Siemens CPU 948 User Manual

Explanation of the ISTACK
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DEPTH Information level of the ISTACK when more than one error has
occurred:
DEPTH 01 = last cause of stop to occur
DEPTH 02 = next to last cause of stop to occur
......
DEPTH05 = ...... (maximum depth)
Information about the error The following table contains information about the ISTACK IDs with
which the statement in the user program can be found which caused
the CPU to change to the STOP mode.
Information about the error
ISTACK ID Meaning
OP-REG Operation register:
Contains machine code (first word of the
instruction processed last in an interrupted
program processing level.
SAC (new) STEP address counter (new):
Contains the absolute address of the next
operation in the program memory to be
processed. When a warm restart occurs,
the CPU continues the program with this
operation.
DB-ADD Absolute start address (DW 0) in the
program memory of the data block currently
opened (= 0000 if no data block was
opened)
BA-ADD Absolute address in the program memory
for the operation to be processed next in the
block where the last block call was made
BLK-STP Block stack (BSTACK) pointer:
Contains the 20-bit offset address of the
last BSTACK entry (always Exxxx).
PB-NO
(depending on type
PB, OB ...)
Block type and number of the most
recently processed block
Table 5-5 Meaning of the ISTACK IDs for errors
Control Bits and Interrupt Stack
CPU 948 Programming Guide
C79000-G8576-C848-04
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Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English