Hey Steve,
The DAQmx driver installs several examples into LabVIEW that
demonstrate how to implement various event counting applications. I
recommend you look over these and see if any of them accomplish what
you're trying to do. They're usually very simple to understand and
well documented, but I'd be happy to help you out with any of them if
you had a particular question.
You can find them in the Example Finder (Help >> Find Examples)
in LabVIEW. Drill down to the following location in the directories:
Hardware Input and Output >> DAQmx >> Counter Measurements >> Count Digital Events
You'll see a number of examples, but I recommend starting with 'Count Digital Events.vi'
Since PFI8 corresponds to CTR0 SRC, make sure you set it to use counter 0. This should work correctly.
Elijah Kerry
NI Director, Software Community