Description:
DP communication is the cyclical exchange of user data between master and slave. When configuring with STEP 7 you assign logical addresses for these user data areas so that the data to be exchanged can be addressed with load/transfer commands from the user program.
Thanks to the proxy functionality of the SIMATIC S7 31x-2 PN/DP CPU (= the CPU takes over the communication via PROFINET instead of the relevant PROFIBUS components), DPV0 slaves can also participate in PROFINET CBA communication. Unlike pure PROFIBUS DP communication, the logical addresses for user data communication between DP master and DP slave are generated automatically when the technological functions are interconnected in iMap and stored by default in an area interfacing with the PIO (process image of the outputs). Therefore, the user has no influence on the assignment of addresses.
If you now load the configuration of a SIMATIC S7 315-2 PN/DP CPU, which has only a PI (process image) range of 0...127 bytes, into a SIMATIC S7 317-2 PN/DP CPU with a PI range of 0...255 bytes, the logical addresses of the DP slaves, which are communicating via CBA (Component-Based Automation), lie within the PIO range and are continuously overwritten by the PI transfer.

Remedy:
The system data generated by SIMATIC iMap must not be loaded unchecked into a CPU (including the hardware) that does not correspond to the relevant iMap configuration. You must always make sure that the PI ranges (process image ranges) of the configured CPU match those of the actual CPU (including the hardware). Use an appropriate CPU. The problem is rectified in firmware version 2.5.