HP 7925D Service Manual page 224

7925
Table
A-B.
Self-Test Function Test Description (Continued)
Appendix A
TEST
NO. TEST DESCRIPTION
11 CRC/Data Path This test checks the CRC generator/checker (9401) and the data path switch (CRC
Switch multiplexer). It checks that the CRC chip generates the proper CRC pattern and
properly detects CRC errors. A known pattern is loaded into the FIFO, sent
through the CRC chip, and returned through the formatter/separator to the FIFO.
The generated CRC pattern is then switched into the. data path and loaded into the
FIFO, where it is checked against the expected results. The ANYER (CRC error)
flag is also checked as data is shifted through the CRC chip.
10 Drive Status
This test looks at the drive status register and reports an error if the disc drive is busy
with drive ready set or if the drive is faulted. Self test will loop on Tests 17 through 10
until Drive Ready becomes active, flashing octal 10 every time test 10 is executed. If
Drive Ready does not become true before 92 seconds have elapsed, the S.T.
FAILED LED will light and the TEST RESULT LED's will display octal 1O. Note: If the
disc drive is powered on and the RUN/STOP switch is not in the RUN position or the
disc pack is not in place, the resulting absence of Drive Ready will cause the S.T.
FAILED indicator to come on approximately 92 seconds after power on is initiated. If
this occurs, proper preparation of the disc drive for operation (disc pack installed and
RUN/STOP switch set to RUN) will allow the self-test routine to start again.
7 Head/Sector Logic This test checks much of the I/O sector logic of the controller. The head register is
first tested for stuck-at faults. Disallowing drive types (set via the drive type
jumpers) will also be reported as an error. The index counters, sector counters,
sector comparators, sector registers, and sector compare flip-flop are also tested
here. This section of the test is executed twice, once with head 1 addressed and once
with head 2 addressed. This tests both sets of sector counters if the drive type is set
to a 7906.
6
Recali brate Test
This test issues a RECALIBRATE command to the drive, waits for drive attention
(with a time limit of 1275 milliseconds), and checks the resulting drive status. If
the recalibrate does not complete in time, a timeout error is reported. If an attention
is received in time, the drive status is then checked; bad drive status is reported to
the TEST RESULT LED's.
5
Seek Test
This test exercises the seek function of the disc drive by issuing a seek to the maxi··
mum cylinder address. If the seek completes within 100 milliseconds, the controller
issues a seek to the maximum cylinder address + 1, forcing a seek check. If a seek
check does in fact occur, the controller then issues a seek to cylinder 0, again with
a 100 millisecond timeout. No address verification is done in this test, but if the
drive does not end up on cylinder 0, the verify test which follows will fail.
4 Set Offset Test The purpose of this test is to see if a set offset drive order to the disc drive will com-
plete. The maximum positive offset (+63), maximum negative offset (-63), and zero
offset are sent to the disc drive in that order. If attention is not received within 10
milliseconds, a timeout error is reported. This test does not verify that the heads are
actually offset the proper direction and magnitude.
3
Verify Cylinder 0 This test attempts to verify cylinder 0 with no head offset. The purpose of this test
is to check the read data path from the heads, through the preamp, and to the data
separator. This test also verifies that the heads are on cylinder 0 by checking the
address field in a sector. The entire cylinder is verified in cylinder mode with track
sparing enabled. If a data error is found in any sector, one retry is attempted. If the
retry also results in a data error, the test is aborted, and the failure is reported to
the test panel LED's. No limit is placed on the number of retries allowed for the
entire cylinder. Test 3 can fail due to several non-hardware related problems. Bad
media, a track flagged defective but not properly spared, or a spare track in cylin-
der 0 will cause a test 3 failure. However, the drive can still be used after a test 3
failure.
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