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The Modbus slave from the FAQ Modbus Communikation Master/Slave via Ethernet is used here.

  • Create a "Standard project" and select CODESYS Control Win V3 as the device.
  • Define the target system by means of the Network scan.

  • Insert an Ethernet adapter in the device tree and specify the interface to be used.

    If a target system is not defined yet, then the error message "Gateway not configured" is displayed.

  • Insert a Modbus TCP Master below the Ethernet adapter in the device tree.

  • Insert a Modbus TCP Slave below the Modbus TCP Master in the device tree.

  • Insert it in the Modbus Slave Channel tab and set the properties as follows:

  • Adapt the POU PLC_PRG as follows:


        xExec                :    BOOL;
        wMasterSend          :    WORD := 100;
        mbChannel            :    ModbusChannel;


    mbChannel(slave := Modbus_TCP_Slave, xExecute := xExec);

  • Assign the variable wMasterSend to the output Channel 0[0] in the tab ModbusTCPSlave I/O Mapping.

  • Start the project and set the variable xExecute to TRUE so that the new value is passed to the slave.