Modbus

Guide to Controls (BG 83/2023) written by John Marrow and published by BSRIA in June 2023, defines modbus as: ‘An open control protocol typically used by programmable logic controllers (PLCs).’

It states: 'The Modbus protocol was originally developed by Modicon, for use with programmable logic controllers (PLCs). A device in the network called the Modbus client, formerly known as a master, requests information from other devices called Modbus servers, formerly known as slaves. Each server has a unique address on the network which the client uses to send or request information. Within a server device are register tables, which allow the client to read or write information from or to any server on the network. Certain limitations exist depending on the type of network connection made. Recommended standard RS 485 is limited to a maximum of 1200 m between devices whereas Transmission Control Protocol/ Internet Protocol (TCP/IP) is limited to a maximum of 100 m between devices.'

--BSRIA

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