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4-9
Buffer Considerations
DAQmx supports configuring and using the waveform buffer in different ways to support a wide
variety of applications. For example, you can configure DAQmx to:
•
read data from the buffer once and stop.
•
read data from the buffer multiple times (or continuously).
•
update the buffer while the device is generating waveforms.
Refer to the
Buffering
topic in the
NI-DAQmx Help
for more information.
Other Features
Frequency Division
The counters can generate a signal with a frequency that is a fraction of an input signal. With
frequency division, the NI 6614 receives a signal with frequency, f, and outputs a signal with
frequency, f/N.
For frequency division, use the steps described in
Generating a Waveform with Constant
. Also:
•
Route the input signal, f, to be the counter timebase using the Co.CtrTimebaseSrc DAQmx
Channel property.
•
Create the channel in terms of ticks.
Frequency Generator
To generate a square wave of a fixed frequency you can use a counter to create a continuous
pulse train. Refer to the
Generating a Waveform with Constant Frequency and Duty Cycle
section for more information.
In addition to the eight counters, the NI 6614 has a dedicated Frequency Generator circuit. The
Frequency Generator circuit is more limited than one of the eight counters. However, it may be
useful if all of the counters are dedicated to other tasks.
Figure 4-9 shows the Frequency Generator circuit.
Figure 4-9.
100 kHz Time
bas
e
20 MHz Time
bas
e
Fre
qu
ency
O
u
tp
u
t
Time
bas
e
FREQ OUT
Divi
s
or
(1–16)
Fre
qu
ency Gener
a
tor
÷
2
