Chapter 8 PFI
X Series User Manual 8-6 ni.com
The filter setting for each input can be configured independently. On power
up, the filters are disabled. Figure 8-3 shows an example of a low to high
transition on an input that has a custom filter set to N = 5.
Figure 8-3. Filter Example
Enabling filters introduces jitter on the input signal. The maximum jitter is
one period of the timebase.
When a RTSI input is routed directly to PFI, the X Series device does not
use the filtered version of the input signal.
Table 8-1. Filters
Filter Setting Filter Clock
N (Filter Clocks
Needed to
Pass Signal)
Pulse Width
Guaranteed to
Pass Filter
Pulse Width
Guaranteed to
Not Pass Filter
None — — — —
90 ns
(short)
100 MHz 9 90 ns 80 ns
5.12 μs
(medium)
100 MHz 512 5.12 μs 5.11 μs
2.56 ms
(high)
100 kHz 256 2.56 ms 2.55 ms
Custom User
configurable
N N/timebase (N – 1)/timebase
1 2 3 1 4 1 2 3 4 5
RTSI, PFI, or
PXI_STAR Terminal
Filtered input goes
high when terminal
is sampled high on
five consecutive filter
clocks.
Filter Clock
Filtered Input
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