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Error Diagnostics
5.1
Interrupt Analysis
When malfunctions occur, the operating system sets various "analysis bits" that can be scanned
with the programmer using the "ISTACK" function. LEDs on the CPU also report some malfunc-
tions.
5.1.1
"ISTACK" Analysis
The interrupt stack (ISTACK) is an internal memory of the CPU where malfunction reports are
stored. When a malfunction occurs, the appropriate bit is set.
Use a programmer to read this memory byte by byte.
Note
You can read only part of the ISTACK when the PLC is in the "RUN" mode.
The following tables show which control bits and which malfunction causes are reported in the
ISTACK. The system data words containing the ISTACK bits are also specified.
See the subsequent tables for an explanation of the abbreviations or error codes used here.
5-2
S5-115U Manual
EWA 4NEB 811 6130-02b
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