Chapter 4 Analog InputM Series User Manual 4-30 ni.comA counter on your device internally generates ai/SampleClock unless youselect some external source. ai/StartTrigger starts this counter and eithersoftware or hardware can stop it once a finite acquisition completes. Whenusing an internally generated ai/SampleClock, you also can specify aconfigurable delay from ai/StartTrigger to the first ai/SampleClock pulse.By default, this delay is set to two ticks of the ai/SampleClockTimebasesignal. When using an externally generated ai/SampleClock, you mustensure the clock signal is consistent with respect to the timing requirementsof ai/ConvertClock. Failure to do so may result in ai/SampleClock pulsesthat are masked off and acquisitions with erratic sampling intervals. Referto AI Convert Clock Signal for more information about the timingrequirements between ai/ConvertClock and ai/SampleClock.Figure 4-16 shows the relationship of ai/SampleClock to ai/StartTrigger.Figure 4-16. ai/SampleClock and ai/StartTriggerAI Sample Clock Timebase SignalYou can route any of the following signals to be the AI Sample ClockTimebase (ai/SampleClockTimebase) signal:• 20 MHz Timebase• 100 kHz Timebase• PXI_CLK10• RTSI <0..7>• PFI <0..15>• PXI_STAR• Analog Comparison Event (an analog trigger)ai/SampleClockTimebaseai/StartTriggerai/SampleClockDelayFromStartTrigger
