Siemens SIMATIC S7-1500 System Manual page 285

Transition Description
The CPU that you switch from STOP to RUN first remains/becomes the primary
CPU. It switches to the STARTUP operating state and processes the startup
blocks.
The backup CPU remains in STOP.
Operating state STOP → STARTUP
transition After switch-on, the primary CPU switches to the STARTUP operating state if:
• The hardware configuration and program blocks are consistent
and
• You set the CPU to RUN via the PG/PC or the display and the mode selector
is set to RUN
or
• You set the mode switch from STOP to RUN.
④
STARTUP → RUN-Solo, STARTUP → RUN
Transition Description
System state trans­ STARTUP → RUN-Solo
ition The redundant system switches from STARTUP to the RUN-Solo system state if:
• The primary CPU has initialized the PLC tags
and
• The primary CPU has executed the startup blocks successfully
and
• "Startup CPU only if compatible" is configured, there is feedback from all IO
devices before the end of the configuration time and all IO devices match
the configured hardware configuration or "Startup CPU even if mismatch" is
configured and the configuration time is up.
The backup CPU remains in STOP.
Operating state STARTUP → RUN
transition The primary CPU switches to the RUN operating state if:
• The CPU has initialized the PLC tags;
• The CPU has executed the startup blocks successfully;
and
• "Startup CPU only if compatible" is configured, there is feedback from all IO
devices before the end of the configuration time and all IO devices match
the configured hardware configuration or "Startup CPU even if mismatch" is
configured and the configuration time is up.
⑤
RUN-Solo → SYNCUP, RUN → RUN-Syncup, STOP → SYNCUP
Transition Description
System state trans­ RUN-Solo → SYNCUP
ition
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
Commissioning
11.4 Operating and system states
Effects
DB contents are
retained.
If there is a role change
between primary and
backup CPU, connected
IO devices are temporar­
ily unavailable.
Effects
The process image is
updated and processing
of the cyclic user pro­
gram begins.
The outputs of the IO
devices are initialized.
Effects
See section SYNCUP sys­
tem state (Page 270)
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