8-bit AVR Microcontroller

ADC Multiplexer Selection Register

Name:
ADMUX
Offset:
0x1B
Reset:
0x00
Access:
-
Bit76543210
REFSn[1:0]MUXn[2:0]
AccessR/WR/WR/WR/WR/W
Reset00000

Bits 7:6 – REFSn: Reference Selection [n = 1:0]

Reference Selection [n = 1:0]

These bits select the voltage reference for the ADC. If these bits are changed during a conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSRA is set).

Table 2. ADC Voltage Reference Selection
REFS[1:0] Voltage Reference Selection
00 Vcc
01 Internal 1.1V reference
10 Internal 2.2V reference
11 Internal 4.3V reference

Bits 2:0 – MUXn: Analog Channel Selection [n = 2:0]

Analog Channel Selection [n = 2:0]

The value of these bits selects which analog inputs are connected to the ADC. If these bits are changed during a conversion, the change will not go in effect until this conversion is complete (ADCSRA.ADIF is set).

Table 1. Input Channel Selection
MUX[2:0] Single Ended Input Pin name
000 ADC0 PA[0]
001 ADC1 PA[1]
010 ADC2 PA[5]
011 ADC3 PA[6]
100 ADC4 PB[0]
101 ADC5 PB[1]
110 ADC6 PB[2]
111 ADC7 PB[3]