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:


    Declaration

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



    Implementation

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



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



Please note, that under the ModbusTCPSlave I/O Mapping tab, the 'Always update variables' is set to 'Enabled 1' :



See also our OLH for Basic settings with Fieldbus Devices and I/O Drivers.


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