Configure input trigger points

To configure trigger-based input points, configure the following point attributes.

1. Configure the scan class. Set location4 to 0.

2. Specify the trigger point name and the condition in the extended descriptor (exdesc) attribute.

   You can specify the trigger point in the exdesc attribute in three ways:

   • event='trigger_point_name'

   • trigger='trigger_point_name'

   • trig='trigger_point_name'

     The trigger point name must be in single quotes.

     The following table shows valid conditions for the extended descriptor (exdesc) attribute.

     Condition	Description
     anychange	Trigger on any change if the value of the current event is different than the value of the previous event. System digital states also trigger events. For example, an event is triggered on a value change from 0 to Bad Input, or a change from Bad Input to 0
     increment	Trigger on any increase in value. System digital states do not trigger events. For example, an event is triggered on a value change from 0 to 1, but not on a change from Pt Created to 0 or from 0 to Bad Input.
     decrement	Trigger on any decrease in value. System digital states do not trigger events. For example, an event will be triggered on a value change from 1 to 0, but an event will not be triggered on a value change from Pt Created to 0, or on a value change from 0 to Bad Input.
     nonzero	Trigger on any non-zero value. Events are not triggered when a system digital state is written to the trigger point. For example, an event is triggered on a value change from Pt Created to 1, but an event is not triggered on a value change from 1 to Bad Input.

     For example, event='Sinusoid' anychange.

     Note: Data loss can occur for Event Points (ExDesc contains event='trigger_tag_name' condition) if the connection to the PI Server is lost. The interface signs up for events from Update Manager for the source points configured for the Event Points. When there is no connection, the source point data cannot be sent to PI, nor can updates be received from the Update Manager for the Event Points. Thus, Event Points will not be updated during the time period when connectivity is lost, nor can data be recovered during the period of lost connectivity.