SSZT072 june   2022 AM4379


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    2.     IO-Link Timing
    3.     Additional Resources

Steffen Graf

In industrial factory automation designs, IO-Link has evolved into a popular protocol for sensors and actuators to improve factory efficiency and reduce downtime. The IO-Link master is a crucial component of an IO-Link system, as it initiates the complete communication cycle, handles the cycle timing, and exchanges process data between a programmable logic controller and connected devices.

IO-Link uses half-duplex serial communication with a COM1 (4,800 baud), COM2 (38,400 baud) or COM3 (230,400 baud) data rate at 24 V. The simplicity of the lower protocol layers makes it possible to build an IO-Link device comprising a small microcontroller (MCU) with an integrated universal asynchronous receiver transmitter peripheral and an external physical layer (PHY). The external PHY acts as a level shifter and detects the wakeup pulse to switch the IO-Link device from digital in/out mode into IO-Link mode.

The master side of an IO-Link system is more complex. The PHY is similar, with a small current sink at the communication line (CQ) to support simple transceivers on the device side; it must be able to send the wakeup pulse. The power supply has to provide a 24-V voltage to all connected devices such as sensors and actuators. The master needs to support all three data rates, and typically comes in configurations with four or eight ports.

In this article, I will address how to implement high-performance IO-Link masters in industrial systems to achieve precise cycle times and deterministic latency.