V02.00 | 2019/10
13
Cyclical and Acyclical Communication
The data exchanged between IO-Link master and the IO-Link device can be divided into cyclical
process data and acyclical data. Process data and value states are transferred cyclically. Acyc-
lical data is transferred separately to cyclic process data. Acyclical data includes device data,
parameter functions and events such as diagnostic information, which is only transferred on re-
quest. The two communication types are independent of each other and do not interact.
Cyclical communication
Process data Value status (port qualifier)
n 0…32 bytes of process data possible per
device (each input and output)
n Process data size determined by the device
n The Port Qualifier indicates whether the
process data is valid or not.
Acylical communication
Device data Value status (port qualifier)
n Parameters, identification data or
diagnostic information
n Data exchange on request of the IO-Link
master
n Device data can be written to the device or
read from the device.
n Device indicates event to master: Error mes-
sages and warnings
n Master indicates event to device: e.g. cable
break or communication abort
Combining IO-Link devices with different specifications
Only devices of specification V1.0 can be operated on IO-Link masters of specification V1.0.
Devices of specification V1.0 and V1.1 can be operated on IO-Link masters of specification V1.1.
IO-Link device V1.0 IO-Link device V1.1
IO-Link master V1.0 x -
IO-Link master V1.1 x x
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