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

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Chapter 5 Analog Output
© National Instruments Corporation 5-7 NI USB-621x User Manual
If yo u are u sing any signal as the so u rce of yo u r sample clock, the
generation res u mes as soon as AO Pa u se Trigger is deasserted and another
edge of the sample clock is received, as shown in Fig u re 5-5.
Figure 5-5. AO Pause Trigger with Other Signal Source
Using a Digital Source
To u se AO Pa u se Trigger, specify a so u rce and a polarity. The so u rce can
be any inp u t PFI signal.
The so u rce also can be one of several other internal signals on yo u r
USB-621 x device. Refer to Device Routing in MAX in the NI-DAQmx Help
or the LabVIEW Help in version 8.0 or later for more information.
Yo u also can specify whether the samples are pa u sed when AO Pa u se
Trigger is at a logic high or low level.
AO Sample Clock Signal
Use the AO Sample Clock (ao/SampleClock) signal to initiate AO samples.
Each sample
u pdates the o u tp u ts of all of the DACs. Yo u can specify an
internal or external so u rce for AO Sample Clock. Yo u also can specify
whether the DAC u pdate begins on the rising edge or falling edge of
AO Sample Clock.
Using an Internal Source
One of the following internal signals can drive AO Sample Clock:
• AO Sample Clock Timebase (divided down)
• Co u nter n Internal O u tp u t
A programmable internal co u nter divides down the AO Sample Clock
Timebase signal.
P aus e Trigger
Sa mple Clock