Chapter 6
Digital I/O
X Series User Manual
6-24
ni.com
DI Change Detection
Yo
u
can config
u
re the DAQ device to detect changes on all 32 digital inp
u
t
lines (P0, P1, and P2) and all 16 PFI lines. Fig
u
re 6-11 shows a block
diagram of the DIO change detection circ
u
itry.
Figure 6-11.
DI Change Detection
Yo
u
can enable the DIO change detection circ
u
itry to detect rising edges,
falling edges, or either edge individ
u
ally on each DIO line. The DAQ
devices synchronize each DI signal to the 100 MHz Timebase, and then
sends the signal to the change detectors. The circ
u
itry ORs the o
u
tp
u
t of all
enabled change detectors from every DI signal. The res
u
lt of this OR is the
Change Detection Event signal.
Change detection performs b
u
s correlation by considering all changes
within a 50 ns window one change detection event. This keeps signals on
the same b
u
s synchronized in samples and prevents overr
u
ns.
S
ynch
S
ynch
P0.0
P2.7
En
ab
le
En
ab
le
En
ab
le
En
ab
le
Ch
a
nge Detection Event
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