What is the difference between PROFINET and Modbus TCP?

Generally, overall the PROFINET can be announced as the "better protocol" here but, it comes down to the particular application or industry in use.

When it comes down to the application technology in use, the PROFINET is suitable for all kinds of a factory, process, and motion control applications from the simplest to the most complex ones. Modbus TCP is generally used for process applications because the timing is not critical. After all, it does not support high-speed motion control.

If we compare the data speed, PROFINET wins the battle. PROFINET uses Ethernet for real-time data exchange, full-duplex communication at Layer 2 of the OSI model. Modbus TCP on the other hand uses TCP/IP with a client/server model, utilizing half-duplex communication at Layer 4 of the OSI model.

One more important comparison is the configuration part. Modbus TCP is programmed communication that has to be set up in the PLC code via programming block, functions, or tools. PROFINET supports classic configured communication with the possibility for code programming in special and rare cases.

PROFINET does support many more features than Modbus TCP such as process automation profiles, functional safety (PROFIsafe), controller redundancy, fast startup, shared device, and much more. These multiple features enhance the application functions, enabling the operators to achieve more and future-proof the system. PROFINET is also working towards future goals such as integration with Industry 4.0, IIoT, TSN, APL, and OPC UA, while Modbus TCP keeps the simplicity.