Chapter 4 Analog Input© National Instruments Corporation 4-23 NI 6232/6233 User ManualUsing an Internal SourceOne of the following internal signals can drive ai/SampleClock.• Counter n Internal Output• AI Sample Clock Timebase (divided down)• A software pulseA programmable internal counter divides down the sample clock timebase.Several other internal signals can be routed to ai/SampleClock throughRTSI. Refer to Device Routing in MAX in the NI-DAQmx Help or theLabVIEW 8.x Help for more information.Using an External SourceUse one of the following external signals as the source of ai/SampleClock:• Input PFI <0..5>• RTSI <0..7>• PXI_STARRouting AI Sample Clock Signal to an OutputTerminalYou can route ai/SampleClock out to any output PFI <6..9> or RTSI <0..7>terminal. This pulse is always active high.You can specify the output to have one of two behaviors. With the pulsebehavior, your DAQ device briefly pulses the PFI terminal once for everyoccurrence of ai/SampleClock.With level behavior, your DAQ device drives the PFI terminal high duringthe entire sample.PFI <0..5> terminals are fixed inputs. PFI <6..9> terminals are fixedoutputs.Other Timing RequirementsYour DAQ device only acquires data during an acquisition. The deviceignores ai/SampleClock when a measurement acquisition is not in progress.During a measurement acquisition, you can cause your DAQ device toignore ai/SampleClock using the ai/PauseTrigger signal.
