IBM System/34 Maintenance Manual page 47

05-410 Power Fault Registers
When a Power Check occurs on the System/34, power
fault codes that indicate the cause of the fault are
stored so that you can display the codes and isolate the
cause of the power check.
Power fault codes are divided into two groups: priority
fault codes and additional fault codes.
Priority fault codes indicate that some power supply was
overvoltage, undervoltage, overcurrent, or that a feature
sense card is missing. Priority fault codes all have bit 0
active.
Additional fault codes generally further specify the cause
of the priority fault by either indicating which power
supply has the wrong voltage, or by indicating that all
power supplies have the wrong voltage.
The protect card (C-A 182) has three registers that store
power fault codes when a power check occurs.
Additional Fault Codes
7F 6A
X X
66
X
E1
X
Present
o
Reg 0
Not
Previous SW
Power Check
OR
7
7
Present Reg Contains a
Priority Fault Code *
o
A
7
1.
2.
3.
0
7
o
~~--------------------------------L-
____
~7
Search SW
* Bit 0 On
22
05-410
A
The shift register: _:
tn'
Stores up to 43 fault codes. _
·:F:~
Stores the priority fault code and any
addition~,I;,-,
fault codes controlled by the sensing circuits on
the base sense card, feature sense cards, or
f .'
feature power supplies during 320
microseconds after a power check.
I ncrementseach time a search operation is
performed.
The present register:
Stores one fault code at a time.
Stores the fault code each time the shift
register increments.
Can be displayed by pressing the Dply Pwr Chk
switch.
The previous register:
Stores one priority fault at a time.
Is loaded from the present register if the fault
code in the present register is a priority fault
code (bit 0 on) and either a power check occurs
or a search operation is performed.
Can be displayed by pressing the Dply Pwr Chk
switch and operating the Prev switch.
:H:
0
OR
CE Byte 0
0
Lamp Test SW
A
:HIJ
0
7
7
Dply Pwr Chk
Previous
o
Reg 0
o
o
A
Previous SW 7
7
'-----
7
7
.r---
,
I
1
1
,-.- - "