ATmega88 datasheet(236/340 Pages) ATMEL

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236

7530H–AVR–02/09

ATmega48/88/168 Automotive

20.1

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), MUX2..0 in ADMUX

select the input pin to replace the negative input to the Analog Comparator, as shown in Table

20-2. If ACME is cleared or ADEN is set, AIN1 is applied to the negative input to the Analog

Comparator.

20.1.1

Digital Input Disable Register 1 – DIDR1

• Bit 7..2 – Res: Reserved Bits

These bits are unused bits in the ATmega48/88/168, and will always read as zero.

• 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 20-2.

Analog Comparator Multiplexed Input

ACME

ADEN

MUX2..0

Analog Comparator Negative Input

xxx

AIN1

xxx

AIN1

000

ADC0

001

ADC1

010

ADC2

011

ADC3

100

ADC4

101

ADC5

110

ADC6

111

ADC7

Bit

76543210

––––––

AIN1D

AIN0D

DIDR1

Read/Write

RRRRRR

R/W

Initial Value

00000000

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