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DISC DRIVE (1 HP-IB EOUIVALENT
LOAD)
1 metre X n loads - coble length in metres (up to 15 metres maximum)
MULTIPLE DRIVE INSTALLATION
NOTES:
1. The maximum number of drives that can be connected to a single HP-IB chonnel is host dependent. This information is
is contained in the appropriate host configuration guide.
FIgure
-4-1.
INTRODUCTIONWARNING
The drh'e does not contain operator-serviceable parts. To prevent electrical shock, refer all maintenance activities to service-trained personnel.
No preventive maintenance procedures are required to be scheduled for the drive.
5-1. INTRODUCTION
The HP 7936 and HP 7937 Disc Drives are high performance, random access, data storage devices designed for use in medium-and large-sized heads, servo head, electromagnetic head positioning mechanism (actuator), read preamplifiers, write drivers, head gain reference PROM and DAC, and air filtration system. See figure 5-16. The spindle is belt driven by an ac induction motor mounted ad-jacent to the sealed HOA. The motor speed is regu-lated by the line frequency. This motor also drives a squirrel-cage type cooling fan.
The disc stack is composed of seven 210-millimetre (S.3-inch) diameter nonremovable discs. These dis-cs have seven (HP 7936) or 13 (HP 7937) thin-film magnetic surfaces for data storage. (The same number of discs are used in both drives in order to maintain the dynamic design parameters of the head-disc assembly.) The formatted storage capacity of th(~ drive is 307 megabytes (HP 7936) or 571 megabytes (HP 7937). One movable head is used to service each surface. The bottom surface of the lowest disc in the stack contains prerecorded dedicated servo code which is llsed to generate timing and seeking information. When on track, embedded servo code prerecorded between data sectors on all of the data tracks is sampled to keep the heads on track.
In addition to head-disc assembly A3. a number of printed-circuit assemblies (PCAs) are contained within the enclosure. These include servo PCA-AI, read/write PCA-A2, power supply PCA-A4, power distribution peA-AS, controller PCA-A6, LED PCA-A 7, and primary power PCA-AS.
Servo PCA-AI contains a servo controller, phase-locked loop (PLL) and servo timing counters.
dedicated servo circuit, sampled (embedded) servo circuit, and servo power amplifier. These circuits provide sector timing information, control seeks, and maintain the heads on track.
Read/write PCA-A2 includes a custom-designed read/write controller that, together with associated read chain, ·write chain, and head select electronics, transfers data to and from the disc media. The PCA also maintains data communication with con-troller PCA-A6, and performs amplification of the sampled and dedicated servo codes.
Power supply PCA-A4, in addition to supplying DC voltages for the controller and drive electronics, provides power-on reset and power fail signals.
Power distribution PCA-A5 filters and distributes the outputs from power supply PCA-A4 to the controller and drive electronics.
Controller PCA-A6 is a factory-installed microprocessor-based controller which provides an interface to the host computer. Two different HP-IB controllers are available for this purpose. In the HP 7936H and HP 7937H Disc Drives, inter-face to the host is via an Hewlett-Packard Interface Bus (HP-IB) controller. In the HP 7936XP and HP 7937XP, the controller has HP-IB Cache added. (In this manual, the controllers are identified collectively as PCA-A6.) Both controll-ers interface with the drive electronics via an HP-developed standard interface (ESI).
Self -test diagnostics and fault-finding firmware contained within the controller PCA-A6 exercise key functions of drive operation. Self test is
LED PCA-A 7 contains three light-emitting diodes (LEOs) that signal to the user the operating status of the drive.
Functional Description
5-2.
BLOCK DIAGRAMSA basic block diagram (figure 5-16) for the con-troller and drive electronics is provided in this chapter. Functional block diagrams (figures 12-20 through 12-23) for the servo, read/write, spindle,
The diagrams are identified as follows:
CR = Figure A-3, Controller, Functional Block block diagram for controller PCA-A6.
S1
= Figure 12-20. Servo System, Functional Block Diagram (Sheet 1 of 2)S2
= Figure 12-20. Servo System, Functional Block Diagram (Sheet 2 of 2)RW Figure 12-2l. Read/Write System,
Functional Block Diagram NOTE Functional Block Diagram
PS = Figure 12-23. Power Supply System, Functional Block Diagram
5-3.
SIGNAL NOTATION active high voltage level. Signal mnemonics without an "-L" or "-H" suffix usually indicate analog, data bus, or control bus signals.5-4.
LIST OF MNEMONICSThe mnemonics used in the functional block diagrams and accompanying text are defined in table 5-l. The SOURCE column of table 5-1 gives the identification characters f or the functional block diagram where the signal appears, followed by the number of the assembly where the signal originates.
The following assembly numbers appear in the SOURCE column of table 5-1:
A1 = Servo PCA-Al A2
=
Read/Write PCA-A2 A3 = Head-Disc Assembly A3 A4 = Power Supply PCA-A4A5
=
Power Distribution PCA-A5 blocks in the functional diagrams.5-5.
DISC FORMAT of ID guard band tracks, and a landing zone.The OD guard band is used for calibration. Both the OD and ID guard band tracks allow for over-shooting when seeking to the outermost and the innermost data tracks. The maintenance tracks contain service information including run time er-ror logs, fault: log (data surface 0 only), and erer-ror sequentially-numbered blocks of data called
sec-tors. On each track, there are 124 of these physical
The 14-byte formatter/separator field and the 6-byte header field comprise a 20-byte preamble.
This information is used for synchronization and addressing purposes. The header field specifies status, head, cylinder, and sector addresses, and provides the spare sector information. The head and cylinder are logical addresses and the spare sector and sector bytes are physical addresses. The status byte is used to determine whether a spare is classified as primary (factory) or secondary (field).
If bit 6 of the status byte is zero, the sector is the postamble are checked by controller PCA-A6.
The 2-byte CRC field and 12-byte ECC field form a 14-byte postamble. Controller PCA-A6 generates the CRC and ECC information during a write the hardware is busy transferring subsequent sec-tors in a multiple-sector transfer. In most cases, this scheme will result in no loss of performance for correcta ble data errors.
Functional Description 7936 and 7937
PHYSICAL:
LOGICAL:
S7t37A5J
INNER DIAMETER MAINTENANCE
TRACK
INNER SPARES
1399/0004
1395/0000 USER AREA
OUTER SPARES
OUTER DIAMETER
GUARD BAND
OUTER DIAMETER MAINTENANCE
TRACK
resslSng
SECTOR:
SECTOR:
S7t37A54
FAULT LOG (HEAD 0 ONLY)
0-3 4-7 8-11 12-15 16-19
R/W TEST AREA FOR POWER-ON/
DIAGNOSTIC 0
20-122 12.3
RUNLOG RESERVED SPARE
SECTOR
ERTLOG RESERVED
FOR FUTURE USE