| Quick Summary: Modbus/TCP is the easiest to use, easiest to understand of all the high-level industrial application layer protocols for industrial automation applications. Modbus/TCP combines two extremely popular technologies, TCP/IP and the flat network view of Modbus RTU, to form a simple yet very functional worldwide standard for industrial data networking. Built on top of TCP/IP protocol, Modbus/TCP is compatible with all standard Ethernet hardware and software. Using the flat file structure of Modbus RTU as the network interface gives Modbus/TCP a much more straightforward method of representing device data than EtherNet/IP or PROFInet. TCP/IP, the Modbus RTU command set and the flat network representation make Modbus/TCP an easily understood and not difficult to implement Ethernet protocol.
In the flat network representation carried over from Modbus RTU, devices on the Modbus/TCP network are represented as a set of up to 64K words and up to 64K bits (known as coils). Commands, identical to Modbus RTU commands, are issued from a Client device to read or write the data words or bits of a server device. Modbus/TCP is rapidly ground in applications that formerly used Modbus RTU, Modbus Plus and other serial communications protocols.
Unlike other application layer protocols, Modbus/TCP communications are stateless. Each Client – Server transaction is totally independent of every other transaction.
Advantages: Ease of implementation. Small code size. Easily understood object model. Small, very efficient set of commands.
Disadvantages: No capability to abstract data. Little to no standards for device representation (called profiles in other application layers). An identical device from two different manufacturers will use completely different representations on the network.
More Information: www.rtaautomation.com/modbustcp |
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