Datasheet

ATmega8(L)

2486M–AVR–12/03

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

tive 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 comparator output rise, fall or toggle. A block dia-

gram of the comparator and its surrounding logic is shown in Figure 89.

Figure 89. Analog Comparator Block Diagram

(2)

Notes: 1. See Table 72 on page 192.

2. Refer to “Pin Configurations” on page 2 and Table 28 on page 61 for Analog Compar-

ator pin placement.

Special Function IO Register –

SFIOR

• Bit 3 – 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 Compar-

ator. For a detailed description of this bit, see “Analog Comparator Multiplexed Input” on

page 192.

ACBG

BANDGAP

REFERENCE

ADC MULTIPLEXER

OUTPUT

ACME

ADEN

(1)

Bit 7 6 5 4 3 2 1 0

– – – – ACME PUD PSR2 PSR10 SFIOR

Read/Write R R R R R/W R/W R/W R/W

Initial Value 0 0 0 0 0 0 0 0