7.3 Negative Input-AIN1 Pin Configuration

Except AIN1 pin directly applied to negative input of analog comparator, any of the ADC[7..0] pins can also be applied to replace the negative input to the Analog Comparator, as shown in the table below. The ADC multiplexer is used to select this input, and consequently, the ADC must be switched off to utilize this feature. If the Analog Comparator Multiplexer Enable bit in the ADC Control and Status Register B (ADCSRB.ACME) is '1' and the ADC is switched off (ADCSRA.ADEN=0), the three least significant Analog Channel Selection bits in the ADC Multiplexer Selection register (ADMUX.MUX[2..0]) select the input pin to replace the negative input to the Analog Comparator, when ADCSRB.ACME=0 or ADCSRA.ADEN=1, AIN1 is applied to the negative input of the Analog Comparator.