Rainbow-electronics ATmega163L Manuel d'utilisateur télécharger pdf (Page 95)

ATmega163(L)

The ADC Multiplexer Selection Register - ADMUX

•

Bit 7,6 - REFS1..0: Reference Selection Bits

These bits select the voltage reference for the ADC, as shown in Table 17. If these bits are changed during a conversion,

the change will not go in effect until this conversion is complete (ADIF in ADCSR is set). The user should disregard the first

conversion result after changing these bits to obtain maximum accuracy. The internal voltage reference options may not be

used if an external reference voltage is being applied to the AREF pin.

•

Bit 5 - ADLAR: ADC Left Adjust Result

The ADLAR bit affects the presentation of the ADC conversion result in the ADC data register. If ADLAR is cleared, the

result is right adjusted. If ADLAR is set, the result is left adjusted. Changing the ADLAR bit will affect the ADC data register

immediately, regardless of any ongoing conversions. For a complete description of this bit, see “The ADC Data Register -

ADCL and ADCH” on page 97.

•

Bits 4..0 - MUX4..MUX0: Analog Channel and Gain Selection Bits

The value of these bits selects which combination of analog inputs are connected to the ADC. See Table 41 for details. If

these bits are changed during a conversion, the change will not go in effect until this conversion is complete (ADIF in

ADCSR is set).

Bit 76543210

$07 ($27) REFS1 REFS0 ADLAR MUX4 MUX3 MUX2 MUX1 MUX0 ADMUX

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

Initial value 00000000

Table 40. Voltage Reference Selections for ADC

REFS1 REFS0 Voltage Reference Selection

0 0 AREF, Internal Vref turned off

0 1 AVCC with external capacitor at AREF pin

10Reserved

1 1 Internal 2.56V Voltage Reference with external capacitor at AREF pin

Table 41. Input Channel Selections

MUX4..0 Single-ended Input

00000 ADC0

00001 ADC1

00010 ADC2

00011 ADC3

00100 ADC4

00101 ADC5

00110 ADC6

00111 ADC7

01000..11101

Reserved

11110 1.22V (V

)

11111 0V (AGND)

1 2 ... 90 91 92 93 94 95 96 97 98 99 100 ... 155 156

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Rainbow-electronics ATmega163L Manuel d'utilisateur Page 95

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