Iomega ALPHA 10H Parts list manual

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'1I-~.A®
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TECHNICAL
DESCRIPTION
MANUAL
OEM DISK STORAGE SU'BSYSTEM
AlPHA-10H/10.5HW'TH EXTENDED SCSI
IOMEGA Corporation 1821 West 4000 South Roy, Utah 84067
NOVEMBER 1984 00701300-000

,-- ________ FCC WARNING ________ ----...
This equipment generates, uses, and can radiate ra-
dio frequency energy and if not installed and used
in accordance with this instruction manual, may
cause interference to radio communications. It has
been
tested and found to comply with the limits for
a Class A computing· device pursuant to Subpart J of
Part 15 of FCC Rules, which 'are designed to provide
reasonable protection against
sucb interference when
operated in a commercial environment. Operation of
this ,equipment in a residential area is likely to
cause interference in which case the user at his own
expense will be required to take whatever measures
may be required to correct the interference.
This manual is subject to change without notice.
Information is current as of publication, but may
be superseded in future documents. IOMEGA makes no
guarantee, expressed or impl ied, with 'regard to the
accuracy or completeness of the material.
Normal precautions used in handling electrically
powered equipment should be followed at all times.
Never
work on the Di sk Storage Subsystem with the
power source activated. IOMEGA assumes no liability
for incidents resulting from careless or improper
use
of this equipment or' inaccuracies in this man-
ual.

ALPHA·10H i10.5HTM OEM
DISK STORAGE SUBSYSTEM
WITH EXTENDED SCSI
TECHNICAL -
DESCRIPTION
MANUAL
December 1984
Iomega Corporation
1821 West 4000 South Roy, Utah 84067
[phone]
00701300-000

PREFACE
This' Techni'c'al' Des'criptl0n' Manual provides info.rmati'on for' interfac-
ing of a 10/10.5 megabyte, 8 inch disk storage subsystem, identified
by IOMEGA as Alpha-10H/10.5H
m•
The subsystem consists of a control-
ler, up to two disk drives, and removable 10/10.5 megabyte car-
tridges. Through the flexible magnetic disk media and the unique de- .
sign of its drive, the subsystem offers the advantages of (1) rigid
disk, Winchester-like performance and reliability; and (2) removable,
low cost flexible media. . o·
This document provides original equipment manufacturers (OEMs) a
source of information useful in understanding the function
and oper-
ation of the subsystem. Specifically, the manual includes the fol-
lowing descriptive, interfacing, and operational information~----
• SECTION 1.0, General 'Description, includes an introduction
of the subsystem
and provides an overall description of its
physical characteristics, principles of operation, perform-
ance
specifications, and special features.
• SECTION 2.0, Interface, contains information regarding SCSI
and the hardware and software interface. This materi al is
essential for normal host-to-subsystem SCSI interfacing.
• SECTION 3.0, Operational Information, includes techniques of
cartridge use, a description of operator controls, and iden-
tification of cabling and connections.
• SECTION 4.0, .controller Options, explains the available op-
tions for the controller, operating principles, interface re-
quirements, and operational impact.
• APPENDIX A, Diagnostic Port Error Codes for the 10/10.5 Mega-
byte, 8 Inch Di sk Storage Subassembly with Extended SCSI,
provid~s'error code information for the subsystem.
• APPENDIX B, Interconnect Cable Ordering Information, includes
cable information for
interfacing with host and power supply.
Reference to
IOMEGA or its Alpha-10H/10.5H
m product
is not made' in
the text of this manual to allow the OEM to pass the document, with
new cover and foreword, directly to the ultimate end user.
00701300-000
15 December 1984
11

CONTENTS
Page
1.0 GENERAL DESCRIPTION .............. · ................................ 1-1
1.1
OVE~VIEW OF SUBSYSTEM FEATURES •...... 0................... 1-1
., ','
1.2 PHYSICAL/MECHANICAL CHARACTERISTICS .....•..•.••.•..•..•• 1-2
1.2.1 Function ......••.•....•.....•.•.....................•• 1-2
1.2.2 Drive Characteristics ••..•••••.••.•...•..•...••.••••• ~ 1-2
1.2.3 Controller Characteristics
•.•.••••....••..•••••...•••• 1-3
1.2.4 Cartridge Characteristics
.••••....•...•..••..•....•.•• 1-4
1.3
SUBSYSTEM BLOCK DIAGRAMS .........••.........•...•..•.... 1-4
1.4
PRINCIPLES OF OPERATION ..•...•..•...•....•.•......•...•• 1-6
1.4.1
1.4.1.1
1.4.1.2
1.4.1.2.1
1.4.1.2.2
1.4.1.2.3
1.4.1.2.4
1.4.1.2.5
1.4.2
1.4.2.1
1.4.2.1.1
1.4.2.1.2
1.4.2.2
1.4.2.2.1
1.4.2.2.2
1.4.2.2.3
·1.4.2.2.4
1.4.3
1.4.3.1
1.4.3.2
1.5
1.5.1
1.5.2
1.5.3
1.5.4
1.5.5
1.5.6
1.5.7
1.5.8
Drive ••••••••••••.••••••••••••••••••.•••••••••••••••••
Cartridge Format •.•..•••....•...••.....••...••.••..•
Drive Interface Board ....•.....•....••......••..•...
Preamp Section •......•...............•.•.....•....
Write Current Driver Section ......•.•.......•.....
Motor Speed Control Section ......•.•.•.••••....•••
Operator Interface Section ....................... .
Actuator Driver Section
...............•.•.........
Controller Board.~ •..•..•....................•........
Analog Section ....•.••.•............•....•.•........
Read Channel ••••••••••••••••••••••••••••••••••••••
Servo Error Decoding .•.•..........••.••...........
Digital Section •...............•........•...........
Mi croprocessor Circu i try .........••.••........•.•.
Servo Control •...........••••...•..••.•.••••..•.•.
Interface Circuitry ...•.•.•.••..•..•...•..•••...•.
File Control Circuitry .......••......•••....•.....
Interleaving and Error Correction Code .....•..•...•.
Interleaving .......................•..............
Error Correction Code .......•.•.•....•....•.......
SUBSYSTEM SPECIFICATIONS ...............•...•.............
Capacity ...•...•....•.•.•.•.........•..•..•.•..•......
Performance .•..•.......••..•........ - •...•....•...•....
Re1; ab i 1; ty ••••••••••.••••••••••••••••••••••••••••••••
Env;ronment ••••••••••••••••••••••••••••••••••••••• , ••••
Power ••••••••••••••••••••••••••••••••••. ~ ••••••••••••••
Phys; cal ............................................. .
Organ; zat i on ......•....•..•......•..••.......•..•.•...
Record; ~g •.•.........................•.......•.........
1-6
1-6
1-8
1-8
1-8
1-9
1-9
1-9
1-9
1-9
1-9
1-10
1-10
1-11
1-11
1-11
1-11
1-12
1-12
1-14
1-15
1-15
1-15
1-16
1-16.
1-17
1-17
1-19
1-19
00701300-000
15 December 1984
iii

Co.NT~NTS (cont) ,
2.0 INTERFACE ......................•................................. 2 .. 1
2.1 SMAll COMPUTER SYSTEM INTERFACE (SCSI) .••.•..••.•..••.•• 2-1
,2 ~2'
~ .' t ' • .. ..
'HARDWA'RE·)NTERFACE' •.•••.••.•••• ' •••• , .••... ,••••. ~, ••.•.•. ~ •• : .' •. ,2~.1.;
. .:... . .. . '. ~........., '.' ~... .. ..' . -. .... -"... ..' "." . .'.. . . .. . ~ .. . ..
2.2.1
2.2.2
2.2.2.1
2.2.2.2
2.2.2.3
2.2.2 .. 4
2.2.2.5
2.2.2.6
2.2.3
2.2.4
2.3
203.1
203.2
2.303
2 .. 3.3.1
2.3.3.2
2.3.3.3
2.3.3.3e1
2.3.3.3.2
2.3.3.3.3
2.3.3.3.4
2.3.3.3.5
2.3.3.3.6
2.3.3.4
2.3.3.4.1
2.3.3.4.2
2.3.3.4.3
2.3.3.5
2.3.3.6
2.3.3.7
2.3.3.8
2.3 .. 3.9
2.3.3.10
2.3.3.11
2.3.3.12
2.3.3.13
2'.3.3.14
2.3.3.15
2.3.3.16
2.3.3.17
2.3.3.18
'B us Lines•. •. •• •••. •••. ••••. •. •••. ••. ••••. . ••••••••••• 2-1
Host Interface Protocol •••••••.••.••.•.••..••.•.•••••• 2-4
Selection Sequenc~ •••.••••• ~ •••••••••••••••••.•••••• 2-4
Command Tt"ansfer Sequence........................... 2-5
Data Transfer Sequence.............................. 2-5
Ending Status Transfer Sequence ••••••••••.••. ~ •••••• 2-7
Busy Status Transfer Sequence ••.••••••.•••.•..•.•• ~. 2-8
Abort Sequence ...•.•.••..•.•.•.••.•.•.••....••..•••• 2-9
Res et eo ndit ion. •••••••. . •.'. . ••. ••••••••••••. •. ••••••• 2-9
Electrical Requirements •••••••••••••••••••••••••.••••• 2-9
SCSI SOFTWARE INTERFACE •••••••••• ·•••••••••••••.••••••••• 2-10
Command Structure ••••..•••••••••.••••••••••••.••.••••• 2-10
Logical Block Addressing ..... e,......................... 2-11
Command Description .................................... 2-12
Test Unit Ready Command .••.••••••••••.•••••.•••••••.• 2-12
Rezero Unit Command •••••.••.••••••.••••.••••••••••.• 2-12
Request Sense Command .•••••••.•••••••••••••.•••••••• 2-13
Regular Sense Data ...•.•.•••...•.•••••••...•••••. ~ 2-14
Extended Sense Data ••.••. ~. . . •••. •• ••. ••• .• •• •• •. • 2-14
Extended Sense Plus Error Class and Code .••.•••••• 2-15
Z-Track Data and Current Track Number •••.••••.•.•• 2-15
Sector ID Data •••.•.••..••..•••.•.•...•.••.••••••• 2-17
Flaqqed Track listing •••.•..••••••••.••••••••••••• 2-18
Format Unit Command .. o ••••••••••••••••••••••••••••••• 2-19
Standard Implementation ........... c •••••••• OG •••••• 2-19
Extended Implem.entation .•••••••. e.................... 2-20
Device-specific Implementation..................... 2-'21
Format Track Command................................ 2-24
Reassign Blocks Command............................. 2-24
Read Data Command •••••••••••••••••••••••...•.••••••. 2-25
Wr i te D at a Command.................................. 2-25
Seek Command ••.•••••••••• ' •••••.••••••.••.. '.......... 2-26
Inquiry Command..................................... 2-26
Start/Stop Command .................... '............... 2-27
Send Diagnostic Command •••.•••••••••••••••.••••••••• 2-28
Prevent/Allow Media Removal Command ..••..........•.. 2-28
Read Capacity Command ................................ 2-29
Extended Read Command •••• 0 ••••••••• 0 0 ••• ,. • • • • • • • • ••• 2-30
Extended Write Command •••.•••••..•.••.••.•..••.••••• 2-30
Write and Verify Command •.•.•.••.•••••••....•..•.•.• 2-31
Read Long Command •.•••.••..••.••.•....••.•..•..•.••. 2-31
2.4
POWER INTERFACE •....•..••...•... ~ .•....••.•............• 2-32
00701300-000
15 December 1984
1v

CONTENTS (cont)
Paqe
3.0 OPERATIONAL INFORMATION........................................... 3-1
3.1
.. . ~ ..
CART.RIDG~ .~S.E.:. ' .• ~ . ~ .....' .............. ~ ... ! •.••.•.•• ' .••.••• ~ •••••• , .. 3~1·
3.1.1 Loading and Removal ................................... 3-1
3.1.2 Handling .............................................. 3-2
3.1.3 Write Protect •..••.•....•........ _ ....• ~ ...•..•....••. 3-3
3.2
OPERATOR CONTROLS ......... · ................... 0........... 3-3
3.2.1
Stop Button ...........•............................•.. 3-3
3.2.2 Load Lever ..........................................•. 3-3
3.2.3 Indicators
........................................••.. 3-3
3.3
STARTUP DIAGNOSTICS .....••••.........•......•.......•••• 3-4
3.4
CABLES AND CONNECTORS .•••....•.•••..•.......••..•.•..•.. 3-5
3.4.1 Host Interface Cable.................................. 3-5
3.4.2 Drive Interface
Cable •.•..•.•.•••••••••..••...•.•..••• 3-6
3.4.3 .Power Cable •......•...••.•..•.•....•..••.•....•.•.•..•.. 3-6
3.4.4 DiagnostiC Error Display Port
.•.•.•.•.......•.••..•..• 3-9
3.4.5 Drive Addressing
...........................•..•....... 3-10
3.4.6 Controller Addressing and Option Selection .....•...... 3-10
4.0 CONTROLLER OPTIONS ••...........•.....•.•.••....•.••..•..•..•...•. 4-1
4.1
ERROR CORRECTION CODE ..•............•.•....•••...•.•..•..•..• 4-1
4.2 ARBITRATION •.•••.•••.. · .•............•....••................. 4-2
-- APPENDIX A- Diagnostic Port Error Codes for the 10/10.5 Megabyte,
8 Inch Disk Storage Subassembly with Extended SCSI .... A-1
-- APPENDIX B - Interconnect Cable Ordering Information .•............. B-1
00701300-000
15 December 1984
v

. ."
ILLUSTRATIONS"
Figure
Paqe
----
,I. , The.l0/10.5,)~1egabyt,e, ~a1.f ,.Height 8. Inc~ 'o,i.s~ Sto,ra.ge .
. ," ," . ~ "Sub.sys.t.~m· .... e' ~ : "~ • "~' e _.~" ... ~, .... :, ~ e ""! ......... ' ••• ~,. , ....................... ,- .... ~ " •• ;, 1.:-1
'2' Ofsk Dri vel Contro 11 er Arch i te'cture ..•.... ~ ..... ~ .• ~ . ~ '.~' ... ' .... "1-3
3 810ck Di agr am of the Subsystem Dri ve •............ '. .. . . . . . . . •. 1-4
4 Block Diagram of the Subsystem Analog Functions ..•.........•. 1-5
5
Block Diagram of the Subsystem Digital Functions •..........•• 1-5
6 Disk and Track Formats •...•..•......•.•...•••••.•..•.......•• 1-7
7 Sector Format ................................................. 1-8
8 Servo Signals •••.......•..•...•.•...•...•......•...•.•......• 1-10
9 Example of Interleave 40 ...................................... 1-13
10 Drive Mounting Hole Locations ...•.................•.•........ 1-18
11 'Sample SCSI Configurations •....••...•......•...............•• 2-2
12 J1 Host Interface Connector Pinout ..•.....•.•......•....•..•. 2-2
13 Select and Command Sequence Timing ..•.•...••.•.....•• ~ ..••.•. 2-5
14 Data Transfer Sequence Timing .••..•.••....••..••.............. 2-6
15 Ending Status Transfer Timing .................................. 2-7
16 Hardware Busy Status Transfer Timing ••......•..•............. 2-8
17 Host Adaptor Bus Termination .................................. 2-10
18 Z-Track Format ••.......•••.••..••...•••..•.•••..••••......... 2-16
19 Sector Interleaving ........................................... 2-17
20 Cartridqe with Write Protect Switch ..••.....•..••.....•.•.... 3-2
21 Printed Circuit Board and Main Cable Locations ........•....•. 3-6
22 Cabling and Connectbr Requirements ..•.•. : •..•... L •••••••••••• 3-7
23 DiQital Controller Terminations and Address Options .....•.... 3-8
24 Recommended Ground i ng •....• : •...... '. . •. . . . . . . •. . . . . . . . . . . . . .. 3-9
B-1 Host Interface Cable ....................................•.... B-2
8-2 Power Cable Harness .•...............••.•..••••..•.•....••..•. B-2
8-3 Error Readout Assemb ly ........................................ B-3
TABLES
Table Page
1 Maximum Power Requirements with Controller ..•......••........ 2-32
A-I Error Codes.................................................. A-7
8-1 Cable Connector Identification •.....••..........•..•......... B-3
00701300-000
15 November 1984
vi

1~OGENERAL.· 'DESCRI"PTION
The 10/10.5 megabyte, ha·lf height 8 inch disk storaqe subsystem (Fiqure 1)
is a high capacity, high performance, direct access data storage device us-
ing flexible media. The subsystem, with Small Computer System Interface
(SCSI), is intended for use wi~h small to medium sized systems requiring on-
line storage with· removable cartridqes ·of 10/10.5· megabytes each. ··The sub-
system
consists of a controller with an intelligent host level interface and
up to two disk d~ives attached daisy-chain style to the controller.
Figure 1. The 10/10.5 Megabyte, Half Height 8 Inch Disk Storage Subsystem
1.1 OVERVIEW OF SUBSYSTEM FEATURES
The subsystem incorporates a number of new and innovative technologies that
make it a very versati le and adaptable data storage peripheral. The "fea-
tures described in this section include:
Drive
and Controller
• One or two drives per controller.
• Removable, 10/10.5 megabyte data cartridge.
• Embedded servo control.
• Run length limited code (RLLC) encoding/decoding.
• Use·r transparent error detection and correction (optional).
• Utility commands for sector and track sparing.
• A 1.13 megabyte/sec instantaneous transfer rate.
00701300-000
15 December 1984
1-1

; •. Sector interleave 'capabfl ity·.
• Data buffering
on the controller.
• Logical block addressing. .
• Comprehensive user command set.
• Automatic startup diagnostics.
• Au~omatic idle drive half speed dwell. .
,
.' Ali t'om at ic ;'med i.a" " if e . enh aricemenf 'routi nes ' ..
• ': Autc)matt'c 'e,rrbf'.' recovery procedures> ,,'
• High level, intelligent host interface.
• All direct current (dc) power.
Data Cartri dge
• Hard plastic enclosure for media protection.
• Preformatted media.
• Convenient 8-1/2 X 11 in. size.
• Cartridge write protect switch.
• Maintenance tracks for cartridge-specific information and diagnos-
tics.
A more complete description of subsystem functions and performance charac-
teristics is presented in subsection 1.2.
1.2 PHYSICAL/MECHANICAL CHARACTERISTICS
Subsystem function and operation are described in this subsection, as are
characteristics of the drive, controller, and cartridge.
1.2.1 Function
The subsystem is a hi gh performanc.e di sk storage devi ce. Confi gured with a
controller and up to two drives, the subsystem provides removable media
storage capability to systems requiring up to a total of 20 megabytes online
storage capacity per subsystem.
Data cartridges are interchangeable, giving
the assurance qf drive-to-drive compatibility.
Major functions of the. subsystem include disk rotation, head positioning,
data
transfer, host interfacing, and error identification.
S, nee these func.t; ons are hand1 ed -by the subsystem contro 11 er; once the
drive
is installed in the system, routine operation is fully automated, re-
quiring operator intervention only for cartridge exchange.
1.2.2 Drive Characteristics
The subsystem drive contains all function-a1 mechanical components (base
casting, drive motor, Bernoulli plate, head/actuator, and loading mechanism)
and some electronic circuitry (read preamplifier write driver and power
ampl ifiers for the head/actuator and drive motor). Figure 2 shows the
architectural division of the drive and controller.
00701300-000
15 December 1984
1-2

HOST
TO HOST
POWER
(+5, +12VDC)
CONTROLLER
DIGITAL/CONTROL
.. SECTION
CPU ROM/RAM .
HOST INTERFACE BUFFER
FILE CONTROL LOGIC
ECC LOGIC (OPTIONAL)
SERVO CONTROL LOGIC
ANALOG SECTION
CLOCK AND DE1ECT
CIRCUITS
SERVO DEMODULATION
SERVO COMPENSATOR
rpOWER-'
~~gF.!!~
DRIVE
INTERFACE
BOARD
READ PREAMP AND
io..-- ..... -+l_. I WRITE DRIVER
DRIVE
'---- ..... TO ADDITIONAL DRIVE
Figure 2. Disk Drive/Controller Architecture
1.2.3 Controller Characteristics
SPINDLE
DISK
The subsystem controller integrates drive analog and digital functions and
provides the host with an intelligent, high level interface. The controller
consists of a printed circuit board divided between analog and digital func-
tions (see Figure 2).
The controller provides the following important functions.
• Data detection and clocking.
• Servo demodulation.
• Command decode and execution.
• Buffering of data.
• Data serialization/deserialization.
• Data encoding/decoding.
• Subsystem diagnostics.
• Sector interleaving.
• Automatic idle drive half speed dwell.
• Automatic error recovery procedures.
• Automatic error correction (optional, see Section 4.0).
• Arbitration for host interface (optional, see Section 4.0).
00701300-000
15 December 1984
1-3

'. 1.2.4 .... .Cartridge.Characteristics.
The subsystem cartridge consists of' a durable ~blycarbonate· e~c16sure c6n-
taining a single flexible disk. The cartridge provides a protected environ-
ment for the media and a handy, transportable package for the user. The ac-
cess
door to the media is latched internally. and opens upon cartridge inser-
.
tion fnto"the 'drive~ ·th4·S. pre~entiryg.··any ~ser· co'ntact ·.~;~h the 'disk' i,t'self.··
. . . ..... ~ ..... . ~ . . . '.' .. . . '. .... . -' .
The disk ;s a 3 mil polyester based substrate having a high energy oxide
coating. Disks are preformatted at the
factory with servo positioning in-
formation, sector
and track identifications, and two prewritten diagnostic
tracks called the Z-tracks. Raw media defects occurring within sector and
track boundaries are flagged when the disks are preformatted and alternate
locations are assigned.
A
summary of cartridge and media specifications is presented in subsection
1.5 of this manual.
1.3 SUBSYSTEM BLOCK DIAGRAIYIS
The block diagrams shown here represent the 10/10.5 megabyte hal f hei ght·
subsystem drive (Figure 3), analog section (Figure 4), and digital/control
section (Figure 5). These diagrams are for informational purposes only and
should not be used as wiring documents. Explanations of the diagrams are
pre~ented in subsection 1.4.
r---------------------------,
I
I
I
I
I
I
I
I
I
a:: I
~ I
5 CONTROLI
~ !
z
o
u
STATUS I
I
OPERATOR
INTERFACE
CONTROL
AND
STATUS
DRIVE SELECT
WR DATA
CONTROL AND
SENSE
RD DATA
CONTROLLER t--.=.:SE:.:..:.RV.;.;:0:-i::A~ND~C~U~RR:.:.::E.:..-NT~ ......
INTERFACE COMMAND '--- __ ---'
g I
~_R~U~N __ ~~~,
I READY 1---7'--"'" POWER
AND CONTROL
I I
L I
HALl·EFFECT SENSE
__ - - _, _______ ~_--:.;.:..:.=~::.:.:....=::o:._ __ _
LO~~T~F~E--I _____________ __I
Figure 3. Block Diagram of the Subsystem Drive
00701300-000
15 December 1984
1-4

· RD DATA
AGC
WINDOW B
NRZ -I
rvARimE1!-1!R§EA~D2.Q;DA~T!:!A~ ~ ~
READ CLOCK ~t
~~
-I
c(
z·
<.:)
Vi
a:
o
a:
a:
w
~~~~~ ________ ~SA~M~P~L~E~W~IN~D~O~W~ __________________________________ ~
RZWRITE DATA
t>-~~~--------~~~~~--------~
z
o
~
Vi
~ >-.JTI~1'- ________ W~R..:::C.:::.U:.:.R R:.:,.:E::.:,N;:.,:T..;C::.;:O:.:,.:N:.:,.T.:.:,RO;;,L=---.....
-I CONTROL RD DATA
~~~~~--------~~~~~~--~
a
o
~
SERVO CURRENT COMMAND
~ SERVO CONTROL SIGNALS TO DRIVE INTERFACE
a:>-~~~~~~~~~------------------------------------------
u. +ANALOG PES OFFSET
-ANALOG PES OFFSET
Figure 4.
Block Diagram of the Subsystem Analog Functions
Figure 5.
STATUS
CONTROL
RECORDING CHANNEL
CONTROL LOGIC
+ANALOG PES OFFSET
-ANALOG PES OFFS T
STATUS
CONTROL )
Block Diagram of the Subsystem Digital Functions
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15 December 1984
1-5

1.4· PRINCIPLES OF OPERATION
• • .' '" ~ • T. • .' •
Th e sub system can be brok en fu ncti on all y into three parts: the dr i ve wi th
its associated electronics and the controller board with analog and digital
sections. Figures 3 through 5 show the functional segments of these major
parts.
1.4.1 . Drive
The drive (Figure 3) consists of the Bernoulli plate, spindle motor, read/
write head, actuator, drive interface board, and operator controls and indi-
cators. The major drive functions are to provide a constant spindle speed,
move the head, preamp1ify read data, control data writes, and provide oper-
ator interface.
When a cartridge is inserted and the load lever is. turned clockwise., the
spindle motor
is engaged and the disk spins up to a constant operating
speed.
As the di sk rotates, it "f1 ies" in close proximity to the Bernou11 i
plate on a cushion of air. Special coupling techniques allow the read/write
head,
which penetrates through an opening in the Bernoulli plate, to estab-
lish a stable recording environment. Motor control circuitry on the drive
interface board senses motor speed and keeps the motor turning at 1,500 rpm.
It also signals the controller that the disk is up to speed, flashes the
gre.en LED during spinup/spindown, and lights the green LED on the front of
the drive when the motor is up to speed.
If the di sk is not accessed. over a peri od 'of time, a timeout occurs and the
drive either begins a steady track-to-track seeking action (drive last used)
or adjusts the motor to half speed (dual drive configuration only). This
prevents the dr i
ve from dwell i ng on one tr ack excessi ve 1y. The 1ength of
time before the motor spins
down to half speed can be progral1111ed onto the
Z-tracks.
When the controller accesses the disk after a timeout, it either
causes the motor to spin again to full speed, or initiates a seek to the
track corresponding with the logical address requested
by the command.
Approximately 1 to 2 seconds are needed for the drive to become ready if it
is at half speed.
1.4.1.1 Cartridge Format
Data cartridqes are preformatted at the factory with information that divid-
es the user recording surface into 306 data tracks of 64 (10 Mbyte) or 67
(10.5 Mbyte) data sectors. Each track also contains five spare sectors (10
Mbyte) or two sp'are sectors (10.5 Mbyte) and one error correction code (ECC)
sector on each track, making a total of 70 sectors per track. Disk and
track formats are shown in Figure 6. The 306 data tracks store the subsys-
tem's 10/10.5 megabytes of data. Four spare tracks are available if any of
the
normal data tracks become damaged or unreliable. Two identical Z-tracks
are present on each di sk; one at the inner edge and one at the outer edge
(Figure 6). The secondary Z-track becomes a backup in the event the primary
Z-track
becomes damaged. The Z-tracks are used for recording such cartridge
00701300-000
15 December 1984
1-6

· speci.fic' informatfon,"as' sector:' inte'rleave~ dwe'll: ti'meout' 'length,: defect;-v'e
and spare 'track lists, and error correct,ion .status. ,Some. sectors, of the .Z-,
tracks are us'ed' to . record speciflc' d'at'a' patterns- required by . the, internal"
self~test of the subsystem, or special customer data. The command for for-
matting' the Z-tracks is presented in subsection 2.3.3.3.4. (Fi~ure 18 in
that text describes the format.of the Z-tracks.).
~~=t:~:::... ~~~bRS G~~~~ ... '" 16
SPARE TRACKS"", 4
SECONDARY
Z·TRACK
,., •• ',... 1
10MEGABYTE TRACK
10.5 MEGABYTE TRACK
~iiiiiiiiiiiiiiiii\'~ ~~~~:~: .., .. .. ... 1
~- .• -- OUTER GUARD
BANOS ".",'". 15
TOTAL 343
10110.5 MEGABYTE DISK
Figure 6. Disk and Track Formats
Each
sector on a track is orqanized as shown in Figure 7. The PAD field
provides space for sector overlap (caused by motor speed variations)" and
allows sufficient recovery time if switching from write to read mode. A
uniquely coded sector timing mark identifies the start of a sector. The
servo field allows head positioni.ng circuitry on the controller board to
keep the head centered on a track. Gaps provide the read circuits with tim-
; ng i nformati on so they can synchroni ze to the frequency and ph ase of the
data. The sector 10 field identifies the sector and track number of each
sector. A tot a1 of 512 bytes of dat a can be stored in each sector, 256
bytes per data field (also called a record). The two data fields can be ad-
dressed independently.
Sectors may be flagged as defective and reassigned to one of the spare sec-
tors. One sector on each track may be used opt iona 11 y for stori ng error
correction information. Use of the ECC sectors (optional and specified on
the Z-tracks) allows the correction of two complete data records per track
(see Section 4.0). '
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15 December 1984
1-7

· ~. PAD.---24 BYTES .
VFO._ •••• _12 SYTES} . .
SECTOR TIMING GAP
MARK. __ 1SYTE
SERVO FIELD __ .27 BYTES
DATA_251 BYTES} DATA 1 FIELD
CAC ___ 2 BYTES' (RECORD 1)
¥~2c::.2~ :~~S } GAP
10._4 BYTES }SECTOR
, ',:~,c_z In ... , I. ftElD'
l"\~ SYNC--l BYTE
"'\: VFO __ 17 BYTES} GAP
SECTORSITRACl(
DATA SECTORS
SPARE SECTORS
ECC SECTOR
70
64
5
Figure 7. Sector Format
1.4.1.2 Drive Interface Board
The purpose of the drive interface board is to: (1) provide the first stage
of head output amplification, (2) switch write current to the head, (3) pro-
vide motor speed control, (4) service the operator interface, and (5) drive
the
actuator.
1.4.1.2.1 Preamp Section
The preamp section of the drive interface board is responsible for managing
write and read signals traveling to and from the head. During a read func-
tion, low level signals from the head are amplified and sent on to the con-
troller board for Signal processing. Its close proximity to the head allows
the preampl ifier to provide primary amp 1 ification, thereby reduci ng the
problems of external
interference.
1.4.1.2.2 Write Current Driver Section
During a write, write information developed on the controller board is rout-
ed to the preamplifier. Circuitry in the preamp section uses the write data
signal
to switch write current in the head.
On-board control circuitry enables write current only when all software and
hardware conditions have been met. When not in the write mode, read cir-
cuitry is constantly enabled for the selected drive.
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15 December 1984
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A single-chip microprocessor'provides commutation of the mofor phases, indi-
cation of motor speed within limits, and motor speed control to 1500 rpm.
It also controls' the latch pin, solenoid, which inhibits unloading of the
..
med1.a. while .:the mq.tor .. i.s .spjnnJt1g •. :
1.4.1.2.4 Operator Interface Section
The on-board microprocessor' also senses the motor has been loaded, flashes
the green LEO when the motor is spinning up or down, and polls the console
pushbutton (which
initi ates motor spindown). It also monitors and manipu-
lates control lines that interface with the controller board.
1.4.1.2.5 Actuator Driver Section
Actuator control and driver circuits use the Servo Current Command signal
from the controller board to direct current to the actuator.
1.4.2 Controller Board
The controller board is comprised of two areas: the analog section and the
digital section.
1.4.2.1 Analog Section
The main purposes of the analog section are to (1) provide a read clock that
is synchronous with the frequency and phase of the data coming from the
disk, (2) filter and shape the read data, (3) interpret servo information
for head positioning, and (4) provide servo loop compensation.
1.4.2.1.1 Read Channel
Read data signals are buffered and shaped through a' series of circuits de-
signed
to recover the original written data. Automatic gain control (AGC)
and threshold detect circuits are included to compensate for changes in the
re 1 at i ve strength 'of the read signa1.
During a read process, the read data lines contain a series of positive and
negative peaks that correspond to flux reversals recorded on the disk.
After shaping and gain control, the peaks are fed into peak detectors that
output uniform pulses for each peak encountered. A variable frequency
oscillator (VFO) phase locks to the trailinq edqe of the pulses, providing a
synchronous clock
that is used to transl ate the data pul ses into standard
nonreturn
to zero (NRZ) ·format. At this point the data bits have not been
decoded, but are in a TTL form that can be used easily by the decoder in the
digital section.
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15 December 1984
1-9

·1- •. 4.2.1.2···· Servo~ Error Decoding
Servo information, av:ailable on the read 'data lines at the 'begin'ning of each'
sector, goes through a filter and gain control process similar to the read
data.
N·orma·l se.rv·o· fields" are· wr·itten· .. one-half. track· off$et. from data tracks,.', as:·
shown: in Figure 8:.:· · .. When··the'· servo code':is,·read,:·the'··re·lative amplitudes .. of
the A and B field peaks indicate how far the head is from a track center.
NORMAL SERVO TRACKS
A
B
A
B
A
DATA TRACKS
TYPICAL SERVO PEAK ARRANGEMENT
A FIELD
~
~ \ \
~
B FIELD
~
\ ~
\
Ar
TYPICAL SERVO SIGNAL AT DIFFERENT HEAD POSITIONS
CENTERED ON TRACK
OFF TRACK TOWARD
rAv
A
~
f \ ,
~
• ,
f
~
A FIELD
, •
.,
• •
OFF TRACK TOWARD
Yr--\
f \ , \ f \
..
~
r , r f
B FIELD
Figure 8. Servo Signals
Servo peak detectors on the contro 11 er board check the amp 1 itude of the A
and B peaks
and send the results to a differential amplifier. The differ-
ence between the amplitude of the A and B peaks is an error signal whose
amplitude will indicate the amount and direction off track. Window gener-
ation circuitry ensures that the peak detectors are turned on at the right
time. This position error signal (PES) acts as an input to the compensator
network, which adjusts the head position to obtain minimum positional error.
If the PES exceeds predefined limits, an error is reported to the digital
section of the controller board.
1.4.2.2 Digital Section
The digital section of the controller performs the functions of format se-
quencing, data encoding and decoding, servo control for seek and track fol-
lowing, error detection, and host interfacing. Two major buses serve the
digital controller: the microprocessor bus, which contains data for the
mi croproces sor; and the channe1 bus, wh ich carri es dat a duri ng reads or
writes.
00701300-000
15 December 1984
1-10

The: di'gital 'controller'uses" two' custom metal oxid'e:semiconduct'or' (Mos)"chip's'
(one, for file ,control an~ one .. for host, ,interface) ,as ,well ,as a Z80A
mi croprocessor. The funct ions as'soci ated with these three major 'components
are explained in this subsection.
The microprocessor circuitry is composed of a Z80-A microprocessor, read
only
memory (ROM), random ~ccess memory (RAM), and I/O ports. This circuit-
ry monitors the drive status lines and controls drtve initialization via the
microprocessor. The microprocessor also monitors bit switches that indicate
field programmable options, controls the idle drive half speed feature, and
outputs status information to the diaqnostic port.
The microprocessor monitors the host interface, recognizes a selection, ac-
cepts
and decodes command and parameter bytes, schedules and controls com-
mand execution, and returns ending status to the host. Any errors encoun-
tered along the
way are flagged to the host and specific error information
is stored, available to the host via a REQUEST SENSE command.
1.4.2.2.2 Servo Control
To initiate a seek operation, the microprocessor introduces position error
information and current offsets into the track following servo loop, which
causes the head to move off tr'ack. By contro,lling the amount and timing of
the
offsets, the proc.essor can control the acceleration, velocity, and posi-
tion of the head. '
1.4.2.2.3 Interface Circuitry
The host-to-controller interface is centered around a custom LSI chip that
includes two 256 byte FIFO buffers. These buffers are controlled in a flip-
flop mode so that data can be accepted from the disk Simultaneously with
data transmitted to the host.
Each transfer between controller and host is accompanied by a REQUEST-AC-
KNQWLEDGE (REQ-ACK) handshake. The microprocessor manipulates the handshake
during the command and status phase. During the data phase of READ or WRITE
commands, the microprocessor enables a hardware transfer mechanism that al-
lows high speed transfers. A detailed explanation and description of the
host
interface is presented in Section 2.0 of this manual.
1.4.2.2.4 File Control Circuitry
The file control circuitry is centered around a custom MOS chip that: en-
codes
and decodes, seri ali zes and, deseri alizes, generates and check s CRC,
compares track and sector IDs, maintains synchronization with the disk,
manipulates signals according to
commands received from the microprocessor,
and gathers and reports error status.
00701300-000
15 December 1984
1-11

The subsystem uses a, run length limited,code that alluws dat~ ~o be tightly
,,packed' on the di sk. The encoder/decoder trans 1ates datarecei ved from the
host
to the code and format required by the cont ro 11 er. It also detects
special marks on the disk that allow bit and byte synchronization.
':' Each"rO" and dataar'~a' ,'orf'~he:disk' is··fQri'q~;ed··,by'a· .CRC, f.ield.·fb.~,:·~rro'r'.:·de~
"tect'iori 'pt.i'rpo·s'es. "Th'e"CRC'byt"es','qenerated as the data bits' are written to
the disk, are appended to the data. As the data bits are read to the con-
troller, the data and CRC are loQical1y manipulated to check for errors. If
an error is detected, the 'incorrect data wi 11 not be transferred to' the
host, but retri es wi 11 be attempted to execute the command correct 1 y. Si x
retries will be attempted in normal operation before error status is sent to
the host. Optional
ECC circuitry also may be invoked (see Section 4.0).
Before any read or write operation, the ID of the sector under the head is
compared with that of the tarqet sector. This function ensures that no cus-
tomer data will
be accidentally overwritten or mistaken for desired data.
A unique mark is written at several places in each sector on the disk. De-
tection of these marks enables the file control format sequencer to maintain
synchronization with the disk.. This sequencer in turn manipulates control
signals required by the analog controller board.
At the beginning of each sector, an operation register is loaded by the mi-
croprocessor. This information is used in conjunction with the format tim-
ing to (1) enable write
gates, (2) set bus directions, and (3) select the
encoder or decoder. As er.rors occur, they are latched for later retrieval
by the microprocessor. Serious errors will cause the operation to abort.
1.4.3 Interleaving and Error Correction Code
A number of important factors control the performance of the subsystem.
Some of these are data transfer rate, latency, interleaving, and the error
correction option. Interleaving and how it affects system performance ;s
described in this subsection. See Section 4.0 for ECC impacts.
1.4.3.1 , Interleaving
Maximum data transfer rate of the subsystem is 1.13 meQabytes/second. How-
ever, the actual rate achieved by the host system is a function of the host
hardware and software plus the interleave selected. Poor choice in the
interleave selection can dramatically de~rade performance. Interleaving
does not
affect the performance of single sector or' sinqle record transfers
nearly as much as does latency, but for multi-sector bursts, interleaving
determines
how quickly the drive will be ready to transfer the next block of
data.
Interleaving
is a system desiqned to achieve the hiqhest possible perform-
ance when working with host systems that cannot transfer data as rapidly as
the maximum transfer rate of the disk subsystem. Durinq a data read, for
00701300-000
15 December 1984
1-12