Modbus is an openly published communications protocol based on master/slave or client/server architecture, designed by Modicon for use with its programmable logic controllers (PLCs). Versions of the Modbus protocol exist for serial port and Ethernet. Modbus remote terminal unit (RTU) is a compact, binary representation of the data. Modbus ASCII is human readable, and more verbose. Both of these protocols are serial based. Modbus/TCP is very similar to Modbus RTU, but is transmitted within TCP/IP data packets.
Communication protocol developed by Modicon; widely used in SCADA and process control applications. Operating systems and PROMs containing the MODbus protocol are available for many Campbell Scientific dataloggers.
This protocol provides the internal standard that Modbus ready devices use for parsing messages. During communications on a Modbus network, the protocol determines how each device will know it's address, recognize a message addressed to it, determine the kind of action to be taken and extract any data or other information contained in the message. If a reply is required, the device will construct the reply message and send it using Modbus protocol.