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IO-Link: The open communication standard for sensors and actuators

The digital communication of intelligent field devices and the transmission of process, device and diagnostic data are becoming increasingly important in process automation.
IO-Link, a fieldbus-independent communication protocol, enables the connection of field devices (e.g. sensors, actuators) to the controller via a point-to-point connection.
IO-Link can be easily and flexibly integrated into all standard fieldbus and automation systems and is characterised by its high efficiency and excellent diagnostic capabilities. But what is IO-Link exactly? Which data can be transmitted? And which advantages does IO-Link offer?

The advantages of IO-Link at a glance:

  • Comprehensive functionality for parametrisation and diagnostics
  • Simple integration of field devices at control level
  • Simple start-up and cabling
  • Simple integration into existing plants
  • Faster device replacement for service and maintenance

Fundamentals of IO-Link

Standardized communication technology

IO-Link is a standardized I/O (Input/Output) technology (IEC 61131-9) that enables communication between sensors and actuators. With IO-Link, field devices can be connected to and controlled at control level via a cost-effective point-to-point connection.

IO-Link is therefore not a fieldbus but a communication protocol that builds on the traditional connection technology of sensors and actuators and offers integrated communication right down to field device level. The data exchange between the higher-level controller and the IO-Link devices is bidirectional, i.e. takes place in both directions. Both cyclic (e.g. process values) and acyclic (e.g. diagnostic messages) data can thus be transmitted separately.

Programmable logic controller
The programmable logic controller, or PLC, is a digitally programmed device designed to control or regulate a plant.
IO-Link master
Up to eight IO-Link devices can be connected point-to-point to the IO-Link master.
Control head Type 8691
Control head for decentralised automation of process valves. Discover more. Discover more.
Positioner Type: 8694
Digital electropneumatic positioner for the integrated mounting on process control valves.. Discover more.

The IO-Link protocol

The IO-Link master

The IO-Link master is an interface between the actual controller and the field devices (e.g. sensors or actuators). Depending on the IO-Link master used, up to eight IO-Link devices can be connected point-to-point to a master, thus enabling the user to reliably transmit and exchange device, process and diagnostic data .

Master-slave communication: Configuration of the IO-Link port

The IO-Link ports of the master are used for communicating with the IO-Link devices. The following operating modes are available for the ports:

  • “IO-Link”: In this mode, the port is in the IO-Link communication.
  • “DI”: This port serves as the digital input for entering data.
  • “DQ”: This port serves as the digital output or data output.
  • “Deactivated”: This port is deactivated. Can be used with unused ports, can be reactivated, if required.

IO-Link: Transmission of various types of data

Various types of data, such as process data, value status, device status and events can be transmitted via IO-Link.

The process data shows the current process values of a device (between 1 bit and 32 bytes of information). This data is transmitted bidirectionally via the master, between the controller and the field devices.

Each port has a value status that checks the validity of the process data. This value status is transmitted cyclically along with the process data. The device data transmits detailed information about the connected devices to the IO-Link master. This data can be parameters, identification data and diagnostic information and may only be exchanged on request (acyclically).

The last type of data is events. These events are transmitted to the master as they occur. They may be error messages, warnings or maintenance data.

Data transmission speed

In the IO-Link specification, three data transmission rates have been defined for the IO-Link operating mode

  • 4.8 kBaud (COM 1)
  • 38.4 kBaud (COM 2)
  • 230.4 kBaud (COM3)

An IO-Link master can support one of three data transmission speed settings. Depending on the connected device, the transmission speed is set automatically by the master during the first communication with the device.

Your advantages with IO-Link

Our Bürkert expertise

At Bürkert, we have been a reliable industry partner for many years and offer high-quality products and technology solutions. We also offer future-oriented products and system solutions in the field of automation technology.
As a member of the IO-Link community, we provide active support and certify our products and systems accordingly.
To provide you with the best possible support when automating your production plants, we already offer the IO-Link digital communication interface in many of our products and system solutions.

Application examples with IO-Link

IO-Link is mainly used in machine or machine-related applications, such as in filling plants and in the food and beverage industry. Online parameterisation and remote diagnosis functions make IO-Link particularly suitable for hygiene-critical applications and food processing plants.

Our control heads and positioners with IO-Link

Type 8691

Control head for decentralised automation of ELEMENT process valves

Type 8691
  • Contact-free inductive valve position registration (Teach function)
  • Colour illuminated status display
  • Integrated pilot air duct in the actuator
  • Fieldbus interface AS-Interface, IO-Link or Bürkert system bus (büS)
  • With ATEX II cat. 3G/D / IECEx approval

Type 8681

Control head for decentralized automation of hygienic process valves

Type 8681
  • Universal attachment for hygienic process valves
  • Contactless position measurement system with 3 switching points (Teach-In function)
  • Coloured status display
  • Manual override operative with closed housing
  • AS-Interface, IO-Link, büS/CANopen

Type 8694

Digital electropneumatic positioner for integrated mounting on process control valves

Type 8694
  • Compact and robust stainless steel design
  • Start-up with automatic TUNE function
  • Contact-free position sensor
  • Integrated pilot air duct in the actuator
  • AS interface, IO-Link or Bürkert system bus (büS)

Type 8791

Digital electropneumatic positioner SideControl BASIC

Type 8791
  • Compact and robust design
  • Easy start-up using Tune function
  • Integrated diagnostic functions for valve monitoring
  • Dynamic actuating system with no air consumption in controlled state
  • IO-Link, AS interface or Bürkert system bus (büS)