Chapter 3
Hardware Overview
NI PXI-6682 User Manual
3-12
ni.com
Using Front Panel PFI Terminals as Outputs
The front panel PFI output signals use +3.3 V signaling for high-impedance
loads. You can use the PFI terminals to generate future time events and
clock signals up to 1.5 MHz. PFI output signals are suitable for driving
most LEDs. To ensure proper signaling for fast edge rate signals, ensure
that the system terminates to 50
Ω
on the receiving end. Cabling should
also be 50
Ω
impedance. In a 50
Ω
environment, the PFI terminals will
output less than +3.3 V in the high state. Refer to Appendix A,
Specifications
, for more information. Refer to the
NI-Sync User Manual
for
information on how to set up the PFI lines for output.
Caution
Do not attempt to drive signals into PFI terminals set up as outputs. Doing so can
damage the NI PXI-6682 or the device driving the PFI terminal.
You can independently select the output signal source for each PFI trigger
line from one of the following sources:
•
Another PFI <0..2>
•
PXI_TRIG <0..7>
•
PXI_STAR <0..12>
•
Future time events
•
PXI_CLK10
•
Ground
The PFI trigger outputs may be synchronized to CLK10 except when
routing future time events. Refer to the
Choosing the Type of Routing
section for more information about the synchronization clock.
Using Front Panel PFI Terminals as Inputs
The front panel PFI terminals can be configured by software to accept input
signals. Refer to the
NI-Sync User Manual
for information on how to set up
the PFI terminals to accept input signals. You can use these terminals to
timestamp triggers with the synchronized system time or to route signals to
other destinations (refer to Table 3-6). The input terminals accept native
+3.3 V signaling, but are +5 V tolerant. Use 50
Ω
source termination when
driving signals into PFI terminals.
The voltage thresholds for the front-panel PFI input signals are fixed. Refer
to Appendix A,
Specifications
, for the actual voltage thresholds. The
front-panel PFI input signals can be timestamped on rising, falling, or both
edges of an input signal.
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