Introduced by Schneider Electric (Modicon) in 1979, the Modbus® fieldbus is still an essential, open communications standard, supported by a large number of products on the market today. Serial links allow you to connect any equipment without using protocols.

In a typical Modbus network, Modbus messages are sent over an RS232/RS485 asynchronous serial communication link (EIA standard); e.g., the Modbus-Master initiates a request for information and the Modbus-Slave device responds with the appropriate information sent back. General broadcasts of information are also possible, with no response needed. The two modes of communication within the Modbus network are 10-bit ASCII and 11-bit RTU.

The following guidelines and standards apply to the fieldbus handling of products which are responded to by the modbus:

• RS485 standard,
• EIA RS485.2-4 serial interface

Modbus application

• PLCs (Series 7, Series 1000, Modicon TSX Micro, Premium, Quantum, Momentum, Compact, Twido)
• Most Telemecanique devices