Rainbow-electronics ATmega128RFA1 Manuel d'utilisateur télécharger pdf (Page 407)

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8266A-MCU Wireless-12/09

ATmega128RFA1

26 AC – 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 comparator output rise, fall or toggle. A block

diagram of the comparator and its surrounding logic is shown in Figure 26-1 below.

The Power Reduction ADC bit PRADC in PRR0 (see "PRR0 – Power Reduction

Register0" on page 167) must be disabled by writing a logical zero to be able to use the

ADC input multiplexer.

Figure 26-1. Analog Comparator Block Diagram

Note:

1. See Table 26-1 below.

2. Refer to Figure 1-1 on page 2 and Table 14-9 on page 197 for Analog Comparator

pin placement.

26.1 Analog Comparator Multiplexed Input

It is possible to select any of the ADC7:0 pins as the negative input of the Analog

Comparator. 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 and MUX2:0 in ADMUX select the input pin to replace the negative input

to the Analog Comparator, as shown in Table 26-1 below. If ACME is cleared or ADEN

is set, AIN1 is applied to the negative input to the Analog Comparator.

Table 26-1. Analog Comparator Multiplexed Input

ACME ADEN MUX5 MUX2:0 Analog Comparator Negative Input

0 x x xxx AIN1

1 1 x xxx AIN1

1 0 0 000 ADC0

1 0 0 001 ADC1

1 0 0 010 ADC2

1 0 0 011 ADC3

1 0 0 100 ADC4

1 2 ... 402 403 404 405 406 407 408 409 410 411 412 ... 523 524

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Rainbow-electronics ATmega128RFA1 Manuel d'utilisateur Page 407

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