MEXM Communications Modes

The MEXM uses the Modbus protocol. Modbus is a serial communications protocol published by Modicon in 1979 for use with its programmable logic controllers (PLCs). It has become a de facto standard protocol for industrial communications, and is now the most commonly available means of connecting industrial electronic devices.

The MEXM may be configured to communicate in one of these two Modbus protocol versions: RTU (Remote Terminal Unit) or TCP (Transmission Control Protocol).

Modbus RTU is used with serial communications (RS422/RS485) whereas Modbus TCP is used for communications over TCP/IP networks.

In TCP mode, a single MEXM may be connected to a Davicom unit with a crossover Ethernet cable. Up to 8 MEXMs (the Davicom units do not support connection to more than 8 MEXMs) can also be connected to an existing network infrastructure through an Ethernet switch (not provided).

In RTU mode, up to 7 MEXMs can be “daisy chained” to a Davicom unit. When using the RTU mode, no additional equipment other than the Davicom unit and the MEXMs are required.

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