IODD 101 (Tutorial)

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iqMAXREFDES23 Demo Board 



Maxim's Santa Cruz (MAXREFDES23#) reference design is the world's smallest IO-Link® light sensor compliant with IEC 61131-9. The entire design fits onto a 6.5mm x 25mm printed circuit board (PCB).

Sensor simple logic

In iqMAXREFDES23 have been implemented simple switch-point hysteresis logic and additionally can be configured as normally open (NO) or normally closed (NC).

By default light switch-point settings (255 is the maximal value):


WhatSP (Level)HysteresisMode
Light intensity128 (0x80)16 (0x10)Normally Open (NO)
Darkness control16 (0x10)4 (0x04)Normally Closed (NC)

IODD Introduction

An IODD (IO Device Description) is a set of files that formally describes an IO-Link Device. An IODD is mandatory for each IO-Link Device.

The IODD is created by the device vendor and shall be sufficient for IO-Link Tools to identify, communicate, parameterize and diagnose the device.

The file name shall follow the following rule:

<vendor name>-<device name>-<date of file creation>-IODD<schema version>.xml

for iqMAXREFDES23 it's correspond for:


  File Modified

XML File Renesas-MAXREFDES23-20140413-IODD1.0.1.xml

Apr 07, 2015 by du

XML File Renesas-MAXREFDES23-20140413-IODD1.1.xml

Apr 07, 2015 by du

PNG File Renesas-MAXREFDES23-icon.png

Apr 07, 2015 by du

PNG File Renesas-MAXREFDES23-pic.png

Apr 07, 2015 by du

PNG File Renesas-logo.png

Apr 07, 2015 by du

For more IODDs look at IODD Samples.

IODD basic concepts


Actually, the data types form the following hierarchy:

For example (BooleanT with enums):


Process Data

  1. Byte (MSB): Light intensity (from 0 to 255).
  2. Byte (LSB): [.......F - light intensity switch-point flag (1bit)].






IO-Link indexModeDescriptionDefault value
256 (0x0100)read/writeAmbient light switch-point level128 (0x80)
257 (0x0101)read/writeAmbient light switch-point hysteresis16 (0x10)