Siemens SIMATIC S7-1500 System Manual page 329

Basics of program execution
10.3 Events and OBs
Table 10- 5 Response of S7-1500R/H redundant system when cycle time is exceeded with OB 80
Initial situation
System Primary Backup
CPU CPU
RUN- RUN STOP
Solo
SYNCUP RUN- SYNCUP SYNCUP
Syncup
1)
SYNCUP RUN- SYNCUP SYNCUP
Syncup
2)
RUN- RUN- RUN-
Redun- Redun- Redun-
dant dant dant
SYNCUP until snapshot of the work memory contents
1)
SYNCUP after snapshot of the work memory contents
2)
Assignment between event source and OBs
The type of OB determines where you assign OB to event source:
• For hardware interrupts: Assignment in hardware configuration
• For all other OB types: Assignment when the OB is created, where applicable after you
have configured the event source
OB priority and runtime behavior
If you have assigned an OB to the event, the OB has the priority of the event. S7-1500R/H
CPUs support the priorities 1 (lowest) to 26 (highest). The following items are essential to the
execution of an event:
• Call and execution of the assigned OB
• The update of the process image partition of the assigned OB
The user program processes the OBs exclusively on a priority basis. This means the program
processes the OB with the highest priority first when multiple OB requests occur at the same
time. If an event occurs that has a higher priority than the currently active OB, this OB is
interrupted*. The user program processes events of the same priority in order of occurrence.
328
1st time cycle time is ex-
ceeded
System Primary Backup
CPU CPU
RUN- RUN STOP
Solo + OB 80
RUN- SYNCUP
Syncup
+ OB 80
RUN- SYNCUP
Syncup + OB 80
+ OB 80
RUN- RUN- RUN-
Redun- Redun- Redun-
dant dant dant
+ OB 80 + OB 80
2nd time cycle time is ex-
ceeded
System Primary Backup
CPU CPU
STOP STOP STOP
STOP STOP STOP
RUN- RUN STOP
Solo + OB 80
RUN- RUN STOP
Solo + OB 80
System Manual, 01/2024, A5E41814787-AF
3rd time cycle time is ex-
ceeded
System Primary Backup
CPU CPU
--- --- ---
--- --- ---
STOP STOP STOP
STOP STOP STOP
S7-1500R/H redundant system