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Power-On
Voltages may be applied in any sequence.
When the dc voltages are
low, as when the power has failed or has just been applied, the power-
on-reset (PaR) circuit resets the major circuits and keeps them reset
until the voltages are high enough and stable.
At initial power-on, the drive is recalibrated: the actuator seeks to
the inner, outer, and middle tracks; at each location, servo-burst
amplitude measurements are made and from these the microprocessor
calculates and stores adaptive gain parameters that are later used to
optimize seek and settle times.
-------,
I
-------,
HEAD
DISK
ASM
(HDA)
R/W
HEADS
PRE-AMP
WRITE
DRIVER
I
I
I
_ _ _ _ _ _ ...J
ELECTRONIC
RETURN
SPRING
UB
2MHz
RESET uP
OTHER CIRCUIT
ALE. -WR. -RD
*64KB WITH DISCACHE
Figure 2-4: Electronics Block Diagram
2-6
+12V
+5V
50BO
12MHz
SCSI
BUS
TO
HOST
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