ATMEGA649 datasheet(202/375 Pages) ATMEL

202 / 375 page

202

ATmega329/3290/649/6490

2552H–AVR–11/06

Analog Comparator

Multiplexed Input

It is possible to select any of the ADC7..0 pins to replace the negative input to the Ana-

log Comparator. 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 Ana-

log Comparator, as shown in Table 92. If ACME is cleared or ADEN is set, AIN1 is

applied to the negative input to the Analog Comparator.

DIDR1 – Digital Input Disable

• 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 corresponding 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 written logic one to reduce power consumption in the digital

input buffer.

Table 92. 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

7654

321

(0x7F)

–

AIN1D

AIN0D

DIDR1

Read/Write

RRRR

R/W

Initial Value

0000

000

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