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3 IO-Link – Basics
3.1 IO-Link- interface – the fieldbus independent communication interface
IO-Link is a fieldbus-independent communication interface for sensors and actuators.
It is based on the IO-Link specification "IO-Link Interface and System Specification" version 1.1.2,
November 2012, and on the IEC 61131-9 (2013-09), ed. 1.0, „Programmable controllers - part 9: Sin-
gle-drop digital communication interface for small sensors and actuators (SDCI)“.
IO-Link is a point-to-point connection between an IO-Link device (e.g. sensor, I/O hub, valve termi-
nal) and the IO-Link master. Up to now, the binary connection was only designed for transferring
switching information, but IO-Link now allows 2 bytes to be transferred normally in a 2.3 ms cycle
via a combined switching status and data channel.
Other information can be exchanged in addition to the process values, such as parameters or diag-
nostic messages.
This enables communication with sensors and actuators down to the "last meter" to be established
for universal communication.
Further information: : www.io-link.com
3.1.1 Communication
Standard I/O-connection technologies in point-to-point connection, unshielded, 20 m wire
length
Cyclic process data transfer in typ. 2.3 ms
Parallel service data exchange without any impact on the process data
Communication via 24 V-pulse modulation, standard UART protocol
Communication between master and device in 3 different transmission speeds
–4.800 Baud (COM 1)
–38.400 Baud (COM 2)
–230.400 Baud (COM 3)
3.1.2 Data transmission
Basically 4 different types of data exist, which are transmitted either cyclically or acyclically.
Process data cyclic data exchange
Value status cyclic data exchange
Device data acyclic data exchange
Events acyclic data exchange
Process data:
The devices' process data are transmitted cyclically, whereas the process data size is defined
through the device. The device process data can contain from 0 to 32 Byte (for both in- and output).