Siemens SIMATIC S7-1500 System Manual page 393

Commissioning
12.4 Operating and system states
② Restart of the backup CPU
The backup CPU restarts and automatically switches back to the SYNCUP operating state.
The display of the backup CPU shows the "Connecting..." state.
Table 12- 7
③ Finishing tasks
The instructions running asynchronously on the primary CPU are terminated and new ones
are accepted but not started.
From this point on, restarted asynchronous instructions are delayed until the "Copying the
working memory" phase. The "BUSY" output parameter of instructions is"1". However,
processing does not yet start.
392
Restart of the backup CPU
Primary CPU Backup CPU
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF