Siemens SIMATIC PCS 7 CPU 410-5H System Manual page 178

System modifications during redundant operation
10.5 Editing CPU parameters
Reaction of the I/O
Type of I/O
I/O modules
1) Central modules are first reset. Output modules briefly output 0 during this time (instead of the configured substitute or
hold values).
Reaction to monitoring timeout
The update is canceled and no change of master takes place if one of the monitored times
exceeds the configured maximum. The fault-tolerant system remains in single mode with the
previous master CPU and, assuming certain conditions are met, attempts the master
changeover later. For additional information, refer to section Time monitoring (Page 123).
Where the values for the monitoring times in the CPUs differ, the higher values always apply.
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One-sided I/O of previous
master CPU
are no longer addressed by the
CPU.
Output modules output the
configured substitute or holding
values.
One-sided I/O of new master
CPU
are given new parameter set-
tings and updated by the
1)
CPU.
Switched I/O
continue operation without
interruption.
CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB