Hello bahi;

If there is a BusF, then your configuration is very probably not correct.

Please open the master's diagnostic buffer to find messaged that the CPU's OS logs when it encounters faults and other events that cause problems to its operations.

You can save the buffer messages (button Save AS..) and attach the .txt file here so we may help you further.

You could also use the following sample configuration of a CP 4342-5 slave to a S7 master to understand the data exchange mechanism between the two:

DP link between CP 342-5 (slave) and S7-300/400 (master) with STEP 7 V5.1

https://support.industry.siemens.com/cs/ww/en/view/6519580

Hope this helps,

Daniel Chartier