Counters with NI-DAQmx
The cRIO controller has four general-purpose 32-bit counter/timers and one frequency
generator. The general-purpose counter/timers can be used for many measurement and pulse
generation applications. The figure below shows the cRIO controller Counter 0 and the
frequency generator. All four counters on the cRIO controller are identical.
Figure 46. Controller Counter 0 and Frequency Generator
Counter 0
Counter 0 Source (Counter 0 Timebase)
Counter 0 Aux
Counter 0 HW Arm
Counter 0 A
Counter 0 B (Counter 0 Up_Down)
Counter 0 Z
Counter 0 Gate
Counter 0 Internal Output
Counter 0 TC
Input Selection Muxes
Frequency Generator
Frequency Output Timebase
Freq Out
Input Selection Muxes
Embedded Ctr0
FIFO
Counter 0 Sample Clock
Counters 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 Routing
section.
Each counter has a FIFO that can be used for buffered acquisition and generation. Each
counter also contains an embedded counter (Embedded Ctrn) for use in what are traditionally
two-counter measurements and generations. The embedded counters cannot be programmed
independent of the main counter; signals from the embedded counters are not routable.
Counter Timing Engine
Unlike analog input, analog output, digital input, and digital output, the cRIO controller
counters do not have the ability to divide down a timebase to produce an internal counter
sample clock. For sample clocked operations, an external signal must be provided to supply a
clock source. The source can be any of the following signals:
• AI Sample Clock
• AI Start Trigger
• AI Reference Trigger
• AO Sample Clock
cRIO-904x User Manual | © National Instruments | 73
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