Modbus RTU is a famous layer 2 fieldbus protocol used in wide range of applications since the mid 80’s and it has its encapsulation in a Ethernet frame, on TCP/IP protocol of layer 4 – 3 of OSI model. It can be used on Ethernet networks though a logic IP address, Modbus TCP uses the same function codes of RTU. The main advantage is that it is faster and can be used to send or receive data through any Ethernet device such as switches and routers in different topologies like star, tree or other line topologies using TCP/UDP/IP protocols in Layer 3-4. It can be installed in Standard 10, 100 or 1000 Mbit/s Ethernet technology based on copper cables, fiber optics or wireless standards can be used. Number of stations is almost infinite and it can go up to a speed of 1.5 Kbyte per telegram frame.

The full application note can be found here:


The ISPsoft program used is listed here: