Siemens Simatic S7-1500R System Manual page 199

Commissioning
9.4 Operating and system states
Synchronization for redundant mode
In the SYNCUP system state, the operating system synchronizes the user programs in the
two CPUs for redundant operation.
Synchronization ensures that both CPUs can operate redundantly. In the event of failure of
the primary CPU in redundant operation, the backup CPU takes over control of the process
as the new primary CPU at the point of interruption.
Requirements for achieving a redundant system state
A redundant system, i.e. the system state "Redundant", is only achieved if:
● The requirements for use of the S7-1500R/H redundant system have been met (see
section Application planning (Page 49));
● The two CPUs in the redundant system have recognized each other, i.e. pairing has been
successful (see section CPU pairing (Page 184));
● You have commissioned the system as detailed in the section Commissioning procedure
(Page 180).
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S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA