This document explains how to use the “Modbus-RTU Easy Master Function” (Hereafter referred to as “MREM”) feature of certain Omron Compact PLCs in the CP1 and CP2 family. The MREM makes it easy to communicate with external devices over an RS-485 Serial bus using the Modbus-RTU protocol.
The external device used in this example is a Temperature Controller from our E5_C series with RS-485 Communication option. This technique works equally well with other Modbus-RTU equipped devices, such as the Omron MX2-…-V1 frequency inverter, and many third-party devices.
Using this method, the PLC Ladder Program can monitor and control the operation of connected devices using a simple command/response protocol. Up to 247 devices may be connected to a single RS-485 2- wire bus. Prior experience setting up CP1/2 PLCs and basic programming is assumed.
Keywords: E5EC , CP1L-E, CP1W-CIF11, CX Programmer
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