XML config

If you want to change the default mapping, you have to create and edit the configuration file TcModbusSrv.xml in the location /Hard Disk/System.

Hint: The mapping will be enabled after reboot.

Example for a simple mapping:

<Configuration>
    <Port>502</Port>
    <IpAddr/>
    <Mapping>
        <InputRegisters>
            <MappingInfo>
              <!-- Port 801 = PLC1 TC2 -->
                <AdsPort>801</AdsPort>
                <StartAddress>0</StartAddress>
                <EndAddress>32767</EndAddress>
            <!-- IndexGroup 61472 = 0xF020 -> physical plc input register %I -->
                <IndexGroup>61472</IndexGroup>
                <IndexOffset>0</IndexOffset>
            </MappingInfo> 
            <MappingInfo>
                <AdsPort>801</AdsPort>
            <!-- Modbus input registers -->
                <StartAddress>32768</StartAddress>
                <EndAddress>33023</EndAddress>
                <VarName>.mb_Input_Registers</VarName>
            </MappingInfo>
        </InputRegisters>;
        <OutputRegisters/>
        <InputCoils/>
        <OutputCoils/>
    </Mapping>
</Configuration>

This samples maps the input register (IndexGroup 0xF020) of the first TwinCAT2 runtime (port = 801) to the Modbus input registers.

Hint: It is possible to map by variablename or IndexGroup/Offset(better performance).

More XML in the standard configuratuin can be found under Default Modbus-Mapping.