Setting Up the Monitoring of I/O Exchange and Device State

In the ModbusTCPClientSideExample project, open the PLC_PRG.prg.st program.

Declare two variables named readValue and writeValue of type WORD.

Define a variable maxValue of type WORD with the value 100.

Insert the following code into your implementation:

IF writeValue > maxValue THEN
   writeValue := 0;
END_IF
IF readValue = writeValue THEN
   writeValue := writeValue + 1;
END_IF

Open the editor of the Modbus_TCP_Server device and switch to the I/O Mapping tab.

Expand the entries for Channel 1 and Channel 2.

Map PLC_PRG.readValue to the Channel 2[0] entry. The variable receives the value read by the request later.

Map PLC_PRG.writeValue to the Channel 1[0] entry. The variable provides the value to write.

The result looks like this:

Switch back to PLC_PRG.prg.st of the ModbusTCPClientSideExample project.

Declare a variable serverComState of type IoDrvModbusTCP.ModbusTCPComState.

Declare a variable serverErrorCode of type IoDrvModbusTCP.MB_ErrorCodes.

Add the following code to your implementation and adjust the server name to match the name used under Devices. In this sample project, the name is Modbus_TCP_Server.

serverComState := Modbus_TCP_Server.ComState;
serverErrorCode := Modbus_TCP_Server.byModbusError;

In the ModbusTCPServerSideExample project, open the PLC_PRG.prg.st program.

Declare two variables named registerValue and tempValue of type WORD.

Insert the following code into your implementation:

tempValue := registerValue;

Open the editor of the ModbusTCP_Server_Device device and switch to the I/O Mapping tab.

Expand the entry for Holding Registers.

Map PLC_PRG.registerValue to the Holding Registers[0] entry. The variable contains the value of the register.

The result looks like this:

Switch back to PLC_PRG.prg.st of the ModbusTCPServerSideExample project.

Declare a variable serverDeviceClientConnections of type UINT.

Declare a variable serverDeviceErrorCode of type UINT.

Insert the following code into your implementation:

serverDeviceClientConnections := ModbusTCP_Server_Device.uiClientConnections;
serverDeviceErrorCode := ModbusTCP_Server_Device.ErrorCode;