Siemens SIMATIC PCS 7 Operating Manual page 33

● H system STOP:
The entire H system is set to the STOP system mode.
● Standby CPU STOP:
The standby CPU is set to the STOP mode. The master CPU remains in RUN (solo
system mode).
Note
Processing is also paused briefly in the master CPU for the purpose of updating a CPU that
is starting up (see Monitoring times).
If this is only to occur at certain times defined by the plant operator, "Standby STEO" must
be selected as the error reaction. Following this, maintenance personnel must carry out a
self-test on both CPUs at an appropriate point in time, by performing a non-buffered CPU
startup.
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
6.2 Adapting CPU parameters (fault-tolerant F system)
Configuring S7F/FH hardware
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