Datasheet

306
7593L–AVR–09/12
AT90USB64/128
25.1 Analog Comparator multiplexed input
It is possible to select any of the ADC7..0 pins to replace the negative input to the Analog Com-
parator. 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 (ACME in
ADCSRB) is set and the ADC is switched off (ADEN in ADCSRA is zero), and MUX2..0 in
ADMUX select the input pin to replace the negative input to the Analog Comparator, as shown in
Table 25-2. If ACME is cleared or ADEN is set, AIN1 is applied to the negative input to the Ana-
log Comparator.
25.1.1 DIDR1 – Digital Input Disable Register 1
• Bit 1, 0 – AIN1D, AIN0D: AIN1, AIN0 Digital Input Disable
When this bit is written logic one, the digital input buffer on the AIN1/0 pin is disabled. The corre-
sponding PIN Register bit will always read as zero when this bit is set. When an analog signal is
applied to the AIN1/0 pin and the digital input from this pin is not needed, this bit should be writ-
ten logic one to reduce power consumption in the digital input buffer.
Table 25-2. Analog Comparator multiplexed input.
ACME ADEN MUX2..0 Analog Comparator negative input
0xxxxAIN1
11xxxAIN1
1 0 000 ADC0
1 0 001 ADC1
1 0 010 ADC2
1 0 011 ADC3
1 0 100 ADC4
1 0 101 ADC5
1 0 110 ADC6
1 0 111 ADC7
Bit 76543210
– – – – – – AIN1D AIN0D DIDR1
Read/writeRRRRRRR/WR/W
Initial value00000000