HP 7942 Service Manual page 74

Note: In the event of a self -test failure,
the drive will have requested
release to update the error logs. If
the drive is not operating correctly,
this update operation may take
some time to complete. During this
period) the DISPLAY RESUL TS
switch will be inactive. This means
that the DISPLA Y RESUL TS
switch may have to be pressed for a
longer than normal period of time
or pressed after the update opera-
tion has been completed.
Following rele:ase, pressing the switch a number of
times will display one of two specific sequences of
test information. The normal sequence is to dis-
play the test results for units 0, 1, and 2 in order.
However, since unit 2 (the HDC) is tested first, a
failure here will be reported first, and will inhibit
any other results reporting.
Note: A unit 2 (host dependent controller)
self -test failure is a special type of
fail ure. When unit 2 fails self test,
it will enter into an infinite loop
monitoring the DISPLAY RESULTS
switch. The only function that the
drive can perform under this condi-
tion is to toggle out the unit 2 self-
test results. The drive will not
respond to any commands from the
host computer. The red and green
FAULT/ON LINE indicators will
be illuminated at this time. Exit
from the loop can only be achieved
by powering down the drive.
The information displayed for each failed unit will
be, in order, unit failed, field replaceable assembly
(FRA) failed, and subtest failed. The failing unit is
indicated by the display
U.x.,
where numeral
x.
identifies the unit. The failing FRA is indicated by
A.x.,
where numeral
x.
identifies the FRA. A sub-
test failed is indicated by a 2-digit hexadecimal
number. It is possible for a failing unit to have
multiple failing FRA's. Multiple FRA's are listed
in descending order of most probable failure. If a
unit has no failures to report, it will display only
the unit numher. Refer to figure 4- 2 for a listing
of unit and FRA numbers. Host dependent con-
troller (unit 2), disc drive (unit 0), and tape drive
(unit
1)
subtest numbers, together with a brief de-
Service Inf orma tion
7942 and 7946
scription of the sub tests, are listed in the respective
service manuals.
Note: The sequence mode described above
is distinct from the pass/fail mode.
When sequencing test results,
all
of
the results must be displayed with
the DISPLAY RESULTS switch
before the device will go back
on -line (return from release). After
the last result has been displayed,
the display will return to P
.x.
(pass)
or F
.x.
(fail).
4-19. INTERNAL DIAGNOSTICS
The disc drive internal diagnostics include self -test
routines and run time error and fault reporting
circuits. The self -test routines, normally activated
at power-on, consist of a series of subtests which
check overall operation of the disc drive. The disc
drive must pass all host dependent controller (unit
2) subtests to come on line. In the event of a device
dependent controller (DDC) subtest failure, the disc
drive is allowed to come on line. After power-on,
run time error and fault reporting circuits in disc
drive assembly A 1 continually monitor certain
operations of the disc drive. Run -time errors and
faults are logged in the disc drive error logs.
Details of these two diagnostic tools are provided
in the following paragraphs. Refer to table 4- 5
for a summary of the diagnostics.
4-20. SELF TEST
The disc drive can execute self -test diagnostic
routines which are programmed into the host
dependent controller and device dependent
controller servo system firmware. When the disc
drive is powered on, these routines are
automatically initiated to perform a series of
subtests which verify operation of the disc drive.
The subtests perform many hardware checks first
by microdiagnostics and then by higher level
macrodiagnostics such as seeks, reads, and writes.
Go/no-go test results are indicated by the
FAULT/ON LINE indicator on the front panel of
the disc drive and details of subtest failures are
presented on the self -test display on the rear panel.
The host can determine details of self -test failures
using the CS/80 Request Status command. The
internal diagnostics can also be initiated at any
4-5