Siemens SIMATIC S5 Manual page 202

IP 265
Response to a change in the operational status
STOP and RUN commands from the CPU reach expanded IP 265s without any delay.
In order to ensure error-free, reproducible control of both IPs, you should follow the guidelines below
in the event of an IP 265 operational status change:
• The CPU should set both IPs to RUN or STOP at the same time.
• The programmed response to a CPU STOP should be identical for both IPs.
• The CPU must query the operational states of both IPs continually, and match them if
necessary. If one IP has gone to STOP because of a fault or error, the CPU must set the other
to STOP as well.
Note
Should a fault or error occur, failure to observe the last guideline could result in scanning
of only part of the program, and thus servicing of only part of the process.
EWA 4NEB 812 6130-02a
IP 265 Expansion
12-3