AT90USB646 datasheet(304/456 Pages) ATMEL

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7593L–AVR–09/12

AT90USB64/128

25. Analog Comparator

The Analog Comparator compares the input values on the positive pin AIN0 and negative pin

AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on the negative pin

AIN1, the Analog Comparator output, ACO, is set. The comparator’s output can be set to trigger

the Timer/Counter1 Input Capture function. In addition, the comparator can trigger a separate

interrupt, exclusive to the Analog Comparator. The user can select Interrupt triggering on com-

parator output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is

shown in Figure 25-1

The Power Reduction ADC bit, PRADC, in “PRR0 – Power Reduction Register 0” on page 54

must be disabled by writing a logical zero to be able to use the ADC input MUX.

Figure 25-1. Analog Comparator block diagram

(2).

Notes:

1. See Table 25-2 on page 306.

2. Refer to Figure 1-1 on page 3 and Table 11-6 on page 79 for Analog Comparator pin

placement.

25.0.1

ADCSRB – ADC Control and Status Register B

• Bit 6 – ACME: Analog Comparator Multiplexer Enable

When this bit is written logic one and the ADC is switched off (ADEN in ADCSRA is zero), the

ADC multiplexer selects the negative input to the Analog Comparator. When this bit is written

logic zero, AIN1 is applied to the negative input of the Analog Comparator. For a detailed

description of this bit, see “Analog Comparator multiplexed input” on page 306.

25.0.2

ACSR – Analog Comparator Control and Status Register

ACBG

BANDGAP

REFERENCE

ADC MULTIPLEXER

OUTPUT

ACME

ADEN

(1)

Bit

3210

–ACME

–

ADTS2

ADTS1

ADTS0

ADCSRB

Read/write

R/W

Initial value

0000

Bit

7654

ACD

ACBG

ACO

ACI

ACIE

ACIC

ACIS1

ACIS0

ACSR

Read/write

R/W

Initial value

N/A

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