25.3 Pulse Frequency Mode
In Pulse Frequency (PF) mode, the output becomes active on the rising clock edge immediately
            following the overflow event and goes inactive 1 to 128 clock periods later, determined
            by the PWS bits. This provides a pulsed output at the FOVERFLOW frequency. For more
            information, refer to the figure above. 
        Important: When the selected
            pulse width is greater than the accumulator overflow time frame, then the NCO output
            does not toggle.
    The level of the Active and Inactive states is determined by the POL bit.
PF mode is selected by setting the PFM bit.
