The interrupt will be generated only on the transition of the digital line. I've linked an example program below that shows how to use DAQ Event 8 to monitor the transition of digital lines (to generate an interrupt).
I hope this helps.
Using DAQ Event 8 to Send a Message When a Digital Pattern is Matched in Visual C++
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E22F56A4E034080020E74861&p_node=DZ52334&p_source=External
Regards,
Todd D.
NI