HP 7942 User manual

HEWLETT-PACKARD
HP 7942 AND HP 7946 DISC/T APE DRIVES
SERVICE 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.

rlin- HEWLETT
.:~ PACKARD
SERVICE MANUAL
7942 AND 7946
DISC/T APE DRIVES
Manual part no. 07942-90903
Microfiche part no. 07942-90803
PRINTED: FEB 1987
Printed in U.S.A.
Serial Number Prefix
07942-90903
E0287
The main part of this manual applies directly to HP 7942 and HP 7946 Disc/Tape Drives with serial numbers prefixed 2615
and subsequent. Refer to Appendix A for serial numbers prefixed 2614 and prior.
OPTIONS COVERED
In addition to the standard models, this manual
covers
the following options: 01 5 and 550.
FOR U.S.A. ONLY
The Federal Communications Commission (in 47 CFR 15.838) has specified that the fol-
lowing 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 frequeucy energy and if not installed and used properly, that is, in
strict accordalllce with the manufacturer's instructions, may cause interference to radio and television reception. It has
been type test.~d and found to comply with the limits for a Class B computing disc/tape drive in accordance with the
specifications in Subpart J of Part 15 of FCC Rules, which are designed to provide reasonable protection against such
interference ill a residential installation. However, there is no guarantee that interference will not occur in a par-
ticular install~ltion. If this equipment does cause interference to radio or television reception, which can be determined
by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the fol-
lowing measures: reorient the receiving antenna; relocate the equipment with respect to the receiver; move the equip-
ment away from the receiver; plug the equipment into a different branch circuit. If necessary, the user should consult
the dealer or 3,uthorized field service representative for additional suggestions. The user may find the following booklet
prepared by tllte Federal Communications Commission helpful: "How to Identify and Resolve Radio-TV Interference
Problems". This booklet is available from the U.S. Government Printing Office, WashingtoD, DC 20402. Stock No.
004-000-00345-4.
HEWLETT-PACKARD COMPANY
P.O. BOX 39 BOISE, IDAHO 83707, U.S.A.

PRINTING HISTORY
New editions incorporate all update material since the previous edition. Updating Supplements, which are is-
sued between editions, contain additional and revised information to be incorporated into the manual by the
user. The date on the title page changes only when a new edition is published.
First Edition
..
Second Edition
Third Edition .
FEB 1985
AUG 1986
FEB 1987
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 furnish-
ing, performance or use of this material.
This document contains proprietary
information which is protected by copyright. All rights are reserved. No
part of this document may be photocopied or reproduced without the prior written consent of
Hewlett-Packard Company.
COREFILE-PARCORE
11

PREFACEI
This publication provides field service information for the HP 7942 and HP 7946 Disc/Tape Drives. The
HP 7942 consists of a 24-megabyte disc drive and a tape drive combined in a single desktop cabinet to form
an integrated disc/tape drive. The HP 7946 consists of a 55-megabyte disc drive and a tape drive combined
in a similar manner.
This publication
is divided into the following parts:
• Section I - Contains a general description of the disc/tape drive.
• Section II -Provides references to the CS/80 Instruction Set commands applicable to the disc/tape drive.
• Section III -- Describes the operating principles of the disc/tape drive.
• Section IV -- Contains servicing information for the disc/tape drive.
• Section V - Supplies step-by-step removal and replacement procedures for field replaceable assemblies
and parts in the
disc/tape drive.
• Section VI -- Lists and illustrates the field replaceable assemblies and parts in the disc/tape drive.
• Appendix A-Contains removal and replacement and relaceable parts for disc/tape drives with serial
number prefix 2614 and prior.
• Tape Drive -Consists of a Tape Drive Service Manual. This manual provides detailed service informa-
tion for the tape drive portion of the disc/tape drive.
iii/iv

Section I
GENERAL INFORMATION
Introduction
Documentation
Related Manuals
Options
Ch ar act eri st il cs
Section II
CHANNEL INTERFACE
Introduction ...... .
CS/80 Instruction Set
Transaction Structure
Real Time Commands
Complementary Commands
General Purpose Commands
Diagnostic Commands ..
Transparent Messages .
Hewlett-Packard Interface Bus
HP-IB Communications
Channel Management
Paralll~l Poll
Universal Device Clear
Message Structure
Section III
THEOR Y OF OPERATION
Introduction
Disc Drive Introduction
Disc Format ........ .
HOC peA-AS ......... .
HOC Internal Bus Architecture
HP-IB Data Bus ........ .
RAM Data Bus .
Microprocessor Address Bus
Microprocessor Data Bus
DMA Gate Array Data Bus
Read/Write Data Bus
Data/Control Interface Bus
Control/Status Data Bus
Control/Status Read Strobe
Control/Status Write Strobe
CONTENTS
Page
1-1
1-1
1-2
1-2
1-2
Page
2-1
2-1
2-1
2-1
2-1
2-9
2-9
2-9
2-9
2-12
2-13
2-13
2-13
2-13
Page
3-1
3-2
3-4
3-6
3-6
3-7
3-7
3-7
3-7
3-7
3-7
3-7
3-8
3-8
3-8
v

CONTENTS (continued)
Control/Status Address Bus
Select .............. .
Read/Write Data Bus
Data Request In/Data Request Out ...... .
Da ta St robe In/Da ta St robe Ou t ........ .
HP-IB
Interface IC ., ................ .
Microprocessor .....
HP-IB Address Switch
Channel Status ...
Sel f Tes t Swi tches ....................................... .
Self Test Display . . . . . . . . . . . . . . . . . . . . . . .............. .
DMA Ga te Array IC . . . . . . . . . . . . . . . . . . . . . . ..... .
RAM ........... ...................... . .............. .
EXEC EPROM . . . . .. ...................... . .............. .
DOC 0 EPROM ......................................... .
DOC 1 E PROM .................................. , . . . . .
Address Multiplexer ........................................ .
Clocks And Control Logic .................................... .
ROM Sw i t ch . . . . . . . . . . . . . . . _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buffers
Typical HOC Transaction ..................................... .
DOC PCA-A2 ................................................. .
HOC/DOC Commu ni cat ion .................. . . . . . . . . . . . . . . . .
Control/Status Data and Address Buses ..................... .
Read/Wri
te Data Bus ..................................... .
Receiver/Driver ........................................ .
Transceivers .......................... . .............. .
DOC/Disc
Drive A1 Communication ............. . .............. .
Controller IC and Register Decode Logic ....... . .............. .
HDA Desc r ipt ion PROM ..................................... .
Self-Test Register ....................... . ......... .
GPC Register ........................................... .
DOC Err 0 rs Reg i s t er ..................................... .
PUPO Register ........................... . ..... .
Disc Controller IC .................... . ......... .
Phase- Loc ked Loop IC ....................................... .
Latch ................................................... .
DMA Handshake Cont rol ...................................... .
Clock Generator ......................................... .
Write Precompensation .................................... .
Disc Drive A1 ............................................. .
Disc Drive A1/DDC Control Communication ...................... .
Input Buffers .......................................... .
Output Drivers .......................................... .
Disc Drive A1/DDC Data Communication ........................ .
Microprocessor and PLA ..................................... .
Microprocessor/PLA Control Signals .......................... .
Clock Generator ........................................... .
Head-Disc Module .......................................... .
3-8
3-8
3-8
3-8
3-8
3-8
3-8
3-8
3-8
3-9
3-9
3-9
3-9
3-9
3-9
3-9
3-9
3-9
3-9
.... ,3-10
3-10
3-10
3-10
3-10
3-11
3-11
3-11
3-11
3-12
3-12
3-12
3-12
3-12
3-12
3-12
3-13
3-13
3-13
3-13
3-13
3-14
3-14
3-14
3-14
3-15
3-15
3-15
3-15
3-15
Actuator .....
............................ 3-15
vi

Recording Medium ............ .
Read/Wri te Heads ............ .
Read Preamplifier/Write Driver IC
Servo Head ........ .
Servo Preamplifier IC .
Spindle Moto r ...... .
Air Filtration Components
Actuator Lock Driver .
Spindle Speed Control
Spindle Speed Checker
Spindle Motor Brake Relay and Relay Driver
Actuator Servo Control
Demodu la to r ..... .
Mode Select Switch
Seek
~Iode
Velocity DAC
Tachometer .,
Slclpe Selector
Current Inverter
On-Peak Detector
Power Amplifier
Inverter ..... .
Track--Follow Mode .
Off-Track
Detector
Seek Operation
Restore to Track 0 Operation
Read/Wri t.e Data Channel .....
Head SelE!ct and Control Logic .
Read Chain ............ .
Ampli f
ier/Signal Condi tioner ..
Differential Line Driver
Wri te Chain ........ .
Line Receiver .... .
Transition Generator
Write Current Source
Write
Fault Detector
Sel f test ...... .
Power Supph' A4
AC Input Circuits
Swi tch-Mc)de Supply
Power-On Reset ....
Section IV
SERVICE INI4'ORMATION
Introduction
Service Tools
FRA Locations
CONTENTS (continued)
3-15
3-16
3-16
3-16
3-17
3-17
3-17
3-17
3-17
3-17
3-17
3-17
3-18
3-18
3-18
3-18
3-18
3-19
3-19
3-19
3~19
3-19
3-19
3-19
3-19
3-19
3-20
3-20
3-20
3-20
3-20
3-20
3-20
3-20
3-21
3-21
3-21
3-21
3-21
3-22
3-22
Page
4-1
4-1
4-2
vii

CONTENTS (continued)
Cable Connections ..
Signal Distribution
Power Distribution
Signal Notation
Block Diagram ..
Power Supply A4
HDC PCA-AS ... .
Self Test .... .
Self-Test Controls
Tape Drive FAULT Indicator
Tape Drive BUSY Indicator
Disc Drive FAULT/ON LINE Indicator
Se 1f T est Sw i tch ....
Self-Test Display
DISPLAY RESULTS Switch
Internal Diagnostics
Sel f Test ........... .
Self-Test Subtests
Self-Test Error Reporting
Fault/On Line Indicator
Self-Test Display ... .
Request
Status ..... .
Request
Status Example
Run Time Error and Fault Reporting
External Exerciser ........ .
Amigo Clear (AMCLEAR)
Cancel Transaction (CANCEL)
Test HP-IB Channel (CHANNEL)
Channel Independent Clear (CICLEAR)
Clear Logs (CLEAR LOGS) ........ .
Describe Selected Unit (DESCRIBE) .
Perform
Internal Diagnostics (DIAG)
Output Error Rate Test Log (ERT LOG)
Exit Program (EXIT) ....... .
Output Fault Log (FAULT LOG) .
Output Help Information (HELP)
Initialize Media (INIT MEDIA)
Update Device Logs (PRESET)
Request Status (REQSTAT) ....
Perform Read-Only Error Rate Test (RO ERT)
Output Run Log (RUN LOG) ..... .
Spare Sector (SPARE) ........ .
Output Spare Table (SPARE TABLE)
Output Device Table (TABLES)
Perform Servo Test (SERVO)
Set Unit Number (UNIT) ...... .
Perform Write-Then-Read
Error Rate Test (WRT ERT)
Troubleshooting
Disc Drive Maintenance
Tape Drive Maintenance .
viii
4-2
4-2
4-2
4-2
4-2
4-2
4-3
4-3
4-3
4-3
4-3
4-4
4-4
4-4
4-4
4-5
4-S
4-6
4-6
4-6
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4-8
4-9
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4-9
4-9
4-10
4-10
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4 -11
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4 -11
4-11
4-11
4-11
4-11
4-11
4-11
4 -11
4-11
4-11
4-11
4-12
4-12

CONTENTS (continued)
Section V Page
REMOVAL AND REPLACEMENT
Introduction
Preparation For Service ............................................... .
Removal And Replacemen t
............................................... .
Top ShroUid
....................................................... .
EPROM Ki t s ....................................................... .
FRA5 (HDG PCA-A5) ................................................. .
Front Panel ...................................................... .
U1-FRA1 (Tape
Drive Assembly A1) ...................................... .
5-1
5-2
5-2
5-2
5-2
5-3
5-3
5-3
5-4
5-5
5-5
5-6
5-6
5-7
Fan ............................................... . ........... .
UO-FRA4 (Power Supply Assembly A4) .................................... .
UO-FRA1 (Disc Drive Assembly A1) ...................................... .
UO-FRA2 (Disc Drive DDC PCA-A2) ...................... . .............. .
U1-FRA2 (Tape
Drive DDC PCA-A2) ............................... . .... .
LED Cable Removal ............................................... .
Section VI
REPLACEABLE PARTS Page
Introduction ..... . .
....... 6-1
Ordering Information ........ 6-1
Appendix A
REMOV AL AND REPLACEMENT
Introduction
Preparation For Service .............................................. .
Removal And
Replacement .............................................. .
Top
Shroud ...................................................... .
EPROM Ki ts ...................................................... .
FRA5 (HDC PCA-A5) ................................................ .
Front Panel ..................................................... .
U1-FRAl (Tape
Drive Assembly A1) ..................................... .
Fan
........................................................... .
UO-FRA4 (Power Supply Assembly A4) ................................... .
UO-FRAl (Disc Drive Assembly A1) ..................................... .
UO-FRA2 (Disc Drive DOC PCA-A2) ..................................... .
U1-FRA2 (Tape
Dr i ve DOC PCA-A2) ..................................... .
Appendix A
REPLACEABLE PARTS
Introduction ..... .
Ordering Information
Page
A5-1
A5-1
A5-2
A5-2
A5-2
A5-3
A5-3
A5-3
A5-4
A5-5
A5-5
A5-6
A5-6
Page
A6-1
A6-1
Appendix B
SERVICE NOTES Page B-1/B-2
ix

ILLUSTRATIONS
Figure
Transaction Structure ...... .
Hewlett-Packard Interface Bus Signal Lines
Disc Recording Format
Track Recording Format
Disc/Tape
Drive, Block Diagram
Disc
Drive, Block Diagram
Disc
Drive, Functional Block
Disc
Drive, Functional
Block
Disc
Drive,
Functional Block
Front Panel Self-Test Display
Rear Panel Self-Test Display
Diagram,
Diagram,
Diagram,
P8 Signal Source (Sheet 1 of 3)
P8 Signal Source (Sheet 2 of 3)
P8 Signal Source (Sheet 3 of 3)
(Sheet
(Sheet
(Sheet
Field Replaceable Assembly (FRA) Locations
Power Distribution, Cable Assembly Wl
1 of 3)
2 of 3)
3 of 3)
UO-FRA4 (Power Supply Assembly A4), Layout and Cable Connections
UO-FRA4 (Power Supply Assembly A4), Test Points and Voltages
FRA5 (HOC PCA-A5), Layout and Cable Connections
FRAl (Disc Drive Al), Layout and Cable Connections
FRA2 (DOC PCA-A2), Layout and Cable Connections
Disc/Tape Cabling Diagram
Disc
Signal Distribution
Order of Disassembly
HP 7942/HP 7946 Cable Interconnections
HP 7942/HP 7946 Major Assemblies
Disc/Tape
Drive, Exploded View
Order of Disassembly
Disc/Tape
Drive, Exploded View
x
Page
2-10
2-11
· 3-5
· 3-6
3-31/3-32
3-33/3-34
3-35/3-36
3-37/3-38
3-39/3-40
4-12
4-13
4-21
4-22
4-23
4-28
4-29
4-30
4-31
4-32
4-33
4-34
4-35/4-36
4-37/4-38
..... 5-8
. 5-9/5-10
5-11/5-12
· 6-3
A5-8
A6-3

Tables
Disc Drive Characteristics
Device Command Summary
Disc Drive Utilities
HP-IB Definitions .....
Universal Command Formats
HP-IB Message
Structure
list of Mnemonics .....
Host Dependent Controller (Unit 2)
Self-Test Subtest List ...... .
Disc Drive (Unit 0)
Self-Test Subtest List
Disc Drive Error Condition List
Fault Code List
Diagnostic Summary ......... .
Disc/Tape Drive
Replaceable Parts
Abb rev ia t ions ......... .
Code list o'f Manufacturers ..... .
Disc/Tape Drive
Replaceable Parts
Abbreviations ......... .
Code list o'f Manufacturers ..... .
TABLES
Page
1 -3/1-4
2-2
2-9
2-12
2-12
2-14
3-23
4-14
4-15
4-20
4-24
4:-27
6-2
6-4
6-5/6-6
A6-2
A6-4
A6-5/A6-6
xi

SAFETY CONSIDERATIONS
GENERAL -This product and related documenta-
tion must be reviewed for familiarization with
safety markings and instructions before operation.
-
-
WARNING
CAUTION
SAFETY SYMBOLS
Instruction manual symbol: the
product will be marked with this
symbol
when it is necessary for
the user to refer to the instruc-
tion manual in order to protect
the product against damage.
Indicates hazardous voltages.
Indicates
earth (ground) terminal.
The
WARNING sIgn denotes a
hazard. It calls
attention to a
procedure
or practice which, if
not correctly performed or ad-
hered to, could result in personal
injury. Do
not proceed beyond a
WARNING sign until the indi-
cated conditions are fully under-
stood and met.
The CAUTION sign denotes a
hazard.
It calls attention to an
operating procedure or practice
which,
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
un til 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 un interruptible safety earth
ground must be provided from the main power
source to
the product input wiring 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.
xii
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, main-
tenance' 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 per-
sonal injury.
Capacitors inside this product may
still be charged after the product
has been disconnected from the
main power source.
To avoid a
fire hazard, fuses with
the proper current rating and of
the specified type (normal 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
fuseholder by pressing the cap in-
ward and then turning it clockwise
until it locks in place.

GENERAL INFORMATION -
[TI
1-1. INTRODUCTION
The Hewlett'-Packard 7942 and 7946 Disc/Tape
Drives are medium performance, random access,
data storage devices designed for use with small
and medium sized computer systems. The HP 7942
consists of a
24-megabyte disc drive and a tape
drive combined in a single desktop cabinet to form
an integrated disc/tape drive. The HP 7946 con-
sists of a 55-megabyte disc drive and a tape drive
combined in a similar manner. In this manual,
un-
less otherwise specified, "drive" refers to both the
HP 7942 and HP 7946.
The
24- and 55-megabyte disc drives employ two
and four nonremovable 130-millimetre
(5.l2-inch) discs, respectively, for storage media.
Each disc surface 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 accomplished by a rotary ac-
tuator and 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
slelf -contained air filtration system
which supplies clean
air and equalizes temperature
throughout the module.
The tape drive
is a data storage device utilizing a
removable
1/ 4-inch tape cartridge. Two tape
lengths are available: 150 feet (16.7 megabyte) and
600 feet (67 megabyte). The tape drive functions
as a back
-up device for the disc drive. The data
transfer rate for back -up is approximately two
megabytes per minute. (The actual
data transfer
rate is host dependent.) The tape drive includes a
read
-after-write capability for data verification,
as well
as data recovery and automatic sparing.
The tape drive
is compatible with existing
1/4-inch cartridge tape drives contained in other
HP disc/tape drives.
Also included in
the drive are a Hewlett-Packard
Interface Bus (HP-IB)* controller and a power
supply.
The drive contains
internal self -test diagnostics
and a
fault-finding system which exercise key
functions of
the drive. Self test is performed au-
tomatically at power on and can also be initiated
by the host or by a switch on
the rear panel of the
drive.
Go/no-go test results are indicated by
green/red indicators on the front panel. If a
failure occurs, information on the cause
of the
failure can be determined by viewing a 2-digit
numeral display on the rear panel. Fault isolation
is to a unit level (disc drive, tape drive, controller,
and power supply), followed by field replaceable
as-
sembly or assemblies within the identified unit.
Details
of subtest failures are also provided.
The drive
is packaged in a stand-alone desktop
cabinet. Accessories available include a
desk-
height stand-alone cabinet designed to hold the
drive and other desktop stack modules. A kit for
rack mounting
the drive in a standard EIA equip-
ment rack is also available.
1 - 2. DOCUMENTATION
The documentation provided in this publication is
divided into two parts. The first part, HP 7942
and 7946 Disc/Tape Drives Service Manual,
(Sections I through VI) provides details of how the
disc drive and tape drive are combined in a single
cabinet to form
an integrated disc/tape drive.
Information provided includes circuit description,
servlclng details, removal and replacement
procedures, and replaceable parts information.
Detailed information on the disc drive theory
of
operation, service information, and replaceable
parts
is also provided. The second part, identified
by the
liT APE DRIVE" tab, contains service
documentation for
the tape drive.
*Not just
IEEE-488, but the hardware, documentation and support that delivers the shortest path to a
computation system.
1-1

General Inf ormation
7942 and 7946
Note: The two parts of
the publication
will
fit in a 1 1/2-inch 3-ring
binder, part no. 9282-0502. (An
equivalent binder may be used.) A
cover and spine insert kit, part no.
07942-90909, which identifies the
publication as the service manual
for the HP 7942 and 7946
Disc/Tape Drives,
is available for
the 9282-0502 binder.
1-3. RELATED MANUALS
For operating and installation instructions, refer to
the HP 7942 and 7946 Disc/Tape Drives Owner's
Manual, part no. 09742-90901, and the Site
Environmental Requirements for Disc/Tape Drives
Manual,
part no. 5955- 3456. For instruction set
information,
refer to the CS/80 Instruction Set
Programming Manual, part no. 5955- 3442. For
additional servicing information,
refer to the
CS/80 External Exerciser Reference Manual, part
no. 5955-3462. The HP 7942 and HP 7946
Disc/Tape Drive CE Handbook
is part no.
07942-90905.
1-2
1 -4. OPTIONS
The following options are available for the drive:
Option 015. For non-U.S. shipments. Voltage
selector switch set
at factory for 230-Vac
operation.
Option 550. Deletion of
the HP 10833A HP-IB
Interface Cable Assembly.
1 -5. CHARACTERISTICS
Characteristics of the disc/tape drive, including
physical dimensions
and power requirements, are
listed in table
1-1, Disc/Tape Drive
Characteristics. Detailed specifications for
the dis-
c/tape drive, including environmental require-
ments, are listed in Site Environmental
Requirements for Disc/Tape Drives Manual, part
no. 5955-3456. This publication is supplied with
the disc/tape drive. Refer to the HP 9 I44A
Service Manual for specifications and characteris-
tics of the tape drive.

General Information
7942 and 7946
Table
1-1. Disc/Tape Drive Characteristics
SAFETY
Meets all applicable safety standards of IEC 3BO and IEC 435.
UL recognized to UL 47B.
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,
(inclusive tolerance range is 90V to 132V)
Frequency:
230V range; 220V, 240v, single phase, (inclusive
tolerance range is 1Bov to 264V)
47.5 to 66 Hz
Typical Current (true RMS): 115V range; 1.50A
230V range; O.BOA
Typical Power:
SIZE/WEIGHT
Height:
Width:
Depth:
Net Weight:
Shipping Weight:
115V
range; 120W
230V range; 120W
20B
nun
(B.19
in. )
325
nun
(12.B in. )
2B5
nun (11.2
in. )
15.B kg
(34.B lb)
19.6
kg
(43.3 lb)
1-3/1-4

CHANNEL INTERFACE
-
QIJ
2-1. INTR~ODUCTION
Interface to the disc/tape drive is accomplished
through Hewlett-Packard Interface Bus (HP-IB)
hardware and the CS/80 Instruction Set, a set of
commands
formulated for mass storage devices.
The following paragraphs discuss
the types of
CS/ 80 commands. Also provided is an overview of
HP-IB. For full details of CS/80, refer to the
CS/80 Instruction Set Programming Manual, part
no. 5955-3442. For information on how the
CS/80 instructions apply to the tape drive refer to
the HP 9144A Service Manual, Part II, Installation.
2-2. CS/,BO INSTRUCTION SET
The increase in capabilities of both host computers
and mass storage devices has emphasized the need
for
efficient channel communication. The CS/80
Instruction Set increases the efficiency and speed
of channel operations between disc memories and
their associated host computers. Table 2-1, Device
Command Summary, provides a summary of all
CS/80 instructions. The CS/8 0 Instruction Set al-
lows a host computer to access special utilities
within the disc drive. Utilities are routines stored
in firmware which allow error rate tests to be per-
formed and the results of such tests to be examined
or logged. Utilities are listed in table 2-2, Disc
Drive Utilities.
Refer to the External Exerciser
Reference Manual, part no. 5955- 3462, for full
details.
2-3. TRANSACTION STRUCTURE
A transaction is a logically complete operation be-
tween a system host computer and a peripheral
device (the disc drive) over a given channel
(HP-IB). Three phases may occur during each
transaction: command, execute,
and report. A
transaction begins when a command is received by
the disc drive, and ends when a reporting message
indicating the status of the transaction is accepted
by
the host. Figure 2- 1 ill ustra tes the transaction
structure, and shows the relationship between the
disc drive operating states and the channel activity
relative to each phase.
A
unit is a separately addressable entity within a
device (disc drive). A volume
is a separately ad-
dressable portion of the storage media within a
given unit.
2-4. REAL TIME COMMANDS
Real time commands are optimized for execution
time. These commands
are used most often in
host/ device transactions. One or more compie men -
tary commands may precede a real time command
in order to modify the operation of that command.
Real
time commands include: locate and read, lo-
cate and write, and cold load read.
2-5. COMPLEMENTARY COMMANDS
Complementary commands are used to set or up-
date programmable states in the disc drive. The
programmable states define characteristics such as:
set unit, set address, set block displacement, set
return addressing mode, set length, set burst mode,
set
retry time, set release, set status mask, and set
Rotational Position Sensing (RPS) window size.
These commands
may be included within Real
Time,
General Purpose, or Diagnostic command
messages, or they may stand alone.
When a complementary command (or commands) is
embedded within another command, the para-
meters or conditions established by that com-
plementary command(s) are altered only for the
duration of the current command. A stand-alone
complementary command, however, sets the para-
meters or conditions until the same stand -alone
complementary command alters the set value or
until power-on occurs. Power-on resets all com-
plementary commands to their default values.
Therefore,
at power-on, length is defaulted to
equal the entire volume. A stand-alone Set Length
command may give it a lise til value of 1 kbyte to be
used
for an entire sequence of transactions, al-
though some special case commands could tem-
porarily override this value with an embedded
complementary command to set a "current" value
of 256 bytes (for 1 sector).
2-1

Channel In terf ace
7942 and 7946
Table 2 -1. Device Command Summary
LOCA TE AND READ (REAL TIME)
FUNCTION:
OPCODE:
FORMAT:
Locates the data indicated by the target address and trans-
mits the data to the host.
No variables or parameters
LOCA TE AND WRITE (REAL TIME)
FUNCTION:
OPCODE:
FORMAT:
Tranfers data from the host for storage beginning at the ad-
dress specified by the target address.
No variables or parameters
LOCA TE AND VERIFY (GENERAL PURPOSE)
FUNCTION:
OPCODE:
FORMAT:
Instructs the device to perform an internal verification of a
section of data to ensure that it can be read.
No variables or parameters
SPARE BLOCK (GENERAL PURPOSE)
FUNCTION:
OPCODE:
FORMAT:
2-2
Gives the device permission to become temporarily busy while
sparing the block indicated by the target address.
<00000110> <OOOOOSOT>Pl
P1 = sparing mode byte
S = 0 skip spare S = 1 jump spare
T = 0 retain data T = 1 do not retain data
T must equal 1 for tape operation
S must equal 0 for disc operation