Siemens SIMATIC S5 Manual page 172

Changing station You can use the FB IM308C in conjunction with the STEP 5 program to
numbers assign station numbers to DP standard slaves (e.g. for the ET 200C
distributed I/O station).
Parameterization You can directly or indirectly parameterize the FB IM308C call.
If you prefer indirect parameterization, you require a parameter data block.
Calling the In the simplest form, the FB IM308C is called in cyclic program processing.
FB IM308C
If you call the FB IM308C in process-alarm or time-alarm processing, you
must make provision in the STEP 5 application program for ensuring that the
FB IM308C does not interrupt itself. To this end, you must block the alarms
for calling the FB IM308C and release them again after the FB IM308C call
has been implemented.
Note
If the FB IM308C accesses a DP slave for which the error-reporting mode is
"QVZ" (time-out), and this DP slave is not available, QVZ is not reported.
Instead, the corresponding error message is placed in the "ERR" parameter
of the FB IM308C.
FB IM308C in
The FB IM308C can be called in multiprocessor mode. The maximum data
multiprocessor
consistency ensured is byte-by-byte.
mode
If you address an IM 308-C master interface from multiple CPUs via the
FB IM308C, you must implement semaphore interlocks to ensure that only
one CPU can address the FB IM308C at any given time.
For notes on multiprocessor operation, see Section 9.8.2.
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a
IM 308-C – addressing, diagnostics and use of the FB IM308C
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