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MNEMONIC
LEDP
LSB-H
MOTOR+,
MOTOR-
NACC-L
NO CLK-H
NRZ-H
OFTU-L
SIGNAL
LED
Power
Least
Significant
Bit
Actuator
Drive +,-
Negative
Accelera tion
No tOO-kHz
Clock
NRZ
Data
Offtrack
Unlatched*
Functional Description
7936 and 7937
Table 5-1. List of Mnemonics (10 of 23)
SOURCE
~A2
ill
A1
~A1
II
A1
~A1
Ii D J
A2
IIA1
DESCRIPTION
+5V power for three LEOs in front panel
LED display.
LEDP is connected to LED PCA-A 7 via sig-
nal jumper cable W7, power distribution
PCA-A5, and power supply output cable W 4.
SERVO
CONTROLLER
output
to
DEDICATED SERVO TIMING and PLL.
LSB-H is used by the servo system to indicate
when the heads are over odd or even tracks.
Servo power amplifier OUTPUT FILTER
lines which supply drive current to the ac-
tuator voice coil.
MOTOR+ and MOTOR- are connected to the
ACTUATOR in HDA A3 via read/write
PCA-A2 and HDA cable WS.
SERVO CONTROLLER output to SEEK
CURRENT COMMAND GENERATOR. See
figure
~.
NACC-L causes the servo power
amplifier to drive the actuator with -2.90
amperes.
Output
from
MISSING
PWM
CLOCK
DETECTOR. NO CLK-H signals to the
amplifier
CONTROL
AND
FAULT
INDICATION circuit that the tOO-kHz oscil-
lator in the PULSE WIDTH MODULATOR
has failed.
ZERO-CROSSING DETECTOR output to
read chain PLL and DATA SEPARATOR.
NRZ-H goes high each time a flux reversal
occurs in the data path.
OFFTRACK DETECTOR output to FAULT
LATCHES
and
SLEW
RATE
LIMIT
SWITCH. OFTU-L is a pulse that indicates
the start of an off track condition.
OFTU-L can be monitored at pin 45 of the
servo test point PCA.
5-57
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