Fault Events - HP 7925D Service Manual

Appendix A
Table A-6. Fault Events
STEP
EVENT
1 DRIVE FAULT lamp lights (FLTL =
0).
2
Drive fault status bit is active (status bit 5
=
1).
3 Normal head unload operation is initiated (RET
=
1).
4 Drive ready flip-flop is reset (RET =
1).
5
DRIVE READY lamp goes out
(DRDY~
= 1).
6 Servo enable flip-flop is reset (TOF =
1).
7
Head positioning servo is disabled (SEN
=
1).
8
Heads are fully retracted (CRB
=
1).
9
Run spindle flip-flop is reset (TOF. CRB
=
1).
10
Stop spindle command becomes active (RS
=
0).
11 Spindle is braked to a stop (SPD
=
0).
12 Door unlock solenoid is energized (SPD
=
0).
13
DOOR UNLOCKED lamp lights (DU
=
0).
the heat sink on PMR PCA-A9 rises above a specified
value, or a spindle fault is detected, an interlock fault will
be declared. When an interlock fault is detected, the fol-
lowing events will occur:
• PSU LED is on when
+
5 Vdc and
+
12 Vdc are present.
• ILFL signal becomes active (lLFL
=
0).
• IL fault LED lights (lLFL
=
0).
• Heads are unloaded, spindle is braked to a stop, and the
pack chamber door is unlatched. Refer to table A-7 for
the specific events.
If an interlock is indicated because the +5, + 12, or -12
Vdc is missing, or spindle logic PCA-AS is unplugged, the
spindle will not be braked to a stop and the pack chamber
door will not be unlocked. Under these conditions, the
following events will occur:
• PSU LED goes out because PSF
=
O.
• ILFL signal becomes active (ILFL
= 0)
• IL fault LED lights (lLFL
=
0)
• Heads are unloaded and steps 1 through S of table A-7
apply.
Note: If drive control PCA-A4 is unplugged,
then the DRIVE FAULT and IL indi-
cators will not light.
A-62. READ/WRITE FAULT DETECTION. The
read/write fault detection circuitry on drive control
PCA-A4 continually monitors internal disc drive signals
to detect five fault conditions. These fault conditions are
A·28
7925
classified as either non-destructive or destructive write
faults. There are two non-destructiv'e and three destruc-
tive write faults. Each is discussed in detail in the follow-
ing paragraphs.
A-63. Non-destructive Write Faults. The two fault
conditions classified as non-destructive are:
• Write without Access Ready (W • AR).
• Simultaneous read or write (R • W).
In the first condition, the state of the ACRY signal is
continually monitored. If the heads are not settled over
the specified cylinder (ACRY
=
1) during the write mode
(WRITE
=
1) and no other write faults exist
(W'FLT
=
1),
a W
0
AR fault is declared. When a W • AR fault is
detected, the following events will occur:
• W. AR fault flip-flop is set (W • AR •
WFI7F
=
1).
• WRFL signal becomes active (WRFL
=
0).
• W. AR fault LED lights (WRFL
=
0).
• NDWF signal becomes active (NDWF
=
0).
• WFLT signal becomes active (WFLT
= 0).
• Subsequent read/write faults are inhibited
(WFLT
=
0).
• DRIVE FAULT lamp lights (FLTL
=
0),
• Drive fault status bit becomes active (status bit 4
=
1),
The W • AR fault flip-flop is reset by NDPS whenever the
power-on sequence is initiated (lLF
=
1), the RUN/STOP
switch is set to RUN (RUN
=
1), or a CPS command is
decoded (CPS
=
1),
In the second condition, the state of the' URG signal is
continually monitored. If the URG signal becomes active
(URG
=
1) during the write mode (WRITE
=
1) and no
other write faults exist
(W'FLT
=
1), a R • W fault is
declared. When a R • W fault is detected, the following
events will occur:
oRo \V fault flip-flop is set (R
0
W
0
WFLT
=
1).
• RWFL signal becomes active (RWFL
=
0
l.
• R • W fault LED lights (RWFL
=
0),
• NDWF signal becomes active (NDWF
=
0).
• WFLT signal becomes active (WFLT
=
0).
• Subsequent read/write faults are inhibited
(WFLT = 0>.