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Using the Frequency Generator

    Last Modified: February 26, 2018

    The frequency generator can output a square wave at many different frequencies. The frequency generator is independent of the four general-purpose 32-bit counter/timer modules on the cRIO controller.

    The following figure shows a block diagram of the frequency generator.

    Figure 1. Frequency Generator Block Diagram

    The frequency generator generates the Frequency Output signal. The Frequency Output signal is the Frequency Output Timebase divided by a number you select from 1 to 16. The Frequency Output Timebase can be either the 20 MHz Timebase, the 20 MHz Timebase divided by 2, or the 100 kHz Timebase.

    The duty cycle of Frequency Output is 50% if the divider is either 1 or an even number. For an odd divider, suppose the divider is set to D. In this case, Frequency Output is low for (D + 1)/2 cycles and high for (D - 1)/2 cycles of the Frequency Output Timebase.

    The following figure shows the output waveform of the frequency generator when the divider is set to 5.

    Figure 2. Frequency Generator Output Waveform

    Frequency Output can be routed out to any PFI terminal. All PFI terminals are set to high-impedance at startup. The FREQ OUT signal also can be routed to many internal timing signals.

    In software, program the frequency generator as you would program one of the counters for pulse train generation.

    For information about connecting counter signals, refer to the Default Counter/Timer Routing section.

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