Events can occur for different reasons. An IO-Link Master can generate vendor-specific Events; an IO-Link Port generates Events when the communication to the device fails, the device gets exchanged, etc.
The IO-Link Device itself provides event information. The IO-Link Master shall observe the event flag provided with each message. In case it is set, the IO-Link Master shall receive the event information via the acyclic communication mechanisms of IO-Link and forward it to the OPC UA Server and the server provides the received events via the OPC UA interface.
Events provided as IO-Link “Error” or “Warning” are mapped to OPC UA Alarms (see OPC 10000-9), events provided as IO-Link “Notification” as OPC UA Events.
Additional to the observation of the event flag there is the possibility to get information about the status of a stateful IO-Link Event (that is mapped to OPC UA Alarms) by using the DiagEntries of PortStatusList as defined in the SMI (see IO-Link Addendum) and the DetailedDeviceStatus (ISDU Index 0x0025).