Siemens Simatic S7-1500 Function Manual page 23

Cyclic program execution
3.1 Cycle
The figure below illustrates the phases that are passed through during a cycle. In the
example below the user has configured a minimum cycle time. Updating of the process
image partitions and processing of the cyclic program is completed before the end of the
configured minimum cycle time. Therefore, the CPU waits until the configured minimum
cycle time has expired before the next program cycle starts.
①
②
③
④
⑤
⑥
⑦
Figure 3-2
22
The operating system starts measurement of the cycle time.
The CPU writes the states from the process image output to the output modules.
The CPU reads the status of the inputs at the input modules and writes the input data to the
process image input.
The CPU processes the user program and executes the instructions specified in the program.
The CPU updates the process image partitions and processes the cyclic program.
Wait phase until end of configured minimum cycle time
The operating system restarts the monitoring of the maximum cycle time, evaluates the calcu-
lated cycle time, and starts the new measurement.
Cycle
Cycle and response times
Function Manual, 10/2018, A5E03461504-AD