30.2.1 Block Diagram
The analog input channel is selected by writing to the MUXPOS bit field
         in the MUXPOS (ADCn.MUXPOS) register. Any of the ADC input pins, GND, internal Voltage
         Reference (VREF), or temperature sensor, can be selected as a single-ended input
         to the ADC. The ADC is enabled by writing a ‘1’ to the ENABLE bit in the
         Control A (ADCn.CTRLA) register. The voltage reference and input channel selections will
         not go into effect before the ADC is enabled. The ADC does not consume power when the
         ENABLE bit in the ADCn.CTRLA register is ‘0’.
The ADC generates a 10-bit result that can be read from the Result (ADCn.RES) register. The result is presented right-adjusted.
