Changing the offset of a data item of a Modbus RTU server

The offset specifies the address of the data to be accessed within a data block. The data block itself is specified by selecting the appropriate function code (e.g. FC 1 for reading Coils). The data addresses are defined by the manufacturer of the Modbus RTU device.

  1. Prerequisite
  2. You must add a data item to the Modbus RTU server.
  1. Open the device view.
  2. In the device tree, double-click the server whose data item you want to edit.
  3. Select the data item you want to change.
  4. Double-click the Offset text box.
  5. In the text box, enter a new offset value in either decimal format or hexadecimal format ( e.g. 163 or 0xA3).
  6. Press Enter.