IO-Link is a standardized communication concept for the field level via which intelligent sensors and actuators communicate with each other. As an industry standard for automation, IO-Link implements a point-to-point connection via which the connected field devices exchange their data serially and in half- duplex.
The IO-Link concept uses voltage modulation from 0 to 24 V on the C/Q line and transmits already digitized analog values in the form of telegrams, which can correspond to +/-10 V or 4 mA to 20 mA. In addition, most of the values that are transmitted are unit-based measured values of the sensors. The concept is a sensor- actuator network consisting of the field devices, the sensors and actuators, and the IO-Link master, which transmit their signals via an unshielded 3- wire sensor/actuator cable. The sensors and actuators are described using the IO-Link Device Description( IODD). The IO-Link master can have several ports, to each of which only one IO-Link device( slave) is connected. Usually, the IO-Link devices are connected to the master via M5, M8 or M12 connectors.
The IO-Link master forms the interface to the higher-level programmable logic controllers. The IO-Link devices transmit their characteristic data and parameters via the IO-Link protocol and can change the parameters via the IO-Link master. The masters distinguish two port constellations in the connection technology: Type A and Type B. While with type A the function of the contact of pin 2 of the 5-pin M12 connector can be defined by the manufacturer and sensors and actuators can also be supplied with power via this pin, only devices with a special power supply can be connected to type B. The power supply is connected via pin 2 of the 5-pin M12 connector. In this case, the supply voltage is fed in via pin 2.
As far as data rates are concerned, the standard supports three data rates, namely COM1 with 4, kbit/s, COM2 with 38.4 kbit/s and COM3 with 230.4 kbit/s, whereby the master transceiver transmits 8 bits, 12 bits or 16 bits in analog and digital mode. With digital IO-Link, the analogsignal transmissionis replaced by digital signals. This means that the signals can also be transmitted over greater distances without being affected by interference signals.