Difference between Profibus and Modbus?

Difference between Profibus and Modbus ?

Profibus has two standards. First one is Profibus DP (Decentralized Peripherals) which works over a physical protocol called RS485 but doesn’t get information from devices directly. It’s function is to communicate with Profibus hubs which, in their place, will communicate with Profibus devices using the second Profibus standard: Profibus PA (Process Automation).

While MODBUS also works over physical protocol RS485 (sometimes can be used with RS232 also), Profibus PA works over a physical protocol called Manchester Bus Powered (MBP), which is completely different from RS485.

Therefore, there is no way you can convert your MODBUS device to Profibus. You’ll have to use any third party hardware to do this conversion. In one side it will have to be master to the MODBUS device and on the other side it will have to be slave to the PROFIBUS master. However, the normal thing is to install a MODBUS master module/card in the PLC.