HP 7957A User manual

HEWLETT - PACKARD
HP 7957A AND HP 7958A DISC DRIVES
HARDWARE SUPPORT MANUAL

CERTIFICATION
Products, materials, parts, and services furnished on this order
have been provided in accordance with all applicable Hewlett-
Packard specifications. Actual inspection and test data per-
taining to this order is on file and available for examination.
Hewlett-Packard's calibration measurements are traceable to
the National Bureau of Standards to the extent allowed by the
Bureau's calibration facilities.
The Hewlett-Packard Quality Program satisfies the require-
ments of FAR 52.246-15.

HP 7957A AND 7958A DISC DRIVES
HARDWARE SUPPORT MANUAL
Manual part number: 07957-90903
Microfiche part no. 07957-90803
Printed: SEPTEMBER 1987
Printed in
U.S.A.
MODELS COVERED
Edition 2
E0987
This manual covers the following models: HP 7957A and
HP 7958A.
OPTIONS COVERED
In addition to the standard model, this manual covers the
following options: 015, 550.
r1
1
;- HEWLETT
a!~ PACKARD
HEWLETT-PACKARD
P.O. Box 39, Boise, Idaho 83707-0039

Notice
The information contained in this document is subject to change without notice.
HEWLETT-PACKARD MAKES NO WARRANTY
OF ANY KIND WITH REGARD TO THIS
MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. HEWLETT-PACKARD shall
not be liable for errors contained herein or for incidental or consequential damages in connection with the
furnishing, performance or use of this material.
HEWLETT-PACKARD assumes no responsibility
for the use or reliability of its software on equipment
that is not furnished by HEWLETT-PACKARD.
This document contains proprietary information, which
is protected by copyright. All rights are reserved.
No part of this document may be photocopied, reproduced or translated to another language without the
prior written consent
of HEWLETT-PACKARD Company.
2
Copyright © 1986,1987 by HEWLETT-PACKARD
FOR U.S.A. ONLY
The Federal Communications Commission has specified that the following notice
be brought
to the attention of the users of this product.
FEDERAL COMMUNICATIONS COMMISSION
RADIO FREQUENCY INTERFERENCE
STATEMENT
Warning: This equipment generates and uses radio frequency energy and if not installed and used
properly,
that is, in strict accordance with the manufacturer's instructions, may cause interference
to radio and television reception. It has been type tested and found to comply with the limits for a
Class B computing device in accordance with the specifications in Subpart J
of Part 15 of FCC
Rules, which are designed
to provide reasonable protection against such interference in a residential
installation. However, there
is no guarantee that interference will not occur in a particular installa-
tion.
If this equipment does cause interference to radio or television reception, which can be deter-
mined
by turning the equipment off and on, the user is encouraged to try to correct the inter-
ference by one
or more of the following measures: re-orient the receiving antenna; relocate the
computer with respect to the receiver; move the computer away from the receiver; plug the com-
puter into a different branch circuit.
If necessary, the user should consult the dealer or authorized
field service representative
for additional suggestions. The user may find the following booklet
prepared by the Federal Communications Commission helpful: "How
to Identify and Resolve
Radio-TV Interference Problems". This booklet
is available from the U.S. Government Printing
Office, Washington, DC 20402. Stock No. 004-000-00345-4.

GENERAL -This product and related documenta-
tion must be reviewed for familiarization with
safety markings and instructions before operation.
SAFETY SYMBOLS
-'-
Instruction manual symbol: the product
will be marked with this symbol when it
is necessary for the user to refer to the
instruction manual in order to protect
the product against damage.
Indicates hazardous voltages.
Indicates
earth (ground) terminal.
WARNING
The WARNING sign denotes a hazard.
It calls attention to a procedure or prac-
tice that,
if not correctly performed or
adhered to, could result in personal in-
jury.
Do not proceed beyond a
WARNING sign until the indicated
conditions are fully understood and met.
ICAUTION I
The CAUTION sign denotes a hazard.
It: calls attention to an operating proce-
dure or practice that, if not correctly
performed or adhered to, could result in
damage to or destruction of part or all
of the product. Do not proceed beyond
a CAUTION sign until the indicated
conditions are fully understood and met.
SAFETY EARTH GROUND -This is a safety
class I product and is provided with a protective
earthing terminal. An uninterruptible safety earth
ground must be provided from the main power
Safety Considerations
source to the product input wlnng terminals,
power cord, or supplied power cord set. Whenever
it is likely that the protection has been impaired,
the product must be made inoperative and be
secured against
any unintended operation.
BEFORE APPLYING POWER - Verify that the
product is configured to match the available main
power source according to the input power con-
figuration instructions provided in this manual.
If this product is to be operated with an autotrans-
former make sure that the common terminal is
connected to the earth terminal of the main power
source.
SERVICING
WARNING
Any servlcmg, adjustment, maintenance, or
repair of this product must be performed only
by service-trained personnel.
Adjustments described in this manual
may be
performed with power supplied
to the product
while protective covers are removed. Energy
available
at many points may, if contacted,
result in personal injury.
Capacitors inside this product may still be
charged
after the product has been disconnec-
ted from
the main power source.
To avoid a fire hazard, fuses with
the proper
current rating and of the specified type (nor-
mal blow, time delay, etc.) must be used
for
replacement. To install or remove a fuse, first
disconnect the power cord from the device.
Then, using a small flat-bladed screw driver,
turn the fuseholder cap counterclockwise until
the cap releases. Install either end of a
properly
rated fuse into the cap. Next, insert
the fuse and fuseholder cap into the fusehold-
er by pressing
the cap inward and then tUfiting
it clockwise until it locks in place.
3

Printing History
New editions are complete revisions of the manual. Update packages, which are issued between editions,
contain additional and replacement pages
to be merged into the manual by the customer. The dates on the
title page change only when a new edition or a new update is published. No information is incorporated
into a reprinting unless it appears
as a prior update; the edition does not change when an update is
incorporated.
A software code may be printed before the date; this indicates the version level
of the software product at
the time the manual or update was issued. Many product updates and fixes do not require manual changes
and, conversely, manual corrections may be done without accompanying product changes. Therefore,
do
not expect a one-to-one correspondence between product updates and manual updates.
4
Edition 1
.................................................. DECEMBER 1986
Edition 2 ................................................. SEPTEMBER 1987
Herstellerbescheinigung
Hiermit wird bescheinigt, daB das Gerat/System HP 7957 A/HP 7958A in
Obereinstimmung mit den Bestimmungen von Postverfligung 1046/84
funkentstort ist.
Der Deutschen Bundespost wurde das Inverkehrbringen dieses
Gerates/Systems angezeigt und die Berechtigung zur Oberpriifung der Serie
auf Einhaltung der Bestimmungen eingeraumt.
Manufacturer's Declaration
This is to certify that the product(s) HP 7957 A/HP 7958A is in accordance
with the Radio Interference Requirements
of Directive FTZ 1046/1984. The
German Bundespost was notified that this equipment was put into circula-
tion; the right to check the series for compliance with the requirements was
granted.
Additional Information
for Test and Measurement Equipment
If Test and Measurement Equipment is operated with unscreened cables
and/or used for measurements on open setups, the user has to assure that
under operating conditions the Radio Interference Limits are still met at the
border
of his premises.

Chapter 1
General Information
Contents
Page
1-1
Introduction ........................... ' .......... : ........................................................... 1-1
Scope of Manual. ............................................................................................ 1-1
Options ...................................................................................................... 1-2
Related Manuals ............................................................................................. 1-2
Characteristics ............................................................................................... 1-2
Chapter 2
Interface Information Page
2-1
Introductioll ................................................................................................. 2-1
Supported I~SDI Features .................................................................................... 2-1
Drive Interface Characteristics .............................................................................. 2-1
Interface Signals ............................................................................................. 2-1
Drive Operating Features .................................................................................... 2-8
Drive/Head Selection Sequence .......................................................................... 2-8
Media Fc)rmat ........................................................................................... 2-12
Sector Format ........................................................................................ 2-12
Sector Offset
......................................................................................... 2-12
CS/80 Command Set Implementation ...................................................................... 2-12
Chapter 3
Theory
Of Operation Page
3-1
Introdllction ................................................................................................. 3-1
CS80/ESDI Controller [CEC] PCA-A2 .................................................................... 3-1
Transfers .................................................................................................. 3-2
Disc Format ................................................................................................. 3-2
Sparing ....................................................................................................... 3-5
Sequencc;~ .................................................................................................. 3-5
Sector SI)aring ............................................................................................ 3-5
Track Sparing ............................................................................................. 3-5
Errors
........................................................................................................ 3-6
Error Definition .......................................................................................... 3-6
Error Logs ................................................................................................ 3-6
Error Detection and Correction .......................................................................... 3-6
Disc Drive :PCA-Al
.......................................................................................... 3-7
Drive Mechanics .......................................................................................... 3-7
Preamplifier Board ....................................................................................... 3-9
5

Contents (continued)
Motor Control Board ..................................................................................... 3-9
Device Electronics Board ................................................................................. 3-9
Read/Write Functional Description ......................................................................... 3-9
Write Channel ............................................................................................ 3-9
Read Channel. ........................................................................................... 3-10
Read/Reference Clock Multiplexer ..................................................................... 3-10
Read/Write Head Select .............................................................................. 3-10
Power Supply Assembly PCA-A3 ........................................................................... 3-11
AC Input Circuits ........................................................................................ 3-11
Switch-Mode Supply ..................................................................................... 3-11
Power-On Reset ......................................................................................... 3-12
Summary
of Write Data Operation ........................................................................ .3-12
Summary
Of Read Data Operation ......................................................................... 3-12
CEC Functional Theory
.................................................................................. ~ .. 3-12
Bus Structure
............................................................................................ 3-12
Microprocessor Data
Bus ................................................................................ 3-13
Control, Clock Generator And Stretcher Circuit
....................................................... .3-14
Disc Data Controller (DDC)
IC ......................................................................... 3-14
Remote DMA Transfer
.................................................................................. 3-15
ESDI PAL ............................................................................................... 3-16
Write Gate And Address Mark Enable Delay Circuit
................................................ 3-16
Error Correction
......................................................................................... 3-16
Format
................................................................................................... 3-17
HP-IB Interface
IC ...................................................................................... 3-17
Buffers
................................................................................................... 3-1 7
DMA Bus Arbiter
........................................................................................ 3-18
Local DMA Transfers
................................................................................ 3-18
Microprocessor Transfers
............................................................................ 3-18
Remote DMA Transfers
.............................................................................. 3-18
EEPROM (When Used) .................................................................................. 3-18
LED Control.
............................................................................................ 3-19
Chapter 4 Page
4-1
Service Information
Introduction
................................................................................................. 4-1
Service Tools ........................................ ~ ......................................................... 4-2
PCA Locations ............................................................................................... 4-2
Cable Connectors ............................................................................................ 4-2
Signal Distribution ........................................................................................... 4-2
Power Distribution .......................................................................................... 4-2
Signal Notation .............................................................................................. 4-8
Block Diagram ............................................................................................... 4-8
Test Points ................................................................................................... 4-8
CS/80 Implementation Information ......................................................................... 4-8
Initialize Me~dia Command ................................................................................ 4-8
6

Contents (continued)
Initiate Diagnostics Command (DIAG) ................................................................... 4-9
CS/80 Describe Command Response ..................................................................... 4-9
Self-Test Controls ........................................................................................... 4-10
Fault/On Line Indicator ................................................................................. 4-10
Internal Diagnostics ......................................................................................... 4-10
Self Test
.................................................................................................... 4-12
Self-Test Subtests
........................................................................................ 4-14
Micro:processor Self Test
............................................................................. 4-14
RAM Self Test
....................................................................................... 4-14
ROM 'Checksum Test ................................................................................. 4-15
HP-IB Interface
IC Loopback Test .................................................................. .4-15
Buffer Test
........................................................................................... 4-16
Hardware/Software Initialization
................................................................... .4-16
Select A Drive ........................................................................................ 4-16
Command Complete
.................................................................................. 4-17
ESDI Status Check .................................................................................... 4-18
Reset Attention
....................................................................................... 4-19
Check
for Drive Ready ............................................................................... 4-19
Request Configuration
............................................................................... 4-20
Disc Drive Assembly PCA-Al Self Test ............................................................. .4-20
Seek Test Without Position Verify
.................................................................. .4-21
Read Write ECC Test ................................................................................ 4-21
Build Spare Tables .................................................................................... 4-22
Copy EEPROM Logs
to Self Test Cylinder (for drives with EEPROM only) ........................ .4-2
Finish HP-IB Interface
IC Initialization ............................................................. .4-22
Request Status
........................................................................................... 4-22
Request Status Example
................................................................................. 4-23
Utilities
..................................................................................................... 4-23
Run Time and Fault Logs (Media Based)
............................................................... .4-24
Run Time and Fault Logs (EEPROM Based)
........................................................... .4-24
EEPROl\l[ ................................................................................................ 4-25
Fault Status Bytes
........................................................................................ 4-26
Physical Jt\ddress Reporting
.............................................................................. 4-27
Run Time Sectors Read Count (Media and EEPROM Based)
........................................... 4-27
Error Rate Test
(.ERT) Log .............................................................................. 4-28
Error Byte Description
.................................................................................. 4-29
CS/80 No Execution Message Utilities ................................................................. .4-30
Clear :Logs ............................................................................................ 4-30
Preset ................................................................................................. 4-30
Faults/Errors During Error Rate Testing ............................................................ .4-30
CS/80 Send Message Utilities
........................................................................... .4-31
Read Fault Log ....................................................................................... 4-31
Read Run Time Error Log ........................................................................... 4-31
Read Error (ERT) Log ............................................................................... 4-32
Measure Seek Time
................................................................................... 4-33
Read Spare Table
..................................................................................... 4-33
Locatc~ And Read Full Sector ........................................................................ 4-34
Servo Test ............................................................................................ 4-34
7

Contents (continued)
Pattern Error Rate Test (ERT) (Log Option) ........................................................ .4-35
Random Pattern Error Rate Test (Log Option) ..................................................... .4-36
Read Only Error Rate Test (Log Option) ............................................................ .4-37
Random Read Only Error Rate Test (Log Option) .................................................. .4-38
Read Revision Numbers
.............................................................................. 4-38
Troubleshooting
............................................................................................ 4-39
Chapter 5 Page
5-1 Remo,'al and Replacement
Introduction ................................................................................................. 5-1
Preparation For Service ..................................................................................... 5-3
Removal and Replacement
.................................................................................. 5-3
Top Shroud ............................................................................................... 5-3
Front Panel ............................................................................................... 5-3
LED Cable Removal. ..................................................................................... 5-4
ROM RemovaL ........................................................................................... 5-4
CS80/ESDI Controller (CEC) PCA-A2 ................................................................... 5-4
Fan ....................................................................................................... 5-5
Power Supply Assembly PCA-A3 ......................................................................... 5-5
Disc Drive Assembly (HDA) PCA-AI
.................................................................... 5-6
Tray Removal and Replacement ......................................................................... 5-6
Chapter 6
Replaceable
Parts
Page
6-1
Introduction ................................................................................................. 6-1
Ordering Information ........................................................................................ 6-1
8

Figures and Tables
Figure or Table Page
Figure
2-1. Drive Selection/Deselection Timing ............................................................. 2-6
Figure 2-2. Write Gate Timing During Format ............................................................. 2-7
Figure
2-3. Write Gate Timing During Normal Write ...................................................... 2-7
Figure 2-4. Read Gate Timing .............................................................................. 2-8
Figure 2-5. TRANSFER REQ/TRANSFER ACK Handshake Timing ..................................... 2-10
Figure 2-6. Index/Sector Timing ........................................................................... 2-11
Figure 2-7. Track-To-Track Sector Offset ................................................................. 2-11
Figure 2-8. Recommended Drive/Head Selection Sequence ................................................ 2-12
Figure
2-9. Sector Offset ................................................................................... 2-13
Figure
3-1. Disc Recording Format ......................................................................... 3-3
Figure
3-2. Sector Format ................................................................................... 3-4
Figure 3-3. Disc Drive Assembly PCA-Al Block Diagram .................................................. 3-7
Figure 3-4. Disc Drive Assembly PCA-Al Functional Elements ............................................ 3-8
Figure 3-5. Disc Drive Functional Block Diagram ......................................................... 3-25
Figure
3-6. CS80/ESDI Controller (CEC) PCA-A2 Functional Block Diagram ............................ 3-27
Figure
4-1. Field Replaceable Assembly (FRA) Location ................................................... 4-3
Figure
4-2. CS80/ESDI Controller (CEC) PCA-A2 Layout and Cable Connections ........................ .4-4
Figure
4-3. Disc Drive Assembly PCA-Al, Layout and Cable Connections ................................ .4-5
Figure
4-4. Power Supply (PCA-A3) Test Points and Voltages .............................................. 4-6
Figure
4-5. Cabling Diagram ............................................................................... .4-7
Figure
4-6. Self-Test Display .............................................................................. .4-11
Figure 4-7. Signal Distribution ............................................................................ .4-47
Figure
5-1. Order of Disassembly ........................................................................... 5-2
Figure 6-1. Disc Drive, Exploded View ..................................................................... 6-3
Table
1-1. Disc Drive Characteristics ....................................................................... 1-3
Table 2-1. General Configuration Response Bits ............................................................ 2-2
Table 2-2. Specific Configuration Response Bits ............................................................ 2-3
Table
2-3. Standard Status Response Bits ................................................................... 2-4
Table 2-4. ~(alid I-lead Select Values ........................................................................ 2-6
Table 2-5. CS/80 Command Implementation ................................................................ 2-9
Table
2-6. Request Status Summary ........................................................................ 2-14
Table
2-7. Utility Command Summary ..................................................................... 2-15
Table
3-1. I)isc Drive Capacity .............................................................................. 3-3
Table
3-2. llead Selection .................................................................................. 3-10
Table 3-3. Mnemonic Table ................................................................................ 3-20
Table 3-4. I:<'lag Status Values ............................................................................... 3-23
Table 4-l. Supported ·Utilities
.............................................................................. 4-13
Table
4-2. Error Codes ..................................................................................... 4-40
Table 6-l. Disc Drive Replaceable Parts .................................................................... 6-2
Table
6-2. j:\bbreviations .................................................................................... 6-4
Table
6-3. Code List of Manufacturers ..................................................................... 6-5
9

General Information
1-1. INTRODUCTION
The Hewlett-Packard 7957A and HP 7958A Disc
Drives are random access, data storase devices
designed
for use with small and medium sized
computer systems. The formatted storage
capacities
of the HP 7957 A and HP 7958A are 81
megabytes and 130 megabytes, respectively. In this
manual, unless otherwise specified, "disc drive"
refers
to the HP 7957A and HP 7958A.
The disc drive employs three (HP 7957 A) or five
(HP 7958A) nonremovable 130-millimetre
(5.12-inch) discs
for storage media. Each disc sur-
face employs one movable head
to service its data
tracks. The bottom surface
of the lowest disc in
the stack contains continuous prerecorded servo
data which
is used to ensure the precise positioning
of the read/write heads.
Head positioning
is performed by a rotary actuator
and a closed-loop servo positioning system.
Mechanical and contamination protection
for the
discs, heads, and the rotary actuator
is provided by
a sealed head-disc module. The head-disc module
includes a self-contained air filtration system
which supplies clean air and temperature equaliza-
tion throughout the module.
Also included in the disc drive are a
Hewlett-Packard Interface
Bus (HP-IB) controller
and a power supply.
The disc drive contains internal self-test diagnostics
and a fault-finding system which exercise key
functions
of the disc drive. Self test is performed
automatically
at power on and can also be in-
itiated by the host. Go/no-go test results are indi-
cated by a green/red indicator
on the front panel.
If a failure occurs, information on the cause of the
failure
can be determined by viewing the status of
the green/red indicators.
The disc drive is packaged in a stand-alone desktop
cabinet.
AClcessories available include a desk-height
stand-alone cabinet designed
to hold the disc drive
and
other desktop stack modules. A kit for rack
1
mounting the disc drive in a standard EIA
equipment rack
is also available.
This manual provides all the service information
needed
to maintain the disc drive. Details of the
control functions provided by the host computer
are described in the installation documentation
provided with the computer.
1-2. SCOPE OF MANUAL
The manual is divided into six chapters as follows:
a. Chapter 1 contains a general description of the
disc drive.
b. Chapter 2 provides information about the ESDI
Interface between the controller PCA and
the
head disc assembly (HDA). It also contains in-
formation
on CS/80 Command Set implementa-
tion, Request Status Summary
and Utility
Command summary.
c. Chapter 3 describes the operating principles of
the disc drive.
d. Chapter 4 contains servicing information for the
disc drive, including instructions on how to use
the diagnostics tools.
e. Chapter 5 supplies step-by-step removal and
replacement procedures for all field-replaceable
assemblies and parts in
the disc drive.
f. Chapter 6 lists and illustrates all of the field-
replaceable assemblies and parts in
the disc
drive.
Appendix A provides a listing and copy
of all the
service notes applicable to the HP 7957A and HP
7958A Disc Drives.
1-1

General Inf orma tion
7957 A/7958A
1-3. OPTIONS
Option 015 is the power option. The only
requirement is for the switch in the power module
to be placed in the proper position. Option 550 is
the deletion of the Model 10833B HP-IB Cable
from the order.
1-4. RELATED MANUALS
For operating and installation instructions. refer to
the H P 7957A and H P 7958A Disc Drive Owners
Manual, part no. 07957-90901. and the Site
Environmental Requirements lor Disc/Tape Drives
Manual,
part no. 5955-3456. For instruction set in-
formation. refer to the CS/80 Instruction Set
1-2
Programming Manual, part no. 5955-3442. For
additional service information, refer to the CS/80
External Exerciser Reference Manual, part no.
5955-3462.
The CE Handbook for the HP 7957A
and HP 7958A Disc Drive is part no. 07957-90905.
1-5. CHARACTERISTICS
Characteristics of the disc drive. including physical
dimensions
and power requirements, are listed in
Table
1-1, Disc Drive Characteristics. Detailed
specifications for the disc drive, including en-
vironmental requirements.
are listed in the Site
Environmental Requirements for Disc/Tape Drives
Manual,
part no. 5955-3456. This publication is
supplied with the disc drive.

General Information
7957 A/7958A
Table 1-1. Disc Drive Characteristics
SAFETY
Meets all applicable safety standards of IEC 380 and IEC 435.
UL Listed UL 114 and UL 478.
CSA certified to CSA C22.2 No. 143 and No. 154.
POWER REQUIREMENTS
Specified Source (selected by rear panel VOLTAGE SELECTOR
switch)
Voltage (true RMS): 115V range; 100V, 115V, 120V, single phase,
Freqw3ncy:
Typical Current
Typical Power:
SIZE/\~EIGHT
Height:
Width:
Depth:
Net W~:dght:
Shipping Weight:
(inclusive tolerance range is 90V to 132V)
230V range; 220V, 240V, single phase, (inclusive
tolerance range is 180V to 264V)
47.5
to 66 Hz
(true RMS): 115V range; 0.87A
230V range;
0.48A
115V range; 65W
230V range; 65W
132
mm (5.2
in. )
325
mm (12.8
in. )
285
mm (11. 2 in. )
9.9
kg
(21.8
lb)
14.0
kg
(31.0
lb)
1-3

Interface Information
2-1. INTRODUCTION
This chapter describes the implementation of the
Enhanced Small Device Interface (ESDI) on the
disc drive mechanisms. Also included at the end
of this section is information on the CS/80
Command Set implementation, request status sum-
mary and utility command summary. Included
is
the ESDI information specific to these products, as
well as a discussion of operating features designed
to improve system performance. The information
in this chapter
is intended to give the user an in-
sight into how the product operates within the
ESDI environment.
The disc drives conform fully to the specifications
defined in the following industry-standard docu-
ment: Enhanced
Small Device Interface
Specification (REV F). It is assumed that the
reader
is thoroughly familiar with the general
operation
of ESDI as defined in the specification.
When used in conjunction with the ESDI
specification, this chapter provides the additional
information necessary
to successfully communicate
with the drive
'Over ESDI.
NOTE
To maintain consistency with standard
ESDI terminology, the term "drive" is
used to refer to the disc mechanism in
this chapter.
2-2. SUPPORTED ESDI FEATURES
The disc drives support the following standard
ESDI features:
• Serial Mode Operation
•
10 Megabit Per Second Transfer Rate
• Configuration Reporting
• Drive Hard Sectoring
• Daisy Chain Configuration (up to 7 drives)
• Power-On Sequencing
• Track Offsets
• Internal Self-Test Diagnostics
• Media Defect List
2-3. DRIVE INTERFACE
CHARACTERISTICS
2
The drive complies with the physical interface
characteristics defined in the ESDI specification.
Refer
to the specification for cabling requirements
and connector pin assignments. The physicalloca-
tion
of the two interface, one power and one
ground connectors are shown in figure 6-1. (For
clarity, the power connector pin assignments
are
also shown.)
The drive electrical interface circuits
conform to
the specified electrical requirements. The drive uses
the 220/330-ohm termination option
to terminate
all control signals originating
at the controller.
2-4. INTERFACE SIGNALS
The serial-mode use of all data and control signal
lines
is defined in the ESDI specification. The fol-
lowing paragraphs include additional product-
specific considerations regarding the use
of each
signal line. Tables
2-1, 2-2 and 2-3 provide response
bit information.
• DRIVE SELECT LINES. The drive responds
to selection by asserting its DRIVE SELECTED
line within 250 nanoseconds (see figure
2-1).
When selecting a drive, the controller must en-
sure that all drive select lines change within less
than
100 nanoseconds. This precludes any un-
desired drive selection during transition
of the
drive select lines.
2-1

Interface Information
7957 A/7958A
BIT
POSITION
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
o
Table 2-1. General Configuration Response Bits
DRIVE FEATURE
Tape Drive
Format Speed Tolerance Gap Required
Track Offset Option Implemented
Data
Strobe Offset Option Implemented
Rotational Speed Tolerance> 0.5%
Transfer Rate> 10 MHz
Transfer Rate> 5 MHz <= 10 MHz
Transfer Rate <= 5 MHz
Removable Cartridge Drive
Fixed Media Drive
Spindle Motor Control Option Implemented
Head
Switch Time> 15 usec
RLL Encoded (not MFM)
Controller Soft Sectored (Address Mark)
Drive Hard Sectored (Sector Pulses)
Controller Hard Sectored (Byte Clock)
* 1 indicates that drive implements specified feature.
BIT
VALUE*
o
o
1
1
o
o
1
o
o
1
1
o
1
o
1
o
If the controller attempts a write with an in-
valid head selected, the drive responds by set-
ting A
TTENTION and Invalid Or
Unimplemented Command status bit. If the
controller attempts
to read with an invalid
head, the read will be executed with the last
valid head selected.
• WRITE GATE. The WRITE GATE timing
used during formatting and normal writing
is
shown in figures 2-2 and 2-3, respectively.
• HEAD SELECT LINES. When selecting a
head, the controller must ensure that all head
select lines change within
less than 100
nanoseconds. This avoids an inadvertent head
selection during transition
of the head select
lines. Valid head select values
for each drive
are shown in table
2-4.
2-2
The following timing restrictions apply to the
WRITE GATE signal:
-When the drive performs a head switch opera-
tion, the controller must not activate WRITE
GATE until COMMAND COMPLETE is ac-
tivated, indicating completion
of the head
switch.
-When performing a write following a read,
WRITE GATE must
not be activated for a min-
imum
of 500 nanoseconds after READ GATE
is deactivated.

Table 2-2. Specific Configuration Response Bits
CMD
MODIFIER
BITS CONFIGURATION DATA
REQUESTED
11
10
9 8
0 0 0 1
Number of
cy1 inders,
fixed
0 0 1 0
Number of
cy1 inders, removable
0 0 1 1
Number of heads
Bits 15-8: Removable drive heads
Bits
2-0:
Fixed heads
0 1 0 0
Minimum
unformatted bytes per
track
0 1 0 1
Unformatted bytes per sector
0 1 1 0
Sectors per track
0 1 1 1
Minimum bytes in ISG field (not
including intersector speed
tolerance) :
Bits 15-8:
ISG bytes after
INDEX
Bits 2-0: Bytes per
ISG
1 0 0 0
Minimum bytes per
PLO
Sync field
1 0 0 1
Number of words of vendor-unique
status available
*HP 7957A - 06/6; HP 7958A - 09/9
(includes servo head)
Interface Information
7957A/7958A
DRIVE
RESPONSE
HEX DEC
05DD
1501
0000 0
00 0
* *
5780 22400
015E 350
0040
64
OC
12
2E 46
OOOE
13
0001 1
-When formatting the disc media, the controll-
er must activate WRITE GATE a minimum of
2.5 microseconds before the beginning of the
Address PLO Sync field (see figure
2-2). Once
activated, WRITE GATE may remain active for
the entire track. If deactivated. WRITE GATE
must remain inactive
for at least 200
nanoseconds.
two additional bytes of dummy data must be
written. This
is due to encoding delays, which
cause an 8-bit delay between the time the data
is transmitted to the drive and when it is actual-
ly written
on the media. This dummy data is
written in the Address Pad or Data Pad field as
appropriate.
-After writing the address field
or data field, -The drive must not be deselected while
WRITE GATE
is activated.
2-3

Interface Information
7957A/7958A
BIT
POSITION
15
14
13
12
11
10
9
8
7
6
5
4
2-4
Table 2-3. Standard Status Response Bits (l of 2)
DESCRIPTION
Reserved. This bit is always zero.
Removable Media
Not Present. The drive does not use removable media,
therefore this bit is always zero.
Write Protected, Removable Media. The drive does not use removable media,
therefore this bit is always zero.
Write Protected, Fixed Media. The drive does not include a write protect fea-
ture,
therefore this bit is always zero.
Reserved. This bit
is always zero.
Reserved. This bit
is always zero.
Spindle
Motor Stopped. This bit indicates the spindle motor is not up to speed.
If this bit is set, the controller should send a Control command specifying a
Start Spindle Motor operation. A change of state on this bit due to the suc-
cessful execution
of a Start Spindle Motor or Stop Spindle Motor operation
does not cause ATTENTION to go active.
Power-On Reset Conditions Exist. This bit notifies
the controller that the
drive operating parameters have been set to their default values. This bit is set
following a
power-on sequence or when an internal drive fault condition oc-
curs that causes an internal power-on reset operation to occur (e.g., a momen-
tary loss of dc power). The controller may have to reconfigure drive operat-
ing conditions. The controller should also check the Spindle Motor Stopped
status bit (bit 9) and perform a motor-on sequence if necessary.
Command
Data Parity Fault. This bit indicates that the drive detected a
parity
error on the serial command data received from the controller. The
drive will not attempt execution of the command if a parity error is detected.
Interface Fault. This bit indicates that the drive has detected an interface
protocol timeout. An Interface Fault occurs when the controller fails to
respond to an edge of the TRANSFER REQ/TRANSFER ACK handshake
protocol within 13 milliseconds (see figure 2-5).
Invalid
Or Unimplemented Command. This bit indicates that the drive has
received an invalid
or reserved command, command modifier, or command
parameter. The drive will also set this bit if the controller sends a valid com-
mand that the drive is currently unable to execute (e.g., a Seek command while
the spindle motor is stopped).
Seek Fault. This bit indicates that a catastrophic seek failure occurred. This
bit will be set
only after the drive has made every attempt to successfully
complete the seek. The controller may elect to retry the seek operation,
however such retries will most likely be unsuccessful.