Siemens Simatic S7-1500R System Manual page 215

Commissioning
9.4 Operating and system states
SYNCUP system state aborts
Abort is possible in a range of cases even if you have successfully launched the SYNCUP
system state:
● If one of the two CPUs POWERS OFF.
● If you switch the backup CPU to STOP; the primary CPU continues operating in RUN
operating state.
The cancellation of the SYNCUP may take a few seconds.
● If you set the primary CPU to STOP; the redundant system switches to the STOP system
state as the backup CPU was not ready to take over control of the process. The backup
CPU restarts.
● If the backup CPU lag is not reduced to less than the smallest value after 100 program
cycles, the primary CPU aborts SYNCUP. Evaluate the diagnostics buffer of the primary
and the backup CPU.
● If one of the CPUs detects an error that impedes progress, for example if the cycle time is
exceeded in the primary CPU.
● If the PROFINET ring was already interrupted before changing to the SYNCUP system
state or if the PROFINET ring is interrupted during SYNCUP.
You can find a detailed list of the causes of error and remedies in the table SYNCUP abort:
Causes and solutions.
Figure 9-8 SYNCUP system state aborts
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S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA