National Instruments DAQ M Series - Manual (Page 104)

Chapter 8 PFI
NI 6236 User Manual 8-4 ni.com
Figure 8-3. PFI Input Signals Connections
PFI Filters
You can enable a programmable debouncing filter on each PFI, RTSI, or
PXI_STAR signal. When the filters are enabled, your device samples the
input on each rising edge of a filter clock. M Series devices use an onboard
oscillator to generate the filter clock with a 40 MHz frequency.
Note NI-DAQmx only supports filters on counter inputs.
The following is an example of low to high transitions of the input signal.
High to low transitions work similarly.
Assume that an input terminal has been low for a long time. The input
terminal then changes from low to high, but glitches several times. When
the filter clock has sampled the signal high on N consecutive edges, the low
to high transition is propagated to the rest of the circuit. The value of N
depends on the filter setting; refer to Table 8-1.
PFI 0
Source
PFI 2
Source
M Series Device
D GND
PFI 2
PFI 0
I/O Connector