2.6 Window Comparator
The ADC can raise the Window Comparator Interrupt (WCMP) flag in the Interrupt Flags (ADCn.INTFLAGS) register and request an interrupt (WCMP) when the output of a conversion or accumulation is above and/or below certain thresholds. The available modes are:
- ABOVE – The value is above a threshold
- BELOW – The value is below a threshold
- INSIDE – The value is inside a window (above the lower threshold and below the upper threshold)
- OUTSIDE – The value is outside a window (below the lower threshold or above the upper threshold)
The thresholds are set by writing to the Window Comparator Low and High Threshold (ADCn.WINLT and ADCn.WINHT) registers. The Window mode to use is selected by the Window Comparator Mode (WINCM) bit field in the Control D (ADCn.CTRLD) register.
The Window Mode Source (WINSRC) bit in the Control D (ADCn.CTRLD) register selects if the comparison is done on the 16 LSb of the Result (ADCn.RESULT) register or the Sample (ADCn.SAMPLE) register. If an interrupt request is enabled for the WCMP flag, WINSRC selects which interrupt vector to request, RESRDY or SAMPRDY.
When accumulating multiple samples, if the Window Comparator source is the Result register, the comparison between the result and the threshold(s) will happen after the last conversion is complete. If the source is the Sample register, the comparison will happen after every conversion.
The following code shows how to configure the thresholds of the window comparator, and how to configure the INSIDE mode comparing against the Result register.
ADC0.WINHT = 200; /* Window High Threshold */ ADC0.WINLT = 100; /* Window Low Threshold */ ADC0.CTRLD |= ADC_WINCM_INSIDE_gc | ADC_WINSRC_RESULT_gc; /* Result as Window Comparator source*/