MODBUS RTU - will it work on this way

Hello,
We had CPU ET200s (6Es7 151-8AB01-0AB0) and ET200S 1SI Modbus CP MLFB No. 6ES7-138-4DF11-0AB0.
We were modbus master and all worked fine.

Now we have to change PLC, instead of Et200s we gonna put CPU315-2 PN/DP.
Since we have to change PLC, if we add also distributed module for ET200s ->
6Es7 151-3AA23 - 0AB0 and put
ET200S 1SI Modbus CP MLFB No. 6ES7-138-4DF11-0AB0 on it will MODBUS RTU - will it work on this way with the same code that was running on previous configurationWe had CPU ET200s (6Es7 151-8AB01-0AB0) and ET200S 1SI Modbus CP MLFB No. 6ES7-138-4DF11-0AB0.) with FB2 and FB3 functions.

The system should work. Information may not all be the same.
You have to map out the registers that the master is looking for in the CPU units and insure that the same information is being obtained.
http://www.rtaautomation.com/technologies/modbus-rtu/

Regards,