Functionality of PFI Lines on NI 6581/6581B

Updated Apr 24, 2023

Reported In


  • NI-6581
  • NI-6581B

Issue Details

I ran out of data lines on the 3 ports of my NI 6581/6581B. Can I use the PFI lines as extra data lines?


PFI stands for Programmable Function Interface, and many National Instruments devices include several PFI lines. These PFI lines are most commonly used for control signals, such as clocks and triggers.

However, the specification sheet lists the signal type for the NI 6581(B)'s as "Control/Data", and it describes them as "bidirectional digital I/O channels", just like the other data lines. Furthermore, other specifications of these PFI lines (input range, impedance, etc.) are specified alongside the data lines of the 3 ports. In other words, the PFI lines have the same characteristics as all of the other data lines and can be used for the same purpose.

Additional Information

Note: the functionality and versatility of PFI lines will vary on each specific device. If you are using another device, be sure to consult the specification sheet for that device to determine the functionality of that device's PFI lines.