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CHAPTER 5. HDD
5-1-1. Introduction
The Hard disk drive (HDD) is a 2.5 inch ruggedized high performance
disk drive optimized for an IBM PC-AT or XT compatible laptop or
portable computer. The HDD contains an on-board controller with
selectable interface that requires a simplified adapter board for inter-
facing to an
AT
or
XT
compatible bus.
5-1 '2; Overview
This Manual describes the key features, specifications. charac-
teristics, functional description and hardware and software considera-
tions required to utilize the HDD in both the AT and XT interface
modes.
5-1-3. Features
Unique ramp loading mechanism for loading and unloading the
disk heads during power-downs and periods of inactivity.
User invoked low power modes and power-downs for power
sensi~
tive applications.
High performance rotary voice coil actuator with embedded servo
system.
On~board
controller for direct connection to a
50~pin
interface.
Microprocessor-controlled diagnostic routines that are
automat~
ically performed at
power~up.
Internal air filtration and dessicant system.
Automatic error detection and correction.
_._<_--
Dessicanl pack
Actuator mag.
nel assembly
Balanced, moving coil
rotary actuator
Read/Write - - " " ' -
preamp
(shown in unloaded r
~
:-+_~_
Recirculation
filter
In-hub spindle molar
2_5
inch disk
Integrated ATJXT interface!
drtve controller sIngle PWB
ReadlWrite heads
~
"'k'dl
PO.;ili~~~~~
50 pin intertace connector
Fig. 5·1 HOD unit
-31-
5-1-4. Functional Description
-
P C-6220
The HOD contains all the necessary mechanical and electronic
com~
ponents to interpret control signals, properly pOSition the recording
heads, read and write data, and maintain a contaminant free
environ~
ment for the disks and recording heads.
5-1-4-1. ReadIWrite and Control Electronic
The HOD has an integrated circuit attached to the flexible circuit
connected to the actuator and read/write heads to provide one of two
read
selections~
read
preampli!i~ati_?n,
and write drive circuitry.
The microprocessor controlled circuit board provides the remaining
electronic functions including:
Read/Write Circuitry
Rotary Actuator Control
Interface Control
Power Management
Spin Speed Control
• Automatic Head Unloading
5-1-4-2. Drive Mechanism
The HOD has a spin speed of 3,307 RPM_ The spin speed of the
brushless DC direct drive spindle motor is maintained by using the
motor in a synchronous mode.
Energy stored in the spindle motor is used to unload the read/write
heads upon drive powerdown.
5-1-4-3. Head Positioner Mechanism
The two read/write heads of the HOD are directly attached to the
actuator body which also supports the moving coil. The read/write
heads are unloaded when the drive is spun down. This dynamically
ramp loaded mechanism insures that the disk heads never come in
contact with the disk media.
5-1-4-4. ReadIWrite Heads and Disks
Data is recorded on a 65mm diameter disk through two 3370 type
heads.
5-1-4-5. Air Filtration System
The HOD HOA breathes through a high efficiency ambient filter. A
high flow recirculative filter maintains a clean environment of better
than class 100 for the head and disk enclosure.
5-1-4-6. Error Correction
The HOD periorms internal error correction through the use of a
polynomial capable of correcting one error burst with a maximum of
11 bits per 512 byte block.
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