Chapter 4
Analog Input
©
National Instruments Corporation
4-29
Using an Internal Source
One of the following internal signals can drive ai/SampleClock.
•
Counter
n
Internal Output
•
AI Sample Clock Timebase (divided down)
•
A pulse initiated by host software
A programmable internal counter divides down the sample clock timebase.
Several other internal signals can be routed to ai/SampleClock through
RTSI. Refer to
Device Routing in MAX
in the
NI-DAQmx Help
or the
LabVIEW Help
in version 8.0 or later for more information.
Using an External Source
Use one of the following external signals as the source of ai/SampleClock:
•
PFI <0..15>
•
RTSI <0..7>
•
PXI_STAR
•
Analog Comparison Event (an analog trigger)
Routing AI Sample Clock Signal to an Output
Terminal
You can route ai/SampleClock out to any PFI <0..15> or RTSI <0..7>
terminal. This pulse is always active high.
You can specify the output to have one of two behaviors. With the pulse
behavior, your DAQ device briefly pulses the PFI terminal once for every
occurrence of ai/SampleClock.
With level behavior, your DAQ device drives the PFI terminal high during
the entire sample.
All PFI terminals are configured as inputs by default.
Other Timing Requirements
Your DAQ device only acquires data during an acquisition. The device
ignores ai/SampleClock when a measurement acquisition is not in progress.
During a measurement acquisition, you can cause your DAQ device to
ignore ai/SampleClock using the ai/PauseTrigger signal.