Siemens SIMATIC S7-1500 System Manual page 283

Transition Description
Operating state • The hardware configuration and program blocks are consistent,
transitions and
The startup type "Warm restart - RUN" is set
or
• The startup type "Warm restart - Operating mode before POWER OFF" is set
and the CPU was in STARTUP, RUN, RUN-Syncup or RUN-Redundant before
POWER OFF.
POWER ON → SYNCUP
The CPUs implement pairing after switch-on. The backup CPU then switches to
the SYNCUP operating state if:
• The mode selector is in the RUN position
and
• The primary CPU is in the STARTUP or RUN operating state.
Automatic STARTUP after POWER ON only possible for the primary CPU
NOTE
The automatic STARTUP after POWER ON only for the primary CPU prevents a CPU with
outdated, retentive data from automatically changing to the RUN operating mode.
You can switch the backup CPU manually to RUN, this then automatically becomes the
primary CPU and starts with its retentive data.
If you have parameterized "Startup after POWER ON" "Warm restart..." as the startup type,
then the primary CPU only carries out the startup if the CPU became the primary CPU in
POWER ON, i.e.:
• No partner CPU found
or
• Due to the role assignment, the local CPU became the primary CPU and the partner CPU
became the backup CPU
If a CPU became the backup CPU in POWER ON, then:
• if all the requirements are met, this results in an automatic SYNCUP
or
• the backup CPU changes to STOP
In both cases the CPU remains the backup CPU and can therefore not automatically carry
out the STARTUP.
To illustrate the process, here are two examples:
①
No STARTUP after parameterization "Warm restart - RUN"
Requirements:
• You have parameterized "Warm restart - RUN" for both CPUs.
• The pairing was successful for both CPUs.
• Both CPUs are in STOP.
• Both mode switches are set to RUN.
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
Commissioning
11.4 Operating and system states
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.
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