What is Modbus TCP/IP?

Since EtherNet/IP uses the same application layer protocol used by both DeviceNet and ControlNet, this allows these protocols to share common device profiles and object libraries, and also helps to make these types of devices interoperable on the same network.

Modbus TCP/IP (also Modbus-TCP) is simply the Modbus RTU protocol with a TCP interface that runs on Ethernet.

The Modbus messaging structure is the application protocol that defines the rules for organizing and interpreting the data independent of the datatransmission medium.

TCP/IP refers to the Transmission Control Protocol and Internet Protocol, which provides the transmission medium for Modbus TCP/IP messaging.

Simply stated, TCP/IP allows blocks of binary data to be exchanged between computers. It is also a world-wide standard that serves as the foundation for the World Wide Web. The primary function of TCP is to ensure that all packets of data are received correctly, while IP makes sure that messages are correctly addressed and routed. Note that the TCP/IP combination is merely a transport protocol, and does not define what the data means or how the data is to be interpreted (this is the job of the application protocol, Modbus in this case).

So in summary, Modbus TCP/IP uses TCP/IP and Ethernet to carry the data of the Modbus message structure between compatible devices. That is, Modbus TCP/IP combines a physical network (Ethernet), with a networking standard (TCP/IP), and a standard method of representing data (Modbus as the application protocol). Essentially, the Modbus TCP/IP message is simply a Modbus communication encapsulated in an Ethernet TCP/IP wrapper.

Acromag manufactures a full line of Ethernet I/O modules with Modbus TCP/IP communication.

For more information, download our Introduction to Modbus TCP/IP White Paper.

Acromag also offers Ethernet/IP I/O modules.