National Instruments NI USB-621x - Manual (Page 120)

Chapter 10 PFI
NI USB-621x User Manual 10-2 ni.com
Figure 10-2. NI 621x PFI Output Circuitry
When a terminal is used as a timing input or output signal, it is called PFI x.
When a terminal is used as a static digital input or output, it is called P0.x
or P1.x. On the I/O connector, each terminal is labeled PFI x/P0 or
PFI x/P1.
The voltage input and output levels and the current drive levels of the PFI
signals are listed in the specifications of your device.
Using PFI Terminals as Timing Input Signals
Use PFI terminals to route external timing signals to many different
M Series functions. Each input PFI terminal can be routed to any of the
following signals.
• AI Convert Clock
• AI Sample Clock
• AI Start Trigger
• AI Reference Trigger
• AI Pause Trigger
• AI Sample Clock Timebase
• AO Start Trigger
• AO Sample Clock
• AO Sample Clock Timebase
• AO Pause Trigger
• Counter input signals for either counter—Source, Gate, Aux,
HW_Arm, A, B, Z
Timing Signals
Direction Control
I/O Protection
47 k Ω Pull-Down
PFI <4..7>/P1,
PFI <12..15>/P1
Static DO
Buffer
Isolation
Barrier
(USB-6215
and USB-6218
devices only)
Digital
Isolators