Communication between two CU320-2 PN

Hello

I have two CU320-2 PN modules, used for motion control.

The drives connected to one CU need to loadshare with the drives connected to the second CU. We want to transfer the torque setpoints between them using PROFInet. The connection should look similar to that of the attached file.

My question is this: How do we setup this network when there is no PLC or other device which can act as a master? I imagine the drive will need to know which address/device it should send telegrams to, but cannot find anywhere to do this in Starter. 

Thank you for your reply.

Thank you very much, this looks very promising. 

I have heard about another solution using the Drive-Cliq interface (I believe it was called OA link?) which became available as of firmware version 4.7. 

However, I was not able to find much information about it. Do you have a manual or product description available?

Thank you again.