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FAQ about IO-Link

System overview

IO-Link masters – gateways between intelligent IO-Link enabled devices and the fieldbus. Available in 4-port and 8-port versions for IP67 industrial automation environments, IP69K washdown environments and IP20 cabinet mount versions.

LR Device parameterization software – read and write parameter sets on IO-Link masters and devices via a central point on the network.

Ethernet / Fieldbus cabling – adding IO-Link technology to your current controls architecture requires very little changes and cost. IO-Link is not a fieldbus, but rather a new way to communicate to sensors. It uses the same cabling and system design as your current control system. In fact, if you are using ifm sensors, you might already have IO-Link!

IO-Link devices – IO-Link is a serial, bi-directional, point-to-point connection for signal transmission. Sensors featuring embedded IO-Link behave the same way as standard I/O sensors you’re already using until you connect them to an IO-Link master. That’s how you access all the advanced data and configuration capabilities of IO-Link with a conventional 3-wire unshielded patchcord.

Standard industrial cordsets – IO-Link uses standard unshielded cordsets to connect to IO-Link enabled sensors.

Input / Output hubs – use the IO-Link bandwidth to transport the status of simple ON / OFF devices.

IIoT communication port – separate Ethernet connection from the DataLine and CabinetLine masters. The IIoT port requires its own IP address and offers a safe physical connection to the IT world so you can transfer data directly to your higher-level software without tying up the resources of your PLC.

FAQ about IO-Link

What is an IODD?

IO-Link Device Description, the electronic description of the device characteristics: The IODD file provides information for integration into the system e.g. identification, process, and diagnostic data.

Where do you find the IODD?

The IODD for every IO-Link product is available on ifm's website under "Documents & downloads → IODD Downloads".
A manufacturer-independent IODD finder is available on the website of the IO-Link community: or directly at:

Where is the IODD saved?

The IODD is saved in the LR DEVICE parameter setting software or another software for IO-Link device and port configuration tools from ifm provided the IO-Link devices are sold through ifm.

What is a "measured value"?

This is a digital value sent from the sensor to the main system.

Does IO-Link transmit measured values?

If a sensor generates a measured value or determines a process value, this can be transmitted digitally to the controller via IO-Link.

How does the IO-Link measured value differ from a 4 - 20 mA signal?

There are no conversion, scaling or transmission losses.
The entire measured value transmission is digital. Error-prone transmission and conversion of analogue signals are eliminated. The digitally transmitted measured values can be directly displayed in the control room.

How can wire break be detected with IO-Link?

The IO-Link master checks all IO-Link devices within a communication cycle. If a device does not respond, the wire break is immediately detected and signalled irrespective of the measured value.

How can IO-Link reduce the variety of I/Os?

When using IO-Link the user receives both input and output data via the port of a sensor/actuator device. The typical differentiation of the port as input/output no longer applies.
In standard mode without IO-Link every port of an IO-Link capable device can still be configured as input or output.

What is bidirectional data?

Data that goes in both directions; from and to the IO-Link master.

What is the difference between an A port and a B port?

An A port has an integrated, low-current power supply for  devices; a B port allows a second isolated supply for outputs.

What is an IO-Link master?

The IO-Link master connects one or several IO-Link devices to the gateway in higher-level fieldbus systems.
Click here for the selection of IO-Link masters from ifm:

What functions can the Memory Plug carry out?

For installations without IO-Link the Memory Plug allows transmission of parameters to replacement units. To do so, it reads and saves the data of a connected IO-Link sensor. The saved parameters can be copied to sensors of the same type with factory setting.
Click here for the IO-Link Memory Plug:

What needs to be done with an IO-Link master before it can be used?

Every master port must be configured by the user according to the requirements of the user's application: master port mode (DI, DO, IO-Link), process data width and data length. Recommendation: activate the device identification for future compatible replacements.
The LR DEVICE software makes this task easier by scanning the network for available IO-Link masters and connected devices.

Click here for LR DEVICE:

How does an IO-Link master know when to download or upload parameters from an IO-Link device?

Whether a port automatically uploads or downloads depends, on the one hand, on the parameter setting of the IO-Link device and, on the other hand, on the configuration of the master port. The parameter setting of the IO-Link device and the master configuration are carried out using an engineering tool such as LR DEVICE.

Click here for LR DEVICE:

How can process data from sensors be integrated in a controller?

Via the startup package for easy integration of ifm IO-Link masters into your industrial controller.