Io-Link Is Easy; Overview Of Io-Link Technology; Components Of An Io-Link System; After Power-Up - Siemens SIMATIC S7-1200 Manual

IO-Link is easy

12.1

Overview of IO-Link technology

IO-Link is an innovative communication technology for sensors and actuators defined by the
PROFIBUS user organization (PNO). IO-Link is an international standard according to IEC
61131-9. It is based on a point-to-point connection between the sensors and actuators
(slaves) and the controller (master). It does not therefore represent a bus system, but is an
upgrade of the conventional point-to-point connection.
In addition to cyclic operating data, extensive parameter and diagnostic data is transmitted
by the connected sensors/actuators. The same 3-wire connecting cable that is used for
standard sensor technology is used for data transmission.
12.2

Components of an IO-Link system

An IO-Link system consists of IO-Link devices (usually sensors, actuators, or combinations
thereof), a standard 3-wire sensor/actuator cable, and an IO-Link master. The master can be
a device with any design and degree of protection.
An IO-Link master can have one or more ports. The SM 1278 4xIO-Link Master has four
ports. One IO-Link device or one standard sensor/actuator can be connected to each port.
IO-Link is a point-to-point communication system.
12.3

After power-up

At power-up, the IO-Link device is always in SIO mode (standard I/O mode). The ports of the
master can have different configurations. See the IO-Link chapter in the S7-1200 System
Manual for details.
If a port is set to SIO mode, the master acts on this port like a normal digital input. If the port
is set to IO-Link mode (communication mode), the master tries to find the connected IO-Link
device. This process is called wake-up.
During wake-up, the master sends a defined signal and waits for the slave device to
respond. Initially, the master attempts to do this with the highest possible baud rate. If this is
unsuccessful, the master tries the next lower baud rate. The master tries to address the
device three times with each baud rate. The device always supports only one defined baud
rate. If the master receives a response (that is, if the device has been woken up), both will
start communication. At first, they exchange the communication parameters, and then they
start the cyclical exchange of process data.
If the slave device is removed during operation, the master detects the communication abort,
reports it with fieldbus specificity to the controller, and attempts to wake up the device again
cyclically. After another successful wake-up, the communication parameters are read out
again, validated if applicable, and then the cyclic communication channel starts again.
Easy Book
Manual, 03/2014, A5E02486774-AF
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