Every IO‑Link system consists of an IO‑Link master and at least one IO‑Link device – a sensor or an actuator.

The IO‑Link master is the I/O module that represents the process interface toward the higher-level control system (PLC) and controls communication with the connected IO‑Link devices. This communication takes place through a 3-wire line, in accordance with IEC 60947‑5‑2. The IO‑Link master is capable of two communication modes, both conventional transmission of a 24‑V switching signal (standard IO mode) and also communication via a serial, bidirectional data stream (IO link mode).

With IO‑Link master modules, the SIMATIC ET 200 distributed I/Os and the controller S7‑1200 integrate fast and easy IO‑Link communication with sensors and actuators to the established PROFIBUS and PROFINET fieldbus systems and thus to Totally Integrated Automation.

The IO‑Link masters for SIMATIC ET 200SP, ET 200AL and S7‑1200 are based on the current IO‑Link specification V1.1. One advantage resulting from this is consistent storage of the IO‑Link device parameters in the master. Thus, if a device changes, the current parameters are automatically transferred to the exchanged IO‑Link device, without the need for any additional action on the part of the operator.