Siemens SIMATIC CPU 410 System Manual page 358

Supplementary information
18.16 CPU 410 cycle and reaction times
Sequence of cyclic program processing
The table below shows the various phases in cyclic program execution.
Table 18- 9
Step
1
2
3
4
5
6
Elements of the cycle time
Figure 18-27 Elements and composition of the cycle time
358
Cyclic program processing
The operating system initiates the scan cycle monitoring time.
The CPU copies the values from the process output images to the output modules.
The CPU reads the status of inputs of the input modules, and then updates the process
image of the inputs.
The CPU processes the user program in time slices and executes the instructions spec-
ified in the program.
At the end of a cycle, the operating system executes pending tasks, e.g., loading and
deleting of blocks.
Finally, on expiration of any given minimum cycle time, the CPU returns to the start of
the cycle and restarts cycle monitoring.
Sequence
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC