National Instruments cRIO-904 Series User Manual

National Instruments cRIO-904 Series User Manual Manual pdf 73 page image

Counters with NI-DAQmxThe cRIO controller has four general-purpose 32-bit counter/timers and one frequencygenerator. The general-purpose counter/timers can be used for many measurement and pulsegeneration applications. The figure below shows the cRIO controller Counter 0 and thefrequency generator. All four counters on the cRIO controller are identical.Figure 46. Controller Counter 0 and Frequency GeneratorCounter 0Counter 0 Source (Counter 0 Timebase)Counter 0 AuxCounter 0 HW ArmCounter 0 ACounter 0 B (Counter 0 Up_Down)Counter 0 ZCounter 0 Gate Counter 0 Internal OutputCounter 0 TCInput Selection MuxesFrequency GeneratorFrequency Output Timebase Freq OutInput Selection MuxesEmbedded Ctr0FIFOCounter 0 Sample ClockCounters have eight input signals, although in most applications only a few inputs are used.For information about connecting counter signals, refer to the Default Counter/Timer Routingsection.Each counter has a FIFO that can be used for buffered acquisition and generation. Eachcounter also contains an embedded counter (Embedded Ctrn) for use in what are traditionallytwo-counter measurements and generations. The embedded counters cannot be programmedindependent of the main counter; signals from the embedded counters are not routable.Counter Timing EngineUnlike analog input, analog output, digital input, and digital output, the cRIO controllercounters do not have the ability to divide down a timebase to produce an internal countersample clock. For sample clocked operations, an external signal must be provided to supply aclock source. The source can be any of the following signals:• AI Sample Clock• AI Start Trigger• AI Reference Trigger• AO Sample ClockcRIO-904x User Manual | © National Instruments | 73