HP 7957A Hardware Manual page 71

Service Information
7957 A/7958A
drive selected line in response. If the drive selected line is not asserted within the
timeout period the mechanism self test will terminate and the disc drive will not
attempt to come on line. The disc drive is not allowed to come on line because
the "drive not selected" condition may be the result of a disconnected ESDI Data
Cable (W2). If this is the case the READ CLOCK to the DDC IC which would
make DMA transfers to the host impossible.
Fault Reporting: In this case both LED's are on solid. In the second case, the disc
drive comes on line and reports self-test fault #69 in P7 and P3. The diagnostic
result bit will be set. PI contains the code for the first suspect FRA. It will be
1
(Disc Drive Assembly PCA-AI). P2 contains the code for the second suspect
FRA. a two (2) indicates the CEC PCA-A2. The ribbon cables between the CEC
PCA-A2 and the Disc Drive Assembly PCA-AI are also suspect but no FRA
number exists for this component.
Note: Disc Drive Assembly PCA-AI must be de-selected and re-selected as part of
the initialization. If the disc drive fails to respond with "drive selected" then the
"Can't Select Drive" diagnostic fault is generated. The remainder of the self test
and initialization is skipped and the disc drive comes on line to report the fault.
Once the power-on sequence completes Select A Drive the disc drive will always
come on line and report the nature of subsequent self-test failures using the
CS/80 status bytes PI, P2, P3, P7, P8, and P9. This does not mean that subsequent
self-test failures are less critical or that the disc drive is operable. On the
contrary, it is strongly advisable for the host not to issue commands to the Disc
Drive Assembly PCA-AI after any self-test failure. If the diagnostic result bit is
set during the power on self test, any operation initiated by the host can have
unpredictable results.
The only reason that the disc drive is allowed to come on line is to report the
nature of the self-test failure to the operator.
At this point in the power-on process the red LED will be turned off. The green
LED will blink if an index pulse is available from the Disc Drive Assembly
PC A-A I.
4-26. Command Complete
Process: The CEC PCA-A2 will wait up to 60 seconds for the Disc Drive
Assembly PCA-AI to assert the ESDI command complete line. If the command
complete line is not asserted within the timeout period a fault will be generated.
The remainder of the self test and initialization is skipped and the disc drive
comes on line to report the fault.
Fault Reporting: The disc drive comes on line and reports self-test fault #70 in P7
and P3. The diagnostic result bit will be set. PI contains the code for the first
suspect FRA. A one (1) indicates Disc Drive Assembly PCA-A
1. P2 contains the
code for the second suspect FRA. A two (2) indicates CEC PCA-A2. The ribbon
cables between the CEC PCA-A2 and the Disc Drive Assembly PCA-AI are also
suspect but no FRA number exists for this component.
4-17