PRIAM DISKOS 3450 User manual

OEM/SERVICE MANUAL
DISKOS 3450
DISKOS 7050
EIGHT INCH
WINCHESTER
DISC DRIVES

IPIRllAM
a-Inch Winchester Disc Drives
OEM/Service Manual
JULY 1982

IPRllAM
a-Inch Winchester Disc Drives
OEM/Service Manual
Changes to this Manual
This manual will be changed periodically to keep
it current with improvements as we make them.
Changes start with Field Engineering Bulletins
that alert field service technicians to critical prob-
lem areas and changes in maintenance procedures.
After aseries of these notes are issued or acriti-
cal one is issued, we will publish changed pages,
which are the remove-the-old and insert-the-new
type. Avertical bar in the margin of the changed
page indicates the revised material. After about
20% of the manual's pages are changed, we will
reissue the entire manual. When PRIAM prepares
achange package, it sends announcements to its
users. The change packages are available upon
request and without charge.
Reader Comments
If you are dissatisfied with this publication, we
want to hear from you. Tell us about inaccurate in-
formation, typographical errors, or missing infor-
mation. If you know away to improve aprocedure,
please let us know about that, too. Please be spe-
cific and give the page number, line reference, and
the paragraph number, if possible.
Change Notation
Avertical line in the outer margin of apage indi-
cates the portion of text affected by changes.
Shaded areas indicate changes to illustrations
and diagrams.
The total number of pages in this document is 69.
Safety Precautions
As with any electronic equipment, precautions
consistent with all standard industrial safety prac-
tices must be observed while servicing this equip-
ment since it contains potentially dangerous
voltages. Any servicing that requires removing
cabinet covers should be performed by qualified
service personnel. Always disconnect power prior
to inspection or servicing.
Admonishments are included throughout this
manual to alert the reader to problem areas or
situations that could cause loss of data, hardware
damage, or personal injury.
AWARNING statement precedes the text of pro-
cedures that, if not strictly observed, could result
in injury to the service technician. ACAUTION state-
ment precedes the text of aprocedure that, if not
strictly observed, could result in damage or de-
struction of equipment (hardware or software). A
NOTE statement highlights essential operating or
maintenance procedures, conditions, or clarifying
facts. NOTEs also provide information that, though
not necessary, is helpful to the understanding of a
concept or the completion of aprocedure.
The following are general safety precautions that
are not related to any specific procedure and
therefore do not appear elsewhere in this manual.
Personnel must heed these warnings during many
phases of installation and maintenance.
WARNING
Page No. Change Number* Page No. Change No.*KEEPAWAY FROM LIVE CIRCUITS.
Dates of issue for original and changes pages are: *0 in this
column indicates an original page.
Observe safety precautions at all times. Observe
all the CAUTIONS and WARNINGS in this manual
when working with the equipment.
DO NOT SERVICE OR ADJUST ALONE.
Never reach into the cabinet to service the equip-
ment unless someone capable of giving aid is
present.

The following WARNING applies to any service
inside the equipment cabinet. It appears else-
where in the text of this manual and is introduced
here for emphasis:
WARNING
Voltage hazardous to human life are exposed in
the cabinet. Use extreme caution when servicing
either the power supply or any area where power
terminals are exposed.
Warranty
For warranty information, contact PRIAM:
[phone].
TABLE OF CONTENTS
3. FUNCTIONAL DESCRIPTION. .......... 9
3.1 Overview. ..................... 9
3.2 Servo Surface. ................. 9
3.3 Servo Pattern. ............... .. 9
3.4 Data Surface.................. 10
3.5 Track
Format.................. 11
3.6 Defect Location Record Format.. 11
3.7 Data Sector Format. .......... .. 11
3.8 Overview. ................... .. 12
3.9 Drive
Selection................ 12
3.10 Power Up/Down Sequences 12
3.11
Motor Control Circuitry. ....... .. 12
Spare Parts List ". 64
Schematics. ................ .. 65
4. TROUBLESHOOTING ". 57'
4.0 Introduction. ................ .. 57
4.1 Field Adjustments and Preventive
Maintenance ". 57'
4.2 General Inspection ". 57
4.3
Status and Error Codes ". 57
4.4 Symptoms and Causes ". 57
4.5 Seek Errors and Fault
Conditions. 62
4.6
Precautions. ................ ... 63;
4.7 Head Disc Assembly ". 63
4.8 Servo and Motor Control PCB .. ". 63
4.9 Read/Write Digital PCB ". 63
4.10 Power Supply ". 63
Section
1. GENERAL INFORMATION .
1.1 Overview .
1.2 Options .
2. INSTALLATION .
2.0 Introduction .
2.1 Unpacking and Receiving
Inspection .
2.2 Shipping Damage Inspection .
2.3 System Unpacking .
2.4 Inspection Procedures .
2.5 Reshipping Procedures .
2.6 Switch Settings .
2.7 Cabling .
2.8 Unlocking .
2.9 Locking .
2.10 Repacking .
2.11 Storage .
2.12 Shipping .
2.13 Spindle and Head Locks .
2.14 Powering Up/Down .
2.15 Performance Check .
Page
1
1
1
3
3
3
3
3
3
3
3
3
4
4
5
5
5
5
7
7
ii
Section
3.12
3.13
3.14
3.15
3.16
3.17
3.18
3.19
3.20
3.20.1
3.20.2
3.20.3
3.20.4
3.20.5
3.20.6
3.20.7
3.20.8
Page
Seek Modes 12
Servo Circuitry. .............. .. 14
Data Read/Write Functions. ... .. 14
PLO/VFO 17
Microprocessor Flow Charts. . . .. 18
PRIAM Interface............... 18
Connectors and Pin Assignments. 18
Interface Signal Descriptions.. .. 35
SMD Interface ". 45
Overview. ................... .. 45
Connectors and Pin Assignments. 45
Interface Signal Descriptions .. ". 46
Interface DC Characteristics ". 50
Interface Timing ". 52
Format Design ". 54
Write Format Procedure ". 54
Control Timing ". 55

LIST OF FIGURES
Figur~
Page Figure Page
2-1. Read/Write Digital PCB ........... 4
3-26.
Calibrate Flow Chart. ............. 34
2-2.
Servo and Motor Control PCB ......
4
3-27.
DBUS Transceiver ................
38
2-3.
Daisy-Chaining an 8-inch Drive with
3-28.
Single End Line Receiver Gated By
PRIAM Interface
................. 5DRIVE SELECT
.................. 38
2-4.
Location of Head and Spindle Lock.
6 3-29. Single End Line Receiver .......... 38
3-1. Servo and Data Surfaces .......... 9
3-30.
Single End Line Driver .............
39
3-2.
Servo Track Signals ............... 10
3-31.
Differential Line Drivers and
3-3. Simplified Block Diagram of aPRIAM Receivers .......................
39
8-inch Disc Drive ................. 13
3-32.
Register Load Timing .............
40
3-4. Motor
Controller .................
14
3-33.
Register Read Timing .............
40
3-5.
Servo Circuitry ................... 15
3-34. Reset Timing
....................
40
3-6. Read/Write Timing and Encoding ... 16
3-35.
INDEX and SECTOR MARK Timing ..
40
3-7.
Data Read and Write Circuitry ...... 17
3-36.
WRITE DATA and
3-8. Initialization Flow Chart ...... ' ..... 19
WRITE CLOCK Timing ............
40
3-9. First Idle Flow Chart .............. 20
3-37. READ DATA and
3-10. Idle Flow Chart ...................
21 READ CLOCK Timing ............. 41
3-11.
Command Decode Flow Chart ......
22
3-38. Record Writing Timing ............
41
3-12. Sequence Up Flow Chart #1 ........ 23
3-39.
Record Reading Timing ...........
42
3-13. Sequence Up Flow Chart #2 ........ 24
3-40. Read and Write Transitions
3-14. Sequence Down Flow Chart ........
25
During Gap ...................... 42
3-15. Restore Flow Chart ............... 25 3-41. Typical Read/Write Data and Clock
3-16. Seek Flow Chart ................. 25 Transmitter and Receiver ..........
50
3-17.
Restore Subroutines Flow Chart ....
26 3-42. Control Line Transmitter ........... 51
3-18.
Seek Subroutines Flow Chart #1 ....
27 3-43. Control Line Receiver ............. 51
3-19. Seek Error Flow Chart. ............ 28 3-44. Tag and Bus Timing ...............
52
3-20.
Last Track Flow Chart #1 ..........
29 3-45. Typical Read Timing ..............
53
3-21.
Last Track Flow Chart #2 ..........
30
3-46. Typical Read Control Timing .......
53
3-22.
Seek Done Flow Chart. ............
31 3-47. Typical Write Control Timing .......
53
3-23.
Fault Reset Flow Chart ............
32 3-48. Index and Sector Mark ............
53
3-24. Read Drive IDand
3-49. Drive Select Timing ...............
53
Read Bytes/Sectors Flow Chart .....
32
3-50.
NRZ Data and Read Clock Timing ... 54
3-25. Seek Start Flow Chart. ............
33
3-51. Recommended Sector Format ...... 55
iii

LIST OF TABLES
Table Page Table Page
1-1. Specifications for PRIAM 8-inch
3-10.
Reset AC Characteristics ...........
40
Disc Drives .......................
2 3-11. INDEX and SECTOR MARKAC
2.4. S~itch Settings on the Read/Write
Characteristics ................. ".
40
Digital PCB .......................
3
3-12.
WRITE DATA and WRITE CLOCK
3-1. Head Selection ................... 37
AC Characteristics ................
40
3-2.
DBUS Transceiver DC 3-13. READ DATA and READ CLOCK
Characteristics ...................
38 AC Characteristics ................
41
3-3.
Single End Line Receiver Gated by 3-14. Record
Writing Control AC
DRIVE SELECTED Characteristics ...
38
Characteristics ...................
41
3-4.
Single End Line Receiver DC 3-15. Record Reading Control AC
Characteristics ...................
38
Characteristics ...................
42
3-5.
Single End Driver DC
3-16. Register Selection ................. 43
Characteristics ................... 39
3-17.
Command Code Summary .......... 43
3-6. Differential Receiver DC
3-18.
Drive ID Assignments .............. 44
Characteristics ................... 39
3-19.
Status Register Bit Definitions ...... 44
3-7. Differential Line Driver DC
3-20. Address Register
Bit Definitions ..... 45
Characteristics ................... 39
3-21. Tag Bus I/O Interface
("A" Cable) .... 46
3-8.
Register Load AC Characteristics ....
39
3-22. Tag Bus Decode ("A" Cable) ........ 47
3-9.
Register Read AC Characteristics ... 40
3-23. "B" Cable Interface ................ 47
iv

1. GENERAL INFORMATION
1.1 The DISKOS 3450 and 7050 use advanced
Winchester and microprocessor technol-
ogies to provide users with low-cost disc drives
having high capacity, fast access, and long-term
reliability. Linear motor voice coil positioners with
track following servos enable the DISKOS 3450
and 7050 to position Winchester type heads
quickly and precisely. These low-force heads as-
sure high data reliability.
Advanced 8-inch Winchester-technology discs are
driven by an outer-rotor, brushless DC motor. The
head positioner coil and carriage, heads and
discs are enclosed in asealed, contamination-
resistant chamber to assure high reliabilIty.
One head serves each disc surface, and afull sur-
face is dedicated to servo information for fully
servoed track following, head positioning, and
write timing. Three discs recorded at 480 tracks
per inch are used in the DISKOS 3450 to provide a
capacity of 35 megabytes, unformatted. In the
DISKOS 7050, the three discs are recorded at 960
tracks per inch to accommodate 70 megabytes
(unformatted) of data.
Microprocessors are used in the disc-drive elec-
tronics to provide interface flexibility and to moni-
tor drive operation. For example, they control
power up and down sequencing, and aself-test
program checks drive performance during each
power-up sequence. Any malfunction detected by
these tests will prevent drive start-up, reducing
the chance of loss of data or damage to the drive.
PRIAM disc drives are constructed in a modular
fashion, so that defective assemblies can be
easily replaced. This greatly reduces down time
due to servicing. The three assemblies are:
Head Disc Assembly
Servo and Motor control PCB
Read/Write Digital PCB
The Head Disc Assembly(HDA) is asealed enclo-
sure. It contains the drive spindle assembly, drive
motor, Hall Effect sensors, voice coil actuator,
head carriage assembly, read/write heads, mag-
netic discs, and air filter assemblies.
The Servo and Motor Control PCB contains the
circuitry associated with driving the spindle mo-
tor. This circuitry receives an On/Off command
from the Read/Write Digital PCB, and spindle ro-
tation feedback from the Hall Effect sensors in
the HDA.
1
The Servo and Motor control PCB also contains
the circuitry used for processing the servo signals
from the servo read head, and for controlling the
position of the head carriage.
The Read/Write Digital PCB contains all the cir-
cuitry associated with read/write control, com-
mand execution, and information transfers across
the user interface.
1.2 Options
1.2.1 Interface Options. The PRIAM 8-inch
disc drives are available with avariety of
interface options. Each of these interface options
can be used, without modification, on any disc
drive in the 8-inch family. All PRIAM interfaces in-
clude on-board data separation.
The standard PRIAM interface is designed for low
cost and for efficient use with microprocessor-
based systems. Up to four drives may be daisy-
chained, when this interface is used. The PRIAM
intEHface provides abasic 8-bit bidirectional bus,
which may be used with the currently popular 8-bit
and 16-bit microprocessors. It also provides bit-
serial NRZ data exchange. No elaborate handshak-
ing protocols are required. The PRIAM interface is
built into the disc drive's read/write digital PCB. A
50-conductor flat ribbon cable is Ulsed between
the PRIAM interface and the host system.
The SMD Interface permits aPRIAM drive to be
used with existing Storage Module Drive (SMD)
controllers. In the 8-inch drives the SMD interface
is available as an adapter which is installed be-
tween the drive electronics and the SMD controller.
The line drivers and line receivers in the SMD in-
terface are matched to those of typical SMD con-
trollers. There are two interface cables between
the host system's SMD controller and the PRIAM
disc drive's SMD Interface- a 60-conductor
twisted-pair flat cable ("A" cable) and a26-con-
ductor flat ribbon cable ("B" cable).
The ANSI interface complies with the disc drive
interface standard proposed by ANSI Technical
Committee X3T9. Characteristics of the ANSI in-
terface include variable and fixed sector sizes,
data transfer rates up to 10 megabits per second,
and radial attention and select capability. Up to
eight drives may be daisy-chained, on a single
50-conductor flat ribbon cable.
1.2.2 Interface Cables and Terminators. I/O
cables are available from PRIAM, for con-
necting the user's controller to the PRIAM disc
drive, and for connecting daisy-chained drives to
one another.

Terminators are available for I/O signal lines, to
minimize reflections and
to ensure maximum data
integrity. One set
of terminators is required for a
single drive, orforthe last drive in adaisychain.
1.2.3 Power Supplies and Cables. PRIAM's
optional power supply allows-PRIAM disc
drives to operate from
100, 120,220, and 240 VAG,
50 or 60 Hz power. The optional power supply
must
be mounted separately from the drive. It
does not
fit within the drive frame.
1.2.4 Mounting Hardware. PRIAM a-inch
drives may be mounted horizontally or
ver-
tically. Standard floppy disc mounting may be
used.
Table
1·1. Specifications for PRIAM a-inch
Disc DrivesDISKOS DISKOS
OPERATING CHARACTERISTICS
3450 7050
Capacity (unformatted)
Transfer rate (megabytes/second)
Track-to-track seek time (typical)
Average seek time (typical)
Maximum seek time (typical)
Average latency
Tracks per inch
Bits per inch
Number
of data surfaces
Number
of data cylinders
Nominal RPM
Bytes per track
35 MB
0.806
8msec
42 mse.c
75 msec
8.3msec
480
6,670
5
525
3,600
13,440
70 MB
0.806
8msec
42 msec
75 msec
8.3 msec
960
6,670
5
1,049
3,600
13,440
Power Requirements
Power requirements are the same for both drives:
DC Voltage Maximum Typical
+24 VDC (±5%)
4.0 A
3.5 seeking
2.2 non-seeking
+5 VDC (±5%)
2.0 A1.5 A
-5 VDC (±5%)
2.0 A
1.5 A
-12 VDC (± 5%)
0.7 A
0.4 A
NOTE: This data does not include adapter/inter-
face option power requirements.
Dimensions
Physical dimensions are the same for both drives:
Weight 20.00 pounds
7.80
±.05
TYP
NO. 8-32-2B x3/8DP
4HOLES
8.12 TYP -----/-ot-
BOTTOM
8.00 -----11+--
-----iL- __
______ .J
I
~--l
I I
II
f------
J
I~f_+---------_r_--_J_--- ..... I
_____ ~-- -J-=-~ ~ ---i+-e-"t+---'-
-------- 14.25 ±.02
LEFT SIDE
J5
REAR
8.55
±.03
J1
GND-POWER SUPPLVCABLE
NO. 8-32 HOLES
2

2. INSTALLATION
2.0 Introduction. This Chapter contains pro-
cedures
for installing the 3450 Disk Drive.
It includes
instructions for unpacking and in-
specting, and procedures
for interconnecting the
equipment
to the powersource.
2.1 Unpacking and Receiving Inspection. When
the 3450 Disc Drive is delivered by atrans-
fer company,
it must be carefully inspected (inside
the shipping
container as well as out) for damage.
If the unit is to be reshipped, it must be repacked
in amannerthatwill prevent damage while in transit.
2.2 Shipping Damage Inspection. Prior
to
accepting delivery of the 3450 Disc Drive
from the carrier, carefully inspect the shipping
container for obvious damage. If damage is found,
note
it on the waybill and require the delivery
agent
to sign the waybill. Notify the transfer com-
pany
immediately and submit adamage report to
the carrier. If no exterior damage exists, unpack
the system and
inspect for hidden damage.
2.3 System Unpacking. The 3450 Disc Drive
is shipped
with the accessories and sche-
matics in one shipping container.
Unpack the system from the shipping
container
with care; avoid using sharp instruments to open
the container.
We recommend saving all packing
materials
for possible reuse in reshipping the
equipment.
If hidden damage is found, immediately notify the
transfer company
of the damage. Save all packing
materials for the transfer
company's inspection,
file adamage report with the carrier. Damage to
the equipment is not covered under warranty. All
repairs for shipping
will be billed. Prompt notifica-
tion of damage will ensure claim validity and will
help expedite payment for necessary repairs by
the transfercompany
or its insurance agent.
2.4
Inspection Procedures. After unpacking
the 3450 Disc Drive, Inspect
it thoroughly
for damage hidden by the packaging and for loose
components or fittings, as follows:
a. Inspect the Interiorfor shipping damage.
b. Examine internally mounted components for
loose or
missing hardware.
c. Tighten all loose hardware.
d. Clean the cabinet
interior by removing loose
debris.
e. Check that head and spindle lock is secure.
3
2.5 Reshipping Procedures. Should the equip-
ment be reshipped prepare the equipment
for shipping as follows:
a. Check the integrity of the cabling and the secu-
rity
of internal mounting hardware.
b. Place the drive flat on abench top and then
place the spindle head
lock in the LOCK position.
c. Repack the equipment in the original shipping
container or other suitable materials.
Table
2.4-1. Switch Settings on the Read/Write
Digital PCB
Switch #Switch Group Location on PCB
in Group 6K
5H
1Drive Select 1 1
sector/track
2Drive Select 22
sectors/track
3Drive Select 34
sectors/track
4Drive Select 48
sectors/track
5
16 sectors/track
6
32 sectors/track
Write Clock
7
Off=Open
64 sectors/track
On =Closed
8On =Write Enable See Note Below
NOTE: 128 SECTORS /TRACK
2.6 Switch Settings. The drive address, write
protect parameters and sector size are all
switch selectable. The switches are located on
the read/write
digital PCB. Referring to Figure 2-1
and to T 2.4-1 ,set the switches according to the
desired operating conditions.
2.7 Cabling. The power cable should
be in-
stalled
to connector J3 on the servo and
motor control board (See Figure 2.2). The DC volt-
ages required at the respective pins on J3 are
listed in the 3.18.2 section. Interface cables
to the
host system are described in the sections cover-
ing each
of the available interface options. Figure
2.3 shows how the interface cables are connected

oSECTOR
oSELECT
____ J3_~
TO SERVO/MOTOR CNTL BOARD
tj
0M lJ035 J253
2716 IlP. BUS
DRIVER
J1 BW
TO CONTROLLER
EJ
DRIVE SELECT
6K WRT CLK PHASE
•WRT CLK LOOP
WRITE PROTECT
D9JB
D9JA
J2 ~
"-;:===~
J1
MOTOR &
HALL
EFFECT
SENSORS
POR
J3
POWER
CONNECTOR
f8l CURVE
l!!1 GEN.
f61
FPOSITION
~ SIGNAL
rJWRITE
~DELAY
r------,
I VFO I
II
L ..J
R15
O
DATA
WINDOW
ADJ.
CC W
FC 3
TRKXING 0
VOICIJ =
COIL
J5
GUARD
BAND
r;;l DELAY
L:J LINE
o 0ENTIATOR
LJ LIMITED DATA
Figure 2·1. Read/Write Digital PCB
for the PRIAM interface. Cabling between assem·
blies within the discdrive is completed at the factory
prior to shipment. More details on inter-assembly
cabling are given in the ASSEMBLY REPLACE-
MENT PROCEDURES section.
2.8 Unlocking. Both the drive spindle and
the head carriage assembly are locked
prior to shipment. After the drive has been com·
pletely mounted and cabled, these must be
unlocked to enable normal operation.
The drive spindle and head carriage lock is fully
accessible from one end of the HDA (Head Disc
Assembly). Referring to Figure 2·4, place this lever
in the UNLOCK position.
4
o INDEX
IT]
Figure 2·2. Servo and Motor Control PCB
CAUTION
Avoid manual rotation of the spindle or
movement of the carriage. Damage to
the disc surface may occur if the heads
are moved across anon-rotating disc
surface. Do not move the drive with the
spindle and head carriage assembly
unlocked.
2.9 Locking. The drive spindle and the head
carriage shou Id be locked whenever the
drive is to be physically moved, even if it is not to
be shipped. To lock the drive, refer to Figure 2-4,
and place the lever in the LOCK Position.

•
~
........
.........
........ ",
TO SPECIAL CONN.
ON FIRST
DRIVE
PN NO. 922576-50-1
................
................ ................
........
........
........
TOJ1
SECOND DRIVE
,
........ ........
........
........
........
'...--
PART NO. 922576-50-1
PLUGS INTO J1 CONN.
ON
DRIVE TOP PCB
•
FROM
CONTROLLER
BOTH CABLES PLUG
INTO PN NO. 922576-50-1
CONNECTOR
* MAY BE DUPLICATED
FOR UP TO 3 DRIVES
Figure 2-3. Daisy-Chaining an a-inch Drive with PRIAM Interface
2.10 Repacking. Repacking is the reverse of
the unpacking procedure. Prior to repack-
ing the drive, make sure that the spindle and car-
riage lock level is in the LOCK position.
2.11 Storage. When the environment is severe,
or when the drive is to be stored for along
time, it should be repacked prior to storage.
When storing unpacked drives, avoid dusty or un-
stable environments.
2.12 Shipping. Contact PRIAM Customer Ser-
vice for areturn authorization number
prior to shipping adrive or assembly to PRIAM.
5
After locking the drive spindle and head carriage,
pack the drive in its original carton or an equiva-
lent one.
2.13 Spindle and Head Locks. Before the
drive can be operated, it is necessary to
have the drive mounted or placed flat on abench,
then place the spindle and head lock lever in the
UN LOCK position. Refer to Figure 2-4 for the
location of this lever.
CAUTION
Whenever the drive is to be moved for any reason,
the spindle and head lock lever should be placed
in the lock position.

;iiiiiiiiiiiiiiiii';_iiiiiiHi iiiiiiiiiiiiiiiiiiiiiiiiiii_iiiiiiii_= _
SPINDLE LOCK
o
Figure 2·4. Location of Head and Spindle Lock
2.14 Powering Up/Down. The exact proce-
dure for powering up the drive depends on
the interface option present:
If the drive has astandard PRIAM interface,
apply DC power, select the drive (via the -DRIVE
SELECT lines) and issue aSequence Up
command.
If the drive has an SMD interface, apply DC
power, select the drive (via the UNIT SELECT
lines), then bring PICK and HOLD to ground.
If the drive has an ANSI interface, apply DC
power, select the drive (via the SELECT/ATTEN-
TION lines), then issue aSpin Up command.
Similarly, the procedure for powering down also
depends on the interface option present:
If the drive has astandard PRIAM interface, is-
sue aSequence Down command and discon-
nect DC power supply.
If the drive has an SMD interface, remove the
ground from PICK or HOLD and disconnect DC
powersupply.
6
If the drive has an ANSI interface, issue aSpin
Down command and disconnect DC powersupply.
2.15 Performance Check. The following pro-
cedures are recommended as an initial
check for properoperation on the disc drive:
a. Watch for the drive to become Ready. If no faults
are detected during the power up sequence,
this will take about 30 seconds. If a fault is de-
tected (by the safety circuits within the drive),
Ready will be inhibited and a fault condition
will be reported. If, after two minutes, the micro-
processor within the drive is unable to sense
that the spindle is rotating at the specified
speed, READY will be inhibited and spindle ro-
tation will stop.
b. Check the head positioning operation by issuing
seek commands. The following seek pattern is
suggested:
From 000 to 001 to 000 to 002 to 000 to 003 to
000 to 004 to 000 to 005 to 000 ... to maximum
cylinder address.
c. Check for proper data transfer operation by writ-

ing and then reading data with each read/write
head.
CAUTION
Write operations alter previously recorded data
Most
disc s/ystems require aformatted disc be-
fore datatransfer can be performed.
7
A disc surface defect map is supplied by PRIAM
with each disc drive. The defect map indicates
the location
of defects discovered during manu-
facturing and testing. Adefect location is spe-
ci'fied by the number of byte positions from the
index mark.

NOTES
8

3. FUNCTIONAL DESCRIPTION
3.1 Overvh!w. The PRIAM 3450 Disc Drive
has three discs, with atotal
of six magnetic
surfaces. Each surface accommodates one head,
as shown in Figure
3-1. On the "bottom" surface,
the head reads the servo information. The remain-
ing heads write and read datasurfaces0through
4.
r---
-
DATAH~
DISC
NO.4
)
DATAH~
NO.3
w
DIHAHE~
t:l
«
DISC
NO.2
~
)«
u
DATAHE~
0
w
NO.1
~
....
:I:
0
Z
g;
DIHAHE~
DISC
NO.O
)
SER\~
HEAD
I-
.....----....
Figure :~·1. Servo and Data Surfaces
The PRIAM 7050 has exactly the same configura-
tion
of disc surfaces and heads as the 3450, but it
achieves twice the storage capacity by having
twice as many data tracks per inch.
3.2 Servo Surface. The purpose of the servo
surface is
to provide acoordinate system
by which the electrical
circuitry of the disc drive
can locate spe'cific areas for writing or reading data.
The servo surface is written once at the factory,
and thereafter is aread-only area. The information
on the servo surface determines the angular posi-
tion
of the disc, as well as the radial position of
the head carriage.
The servo surface is divided into four
distinct
groups of tracks. From the inside (hub) out, these
are as follows:
a. Guardband 2(landing zone)
b. Guardband 1
c. Servo Data Band
d. Guardband 1
Within each
of these bands, ,there are four types
of tracks-odd normal tracks, odd quadrature
tracks, even normal tracks, and even quadrature
tracks. Each track type produces acharacteristic
signal at the servo read head, as described below
in the SERVO
PATTERN section. The closer the
servo read head is
to aparticulartrack, the greater
9
will be that track's contribution to the servo
head's output.
The servo
circuitry compares the amplitudes of
the signals from adjacent tracks, and identifies an
equal-ampliture
condition as a "track crossing."
During seek operations, the servo circuitry counts
the track crossing in order
to stop at the cylinder
address requested by the controller. During write
and read operations, the servo
circuitry adjusts
the position
of the head carriage in such amanner
as
to preserve the equal-amplitude condition,
thus keeping the write/read head
"on track."
3.3 Servo Pattern. Figure 3-2 shows the four
kinds
of servo track signals. The normal
servo data patterns are written on the integer
tracks, and the quadrature servo data patterns are
written on the half-integer tracks.
The negative pulses are sync pulses.
In the all "0"
pattern, these pulses occur at regular intervals,
and serve to define the frame boundaries. When
the servo head reads a
"1," an additional negative
pulse occurs in the mid-frame position. The frame
time interval
(T) is equal to 16 write/read data bit
times. Most of agiven track is written with the "0"
pattern. The "1" pattern occurs once each revolu-
tion
of the disc, and serves to define the INDEX
location.
The positive pulses are used by the servo
circuitry
to recognize track crossings or to maintain the on·
track condition. Referring again
to the all "0"
pattern, it can be seen that the even normal track
generates positive pulses occurring one-third
of
the way across the frame, while the odd normal
track generates positive pulses occurring at the
two-thirds point. The quadrature track patterns
have positive pulses alternately at the one-third
and two-thirds positions.
When the servo read head is midway between two
adjacent tracks (a "track-crossing" position) the
output resembles the patterns shown at the
bottom
of Figure 3-5. Successive frames
produce the equal-amplitude positive peaks,
alternating
with single large peaks. By analyzing
which frames have the equal-amplitude peaks,
and whether the large peaks
occur at the one-third
or the two-thirds locations
within the frame, the
servo
circuitry is able to determine which of the
four kinds
of "track-crossing" positions is being
indicated. Note that the servo read head is mid-
way between
two adjacent tracks when the data
write/read heads are
"on-track."
The servo circuitry counts the track crossing in

order to determine the current cylinderaddress. In
the 3450, data tracks are written at alternate cylin-
der address (all integer or all half-integer).
In the
7050, data tracks are written at both the integer
and half-integer cylinder addresses.
3.4 Data Surface. The configuration
of tracks
on the data surfaces has aone-to-one cor-
LOGICAL FRAME
FRAME
BOUNDARY
ODD NORMAL WRITE DATA
READ BACK ON ODD NORMAL
SERVO TRACK
ODD QUADRATURE WRITE DATA
READ BACK ON ODD QUADRATURE
SERVO TRACK
EVEN NORMAL WRITE DATA
READ BACK ON EVEN NORMAL
SERVO TRACK
EVEN QUADRATURE WRITE DATA
READ BACK ON EVEN QUADRATURE
SERVO TRACK
READ BACK ON DATA TRACK
BETWEEN ODD NORMAL AND
EVEN QUADRATURE SERVO TRACK
READ BACK ON DATA TRACK
BETWEEN EVEN NORMAL AND
EVEN QUADRATURE SERVO TRACK
respondence with the configuration of servo
tracks on the servo surface. Thus, for example,
when the servo head is in the servo data band, all
the write/read heads are in the corresponding po-
sitions in their respective write/read data bands.
When the servo head is in the servo landing zone,
each data head is also in
its own landing zone.
*MISSING SYNC AT THE FRAME BOUNDARY WILL RESULT IN LOW AMPLITUDE SIGNAL AS SHOWN AT A* AND B*
Figure 3·2. Servo Track Signals
10

The format for the Ski·p Defect Record is as
follows:
The write/read data tracks are numbered consec-
utively, starting with track 0nearest the outside
edge of the disc. Each write/read data track is di-
vided into sectors. The division of tracks into sec-
tors can be adjusted by the user through switch
settings on the read/write digital PCB, as detailed
in the INSTALLATION section.
3.5 Track Format. In a typical track format,
each track isdivided as follows:
Data sync (FB hex)
1 st defect location
2nd defect location
3rd defect location
Checksum
Fill characters (zeros)
1byte
2bytes
2bytes
2bytes
2bytes
2bytes
Index Mark
Gap (type 1)
SkiPDefect Record
N Identical Data Sectors
Gap (type 3)
The index mark is a1.92 microsecond (tWO-byte
times) pulse, derived from the index pattern on the
servo data surface.
The type 1gap allows for VFO synchronization for
data separation. It consists of zeros, and has a
minimum length of 23 bytes.
3.7 Data Sector Format. The N identical
Data Sectors have the following structure:
Sector Mark
Gap (type 1)-zeros (23 bytes minimum)
Address Field
Gap (type2)-zeros (11 bytes minimum)
Data Field
The sector mark is a960 nanosecond (one byte
time) pulse which occurs at the beginning of each
sector. It is generated by the servo circuitry, using
abyte clock which is initialized by the index
pulse.
The format for the Address Field is as follows:
The Data Field has the following structure:
The composition of the Skip Defect Record and of
the N identical DataSectors are described below.
The type 3gap is a function of sector size, and is
used to fill (with zeros) the space left over after the
largest possible integer number of sectors (com-
mensurate with the switch settings) have been
written.
It should always be remembered that the switch set-
tings determining sector size are read by the micro-
processor as part of the Sequence Up process.
Thus, achange in these switch settings will not take
effect until the drive is once again sequenced up,
or re-initialized from apower down condition.
Sync pattern (F9 hex)
Head and high order cylinder address
Low order cylinder address
Sector address
Sector length and flag
CRC
Fi II characters (zeros)
Sync pattern (FD hex)
Data bytes (according to sector length)
CRC
Fill characters (zeros)
1byte
1byte
1byte
1byte
1byte
2bytes
2bytes
1byte
2bytes
2bytes
3.6 Defect Location Record Format. The De-
fect Record (PRIAM interface only) can
identify up to three defective sectors on the track.
The following diagram summarizes the typical
track format:
DATA GAP GAP SKIP GAP ADDRESS GAP DATA GAP ADDRESS GAP DATA
FIELD TYPE TYPE DEFECT TYPE FIELD TYPE FIELD TYPE FIELD TYPE FIELD
N 3 1RECORD 1 1 2 1 1 2 22
t
INDEX
MARK
t
SECTOR
MARK
1
11
t
SECTOR
MARK
2

3.8 Overview. Figure 3-3 is asimplified block
diagram of aPRIAM 8-inch disc drive with
the standard PRIAM interface. The overall organi-
zation shown is the same for all drives in the
8"
family. However, the names of the specific inter-
face signals vary as afunction
of the interface
option present.
The
disc drive has its own (8035) microprocessor,
which controls the sequencing
of all the opera-
tions
that occur in the drive.
3.9 Drive Selection. The disc drive must be
properly selected before it wi II respond to
any of the signals on the controller interface. On
the standard PRIAM interface, this is accomplished
by placing the proper address on
t11e DRIVE
SELECT
1-4 lines. On the SMD interface, the
proper address is placed on the UNIT SELECT
1, 2,
4and 8lines and the UNIT SELECT TAG line is ac-
tivated.
In general, the interface lines to be used
may
be determined by referring to the section
(below) describing the
specific interface involved.
The address
of an individual drive is determined
by
switch settings on the read/write digital PCB,
as discussed in the INSTALLATION section. The
drive responds
to the selection procedure only
when
its switch-selected address matches that
placed on the interface by the controller.
3.10 Power Up/Down Sequences. When power
is applied, the Microprocessor Initialization
sequence occurs automatically. The microproces-
sor then goes into the idle state, in which it moni-
tors the controller interface for acommand.
The controller may then issue aSequence
Up
command to the drive (the exact manner in which
this is done depends on the interface option
present). The microprocessor recognizes
this
command and starts the spindle motor. When the
motor is running at the proper speed, the micro-
processor reads the sector length switches, and
configures the drive
to operate in terms of the
chosen sector length. Next
it calls the RSTRGO
subroutine, which moves the heads to cylinder
zero. It then enables the drive ready status, resets
the busy condition, and returns
to the idle state.
The drive is'stopped by issuing aSequence Down
command. This causes the heads
to return to the
landing zone, and stops the spindle motor.
3.11 MotorControl Circuitry. The spindle motor
is abrushless (electronic commutating)
permanent magnet
DC motor. The speed of the
12
motor is controlled by aclosed-loop circuit con-
taining Hall
effect sensors and acomparator.
Figure
3-4 is a block diagram of the motor control
circuitry. The microprocessor sets the OFF signal
true
to inhibit spindle rotation, or false to allow
spindle rotation. The microprocessor monitors
the speed
of spindle rotation. If, during the power
up sequence, the
motor does not reach its speci-
fied speed
within one minute, or if, during normal
operation, the
motor speed passes outsicJe the
specified speed range, the microprocessor
will
set the Fault condition, restore the heads to the
landing zone, and
inhibit the spindle rotation.
3.12 Seek Modes. The servo system has
two
main mocJes of operation - On Track mode
(also called Position mode) and Move mode.
Move mode becomes active when the drive is
commanded
to move the heads. The microplroces-
sor receives the new target cylinder address and
the seek command, determines the direction
of
travel and the number of tracks to be crossed, and
sets Move mode.
When the servo is in Move mode, avelocity profile
(produced by adigital-to-analog converter) is com-
pared (via asumming junction) with the
output of
an electronic tachometer, which indicates the ve-
locity of headmotion. The difference signal from
the summing
junction is fed to the servo power
amplifiers, which control the voice coil motion.
The heads are driven toward the new cylinder
address. The servo
circuitry monitors the track
crossings and decreases the velocity
of head
motion as the selected cylinder is
approachE~d.
When the heads are within 100 microinches of the
new cylinder, the On Track mode becomes active.
In the On Track mode, the heads are held precisely
over the designated track. Any unintended head
movement is detected by the electronic tachom-
eter and fed
to the summing junction. This in turn
causes the servo power amplifiers
to adjust the
head position, so that the heads remain at the
desired location.
Servo safety
circuits drive the heads to the land-
ing zone upon detection
of alow power condition,
or
if both Move and On Track modes occur simul-
taneously. The safety
circuits also monitor the
voice coil speed. If the specified speed is ex-
ceeded,
or if the continuous position information
is lost, an Overspeed signal is established and the
servo power amplifiers are disabled. Seek Fault is
set
if any of the above conditions develop.

C
o
N
T
R
o
L
L
E
R
OR
S
M
A
R
T
--
~
COMMAND
/l
REGISTER
~
uPROC r----v 8035
PORT
L-f'..
uPROC
V1
'"
VL-.- 88-
B-BIT
BUS
IB
r---v-
IB
........,-
V
N--
I I
T
L-J ........
ADDRESS
.....-1
T
--V
REGISTER
BNB
UU
SEL
SS
ADI
ILL
-
ADO
--i
-
OPERATION
,
STATUS
A --.1'.;
-RD
;V
DECODER
REGISTER 8-BIT
BUS
SFCTOR
--
-WR
-
"'i
V
DECODER
-
"'
SECTOR MARK
SELECTED
I
N
T
E
R
F
A
C
E
DRIVE SEL _ DR SEL
LINES .. SWITCHES
READY
-
WRITE CLK ~ RECEIVERS
AND
_RD/REF CLK DRIVERS
WRITE DATA
WRITE GATE_
READ GATE _
_ READ DATA
HEAD SELECI
SEL
-
..
DRIVER
READ/
WRITE
CIRCUITS
~----~ HARDWARE
_ READY STATUS
~------~--~ REGISTER
SECTOR
...
_ INDEX
DRIVER
INDEX
INDEX
DECODER
SERVO
~ARRIER AMPLIFY
AMP AND PLO
-
~
SERVO ~
HEAD "')
-<
Figure 3·3. Simplified Block Diagram of aPRIAM a·inch Disc Drive
13

(3) SOURCES
CURRENT FEEDBACK
J2
hRED r-;l
Ioo-.------- ... ~J.-+-l-----:....:.:;;.;;;;....--......-.:i:........a.-
BLACK 8ITO
MOTOR
-
-
TO
R/W
/-LP
TO
HALl.
EFFECT
SWITCHES
~I I·
'V' L_.J
J1
r-'
+5V I5I •
II
I1I
J2
r-"
@SPD !34 I
CURRENT
1-----1 SOURCE 1---4
DRIVER
8748
J1
r--,
I4I S1
FROM ON/OFF
RIW >---- ..
/-LP
HALL I!
EFFECT I3 , S2
POSITION I2 ,I 53
ENCODER t------0I-------.I
I I
L_.J r--+ 2F
CURRENT
1-----1 SINK r---""-
DRIVER
D/A
-MPOR
J2
L.::£!CP~O~R --11---' -CPOR r-l
-PORD POWER ~--A-PO-R~!~-~I-
RESET ON II
PLO SAFE RESET r--l L_...J
L..------I' I
TO
R/W
PCB
Figure 3-4.
Motor Controller
3.13 Servo Circuitry. Figure
3-5 is ablock dia-
gram
of the servo circuitry. The signal from
the servo head is amplified by apreamp located
adjacent
to the head in the head disc assembly.
On the main PCB it is further amplified by an AGC
amplifier. The
output of this amplifier has the
waveform shown as ABCD in Figure
3-5, when the
servo head is located midway between
an odd
track and an even track, and the servo datapattern
is aliOs. Aand Dare the sync pUlses occurring at
the
bit cell boundaries. When a1 is present in the
servo data stream, an additional
"sync" pulse
appears at the mid-cell position.
Async detect
circuit detects the sync pulses at
the Aand Dpositions, and uses these pulses as
input for the
PLO (phase locked oscillator). The
PLO generates asteady clock signal of approxi-
mately69-MHz, which is phased locked to the servo
data.
ancies as an error signal to the input of the voice
coil power amplifier, in such away that the servo
head remains midwaybetween the
two tracks.
In the Move mode, the Band Camplitudes are
monitored, and the threshold
detector identifies
the track crossings,
outputting aTRK XING signal
which is used to update acylinder address Gounter
(on the read/write digital
PCB). The Velocity Tach-
ometer, Curve Generator, and Combiner together
control the
input to the voice coil power amplifier,
in order
to control the head carriage velocity.
3.14 Data Read/Write Functions. PRIAM disc
drives use the MFM (modified frequency
modulation) recording method. The MFM encod-
ing rules determine the relationship between the
flux transitions on the recording medium, the data
being written, and the
bit cell boundaries. The fol-
lowing three rules must
be observed:
The pulses marked
Band Care the pulses that
occur at the 1/3 and 2/3 points in the bit cell.
In the On Track mode, the Position Demodulator
and
On Track Compensator are used to compare
the
Band Camplitudes, and to apply any discrep-
1. If a 1 Is written, there is aflux transition at the
center
of the bit cell (data bit).
2. There is always aflux transition-at the bit cell
boundary between consecutive
Os (clock bit).
3. There is never aflux transition at the boundary
of a0 and a 1.
14