WAGO 750 Series Manual page 101

Instead of a "task" also a "system event" can be used to call a POU of your
project.
The available system events are target specific (definition in target file). The
list of the standard events of the target may be extended by customer specific
events. Possible events are for instance: Stop, Start, Online Change.
The complete list of all system events is specified in WAGO-I/O-PRO CAA
/register "Resources"/"Task configuration"/"System events".
If you actually want the POU to be called by the event, activate the entry in
the assignment table. Activating/deactivating is done by a mouse click on the
control box.
More Information
The assignment of the system events to the POUs is described in detail in the
manual to the programming tool WAGO-I/O-PRO CAA under:
www.wago.com ->Service->Downloads->Documentation
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Fieldbus Controller 750-841
Programming the PFC with WAGO-I/O-PRO CAA
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