PLC concepts
5.1 Execution of the user program
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
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Startup OBs execute one time when the operating mode of the CPU changes from STOP to
RUN, including powering up in the RUN mode and in commanded STOP-to-RUN transitions.
After completion, the main "Program cycle" begins executing.
The startup event happens one time on a STOP to RUN transition and causes the CPU to
execute the startup OBs. You can configure multiple OBs for the startup event. The startup
OBs execute in numerical order.
Table 5- 3 Start information for a startup OB
True if retentive data are lost
True if date and time are lost
Time delay interrupt OBs execute after a time delay that you configure.
Time delay interrupt events
You configure time delay interrupt events to occur after a specified delay time has expired.
You assign the delay time with the SRT_DINT instruction. The time delay events interrupt the
program cycle to execute the corresponding time delay interrupt OB. You can attach only
one time delay interrupt OB to a time delay event. The CPU supports four time delay events.
Table 5- 4 Start information for a time delay interrupt OB
Identifier passed to triggering call of SRT_DINT
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