What is IO-Link?


If you’re like me you’ve likely used DeviceNet and Hart, but until recently have never heard of IO-Link.

So in today’s article we’ll take a look at the basics of this sensor and actuator communications technology.

1) Point to Point Communications

IO-Link-Circle-Logo-OnlyIO-Link is a simple and fast communications technology, allowing point-to-point communication between a master and sensors or actuators.

Devices which support IO-Link are also easy to spot as each IO-Link device carries the IO-Link logo on their product label.

2) Simple Wiring

The connection between the master and sensor (or actuator) is made with a standard three wire connection, and fully supports M5, M8, and M12 connectors.

And the cable length between the master and device can be up to 20 meters, or 65 feet.

3) Binary Comms

For decades, sensors have been able to output high speed pulsetrains. A common example is an inductive prox sensing the teeth of a spinning gear.

IO-Link takes this ability one step further by substituting the device output with high speed binary communications.

So beyond just providing the status of it’s output, this allows the device to provide additional information including diagnostic and health data.

4) Two ways street

IO Link devices can also accept new configurations and parameter changes over this communications link.

This allows for parameter changes based on the product being manufactured, as well enabling support for automatic device replacement.

5) Move over EDS, the IODD is here.

Every IO-Link device has an IO Device Description (IODD) file. This is an electronic file which contains communication settings and parameters for each device.

6) It’s Standard

If you decide to use IO-Link, the good news is it’s standard. As in, IEC 61131-9 standard. And the claim is that IO-Link provides universal interoperability of devices and masters.

7) Where to go for more information

For more information about IO-Link, check out their website at, http://www.io-link.com.


If you have any experience with IO Link we’d love to hear from you! To share your comments, just fill in the “leave a reply” form at the bottom of this page.


Shawn Tierney
Automation Consultant
Insights In Automation

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Legacy Comments

  1. Just to add some confusion – “IO Link” term has been used by FANUC for years (decades) for their serial communications between CNC controllers, Robot, and FANUC hardwired I/O racks.

    It would be nice if the people who name these things could come up with unique names. Every week I have to deal with a new problem because someone says that their machine tool will talk via Ethernet IP to my PLC only to find out later that they only have only TCP/IP Ethernet. A-B should have called is DH-Ethernet (Data Highway).

  2. So is Fanuc’s I/O Link the same breed as AB’s I/O Link?

    • No – Fanuc’s I/O Link is NOT the same as the new open protocol IO-Link. Fanuc’s I/O link is used for serial communications via Fanuc copper cables or fiber optic cable. It’s often used to talk between Fanuc controllers (robots & CNC machines).

      Allen-Bradley would often use Ethernet IP (Industrial Protocol – not TCP/IP). Allen-Bradley does have modules to connect Ethernet IP to a IO-Link network but I’ve never used them. I have not heard about Fanuc supporting the new IO-Link protocol directly, yet.

      Tom Spisak

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