Hi 9900118714,
Typically, PFI lines are used as inputs for triggers and external clock sources. Most of these signals can be brought in on any PFI line. The PFI lines can also be used to output certain timing and triggering signals. The NI 6013/6014 User Manual gives a lot of information on the
functionality of the PFI lines on page 4-19 in the Connecting Timing
Signals section.
NI 6013/6014 User Manual
http://www.ni.com/pdf/manuals/370636a.pdf
These are some documents you might also find useful if you are familiar with any of our E or M Series devices:
How Do the NI 6013, NI 6014, DAQPad-6015 and DAQPad-6016 differ from E Series Devices?
http://digital.ni.com/public.nsf/allkb/ECA86B184EF3B88086256C240067109C?OpenDocument
PFI Lines (E Series vs. M Series)
http://digital.ni.com/public.nsf/allkb/14F20D79C649F8CD86256FBE005C2BC4?OpenDocument
Regards,
John Bongaarts