National Instruments NI 6225 - AI Sample Clock Timebase Signal

Chapter 4 Analog Input
M Series User Manual 4-30 ni.com
A counter on your device internally generates ai/SampleClock unless you
select some external source. ai/StartTrigger starts this counter and either
software or hardware can stop it once a finite acquisition completes. When
using an internally generated ai/SampleClock, you also can specify a
configurable delay from ai/StartTrigger to the first ai/SampleClock pulse.
By default, this delay is set to two ticks of the ai/SampleClockTimebase
signal. When using an externally generated ai/SampleClock, you must
ensure the clock signal is consistent with respect to the timing requirements
of ai/ConvertClock. Failure to do so may result in ai/SampleClock pulses
that are masked off and acquisitions with erratic sampling intervals. Refer
to AI Convert Clock Signal for more information about the timing
requirements 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/StartTrigger
AI Sample Clock Timebase Signal
You can route any of the following signals to be the AI Sample Clock
Timebase (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/SampleClockTimebase
ai/StartTrigger
ai/SampleClock
Delay
From
Start
Trigger