Analog Comparator Multiplexed Input - Atmel ATtiny25 Manual

17.3

Analog Comparator Multiplexed Input

17.3.1 Digital Input Disable Register 0 – DIDR0
ATtiny25/45/85
110
It is possible to select any of the ADC3..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), MUX1..0 in ADMUX
select the input pin to replace the negative input to the Analog Comparator, as shown in
17-2. If ACME is cleared or ADEN is set, AIN1 is applied to the negative input to the Analog
Comparator.
Table 17-2. Analog Comparator Multiplexed Input
ACME ADEN
0 x
1 1
1 0
1 0
1 0
1 0
Bit 7
–
Read/Write R
Initial Value 0
• Bits 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.
MUX1..0 Analog Comparator Negative Input
xx AIN1
xx AIN1
00 ADC0
01 ADC1
10 ADC2
11 ADC3
6 5 4
– ADC0D ADC2D ADC3D
R R/W R/W R/W
0 0 0
3 2 1
ADC1D AIN1D AIN0D
R/W R/W R/W
0 0 0
Table
0
DIDR0
0
7598H–AVR–07/09