AT90USB64/128
24.1 Analog Comparator Multiplexed Input
It is possible to select any of the ADC15..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 24-2. If ACME is cleared or ADEN is set, AIN1 is applied to the negative input to the Ana-
log Comparator.
Table 24-2. Analog Comparator Mulitiplexed Input
ACME
ADEN
MUX2..0
xxx
Analog Comparator Negative Input
0
1
1
1
1
1
1
1
1
1
x
1
0
0
0
0
0
0
0
0
AIN1
xxx
AIN1
000
001
010
011
ADC0
ADC1
ADC2
ADC3
ADC4
ADC5
ADC6
ADC7
100
101
110
111
24.1.1
Digital Input Disable Register 1 – DIDR1
Bit
7
–
R
0
6
–
R
0
5
–
R
0
4
–
R
0
3
–
R
0
2
–
R
0
1
0
AIN1D
R/W
0
AIN0D
R/W
0
DIDR1
Read/Write
Initial Value
• 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.
315
7593A–AVR–02/06
ATMEL [ ATMEL ]
