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Theory of Operation
7942 and 7946
MNEMONIC
NDAC-L
NRFD-L
PES
PVAL-H
RDY-L
3-26
Table 3-1. List of Mnemonics (Continued)
SIGNAL
Not Data Accep-
ted
Not Ready For
Data
Position
Signal
Error
Power Valid
Ready
SOURCE
AS
III
AS
III
Al
-
A4
III
Al
-
DESCRIPTION
Normally, the signal is a high level
and the transition to a low level indi-
ca tes the start of a track. The signal
is generated by a Hall-effect sensor
in the spindle motor. Output to DOC
PCA-A2
III
via cable W3.
HP-IB handshake line used to indi-
cate the acceptance of data by all
devices.
HP-IB handshake line used to indi-
cate that all devices are, or are not,
ready to accept data over Data I/O
Bus DIOI-H through DI08-H.
Actuator servo control circuit signal
indicating amount and direction of
head off -track displacement.
Indicates that power supply A4 out-
puts
are
up to their proper values.
Output to DOC PCA-A2
III
via
cable Wl.
ST- 506
Interface
control
signal.
ROY -L becomes active (low) follow-
ing power on if: a) dc voltages are
within specification, b) discs are at
speed,
and
c)
head
position
is
recalibrated.
Output
to
DOC
PCA-A2
III
via cable W2.
If there is a fault in the dc voltages
or spindle speed control, ROY -L will
remain inactive (high). ROY -L will
not go low until the fault is cleared
and the head position is recalibrated.
After power on, ROY -L should be-
come active within
25
seconds.
During operation of the disc drive,
the processor is continually monitor-
ing the speed of the spindle motor. If
a speed variation of greater than 2
percent is detected, the processor will
force ROY -L high, lock the actuator,
and stop the motor. Power-on recy-
cling
is
required to restart the disc
drive.
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