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MNEMONIC
FSEN-L
GAP-L
GBD-H
GBDEN-H
GDCLK
SIGNAL
Fine Servo
Enable*
Gap*
Guard
Band
Detect
Guard
Band
Enable*
Good
Clock
Functional Description
7936 and 7937
Table 5-1. List of Mnemonics (8 of 23)
SOURCE
IJA1
IJA1
IJA1
IJA1
IJA1
DESCRIPTION
SERVO
CONTROLLER
output
to
the
POSITION LOOP SERVO switch.
SEEK
CURRENT COMMAND GENERATOR, and
OVERVELOCITY DETECTOR.
See figure
~.
FSEN-L changes the servo system from
a dedicated (seek) to a sampled (track follow)
mode of operation.
FSEN-L can be monitored at pin 44 of the
servo test point PCA.
SAMPLED SERVO TIMING output to AGC
REF DEMOD SWITCH. GAP-L is gated with
SOSEN-H
to
create
DSOS-L,
DSOS-H.
GAP-L is the complete window for the
sampled servo code.
GAP-L can be monitored at pin
26
of the
servo test point PCA.
DEDICATED SERVO TIMING output to
SERVO CONTROLLER. GBD-H is activated
when the guard band mark is detected by the
sector mark decoder. The signal is used during
calibration to indicate when the heads are on
the guard band.
SERVO
CONTROLLER
output
to
DEDICATED SERVO TIMING and PLL.
GBDEN-H determines whether the sector
mark decoder will search for sector marks or
guard band marks.
GBDEN-H can be monitored at pin 42 of the
servo test point PCA.
Output from SAMPLED SERVO TIMING to
MISSING
PWM
CLOCK
DETECTOR.
GDCLK is a reference used to ensure that the
IOO-kHz clock in the servo power amplifier is
present. (The absence of the clock will signal
a servo fault).
5-55
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