Siemens SIMATIC S7-1500 System Manual page 282

Commissioning
11.4 Operating and system states
The following figure shows the operating state transitions of the primary and backup CPU.
Figure 11-10 Operating state transitions
①
POWER ON → STARTUP, POWER ON → SYNCUP
Transition Description
System state trans­ POWER ON → STARTUP
ition The CPUs implement pairing after switch-on. The redundant system then
switches to STARTUP if:
• The mode selector is set to the RUN position,
• The preceding "POWER OFF" was triggered by an interruption of the power
supply,
• The hardware configuration and program blocks are consistent,
and
• The startup type "Warm restart - RUN" is set
or
• The startup type "Warm restart - Operating mode before POWER OFF" is set
and the system was in RUN-Solo, SYNCUP or RUN-Redundant before
POWER OFF.
The CPU that becomes the primary CPU runs the STARTUP.
The primary CPU switches to the STARTUP operating state.
Operating state POWER ON → STARTUP
transitions The CPUs implement pairing after switch-on. The primary CPU then switches
to the STARTUP operating state if:
• The mode selector is in the RUN position;
• The preceding "POWER OFF" was triggered by an interruption of the power
supply,
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Effect
After POWER ON → STAR­
TUP, the primary CPU
clears the non-retentive
memory and resets the
contents of non-retentive
data blocks to the initial
values of the load
memory. Retentive
memory and retentive DB
contents are retained.
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD