Siemens Simatic S7-1500R System Manual page 207

Commissioning
9.4 Operating and system states
Starting SYNCUP
The initial situation is the RUN-Solo system state. The primary CPU of a redundant system is
in the RUN operating state and the backup CPU is in the STOP operating state.
The operating states are shown on the displays:
Table 9- 3
Start SYNCUP if:
● You set the backup CPU to RUN via the PG/PC/HMI device or the display, and the mode
selector is set to RUN.
or
● You switch the mode selector on the backup CPU from STOP to RUN.
or
● You POWER ON the backup CPU (mode selector to RUN) and the system is configured
accordingly.
206
Starting SYNCUP
Primary CPU Backup CPU
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA