Siemens S7-300 appendix Configurable process image with CPU317 FW V2.3.0 or higher

Memory concept 4.1 Memory areas and retentivity

Configurable process image with CPU317 (FW V2.3.0 or higher)

IN STEP 7, you can define a user-specific size of the I/O process images between 0 to 2048 for a CPU317, FW V2.3.0 or higher.

Note the information below:

Note

Currently, the dynamic setting of the process image only affects its update at the scan cycle control point. That is, the process image of inputs is only updated up to the set PII size with the corresponding values of the peripheral input modules existing within this address area, or the values of the process image of outputs up to the set PIO size are written to the peripheral output modules existing within this address area.

This set size of the process image is ignored with respect to STEP 7 commands used to access the process image (for example U I100.0, L EW200, = Q20.0, T AD150, or corresponding indirect addressing commands also). However, up to the maximum size of the process image (that is, up to I/O byte 2047), these commands do not return any synchronous access errors, but rather access the permanently available internal memory area of the process image.

The same applies to the use of actual parameters of block calls from the I/O area (area of the process image).

Particularly if these process image limits were changed, you should check to which extent your user program accesses the process image in the area between the set and the maximum process image size. If access to this area continues, the user program may not detect changes at the inputs of the I/O module, or actually fails to write the data of outputs to the output module, without the system generating an error message.

You should also note that certain CPs may only be addressed outside of the process image.

CPU 31xC and CPU 31x, Technical data	4-7
Manual, Edition 08/2004, A5E00105475-05