National Instruments USB-621 Series - Pfi

© National Instruments Corporation 7-1 NI USB-621x User Manual
7
PFI
USB-621x devices have multiple Programmable Function Interface (PFI)
signals.
Each input PFI can be individually configured as the following:
• A static digital input
• A timing input signal for AI, AO, or counter/timer functions
Each output PFI can be individually configured as the following:
• A static digital output
• A timing output signal from AI, AO, or counter/timer functions
Note (USB-6212/6216 Devices) PFI signals on USB-6212/6216 devices can be configured
as input or output.
Each PFI input also has a programmable debouncing filter. Figure 7-1
shows the circuitry of an input PFI line.
Figure 7-1. USB-621x PFI Input Circuitry
Static DI
I/O Protection
To Input Timing
Signal Selectors
PFI
Filters
Weak Pull-Down
PFI/DIO Pin
Isolation
Barrier
(USB-6215/
6216/6218
devices only)
Digital
Isolators