Siemens CPU 410-5H Process Automation - Page 273

Supplementary information
16.15 Cycle and response times of the CPU 410-5H
CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 10/2013, A5E32631667-AA
273
Sequence of cyclic program processing
The table below shows the various phases in cyclic program execution.
Table 16- 9 Cyclic program processing
Step
Sequence
1
The operating system initiates the scan cycle monitoring time.
2
The CPU copies the values from the process output images to the output modules.
3 The CPU reads the status of inputs of the input modules, and then updates the process
image of the inputs.
4 The CPU processes the user program in time slices and executes the instructions
specified in the program.
5 At the end of a cycle, the operating system executes pending tasks, e.g., loading and
deleting of blocks.
6 Finally, on expiration of any given minimum cycle time, the CPU returns to the start of
the cycle and restarts cycle monitoring.
Elements of the cycle time
Figure 16-26 Elements and composition of the cycle time