Tandon TM100-1 Service manual

O E M
OPERATING AND SERV ICE MANUAL
TM100-1, TM100-2 DISK DRIVES
48 TRACK S PER IN CH
landon c o r p o r a t io n
20320 PRAIRIE STREET
CHATSWORTH, CALIFORNIA 91311 © COPYRIGHT 1983 TANDON CORPORATION

NOTICE
This document, and the information contained herein, is copyright by Tandon Corporation and may
not be duplicated or reproduced, in whole or in part, without the prior written approval of
Tandon Corporation.
This document is intended to provide the user with detailed information adequate for the efficient
installation, operation, and service of the equipment involved.
However, while every effort has been made to keep the information contained herein current and accu
rate as of the date of publication, no guarantee is given or implied as to its accuracy.

C O N T E N T S
Section Page
Number Title Number
SECTION 1 GENERAL DESCRIPTION
Introduction........................................................................... 1-1
1.1 Scope Of The Document .............................................................. 1-1
1.2 Purpose Of The Drive................................................................. 1-1
1.3 Major Features........................................................................ 1-1
Write P rotect ...................................................................... 1-1
Daisy Chain Capability............................................................. 1-1
Internal Trim Erase................................................................ 1-1
Industry Standard Interface Compatibility....................................... 1-1
Track 0 Switch ..................................................................... 1-2
Index Sensor........................................................................ 1-2
Activity Indicator.................................................................. 1-2
1.4 Functional Description............................................................... 1-2
1.5 Physical Description ................................................................. 1-2
SECTION 2 PRODUCT SPECIFICATIONS
Introduction........................................................................... 2-1
2.1 Mechanical Specifications ........................................................... 2-1
2.2 Electrical and Operational Specifications ........................................... 2-1
2.3 Reliability Specifications............................................................. 2-1
2.4 Environmental Specifications ....................................................... 2-1
SECTION 3 OPERATION
Introduction........................................................................... 3-1
3.1 Unpacking The Drive................................................................. 3-1
3.2 Preinstallation Checkout ............................................................ 3-1
3.3 Mounting The Drive.................................................................. 3-1
Dust Cover.......................................................................... 3-2
Cooling ............................................................................. 3-2
3.4 Interface Connections ................................................................ 3-2
Input Control Lines ................................................................ 3-2
Output Control Lines............................................................... 3-4
Typical Interface Characteristics.................................................. 3-4
3.5 D. C. Power............................................................................ 3-5
3.6 Drive Address and Option Patching.................................................. 3-5
DSO Through DS3 Jumpers ........................................................ 3-5
MX Jumper......................................................................... 3-7
HS and HM Jumpers............................................................... 3-7
Power Save Option................................................................. 3-7
Side Select (Wl) ................................................................... 3-7
Write Flip-Flop Control (W2, W3) ................................................. 3-7
Write Protect Control (W4, W5)................................................... 3-7
Activity L.E.D. Control (W6, W7, W9) ................................... 3-7
Drive Select 3 Enable (W8) ........................................................ 3-9
Door Lock Solenoid (W10) ......................................................... 3-9

C O N T E N T S
Section Page
Number Title Number
3.7 Diskettes............................................................................... 3-9
Loading The Diskette .............................................................. 3-9
Write Protect Tab.................................................................. 3-9
Diskette Handling and Storage.................................................... 3-9
SECTION 4 THEORY OF OPERATION
Introduction........................................................................... 4-1
4.1 Data Recording ....................................................................... 4-1
4.2 Components Of The Drive ........................................................... 4-3
4.3 Generate and Interpret Control Signals ............................................. 4-3
Index Sensor ....................................................................... 4-3
Write Protect Switch............................................................... 4-3
Track 0 Switch..................................................................... 4-3
Drive Select ........................................................................ 4-3
4.4 Read/Write Head Positioner........................................................ 4-5
Step and Direction................................................................. 4-5
Stepper Motor Control ............................................................ 4-5
Stepper Motor .............................................................. 4-5
4.5 Read/Write D ata ................................................................... 4-7
Read/Write Head Assembly....................................................... 4-7
Side Select Circuits ................................................................ 4-7
Write/Erase Circuits............................................................... 4-7
Read Data Circuits............................................................... 4-10
4.6 Spindle Control...................................................................... 4-10
Spindle Motor and Spindle Assembly ........................................... 4-10
Spindle Motor Enable Circuit ................................................... 4-10
Spindle Motor Control Circuit..................................................... 4-12
SECTION 5 MAINTENANCE CHECKS AND ADJUSTMENTS
Introduction........................................................................... 5-1
5.1 Visual Inspection ................................................................... 5-1
5.2 Equipment Required ............................................................... 5-1
5.3 Power/Drive Select Check.......................................................... 5-2
5.4 Write Protect Switch Check and Adjustment ..................................... 5-3
Write Protect Switch Check ....................................................... 5-3
Write Protect Switch Adjustment ................................................ 5-3
5.5 Drive Motor Speed Check and Adjustment ........................................ 5-3
Drive Motor Check................................................................. 5-3
Drive Motor Adjustment .......................................................... 5-4
5.6 Radial Track Alignment Check and Adjustment .................................. 5-4
Radial Track Alignment Check .................................................. 5-6
Radial Track Alignment Adjustment ............................................. 5-8
5.7 Index Checks and Adjustment ..................................................... 5-9
Index-To-Data Pulse Check ....................................................... 5-9
Index Sensor Adjustment ......................................................... 5-9
5.8 Azimuth Check...................................................................... 5-11
5.9 Track 0 Switch Check and Adjustment............................................. 5-12
Track 0 Switch Ch eck............................................................ 5-12
Track 0 Switch Adjustment ..................................................... 5-12
5.10 Track 0 Stop Adjustment........................................................... 5-13

C O N T E N T S
Section Page
Number Title Number
5.11 Head Output Check ................................................................. 5-13
5.12 Cone Centering Check .............................................................. 5-14
5.13 Compliance Check and Adjustment (Single-Sided Drives) ......................... 5-15
Compliance Check ............................................................... 5-15
Compliance Adjustment ......................................................... 5-15
SECTION 6 TROUBLESHOOTING GUIDE AND REPLACEMENT PROCEDURE
Introduction......................................................................... 6-1
6.1 Symptom Diagnostic Techniques .................................................. 6-1
6.2 Soft E rrors.......................................................................... 6-1
6.3 Troubleshooting Guide ............................................................. 6-1
6.4 Replacement Procedures ........................................................... 6-5
Tool Requirements..................... .......................................... 6-7
Drive Belt ........................................................................ 6-7
Logic Circuit Board .............................................................. 6-7
Servo Circuit Board.............................................................. 6-9
Cone Lever Assembly ............................................................ 6-10
Cone Assembly.................................................................... 6-13
Activity L.E.D .............................. 6-13
Front Panel....................................................................... 6-16
Guide R a il........................................................................ 6-16
Index Assembly................................................................... 6-17
Drive Motor Assembly ........................................................... 6-20
Track 0 Switch Assembly ........................................................ 6-22
Write Protect Switch Assembly ................................................. 6-25
Upper Arm Assembly (Single-Sided Drives Only)............................... 6-27
Head Module Assembly .......................................................... 6-27
Latch Plate Assembly............................................................ 6-31
Appendix A Recommended Spares and Major Assemblies ...................................... A-1
Appendix B Circuit Board Schematics and Drawings .......................................... B-l

ILLUSTRATIONS
FIGURES
Figure Page
Number Title Number
1- 1 Disk Drive .......................................................................... 1-3
2- 1 Disk Drive Outline Drawing........................................................ 2-2
3- 1 Electrical Interface Characteristics ................................................ 3-5
3-2 Control and Data Timing Requirements ........................................... 3-6
3-3 Logic Board With Programmable Shunts and Option Patching Locations ........ 3-8
3-4 Recording Media .................................................................... 3-10
3-5 Write Protect T a b ................................................................... 3-11
3- 6 Diskette Handling and Storage ...................................................... 3-12
4- 1 Electromagnetic Core .............................................................. 4-1
4-2 FM Recording Magnetization Profiles ............................................. 4-2
4-3 Read Timing Diagram .............................................................. 4-2
4-4 Interconnect Block Diagram........................................................ 4-4
4-5 Soft-Sectored Index Pulse .......................................................... 4-6
4-6 Track 0 Timing...................................................................... 4-6
4-7 Write Data Circuit Block Diagram ................................................. 4-8
4-8 Write Operation Timing Diagram .................................................. 4-9
4-9 Read Circuit Block Diagram........................................................ 4-11
4- 10 Servo Circuit Board.................................................................. 4-12
5- 1 Logic Circuit Board With Test Points .............................................. 5-2
5-2 Write Protect Switch Adjustment ................................................. 5-4
5-3 Location Of R4 Speed Control Potentiometer ...................................... 5-5
5-4 Bottom View Of D rive............................................................... 5-5
5-5 Hub Center Line and Track Locations .............................................. 5-6
5-6 Cats Eye Patterns ................................................................... 5-7
5-7 Head Module Retaining and Cam Screws........................................... 5-8
5-8 Index-To-Data Pulse................................................................. 5-10
5-9 Index Sensor’s Retaining Screw and Adjustment .................................. 5-10
5-10 Optimum Head Azimuth Alignment ............................................... 5-11
5-11 Head Azimuth Alignment of Acceptable Lower L im its............................ 5-11
5-12 Head Azimuth Alignment of Acceptable Upper Lim its............................ 5-12
5-13 Track 0 Stop ......................................................................... 5-13
5- 14 Upper Arm and Screws ............................................................. 5-16
6- 1 Drive Belt and Pulleys............................................................... 6-7
6-2 Logic Circuit Board Mounting ...................................................... 6-8
6-3 Servo Circuit Board Mounting...................................................... 6-9
6-4 Cone Lever Cable Harnessing....................................................... 6-10
6-5 Cone Lever Assembly and Cable Harnessing ...................................... 6-11
6-6 Cone Shaft and E-Ring ............................................................. 6-12
6-7 Cone’s Component Parts ............................................................ 6-14
6-8 Activity L.E.D. Cable Harnessing................................................... 6-15
6-9 Activity L.E.D. Assembly Retaining Collar and Grommet ........................ 6-15
6-10 Front Panel Locating Tabs and Bushings .......................................... 6-16
6-11 Front Panel Mounting Screws ...................................................... 6-17
6-12 Guide Rail Locating Tabs and Bushings ............................................ 6-18
6-13 Index Emitter Sensor’s Mounting and Cable Harnessing .......................... 6-18
6-14 Index Detector Sensor’s Mounting Screw and Cable ............................... 6-19
6-15 Cable Harness ....................................................................... 6-20

FIGURES
Figure
Number Title
Page
Number
6-16 Drive Motor Harnessing and Mounting ............................................ 6-21
6-17 Drive Motor Pulleys ................................................................ 6-22
6-18 Track 0 Cable Harnessing .......................................................... 6-23
6-19 Track 0 Adjustment Screw ......................................................... 6-24
6-20 Track 0 Mounting Screw............................................................ 6-25
6-21 Write Protect Mounting Adjustment Screws ...................................... 6-26
6-22 Write Protect Cable Harness ....................................................... 6-26
6-23 Write Protect Arm and Adjustment Screws ....................................... 6-27
6-24 Upper Arm Screws ................................................................. 6-28
6-25 Upper Arm Parts.................................................................... 6-29
6-26 Felt Pad On Upper Arm ............................................................. 6-29
6-27 Head Module Assembly............................................................. 6-30
6-28 Latch Plate Mounting .............................................................. 6-31
TABLES
Table Page
Number Title Number
2-1 Electrical and Operational Specifications............................................ 2-3
2-2 Reliability Specifications............................................................. 2-4
2- 3 Environmental Specifications ........................................................ 2-5
3- 1 Drive Interface Lines and Pin Assignments ......................................... 3-2
3- 2 D. C. Power Connector Pin Assignments ............................................. 3-5
4- 1 Stepper Logic Truth Table............................................................ 4-5
6-1 Troubleshooting Guide ............................................................... 6-2
6-2 Checks and Adjustments Guide ...................................................... 6-6

SECTION 1
GENERAL DESCRIPTION
INTRODUCTION
This document provides required information in
order to evaluate and incorporate Tandon’s disk
drive into a system.
Tandon Corporation’s Model Number TM100-1
and TM100-2 are full-feature, 5-1/4-inch, flexi
ble disk drives. They are compact data storage
devices that use an ANSI-compatible, industry
standard, 5- 1/4-inch diskette.
Model Number TM100-1 and TM100-2 drives
each have forty-eight (48) tracks per inch. The
TM100-1 is a single-sided recording device. The
TM100-2 is a double-sided recording device.
Both drives are capable of reading and writing
in single-density format on a diskette, using a
proprietary read/write head patented by
Tandon. The drives have a double density capa
bility when Modified Frequency Modulation
(MFM) or other appropriate recording technique
is used. Encoding and decoding of the data is
done by the user’s controller.
1.1 SC O P E OF THE
DOCUMENT
This document contains the major features,
physical and functional specifications, mounting
and power requirements, the interface, and typi
cal timing characteristics of the TM100-1 and
TM100-2 drives. In addition, there is a theory of
operation, checks and adjustment procedures,
troubleshooting guide, replacement procedures,
assembly drawings, and schematics.
1.2 PURPOSE OF THE DRIVE
The TM100-1 and TM100-2 drives are rotating
disk memories designed for random access data
entry, storage, and retrieval applications.
Typical applications include intelligent terminal
controllers, microcomputers, word processing
systems, data communication systems, error
logging, program loading, and point-of-sale
terminals.
1.3 MAJOR FEATURES
WRITE PROTECT
When a write protected diskette is inserted into
the drive, the write electronics are disabled.
DAISY CHAIN CAPABILITY
The drive provides the address selection and
gating functions necessary to daisy chain a
maximum of four units at the user’s option. The
last drive on the daisy chain terminates the
interface. The terminations are accomplished by
a resistor array plugged into a DIP socket.
INTERNAL TRIM ERASE
The drive provides the control signals necessary
for proper trim erasure of data.
INDUSTRY STANDARD INTERFACE
COMPATIBILITY
The drive is compatible with controllers that use
an industry standard interface.

TRACK 0 SWITCH
The Track 0 switch is provided to generate a
logic level at the drive interface, indicating the
read/write head is positioned at the outermost
track.
INDEX SENSOR
An index sensor is provided to generate
electrical pulses at the drive interface
coincident with sensing Index/Sector holes on
the diskette.
ACTIVITY INDICATOR
An activity indicator, located on the front panel,
is automatically illuminated when the drive is
selected.
1.4 FUNCTIONAL DESCRIPTION
The drives are fully self-contained, and require
no operator intervention during normal
operation. Each drive consists of electronics to
generate and interpret control signals, a head
positioning system, a read/write system, and a
spindle drive system.
When the front latch is opened, access is
provided for insertion of a diskette. The diskette
is held in place by plastic guide rails. Its location
is ensured when the diskette is inserted until a
back stop is encountered.
Closing the front latch activates the cone
clamping mechanism, resulting in accurate
centering and clamping of the diskette. The
drive hub is held at a constant speed of 300 RPM
by a servo-controlled D. C. motor. The heads
remain in contact with the recording media
until the front latch is opened.
The heads are positioned over the desired track
by means of a four-phase stepper motor/band
assembly and its associated electronics. This
positioner uses a one-step rotation to cause a one
track linear movement.
Data recovery electronics include a low-level
read amplifier, differentiator, zero crossover
detector, and digitizing circuits. No data
decoding capabilities are provided.
The drive has the following sensors:
1. A Track 0 switch detects when the
head/carriage assembly is positioned at
Track 0.
2. An index/sensor is positioned to generate
a digital signal when an index/sensor
hole on the diskette is detected.
3. A write protect switch disables the write
electronics when a write protect tab is
applied to the diskette.
1.5 PHYSICAL DESCRIPTION
A representative drive is shown in Figure 1-1.
The drive can be mounted in a vertical or
horizontal plane. However, the logic circuit
board must be on the uppermost side when the
drive is mounted horizontally.
The spindle is belt driven by a D. C. motor with
an integral tachometer. The servo control
circuit and tachometer control the speed of the
spindle.
The read/write head assembly is positioned by a
split band positioner mounted to a stepper
motor. The read/write head(s) is a glass-bonded,
ferrite/ceramic structure with a life expectancy
of 20,000 operating hours.
The electronic components of the drive are
mounted on two printed circuit boards. The logic
circuit board is mounted above the chassis. The
spindle motor control circuit board is mounted
at the rear of the chassis. Power and interface
signals are routed through connectors plugged
directly into the logic circuit board.
1-2

FIGURE 1-1
DISK DRIVE

SECTION 2
PRODUCT SPECIFICATIONS
INTRODUCTION
This section contains the mechanical, electrical reliability, and environmental specifications for the
TM100-1 and TM100-2 drives.
2.1 MECHANICAL SPECIFICATIONS
The physical dimensions of the drive are located in Figure 2-1.
2.2 ELECTRICAL AND OPERATIONAL SPECIFICATIONS
The electrical and operational specifications are located in Table 2-1.
2.3 RELIABILITY SPECIFICATIONS
The reliability specifications are located in Table 2-2.
2.4 ENVIRONMENTAL SPECIFICATIONS
The environmental specifications are located in Table 2-3.
landon
CORPORATION, CHATSWORTH, CALIFORNIA 91311
179022-001
REV. B
2-1

NOTES: 1. DIMENSIONS ARE GIVEN IN INCHES. METRIC EQUIVALENTS ARE IN PARENTHESES.
2. TOLERANCE ON ALL DIMENSIONS ±0.020 INCH, UNLESS OTHERWISE SPECIFIED.
3. WEIGHT IS APPROXIMATELY 3 POUNDS (1.35 KILOGRAMS).
FIGURE 2-1
DISK DRIVE OUTLINE DRAWING
landon
CORPORATION, CHATSWORTH, CALIFORNIA 91311
179022-001
REV. B
2-2

TABLE 2-1
ELECTRICAL AND OPERATIONAL SPECIFICATIONS
Media ANSI-compatible, 5-1/4-inch diskette
Media Life (for reference only) 4 x 10 passes per track
Tracks Per Inch 48 TPI, both drives
Tracks Per Drive
TM100-1 40 tracks
TM100-2 80 tracks
Track Spacing 0.529 millimeters, 20.8 milinches
Head Life 20,000 media contact hours
Disk Rotational Speed 300 RPM ± 1.5 percent
Average Rotational Latency 100 milliseconds
Instantaneous Speed Variation (ISV) ± 3 percent
Motor Start Time 250 milliseconds, maximum
Motor Stop Time 150 milliseconds, maximum
Seek Time, track-to-track 5 milliseconds
Head Settling Time 15 milliseconds
Average Track Access Time,
including head settling time 75 milliseconds
Typical Recording Modes FM, MFM, MMFM
Data Transfer Rate 250,000 bits per second, double density
Flux Reversals Per Inch (FRPI),
inside track
Both Models, Side 0 5,535 FRPI
TM100-2, Side 1 5,877 FRPI
1 3 r i d o n C O R P O R A T IO N , C H A T S W O R T H , C A L IF O R N IA 9 1 3 1 1
179022-001
REV. B
2-3

TABLE 2-1 (CONTINUED)
ELECTRICAL AND OPERATIONAL SPECIFICATIONS
Unformatted Recording Capacity
TM100-1 250 kilobytes per disk
TM100-2 500 kilobytes per disk
D. C. Voltage and Current
Requirements
+12 volts D. C. Power +12 volts ± 0.6 volt, 900 milliamperes,
average, 100 millivolts peak-to-peak
ripple.
+ 5 volts D. C. Power + 5 volts ± 0.25 volt, 600 milliamperes,
average, with less than 100 millivolts
peak-to-peak ripple.
Shipment When prepared for shipment by Tandon,
the drive meets the requirements of
NSTA preshipment test procedure Project
1A.
TABLE 2-2
RELIABILITY SPECIFICATIONS
Error Rates, maximum, exclusive of
external sources, e.g.: electronics,
defective and contaminated diskettes
Soft Errors (Recoverable) One in 109 bits
Hard Errors (Nonrecoverable) One in 1012 bits
Seek Errors One in 106 seeks
Mean Time Between Failures 8,000 hours, 25 percent duty cycle
Mean Time To Repair 30 minutes
la n d o n C O R P O R A T IO N , C H A T S W O R T H , C A L IF O R N IA 9 1 3 1 1
179022-001
REV. B
2-4

TABLE 2-3
ENVIRONMENTAL SPECIFICATIONS
Temperature
Operating, media dependent
Nonoperating
Relative Humidity
Operating, noncondensing,
media dependent
Nonoperating, noncondensing
Altitude
Operating or nonoperating
10°C to 46°C, 50°F to 115°F
—40°C to 71°C, — 40°F to 160°F
20-to-80 percent
5-to-95 percent
152.4 meters, 500 feet, below sea level, to
15,240 meters, 50,000 feet, above sea level
CORPORATION, CHATSWORTH, CALIFORNIA 91311
179022-001
REV. B
2-5

SECTION 3
OPERATION
INTRODUCTION
This section contains information on how to
unpack, check out, install, and operate the
TM100-1 and TM100-2 drives.
3.1 UNPACKING THE DRIVE
The drives are packaged in protective containers
to minimize the possibility of damage during
shipment. The following list is the recommended
procedure for unpacking the drive.
1. Place the container on a flat work
surface.
2. Remove the upper half of the container.
3. Remove the drive from the lower half of
the container.
4. Check the contents of the container
against the packing slip.
5. Investigate the contents of the container
for possible damage.
6. Notify the carrier immediately if any
damage is found.
3.2 PREINSTALLATION
CHECKOUT
Before applying power to the drive, the following
inspection should be conducted:
1. Check to ensure the front latch opens
and closes.
2. When the latch is moved to an open posi
tion, the head arm raises.
3. Remove the cardboard shipping insert,
and retain for future shipment.
4. Ensure the front panel is secure.
5. Ensure the drive belt is in place.
6. Manually rotate the drive hub. It should
rotate freely.
7. Ensure both circuit boards are secure.
8. Ensure the connectors are firmly seated.
3.3 MOUNTING THE DRIVE
The drive has been designed to be mounted hori
zontally or vertically. When mounted horizon
tally, the logic circuit board side of the drive
must be the top side.
Four 6-32 tapped mounting holes are provided
on the bottom of the drive, and two 6-32 tapped
mounting holes on each side, for attachment to
user-supplied mounting brackets. When in
stalled in either plane, horizontal or vertical,
only two mounting screws are required to secure
ly hold the drive in place.
Any mounting scheme in which the drive is part
of the structural integrity of the enclosure is not
permitted. Mounting schemes should allow for
adjustable brackets or incorporate resilient
members to accommodate tolerances. In addi
tion, it is recommended that mounting schemes
include no more than two mounting surfaces.
The drive is manufactured and tested with some
critical internal alignments that must be
maintained. Hence, it is important that the
mounting hardware not introduce significant
stress on the chassis.

DUST COVER
The design of an enclosure should incorporate a
means to prevent contamination from loose
items, e.g., dust, lint, and paper chad, since the
drive does not have a dust cover.
COOLING
Heat dissipation from a single drive is normally
15 watts, 51 BTU per hour, under high load con
ditions. When the drive is mounted so the compo
nents have access to a free flow of air, normal
convection cooling allows operation within the
specified temperature range.
When the drive is mounted in a confined envi
ronment, air flow must be provided to maintain
specified air temperatures in the vicinity of the
motors, printed circuit board, and diskettes.
When forced air is used, air flow must be direct
ed outward from the drive. Do not intake air
through the drive or heads and diskettes.
3.4 INTERFACE CONNECTIONS
Interface connections for the TM100-1 and
TM100-2 are made via a user-supplied, thirty-
four pin, flat ribbon connector, 3M Part Number
3463-0001 or Amp Part Number 583717-5, using
contact Part Number 1-583616-1 for twisted
pair or its equivalent. This connector mates
directly with the circuit board connector at the
rear of the drive. The D. C. power connector is a
four-pin connector at the rear of the drive. The
interface description of the connectors, and the
location of each one, is contained in this section.
Interface lines are located in Table 3-1. D. C.
power connector pin assignments are located in
Table 3-2.
The signal wire harness should be of the flat
ribbon or twisted pair type, 26-to-28 gauge
conductor, compatible with the connector to be
used. The recommended cable length is ten feet
maximum.
TABLE 3-1
DRIVE INTERFACE LINES
AND PIN ASSIGNMENTS
Input Control Lines:
Controller-To-Disk Drive
Ground Pin Signal
12Connector Clamp
34Spare
56Drive Select 3
9 10 Drive Select 0
11 12 Drive Select 1
13 14 Drive Select 2
15 16 Motor On
17 18 Direction Select
19 20 Step
21 22 Composite Write Data
23 24 Write Enable
31 32 Side Select
Output Control Lines:
Disk Drive-To-Controller
Ground Pin Signal
78Index/Sector
25 26 Track 0
27 28 Write Protect
29 30 Composite Read Data
33 34 Spare
INPUT CONTROL LINES
DRIVE SELECT LINES
The Drive Select lines provide a means of select
ing and deselecting a drive. These four lines
select one of the four drives attached to the
controller.
When the signal logic level is true (low), the
drive electronics are activated, and the drive is
conditioned to respond to Step or Read/Write
commands. A Drive Select line must remain
stable in the true (low) state until a Step or
3-2