

L-

~

__________ --,r--

L-

PHASEB~---~---~---

PHASE C _ _

---In ... ____________ --'I

PHASED----~r-1

^...

---r-l~---

39259-05

FIGURE 4·11. STEPPER TIMING

4·8

4.11 DRIVE SELECT

The SA300 is configured to operate alone in a single drive system. It can be easily modified to operate with other drives in a daisy chained multiplexed drive system. This is done by selecting the specific drive address and jump- ering the appropriate DRIVE SELECT line. See figure 4-12.

The MX option is used for single drive systems. By shorting MX. the I/O lines are always enabled. The MS option allows the motor to be enabled from DRIVE SELECT.

DS4 ⁶

DS3 14 DS2 12 DS1 10

+5V

+5V

MS IN USE >E---~"""--(;I 4

+5V

MOTOR>E---~---o 16

ON

MX

~

TP13

•

SELECT

IN USE LED

+5V

MOTOR ON

39211·26

FIGURE 4·12. DRIVE SELECT, MOTOR ON AND IN USE 4.12 WRITE PROTECT

This interface signal is provided by the drive to indicate to the user when a write protected diskette is installed. The signal is logic 0 level when it is protected. Under normal operation, the drive will inhibit writing with a protected diskette installed in addition to notifying the interface.

4.13 DRIVE STATUS

This interface line provides information on the status of the drive. The information relayed is determined by whether the TR jumper is open or shorted and whether or not TPll is shorted to TPlO (gnd).

TR Shorted, TPII Open (Disk In), Normal Configuration as Shipped

The DRIVE STATUS line goes to the active (logical zero) level when a cartridge is inserted in the drive.

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