Commissioning
11.5 Operating modes of the CPU
Automation system
System Manual, 12/2017, A5E03461182-AE
237
11.5.3
RUN mode
Function
In "RUN" mode the cyclic, time-driven, and interrupt-driven program execution is performed.
Addresses that are in the "Automatic Update" process image are automatically updated in
each program cycle. See also section Process images and process image partitions
(Page 173).
Execution of the user program
Once the CPU has read the inputs, the cyclic program is executed from the first instruction to
the last instruction. Events with higher priority, such as hardware interrupts, diagnostic
interrupts and communication, can interrupt the cyclic program flow and prolong the cycle
time.
If you have configured a minimum cycle time, the CPU will not end the cycle until this
minimum cycle time has expired, even if the user program is completed sooner.
The operating system monitors the execution time of the cyclic program for a configurable
upper limit known as the maximum cycle time. You can restart this time monitoring at any
point in your program by calling the RE_TRIGR instruction.
If the cyclic program exceeds the maximum cycle time, the operating system will attempt to
start the time error OB (OB 80). If the OB is not present, the CPU ignores that the maximum
cycle time was exceeded. If the cycle monitoring time is exceeded a second time, e.g. while
the time error OB is being processed, the CPU goes to STOP mode.
Reference
Additional information about cycle and response times is available in the Function Manual
Cycle and response times (
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