ATtiny261-ESSZ datasheet(140/227 Pages) ATMEL

140 / 227 page

140

7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

18. AC – Analog Comparator

The Analog Comparator compares the input values on the selectable positive pin (AIN0, AIN1 or

AIN2) and selectable negative pin (AIN0, AIN1 or AIN2). When the voltage on the positive pin is

higher than the voltage on the negative pin, the Analog Comparator output, ACO, is set. The

comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The user can

select Interrupt triggering on comparator output rise, fall or toggle. A block diagram of the com-

parator and its surrounding logic is shown in Figure 18-1.

Figure 18-1. Analog Comparator Block Diagram

(2)

Notes:

1. See Table 18-2 on page 142.

2. Refer to Figure 1-1 on page 2 and Table 12.3.2 on page 66 for Analog Comparator pin

placement.

18.1

18.1.1

ACSRA – Analog Comparator Control and Status Register A

• Bit 7 – ACD: Analog Comparator Disable

When this bit is written logic one, the power to the Analog Comparator is switched off. This bit

can be set at any time to turn off the Analog Comparator. This will reduce power consumption in

Active and Idle mode. When changing the ACD bit, the Analog Comparator Interrupt must be

disabled by clearing the ACIE bit in ACSRA. Otherwise an interrupt can occur when the bit is

changed.

• Bit 6 – ACBG: Analog Comparator Bandgap Select

When this bit is set an internal 1.1V reference voltage replaces the positive input to the Analog

Comparator. The selection of the internal voltage reference is done by writing the REFS2..0 bits

in ADMUX register. When this bit is cleared, AIN0, AIN1 or AIN2 depending on the ACM2..0 bits

is applied to the positive input of the analog comparator.

ACBG

BANDGAP

REFERENCE

ADC MULTIPLEXER

OUTPUT

ACME

ADEN

(1)

MUX

AIN0

AIN1

AIN2

ACM2..1

Bit

76543210

0x08 (0x28)

ACD

ACBG

ACO

ACI

ACIE

ACME

ACIS1

ACIS0

ACSRA

Read/Write

R/W

Initial Value

N/A

00000

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