Technical data

5.7.2
ISTACK Content
If the CPU is in the stop state, you can display the content of the
ISTACK on the screen after the control bit display by pressing the
enter key. When the CPU goes into the STOP mode, the system
program enters all the information it needs in this ISTACK for a
warm restart.
You can use the entries in this ISTACK to see what kind of error
occurred and where it occurred in the program.
If the stop state was caused by
a single error, only one level of the
ISTACK information is displayed. With
several errors, the
corresponding number of ISTACK levels are output (DEPTH 01,
DEPTH 02, etc.). At all levels, only one error is marked as the
CAUSE OF INTERRUPT.
If several errors have occurred DEPTH 01 marks the error detected
immediately before the change to the stop state.
Fig 5-2 is an example of a PG display of the ISTACK content.
INTERRUPT STACK
DEPTH
02
OP-REG:
SAC: 00F3 DB-ADD:
DB-NO.:
DBL-REG.:
OB-NO.:
BA-ADD:0000
0000
0000
0000
C70A
0002 FB-NO.:
REL-SAC:
ICMK: ICRW:
0006
0200
226
0004
KE1 KE2 KE3111 100 111
BLK-STP:
LEVEL:
ACCU1:
ACCU2: ACCU3: ACCU4:0000 C464 0000 00FF 0000 0000 0000 0000
KLAMMERN:
CONDITION CODE:
CC1 CC0 OVFL OVFLS ODER
STATUS
NAU PEU
STP BCF S-6 LZF REG-FE
BAU MPSTP ZYK QVZ
VKE
CAUSE OF INTERR.:
ADF
X
X
X
X
STUEB STUEU WECK DOPP
ERAB
Fig. 5-2 Example of a screen page "OUTPUT ISTACK"
Control Bits and Interrupt Stack
CPU 928B Programming Guide
5 - 18 C79000-B8576-C898-01