Surface Mode Vs. Cylinder Mode - HP 7925D Service Manual

Appendix A 7925
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TRACK N
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SURFACE MODE
SURFACE
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HEAD
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CYLINDER N
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DATA
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DATA
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DATA
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DATA
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SERVO
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SERVO
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DATA
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DATA
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DATA
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DATA
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DATA
CYLINDER MODE
7311-35
Figure A-4. Surface Mode vs. Cylinder Mode
The HP 13356A Formatted Disc Pack is formatted in this
fashion and it must be used as the removable storage
media for this disc drive.
this check information is regenerated and compared in
such a way that the presence of errors is detected. The
present controller will not support error correction and
writes an arbitrary pattern in the 12-byte error correction
code (ECC) field.
Each of these functional systems is discussed in detail in
the following paragraphs. In addition, a functional block
diagram is provided for each system in Part IV, Trouble-
shooting. An alphabetic listing of each signal mnemonic, a
source and destination signal list, and a mainframe wiring
diagram are also provided in Part IV, Troubleshooting.
The disc drive is organized into the controller and eight
functional systems. (See figure A-6.l These eight func-
tional systems are the operation control system, spindle
rotation system, head positioning system, sector sensing
system, read/write system, fault detection system, air cir-
culation and filtration system, and power distribution
system.
The operation control registers appear to the micro-
processor as a bank of I/O registers through which the
microprocessor controls and monitors the state of the disc
drive operation control and sector sensing systems. The
spindle rotation system provides power to the spindle
motor and maintains spindle speed at 2700 revolutions per
minute. It also operates the pack chamber assembly door
lock mechanism. The head positioning system controls the
loading and unloading of heads under both normal and
abnormal (fault) circumstances. The operation control sys-
tem interfaces between the controller and the disc drive.
The sector sensing system continually monitors the physi-
cal sector presently passing beneath the heads. The con-
troller is notified when the present sector equals the ad-
dressed sector. This information is also used to enable the
read/write system for a data transfer operation. The
read/write system provides the means to read information
from a data surface or write information onto a data sur-
face. The fault detection system continually monitors var-
ious conditions within the disc drive, and lights fault indi-
cators, retracts the heads, and brakes spindle rotation
when a fault is detected. The air circulation and filtration
system provides cooling air to the heat generating compo-
nents of the disc drive and cool filtered air to the pack
chamber. The power distribution system supplies all
operating voltages to the controller and the seven other
disc drive systems.
A-B. CONTROLLER
The controller provides a simple interface between the
HP-IB and a disc drive having a storage capacity of 120
megabytes. Upon receipt of command sequences via the
HP-IB, the controller decodes and generates all the neces-
sary timing and control signals for the disc drive. The
controller also handles all of the input/output communica-
tions with the HP-lB.
FUNCTIONAL DESCRIPTION A-7.
The controller consists of three modules: an HP-IB device
interface module, a microprocessor module, and a data
path module. In addition, the controller includes a number
of operation control registers. The HP-IB device interface
module provides a logical interface between the HP-IB
and the controller. The microprocessor module handles all
of the communications and command interpretations for
the controller and in turn generates most of the timing
and all of the control signals needed by the controller and
the disc drive. The data path module contains the circuitry
necessary for the proper transfer of data bidirectionally
between the controller and the disc drive.
A-4