© National Instruments | 4-25
X Series User Manual
Using an Internal Source
One of the following internal signals can drive AI Sample Clock:
• Counter n Internal Output
• AI Sample Clock Timebase (divided down)
• A pulse initiated by host software
• Change Detection Event
• Counter n Sample Clock
• AO Sample Clock (ao/SampleClock)
• DI Sample Clock (di/SampleClock)
• DO Sample Clock (do/SampleClock)
A programmable internal counter divides down the sample clock timebase.
Several other internal signals can be routed to AI Sample Clock through internal routes. Refer
to Device Routing in MAX in the NI-DAQmx Help or the LabVIEW Help for more information.
Using an External Source
Use one of the following external signals as the source of AI Sample Clock:
• 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 Sample Clock out to any PFI <0..15>, RTSI <0..7>, or PXIe_DSTARC
terminal. This pulse is always active high.
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 Sample Clock
when a measurement acquisition is not in progress. During a measurement acquisition, you can
cause your DAQ device to ignore AI Sample Clock using the AI Pause Trigger signal.
A counter/timing engine on your device internally generates AI Sample Clock unless you select
some external source. AI Start Trigger starts this counter and either software or hardware can
stop it once a finite acquisition completes. When using the AI timing engine, you can also
specify a configurable delay from AI Start Trigger to the first AI Sample Clock pulse. By
default, this delay is set to four ticks of the AI Sample Clock Timebase signal.
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