National Instruments NI 6612, Руководство пользователя

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NI 6612 User Manual
polarity selection for DI Sample Clock Timebase can be configured as either rising—or
falling—edge except for the 100 MHz Timebase or 20 MHz Timebase.
The DI Sample Clock Timebase may be used if an external sample clock signal is required, but
the signal needs to be divided down. If an external sample clock signal is required, but there is
no need to divide the signal, then the DI Sample Clock should be used instead of the DI Sample
Clock Timebase.
DI Start Trigger Signal
Use the DI Start Trigger (di/StartTrigger) signal to begin a measurement acquisition. A
measurement acquisition consists of one or more samples. If triggers are not used, a
measurement acquisition can be initiated with a software command. After the acquisition begins,
configure the acquisition to stop:
• When a certain number of points are sampled (in finite mode)
• After a hardware reference trigger (in finite mode)
• With a software command (in continuous mode)
An acquisition that uses a start trigger (but not a reference trigger) is sometimes referred to as a
posttriggered acquisition .
Retriggerable DI
The DI Start Trigger can also be configured to be retriggerable. The timing engine generates
samples and converts clocks for the configured acquisition in response to each pulse on an
DI Start Trigger signal.
The timing engine ignores the DI Start Trigger signal while the clock generation is in progress.
After the clock generation is finished, the timing engine waits for another Start Trigger to begin
another clock generation. Figure 2-5 shows a retriggerable DI of four samples.
Figure 2-5.
Retriggerable DI
Note Waveform information from LabVIEW does not reflect the delay between
triggers. They are treated as a continuous acquisition with constant t0 and dt
information.
Reference triggers are not retriggerable.
DI S t a rt Trigger
DI Sa mple Clock