ATtiny261-ESSZ datasheet(141/227 Pages) ATMEL

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141

7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

• Bit 5 – ACO: Analog Comparator Output

The output of the Analog Comparator is synchronized and then directly connected to ACO. The

synchronization introduces a delay of 1 - 2 clock cycles.

• Bit 4 – ACI: Analog Comparator Interrupt Flag

This bit is set by hardware when a comparator output event triggers the interrupt mode defined

by ACIS1 and ACIS0. The Analog Comparator interrupt routine is executed if the ACIE bit is set

and the I-bit in SREG is set. ACI is cleared by hardware when executing the corresponding inter-

rupt handling vector. Alternatively, ACI is cleared by writing a logic one to the flag.

• Bit 3 – ACIE: Analog Comparator Interrupt Enable

When the ACIE bit is written logic one and the I-bit in the Status Register is set, the Analog Com-

parator interrupt is activated. When written logic zero, the interrupt is disabled.

• Bit 2 – 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 142.

• Bits 1, 0 – ACIS1, ACIS0: Analog Comparator Interrupt Mode Select

These bits determine which comparator events that trigger the Analog Comparator interrupt. The

different settings are shown in Table 18-1.

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.

18.2

Analog Comparator Multiplexed Input

When the Analog to Digital Converter (ADC) is configured as single ended input channel, it is

possible to select any of the ADC10..0 pins to replace the negative input to the Analog Compar-

ator. 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), MUX5..0 in ADMUX

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

18-2. If ACME is cleared or ADEN is set, either AIN0, AIN1 or AIN2 is applied to the negative

input to the Analog Comparator.

Table 18-1.

ACIS1/ACIS0 Settings

ACIS1

ACIS0

Interrupt Mode

Comparator Interrupt on Output Toggle.

Reserved

Comparator Interrupt on Falling Output Edge.

Comparator Interrupt on Rising Output Edge.

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