National Instruments DAQ X Series, Руководство пользователя

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Chapter 7 Counters
© National Instruments 7-35 X Series User Manual
Fig u re 7-33 shows a contin u o u s p u lse train generation ( u sing the rising
edge of So u rce).
Figure 7-33. Continuous Pulse Train Generation
Contin u o u s p u lse train generation is sometimes called freq u ency division.
If the high and low p u lse widths of the o u tp u t signal are M and N periods,
then the freq u ency of the Co u nter n Internal O u tp u t signal is eq u al to the
freq u ency of the So u rce inp u t divided by M + N .
For information abo u t connecting co u nter signals, refer to the Default
Counter/Timer Pinouts section.
Buffered Pulse Train Generation
X Series co u nters can u se the FIFO to perform a b u ffered p u lse train
generation. This p u lse train can u se implicit timing or sample clock timing.
When u sing implicit timing, the p u lse idle time and active time changes
with each sample yo u write. With sample clocked timing, each sample yo u
write u pdates the idle time and active time of yo u r generation on each
sample clock edge. Idle time and active time can also be defined in terms
of freq
u ency and d u ty cycle or idle ticks and active ticks.
Note On b u ffered implicit p u lse trains the p u lse specifications in the DAQmx Create
Co u nter O u tp u t Channel are ignored so that yo u generate the n u mber of p u lses defined in
the m u ltipoint write. On b u ffered sample clock p u lse trains the p u lse specifications in the
DAQmx Create Co u nter O u tp u t Channel are generated after the co u nters start and before
the first sample clock so that yo u generate the n u mber of u pdates defined in the m u ltipoint
write.
Finite Implicit Buffered Pulse Train Generation
This f u nction generates a predetermined n u mber of p u lses with variable
idle and active times. Each point yo u write generates a single p u lse. The
n u mber of pairs of idle and active times (p u lse specifications) yo u write
determines the n u mber of p u lses generated. All points are generated back
to back to create a u ser defined p u lse train.
S OURCE
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Co u nter Armed
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