ATmega16U4 datasheet(292/408 Pages) ATMEL

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292

7766D–AVR–01/09

ATmega16U4/ATmega32U4

When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be disabled by

clearing its Interrupt Enable bit in the ACSR Register. Otherwise an interrupt can occur when the

bits are changed.

23.1

Analog Comparator Multiplexed Input

It is possible to select any of the ADC13..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 23-2. If ACME is cleared or ADEN is set, the Bandgap reference is applied to the negative

input to the Analog Comparator.

23.1.1

Digital Input Disable Register 1 – DIDR1

• Bit 0 – AIN0D: AIN0 Digital Input Disable

When this bit is written logic one, the digital input buffer on the AIN0 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 AIN0 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 23-2.

Analog Comparator Multiplexed Input

ACME

ADEN

MUX2..0

Analog Comparator Negative Input

xxx

Bandgap Ref.

xxx

Bandgap Ref.

000

ADC0

001

ADC1

010

N/A

011

100

ADC4

101

ADC5

110

ADC6

111

ADC7

Bit

7654

–

AIN0D

DIDR1

Read/Write

RRRR

R/W

Initial Value

0000

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