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IOMOD 8DI4RO User Manual IEC 60870-5-103


IOMod 8DI4RO is a small-size stand-alone Modbus RTU, IEC 60870-5-103 or IEC-60870-5-101 digital input and relay output controller (protocol depends on firmware). IOmod can be used for industrial applications, where digital signaling is used and robust communication is needed. IOmod is an ideal solution for applications such as data acquisition, control, and process monitoring at remote places. This user manual is written for IEC 60870-5-103 protocol firmware version.


  • 8 digital inputs;

  • Configurable active input signal polarity or input inversion;

  • 4 relay outputs;

  • Galvanically isolated inputs and outputs;

  • Pulsed or latched mode for individual outputs;

  • Possible output feedback measurement with inputs;

  • Configuration over USB console or MODBUS RTU;

  • Values with data and time information;

  • Drag and Drop firmware upgrade over USB mass storage;

  • Modbus RTU, IEC-60870-5-103, IEC-60870-5-101 communication over RS485;

  • Software selectable RT 120 Ohm termination resistor on RS485 interface;
  • LED indication for input/output and data transmission;

  • Easy integration with WCC Lite gateway and platform;

Operational information

IOmod 8DI4RO uses Modbus RTU, IEC 60870-5-103, or IEC 60870-5-101 protocol to communicate with the master device over the RS485 interface. Protocol used by the device can be changed by uploading the corresponding firmware. Default communication settings are 9600 baud rate, 8E1, Link address – 1.

IOmod 8DI4RO configuration can be changed over a USB interface with a terminal console like PuTTY or similar.

Status LED

Status LED can be in 2 colors :

Blue - Device connected to USB.

Green - Normal operation.


The RX/TX LED on the IOMod flashes when data is either being transmitted or received via the RS485 port.