HP 9130K User manual

~=========== SERVICE MANUAL
HP 9130K
Flexible Disc Drive
Service Documentation
Hewlett-Packard Greeley Division
3404 East Harmony Road, Fort Collins, Colorado 80525

ii
Table of Contents
Chapter 1: General Information
Introduction .............................................................. 1-1
General Description
....................................................... 1-1
Available Options
...................................................... 1-2
Environmental
and Physical Specifications .................................... 1-2
Recording Specifications
................................................ 1-2
Environmental Specifications
............................................ 1-2
Physical Dimensions
and Weight ......................................... 1-3
Performance Specifications
.............................................. 1-3
Flexible Disc Media Use
.................................................... 1-4
Intro.duction .......................................................... 1-4
Operating Cleanliness .................................................. 1-5
Handling Discs ........................................................ 1-5
Do .................................................................. 1-6
Don't ................................................................ 1-7
Write Protection
....................................................... 1-9
Chapter 2: Interface Information
Introduction .............................................................. 2-1
Interface
............................................................. 2-1
Primary Power Requirements
............................................ 2-1
Signal Line Description
.................................................... 2-3
Input Control Lines
.................................................... 2-3
Output Status Lines .................................................... 2-4
Typical Interface Drive/Receiver Circuit ....................................... 2-8
Chapter 3: Theory of Operation
Introduction .............................................................. 3-1
Flexible Disc Recording Fundamentals
...................................... 3-1
Index Pulse
Shaping Network ................. , ........................... 3-3
Write Protect Sensor ....................... " ........................... 3-3
Track 0 Switch ............................ , ........................... 3-3
Spindle Motor Drive Control ............................................. 3-3
Head Position Control .................................................. 3-4
Power On Circuit ...................................................... 3-4
Data Circuitry ......................................................... 3-4
Writing Data .......................................................... 3-4
Reading Data ......................................................... 3-7

iii
Chapter 4: Assembly Access
Introduction .............................................................. 4-1
Chapter 5: Maintenance
Introduction .............................................................. 5-1
Service
Kit Contents .................................................... 5-1
Drive Failure Analysis
.................................................. 5-2
Head Cleaning ................................................... " .... 5-3
Termination Resistor IC U2F ............................................. 5-3
Shunt Block U1E ...................................................... 5-3
Alignment and Adjustments ................................................. 5-3
Introduction ..................................................... , .... 5-3
Spindle Motor Speed Adjustment .................................... , .... 5-3
Spindle Drive Belt Adjustment ........................................... 5-4
Radial Head Alignment ................................................. 5-7
Head Azimuth Alignment ................................................ 5-8
Track 0 Switch Adjustment .............................................. 5-9
Index Emitter/Detector Adjustment ...................................... 5-10
Write Protect Switch Adjustment ........................................ 5-12
Read/Write Test ...................................................... 5-12
DSU Controls and Indicators ........................................... 5-13
Disc Service Unit Operation ............................................ 5-16
Packaging Instructions ................................................. 5-17
Test Point Location and Waveforms ...................................... 5-19
Chapter 6: Schematic Diagrams
Introduction .............................................................. 6-1
Chapter 7: Replaceable Parts
Introduction .............................................................. 7-1
Figures
1-1 Physical Dimensions ................................................. 1-4
1-2 Head/Media Critical Requirements ...................................... 1-6
1-3 Damaged Media
..................................................... 1-8
1-4 Loading the Disc
.................................................... 1-9
1-5 Write Protect Tab Installation
.......................................... 1-9
2-1
Connector J2 Pin Out ................................................ 2-1
2-2
Connector J1 Pin Out (Circuit Side) .................................... 2-2
2-3 General Control
and Data Requirements ................................. 2-5
2-4 Connector Location ................................................... 2-6
2-5 Connector J4 Pin Out ................................................ 2-6

iv
2-6 Connector J3 Pin Out ................................................ 2-7
2-7 Servo Electronics Board
Jl ............................................ 2-8
2-8 Typical Interface DriverlReceiver Circuit
................................. 2-9
3-1
ID and Data Field Content ............................................ 3-1
3-2 Media
Sector and Track Structure ...................................... 3-2
3-3
Head Positioning Assembly ............................................ 3-3
3-4 9130K Functional Block Diagram ....................................... 3-5
3-5 Write Timing Diagram
................................................ 3-6
3-6 Read Timing Diagram ................................................ 3-7
4-1 9130K Flexible Disc Drive Exploded View
............................... 4-2
4-2 Drive Board
and Servo Board Removal .................................. 4-3
4-3 Front Panel
and Latch Removal ........................................ 4-4
5-1 Spindle Motor Speed Adjustment ....................................... 5-4
5-2 Spindle Drive Belt Adjustment ......................................... 5-5
5-3 9130K Test Setup ................................................... 5-6
5-4
Radial Head Alignment Waveform ...................................... 5-7
5-5 Head Assembly Retaining Screws ....................................... 5-8
5-6
Head Azimuth Waveform ............................................. 5-9
5-7 Track 0 Switch Retaining Screw ........................................ 5-9
5-8
Track 0 Waveform .................................................. 5-10
5-9 Index Detector Retaining Screw ....................................... 5-11
5-10 Index to Burst Waveform ............................................ 5-12
5-11 Write IF Waveform ................................................. 5-13
5-12 Write 2F Waveform ................................................. 5-13
5-13 DSU Controls and Indicators ......................................... 5-14
5-14 9130K/DSU Test Setup .............................................. 5-16
5-15 Foam Latch Insert .................................................. 5-17
5-16
Inner Box ......................................................... 5-18
5-17
Foam End Caps .................................................... 5-18
5-18
Outer Box ......................................................... 5-19
5-19 Test Point Locations (09130-66501) ................................... 5-19
5-20 Test Point Locations (82901-66515) ................................... 5-20
6-1 Drive Electronics Board PIN 09130-66501 Schematic Diagram .............. 6-3
6-2 Drive Electronics Board PIN
82901-66515 Schematic Diagram .............. 6-5
6-3 Servo Electronics Board PIN
09130-66500 Schematic Diagram .............. 6-9
6-4 Servo Electronics Board Component Locator ............................ 6-11
6-5 Drive Board PIN
82901-66515 Component Locator ...................... 6-12
6-6 Drive Board PIN
09130-66501 Component Locator ...................... 6-13

Chapter 1
General Information
Introduction
This service manual provides detailed information for servicing the 9130K disc drive.
Service Philosophy
The 9130K Flexible Disc Drive is comprised of three serviceable areas: the mechanical drive
assembly,
the drive electronics assembly and the servo electronics assembly. All assemblies
are serviced on the exchange program with the exception of some parts on the mechanical
assembly.
The field replaceable parts are outlined in the maintenance and assembly access
sections.
General Description
The HP 9130K rnini double sided flexible disc drive is a semi-random access mass storage
system employing a flexible magnetic medium. It consists of a mini disc drive, a servo
electronics circuit board and a drive electronics circuit board.
Each drive
module contains all the mechanical parts necessary for physically handling the
disc. These include the drive spindle and motor, 2 heads each having read/write and erase
capability, write protect sensor, track 0 sensor, index sensor, and activity LED on the front
panel. Each drive
module also contains a servo control board which controls the DC drive
motor speed and a drive electronics board which interprets and generate control signals,
controls
movement of the read/write head to the correct position, and also reads and writes
data.
The flexible magnetic medium used in the 9130K is called a flexible disc. The flexible disc
measures 133.4 mm (5.25 inches) on a side and has a 3.8 cm (1.5 inch) hole for alignment
on the disc drive spindle. The disc is enclosed in a protective polyvinylchloride (PVC) jacket
with a slot for access to
the recording surface. Both sides of the flexible disc are used for data
storage.
The recording head in the drive module is positioned by a mechanism driven by a stepper
motor and taut metal band. The head positioning mechanism operates in an open loop
configuration, that is, there is no feedback to the drive electronics board to determine the
actual position of the head.
The heads are mechanically coupled to the door mechanism so that closing of the door
causes the heads to make contact with the media.

1-2 General Information
Available Options
The following options are available with the 9130K flexible disc drive:
Option #010
This option consists of drive board PIN 09130-66501.
Option #011
This option consists of drive board PIN 82901-60015 found in the 8290X series drives.
Option #050
This option consists of the mechanical drive assembly with servo board and front panel PIN
4040-1838
and latch PIN 4040-1836 and associated hardware.
Option #051
This option consists of the mechanical drive assembly with servo board and front panel PIN
4040-1915
and grey latch PIN 4040-1914 and associated hardware.
Option #052
This option consists of the mechanical drive assembly with servo board and front panel PIN
4040-1915
and brown latch PIN 4040-1913 and associated hardware.
Environmental and Physical Specifications
Recording Specifications
HP Physical Track Format
Recordng Mode: Modified Frequency Modulated (MFM)
Rotational Speed: 300 RPM ± 1.5% (± 4.5 RPM)
Bit Density: 5456 BPI Track 34
Tracks
Per Inch: 48
Sides Per Disc: 2
Tracks
Per Side: 35
Sectors Per Track: 16
Bytes
Per Sector: 256 (362 including overhead bytes)
Bytes
Per Disc: 286,720 (formatted) 420,000 (unformatted)
Transfer Rate
164,000 bits per second nominal burst rate.
Access Time
Track to Track Seek: 5 msec. max.
Head Settling Time: 15 msec. max.
Spindle Motor Start Time: 250 msec. max.
Environmental Specifications
Operating Limits
Temperature: +100e to +44°e (50° F to 111.2° F)

General Information 1-3
Relative Humidity: 20% to 80% with maximum wet bulb temperature not to exceed 29.4°C
(85° F)
Altitude: 0 to 4572M (0 to 15000 feet)
Storage Limits
Temperature: - 41 ° C to 71° C (- 40.5° F to 159.8° F)
Relative Humidity: 20% to 80% with maximum wet bulb temperature not to exceed 29.4° C
(85° F)
Alignment Limits
Radial Alignment: 1.1 mils
maximum of track center at track 16 measured at 20° C (68° F)
and 50% humidity.
Azimuth: 18°
maximum clockwise or counterclockwise on tracks 16 and 34.
Power Requirements: +12VDC ± 0.6V @ 900ma nominal
+5VDC ± 0.25V @ 600ma nominal
Media Life
Revolutions
2,500,000 revolutions on any track.
Head Life: More than 15,000 hours of operation with HP media.
Physical Dimensions and Weight
Figure 1-1 illustrates the physical dimensions.
Weight:
2.04Kg (4.5 lbs)
Height:
85.85mm (3.38 inches)
Width:
149.1mm (5.87 inches)
Length:
203.2mm (8 inches)
Performance Specifications
Soft Read Errors: 1 in 10
9 bits
read on inner most track
Seek Errors: 1 in 10
6
seeks
See the 9130K Specification Document for further details.
"Hard Error" is defined as an error that cannot be recovered from using an HP approved
retry scheme.

1-4 General Information
8.37
(212.72)
~-----(l~~6)---
3.12
(79.37)
1.37
(34.92) SEE NOTE 3
*1.87*
*(47.62)*
14-------- 6.12(155.57) __ ~I
~===~=====::::~~
*5.87(149.22)* ~
14---
337
=]
(85.72)
NOTES:
I. DIMENSIONS GIVEN AS INCHES(MILLIMETRES).
2. * DENOTES DIFFERING TANDON DRIVE DIMENSIONS.
3. THIS DIMENSION FROM BACK OF FACEPLATE.
Figure 1-1: 9130K Physical Dimensions
Flexible Disc Media Use
Introduction
The storage medium used in the HP 9130K disc drive, is a flexible disc commonly called a
floppy. The flexible disc
measures 133.4 mm (5.25 inches) in diameter and has a 27.5 mm
(1.125 inch) hole for alignment
on the disc drive spindle. The disc is enclosed in a protective
plastic jacket with a slot for
head access to the recording surface. Both sides of the flexible
disc
are used for data storage.
By using flexible discs indentified as "double-sided", up to .25 megabytes of data can be
stored on each disc. Since some of the storage is used in subsystem overhead, the exact
amount available for user storage depends upon the controller subsystem. Refer to the
appropriate mainframe programming or reference manual for details. Double-sided flexible
discs (HP
part number 92190A, package of ten) are available from HP's computer supplies
catalog, by calling
the toll free order number 800-538-8787.
Each flexible disc must be initialized before it can be used for data storage. The initialization
procedure marks each disc track, checks for defective tracks, and may establish file director-
ies. Refer to
the mainframe programming or reference manual for correct procedures.

General Information 1-5
CAUTION
ONLY HP MEDIA IS APPROVED FOR USE IN THE 9130K
FLEXIBLE DISC
DRIVE. USE OF OTHER MEDIA MAY RESULT
IN PREMATURE DISC FAILURE OR DAMAGE TO THE DRIVE.
HP MEDIA WILL ALWAYS HAVE AN/HP LABEL ON IT.
HP RIGOROUSLY TESTS EACH BATCH OF MEDIA FOR
ERROR
RATE AND WEAR PERFORMANCE IN ADDITION TO
INITIAL VENDOR QUALIFICATION. ONLY IN THIS WAY CAN
HP ASSURE RELIABLE MEDIA PERFORMANCE.
THE USE OF NON-HP MEDIA FOR SINGLE USE APPLICA-
TlONS SUCH AS DATA INTERCHANGE WILL PROBABLY
NOT
DAMAGE THE DRIVE OR MEDIA BUT, IF EXTENDED
USE
IS ANTICIPATED, THE DATA MUST BE TRANSFERRED
TO HP MEDIA.
EXTENDED USE OF NON-HP APPROVED MEDIA WILL VOID
WARRANTY AND SERVICE CONTRACTS ON THE INSTRU-
MENTS.
Operating Cleanliness
To prevent potential damage or data loss, it is extremely important to maintain the cleanli-
ness of the disc and air within the disc drive. The disc drive should not be operated in an
environment in which dust, smoke, moisture, oil or chemical vapor or other foreign matter
are present. Also, be sure to strictly follow the disc handling gUidelines.
The critical elements involved in the read/write process are shown in Figure 1-2. The
read/write heads must maintain contact with the media during the read and write opera-
tions. Also shown are various types of contaminants and their size relationships. A contami-
nant particle. hard enough and of the right size may scratch either the oxide coating of the
disc or the head surface. Even if the particle is not hard enough to scratch, it may be hard
enough to lift the head from the disc surface and cause data errors.
Handling Discs
The flexible disc is basically maintenance free, but it is delicate and MUST BE HANDLED
CAREFULLY. Remember, the disc contains your valuable data and programs and should
be treated accordingly. A good rule of thumb is to treat the disc as you would a valuable
record album. Here are some specific DO's and DON'Ts to avoid loss of data or damage to
the discs.
EVEN A LITTLE
CARELESSNESS IN DISC HANDLING CAN DRAMATICALLY REDUCE
THE LIFE OF THE DISC.

1-6 Generallnformation
100
80
!
~ 60
«
'C
os
Q)
J:
Q)
~ 40
Qi
II:
20
1 win
r--
r-
r-I'-o
"
'\
Relative Read Signal Strength
VS Head Separation From
The Media Surface
\ \
1\
~
Head To Media Distance (winches)
100W
in 1000
win
I
I
I\.
,,~
........ "
"'t--
1 t
~~
~:;;;~.;~.~.
. ..-AO
Smoke Finger Dust Hair
Particle Print Particle
10.0001'-in
Figure 1-2: Head/Media Critical Requirements
DO
Backup Disc Frequently
There is always a chance'of losing data when mass storage devices are accessed. There are
many causes in any computer system-a programming bug, operator error, power failure,
or hardware failure. In the case of flexible discs, another mode is possible-media failure
from
contamination or wearout. YOUR ONLY PROTECTION AGAINST DATA LOSS IS
FREQUENT BACKUP OF DATA FILES.
Return Disc to Storage Envelope when Not in Use
This is the single most important thing to remember about handling a disc
because it prolongs disc life by protecting it from dust and scratches. Be-
tween uses discs should be stored upright in a dust free container. The box
that the discs are shipped in, or a similar container, is a good choice.
Operate in a Clean Environment
Airborne contaminants and particles accidentally dropped onto the disc
will cause the disc to wear out prematurely and may cause unreliable data
storage and retrieval operations. Some of the most common contaminants
are DUST, SMOKE, ASHES and ERASER PARTICLES. Chemical vapors
may also cause premature wearout.

General Information 1-7
Maintain Proper Temperature and Environment
The proper operating range for the 9130K is 10 C (500 F) to 44 C (1110 F)
and 20% to 80% relative humidity. While temperature is usually easy to
control, it
may be necessary to make special provisions to keep the humid-
ity in
the proper range. Although the disc will continue to operate outside
the normal recommended humidity range, it will wear out more quickly
and will produce a higher error rate.
Avoid Magnetic Fields
Since the data is stored as a pattern of magnetic fields on the disc, it can
easily be erased by an external magnetic field. Avoid placing a disc near
power transformers, magnets or large disc memories. Additionally, while
HP goes to great lengths to confine the magnetic fields produced by CRT
deflection shields,
CRT's with magnetic deflection systems have been
known to destroy data on discs, and it is a good idea to avoid placing discs
on top of CRT's.
Remove Disc from Drive when Not in Use
Remove the disc completely from the drive when access is not needed for
an extended period of time.
Use a Felt Tip Pen to Label Discs
Use a soft felt tip pen to label the disc, and be careful to write only in the
label area provided. Avoid the exposed media while labeling the disc. If
possible, write on the large labels BEFORE applying them to the disc
jacket.
Replace Discs Frequently
j l
~
Although discs are designed to provide several million revolutions of useful life (approx-
imately 2 to 4 months of use), they will eventually wear out. The life of a disc is VERY
dependent upon how carefully it is handled and how much it is used. If there are ever visible
signs of
abrasions on the disc, do an immediate backup and discard the worn disc.
DON'T
Do Not Touch the Exposed Surface of the Disc
The thickness of a fingerprint is enough to lift the head off the disc and
cause errors (See Figure 1-2). The oils in a fingerprint will also collect dust
which can cause a disc to wear out sooner than it normally would. Be
especially careful
when handling the disc as it is very easy to grasp the disc
with a
thumb directly over the exposed media.

1-8 General Information
Do Not Bend or Fold the Disc
The disc is flexible but will not operate if it is creased. Using ball point pens,
rubber bands, paper clips, etc. can crease the disc.
Do Not Try to Clean a Disc
The inside surface of the disc jacket is covered with a special material that cleans the disc as
it rotates. Any other method of cleaning may cause solvent damage to the media or scratch
the disc, causing loss of data. If a disc becomes dirty or scratched, immediately copy the
data to a new disc and dispose of the old disc.
Disc Loading
CAUTION
IF MEDIA IS EVER DESTROYED (IF IT LOOKS ANYTHING
LIKE THE PHOTO BELOW) IN YOUR 9130K DISC DRIVE,
STOP USING THE DRIVE UNTIL IT CAN BE SERVICED. THIS
IS EXCEPTIONALLY IMPORTANT, AS CONTINUED USE OF
THE DRIVE WILL DESTROY MORE MEDIA. IMMEDIATELY
CALL YOUR NEAREST HP SALES SERVICE OFFICE (SEE THE
LIST
IN THE BACK OF THIS MANUAL FOR THE NEAREST
OFFICE).
Figure 1-3: Damaged Media
Insert the flexible disc into the drive as shown in Figure 1-4 (be sure that the label side faces
up).
Push the disc in until you feel it bottom out against the rear of the disc drive, then close
the drive door latch. Never force the latch, as the media can be latched off center within the
protective jacket.

General Information 1-9
Figure 1-4: Loading the Disc
Write Protection
The disc has the capability of being write protected. This feature prevents the accidental
erasure of data previously recorded on the disc. The write protect is enabled when the write
protect notch on the jacket of the disc is covered (see Figure 1-4). When the notch is
uncovered, data can be written on the disc.
The write protect notch may be covered by placing a tab over the notch on the top side of
the disc jacket and then folding it over the edge to cover the notch on the bottom side.
Installation of
the tab is shown in Figure 1-5.
WRITE
PROTECT NOTCH
.,,--------,L
o
TAB
o
Figure 1-5. Write Protect Tab Installation
FOLD OVER TO
BACK OF DISC
o

Chapter 2
Interface Information
Introduction
This chapter provides the interface information for the 9130K Flexible Disc Drive. The
information provided in this chapter includes connector locations and pin-outs, signal line
descriptions
and typical interface driver and receiver circuits.
Interface
The flexible disc drive 110 connector (J1) is located on the rear edge of the drive electronics
board.
The 34 pin edge connector mates with the HP connector part number 1251-3916.
Primary Power Requirements
+12VDC ±0.6VDC @ 900MA (MAX)
+5VD ± 0.25VDC @ 600MA (MAX)
Maximum ripple 100 MV PP
DC power is supplied through a 4 pin connector (J2). The mating connector (not supplied)
is HP part number 1251-4525. Four contacts PIN 1251-4615 are also required.
The connector (J2) pin out is shown in Figure 2-1.
Pin Supply Voltage
1 + 12VDC
2 + 12V Return
3
+5V Return
4
+5VDC
Figure 2-1: Connector J2 Pin Out

2-2 Interface Information
The pin-out for J2 is shown in Figure 2-2.
GND
1
3
5
9
11
13
15
17
19
21
23
31
Circuit
Side
GND
7
25
27
29
33
Circuit
Side
Pin
Pin
Input Control Lines
Signal
Description
2
Connector Clamp
4 (Spare)
6 Drive Select 3
10
Drive Select 0
12
Drive Select 1
14
Drive Select 2
16
Motor On
18
Direction Select
20
Step
22
Composite Write Data
24 Write Gate
32 Side One Select
Component
Side
Output Status Lines
Signal
8
26
28
30
34
Component
Side
NOTE
Description
Index
Track 0
Write Protected
Composite Read Data
Connector Clamp
The drive electronics and bus lines use negative true logic.
34 2
Figure 2-2: Connector Jl Pin Out (Circuit Side)

Signal Line Description
Input Control Lines
Drive Select Lines
Interface Information 2-3
There are four drive select lines which are used for selecting and de-selecting one of three
disc drives attached to the controller.
When
the logic level on the drive select line is low, the disc drive electronics are enabled and
the drive will respond to step or Read/Write commands.
The drive select line must remain stable in
the low state until the step or Read/Write
command is completed.
When
the logic level on the drive select lines are high, the input control lines and output
status lines are disabled.
There
is also a user installed option jumper available to utilize a fourth drive select line.
The disc drive
address is determined by a select code shunt block located on the drive
electronics circuit board.
The drive select lines 1 through 3 provide a means of daisy
chaining a maximum of
three disc drives to a controller. An undefined operation may result
if more than one drive is assigned the same select code or if more than one of the drive
select lines are low simultaneously.
Motor On
A low logic level on this line causes the drive motor to accelerate and stabilize in less than
250 msec. When this line goes high, the drive motor decelerates to a stop.
Direction Select and Step Lines
When a disc drive is selected, a low pulse greater than 1 /-Lsec. but less than 2 msec.
appearing on the step line initiates head assembly motion. The direction of this motion is
determined by the logic level appearing on the direction select line when the step pulse is
issued. A high logic level on the direction select line when the step pulse is issued the
direction of motion is outward (step-out) away from the center of the disc. A logic low on the
direction select line results in the inward direction (step in) of motion toward the disc center.
To
ensure proper positioning, the direction select line should be stable 1 msec. minimum
prior to the
step pulse and remain stable until 1 /-Lsec. after the step pulse. The access
motion
is initiated on the trailing edge of the step pulse.
Consecutive trailing
edges of step pulses should not be less then 5 msec. apart.
The drive electronics
will ignore step pulses if any of the following conditions exist:
• The write gate line is low.
• The direction select is high and the head position is at track O.
• The drive is not selected.

2-4 Interface Information
Composite Write Data
When the disc drive is selected, this line provides the bit serial composite write data pulses
that control the switching of the write current in the selected head. The write electronics
must
be enabled by the write gate line.
Write Gate
When this line is low, the write electronics are enabled for writing data (read electronics are
disabled). This line enables write current to flow in the selected read/write head.
Data
is written under the control of the composite write data line and side one select line.
Changes of state on the write gate line should occur before the first write data pulse. When
the write gate line is high, all write electronics are disabled.
If a write protected disc is installed; the write electronics are disabled irrespective of the state
of the write gate and side one select lines.
Side One Select
The Side One Select line defines which side of a two sided disc is used for information
transfer.
A high logic level selects
the side' '0" read/write head and a low logic level selects the side 1
read/write
head.
Output Status Lines
Index
An index pulse occurs once every revolution of the disc (200 msec. nominal) to indicate the
begining of a track.
The leading edge of this signal is used to insure data accuracy during format. The index line
remains low for
the duration of the index pulse.
Track 0
This line indicates to the controller that the read/write head is positioned on track O. The
track asignal remains low until the head is moved from track O. This is accomplished by
anding the track aswitch and phase aof the stepper motor control.
Write Protected
This line goes low when the disc is write protected to disable the write electronics.
When the write protect line goes high, the write electronics are enabled and write operations
may be performed. If the controller issues a write command when the disc is write protected
an error condition will be reported to the host system.
Composite Read Data
Data and clock transitions are transmitted on this line when the disc drive is selected. Each
flux transition
detected by the head provides a logic low pulse of 1 J-lsec. ±. 25 on this line.

Interface Information 2-5
POWERON ~~------------------------~/I
MOTORON -.l
~F~_1_0_0_M_S_M_I_N ____________ ~/~/ ______ __
DRIVE SELECT ----+--i
VALlDTRKOO
ANDWRT. PROT. ----+--+--t
OUTPUT
~ 250 MSEC MAX
---+--+-- ...........
DIRECT 10 N -----t---t--_
SELECT
I.-1 jJ.sMIN
WRITE DATA __ -+--+-_-I-.JIO:....I..U.JiI~'-+- ___ """'"
VALID
READ
DATA ___ -+--+- __ 2_0_M_S_M_IN ___ ~
75 MS MAX ---1
14---- 250 MSEC~
Figure 2-3: General Control and Data Timing Requirements

2-6 Interface Information
J3
I
SHUNT
~_--'. BLOCK
J4
Figure 2-4: Connector Location
Figure 2-5: Connector J4 Pin Out
: