The company I work for is developing a controller that has three communications ports: two RS485 and one TCP. Modbus TCP and Modbus RTU Master/Slave will be implemented. It has been proposed that each port have a different Modbus device ID, rather than one global ID.
I contend there is no benefit to this, and only adds confusion for integrators. Does anyone know of a precedent for this?
If I am a master it might be that I am talking with several slaves and each slave must have a unique ID. If your address is 5 and I as the master already have a slave with ID 5 then something has to change.
If you are allowing both 485 ports to be RTU slaves then how can you not make each port have a different ID? Or are you not going to allow them on the same chain. That would not be....
As a master I communicate to one slave device with two ports(hot stand- by). I want both ports to have a different ID.
I have worked with MANY slave devices over the years and I can not recall one that had a global slave device ID for multiple ports. Just look at how MODICON does a multi-port PLC.
I can think of several other reasons but I will leave it at it will not be a confusion for integrators.