National Instruments Data Acquisition Device NI USB-621x, Руководство пользователя

Страница: 113 / 185

Chapter 8 Counters
NI USB-621x User Manual 8-20 ni.com
Counter Output Applications
Simple Pulse Generation
Single Pulse Generation
The co u nter can o u tp u t a single p u lse. The p u lse appears on the Co u nter n
Internal O u tp u t signal of the co u nter.
Yo u can specify a delay from when the co u nter is armed to the beginning
of the p u lse. The delay is meas u red in terms of a n u mber of active edges of
the So u rce inp u t.
Yo u can specify a p u lse width. The p u lse width is also meas u red in terms
of a n u mber of active edges of the So u rce inp u t. Yo u also can specify the
active edge of the So u rce inp u t (rising or falling).
Fig u re 8-21 shows a generation of a p u lse with a p u lse delay of fo u r and a
p u lse width of three ( u sing the rising edge of So u rce).
Figure 8-21. Single Pulse Generation
Single Pulse Generation with Start Trigger
The co u nter can o u tp u t a single p u lse in response to one p u lse on a
hardware Start Trigger signal. The p u lse appears on the Co u nter n Internal
O u tp u t signal of the co u nter.
Yo u can ro u te the Start Trigger signal to the Gate inp u t of the co u nter. Yo u
can specify a delay from the Start Trigger to the beginning of the p u lse. Yo u
also can specify the p u lse width. The delay and p u lse width are meas u red
in terms of a n u mber of active edges of the So u rce inp u t.
After the Start Trigger signal p u lses once, the co u nter ignores the Gate
inp u t.
S OURCE
OUT
Co u nter Armed