Siemens S7-300 appendix Process image update, Time

Memory concept

4.1 Memory areas and retentivity

Process image update

The operating system updates the process image periodically. The figure below shows the sequence of this operation within a cycle.

Startup
PIO
	time
PII	Cycle
User program
CCP (OS)

Startup program

Processing the user program (OB 1) and all programs called inside of it.

Reading the inputs from the modules and refreshing the data in the process image of the inputs.

Writing the process image of the outputs into the modules.

4-6	CPU 31xC and CPU 31x, Technical data
	Manual, Edition 08/2004, A5E00105475-05