IO-Link versus AS-i

You’re designing a new machine. Should you use IO-Link or AS-interface (AS-i)? Yes.

Yes, you should use the one appropriate to the task at hand. There’s never a substitute for doing the engineering.

Use AS-i for:

  • A long string of pushbuttons (as along a conveyor).
  • A long string of Emergency Stop pushbuttons (as along a conveyor).
  • A simple analog device with relatively slow update times.
  • Any arrangement of simple I/O devices in a network. (For “simple,” understand “low data.”)
  • When functional safety over the network is needed. AS-I Safety at Work can transparently connect to PROFIsafe.

Use IO-Link for:

  • Intelligent sensors and actuators. (For “intelligent,” understand “high data.”)
  • Where point to point wiring is acceptable.
  • IO-Link does not yet have a functional safety specification, although it is being worked on.

By high and low data, I mean the volume of parameters accessed for configuration or asset management. IO-Link excels when there are high data requirements.

Either technology can work with any fieldbus or connect directly to an I/O rack. There are even products to connect IO-Link to an AS-i network.

AS-i IO-Link
connection network point-to-point
device complexity low data high data
functional safety yes planned
fieldbus integration any any

Do the engineering – use the right technology for the right task: AS-i for a network of low data devices, IO-Link for point-to-point connections of high data devices.

–Carl Henning