How to Communicate Modbus Natively with ControlLogix
The Modbus protocol was originally published in 1979 by Modicon as a simple request-response protocol over serial communications. It was the first open protocol specifically designed to help device manufacturers publish data that could be read by PLCs. In 1999 this protocol was expanded to include communications over TCP/IP and UDP implementations, allowing it to be utilized in more complex situations. Its simplicity and maturity are what continue to drive its use by hardware manufacturers today.