Save And Reload Scratchpad Flags - Siemens SIMATIC S5 Equipment Manual

Operating Instructions
2.6.1 Interru t Processing with Standard Function Block FB 157
When an interrupt occurs, the interrupt OB2 is called. The call for the function block FB 157 with the
parameter assignment BEF = KB is written into this organization block.
After the call by the interrupt OB, parameter ST shows from which channel the interrupt originated
(i.e., you can have your specific interrupt program processed then).
If, during the processing of function block FB 157 in the cyclic program, an interrupt occurs, the
group interrupt at the bus is cancelled again by FB 157 (or by reading byte 7). This interrupt is not
lost when the recommended programming for interrupt OB2 is followed (see example in section
2.3).

2.6.2 Save and Reload Scratchpad Flags

In the S5–135U, OBS with special integrated functions are available for saving and reloading
scratchpad flags. For CPU 922 (version A09 or later) and for CPU 928, these OBS are OB 192 (for
saving) and OB 193 (for reloading).
here only to interrupts and not to timed interrupts.
Because of this, saving and reloading scratchpad flags is necessary only during a warm restart.
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