Stop Mode; Run Mode - Siemens SIMATIC ET 200pro Operating Instructions Manual

Example for the "Comparison preset to actual configuration" parameter
"Startup CPU only if compatible"
The pin assignment and all electrical and functional properties must match.
"Startup CPU even if mismatch"
The CPU also starts with the following differences:
- An analog output module is inserted instead of a configured digital input module.
- No module is present in this slot and the following slots. Although the configured inputs
cannot be accessed, the CPU starts up.
Note that the user program cannot function correctly in this case and take the appropriate
measures.
8.4.3

STOP mode

Response
The CPU does not execute the user program in STOP mode.
All outputs are disabled or react according to the parameter settings for the respective
module: They provide a substitute value as set in the parameters or retain the last value
output and thus hold the controlled process in a safe operating mode.
8.4.4

RUN mode

Response
In "RUN" mode the cyclic, time-driven, and interrupt-driven program execution is performed.
The CPU automatically updates addresses located in the "Automatic Update" process image
in each program cycle. For additional information, see section Process images and process
image partitions (Page 45).
Execution of the user program
Once the CPU has written the outputs and read the inputs, it runs through the cyclic program
from the first instruction to the last instruction. Events with higher priority, such as hardware
interrupts, diagnostic interrupts and communication, interrupt the cyclic program flow and
lengthen 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 CPU has executed the user program in a
shorter period.
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 may 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 cyclic program exceeds the cycle monitoring time a second time,
for example while the time error OB is being processed, the CPU goes to STOP mode.
CPU 1516pro-2 PN (6ES7516-2PN00-0AB0)
Operating Instructions, 11/2019, A5E35873416-AC
Commissioning
8.4 Operating modes of the CPU
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