Stop Mode; Run Mode - Siemens SIMATIC S7-1500 System Manual

Ex ample for the "Comparison preset to actual configuration" parameter
"Startup CPU only if compatible"
The DI 32x24VDC HF input module with 32 digital inputs can be a compatible replacement
for a DI 16x24VDC HF input module with 16 digital inputs. The pin assignment and all
electrical and functional properties are identical.
"Startup CPU even if mismatch"
Instead of a configured digital input module, you insert an analog output module or no
module is present in this slot and thus in all subsequent 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.
10.5.2

STOP mode

Function
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.
10.5.3

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 112).
Ex ecution 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.
Automation system
System Manual, 09/2016, A5E03461182-AD
Commissioning
10.5 Operating modes of the CPU
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