Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Industrial communication

IO-Link

Also known as: SDCI (single-drop digital communication interface)

German: IO-Link

In industrial automation, IO-Link is a point-to-point communication interface between an IO-Link master and a single sensor or actuator over a standard unshielded three-wire cable. It transmits process data, parameters and diagnostics and is standardized in IEC 61131-9 as SDCI.

  • Industrial communication
  • Standards

In one sentence

IO-Link is a point-to-point interface (IEC 61131-9) that connects one smart sensor or actuator to a master for data, parameters and diagnostics.

Example

When a photoelectric sensor is replaced, the IO-Link master automatically downloads the stored parameter set into the new sensor.

How it applies

  • Engineering: An IO-Link master (often a module of a Remote I/O station or a fieldbus device) has several ports; each port connects one device. The master connects upward to a fieldbus or Industrial Ethernet. IO-Link is not a fieldbus itself.
  • Commissioning: Each device is described by an IODD file (IO Device Description). Parameters can be stored in the master (data storage) so that replacement devices are configured automatically.
  • Operation: Diagnostics, counters and extra measured values are available without additional wiring, provided the higher-level system reads and displays them.
  • Documentation: The documentation team provides the IODD, the process data layout, the parameter list with units and default values, and describes the data storage behavior during device replacement. IO-Link Safety is a separate extension with its own requirements.

IO-Link vs. AS-Interface

AS-Interface (AS-i) connects many simple devices on one bus cable. IO-Link connects exactly one device per port but carries more data and parameters.

By knowledge.aitechdoc.world · Published September 28, 2026 · Last reviewed

Source: IEC 61131-9, Programmable controllers — Part 9: Single-drop digital communication interface for small sensors and actuators (SDCI)

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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