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IO-Link Data Types
Accessing IO-Link Data
There are four data types available through IO-Link:
Process data
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Cyclic data
Value status
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Cyclic data
Device data
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Acyclic data
Events
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Acyclic data
Process Data
The process data of the devices are transmitted cyclically in a data frame in which
the size of the process data is specified by the device. Depending on the device,
0...32 bytes of process data are possible (for each input and output). The
consistency width of the transmission is not fixed and is thus dependent on the
master.
Some devices can support multiple process data "modes," which allows for
selection of different cyclic process data themes.
Value Status
The value status indicates whether the process data is valid or invalid. The value
status can be transmitted cyclically with the process data.
Device Data
Device data supports device-specific configurable parameters, identification data,
and diagnostic information. They are exchanged acyclically and at the request of
the IO-Link master. Device data can be written to the device (Write) and also
read from the device (Read).
Events
When an event occurs, the device signals the presence of the event to the master.
The master then reads out the event. Events can be error messages and warnings/
maintenance data. Error messages are transmitted from the device to the
controller via the IO-Link master. The transmission of device parameters or
events occurs independently from the cyclic transmission of process data.
Cyclic Data
In order to exchange the cyclic process data between an IO-Link device and a
controller, the IO-Link data from the IO-Link master is placed on the address
ranges assigned beforehand. The user program on the controller accesses the
process values using these addresses and processes them. The cyclic data exchange
from the controller to the IO-Link device (for example, IO-Link sensor) is
performed in reverse.
Rockwell Automation Publication 42EF-UM001A-EN-P - September 2015
42EF RightSight Sensor with IO-Link Overview
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