ATMEGA163 ATMEL [ATMEL Corporation], ATMEGA163 Datasheet - Page 110

• Manufacturer Part Number: ATMEGA163
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

The ADC Multiplexer Selection
Register – ADMUX
110
ATmega163(L)
• 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.
Table 40. Voltage Reference Selections for ADC
•
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 112.
• 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).
Table 41. Input Channel Selections
Bit
$07 ($27)
Read/Write
Initial Value
MUX4..0
00000
00001
00010
00011
00100
00101
00110
00111
REFS1
Bit 5 – ADLAR: ADC Left Adjust Result
0
0
1
1
REFS0
REFS1
0
1
0
1
R/W
7
0
Voltage Reference Selection
AREF, Internal Vref turned off
AVCC with external capacitor at AREF pin
Reserved
Internal 2.56V Voltage Reference with external capacitor at AREF pin
REFS0
R/W
6
0
ADLAR
R/W
5
0
Single-ended Input
ADC0
ADC1
ADC2
ADC3
ADC4
ADC5
ADC6
ADC7
MUX4
R/W
4
0
MUX3
R/W
3
0
MUX2
R/W
2
0
MUX1
R/W
1
0
MUX0
R/W
0
0
1142E–AVR–02/03
ADMUX