210
Atmel ATmega16/32/64/M1/C1 [DATASHEET]
7647K–AVR–12/13
TS_Offset is the signed twos complement 7-bit temperature sensor offset reading stored as previously in the signature row at
address 0x0005.
See section 24.7.10 in the ATmega32M1 Automotive datasheet for details of reading the signature row.
18.9
ADC Register Description
The ADC of the ATmega16/32/64/M1/C1 is controlled through 3 different registers. The ADCSRA and The ADCSRB registers
which are the ADC control and status registers, and the ADMUX which allows to select the Vref source and the channel to be
converted.
The conversion result is stored on ADCH and ADCL register which contain respectively the most significant bits and the less
significant bits.
18.9.1 ADC Multiplexer Register – ADMUX
Bit 7, 6 – REFS1, 0: ADC Vref Selection Bits
These 2 bits determine the voltage reference for the ADC.
If bits REFS1 and REFS0 are changed during a conversion, the change will not take effect until this conversion is complete (it
means while the ADIF bit in ADCSRA register is set).
In case the internal Vref is selected, it is turned ON as soon as an analog feature needed it is set.
Bit 5 – ADLAR: ADC Left Adjust Result
Set this bit to left adjust the ADC result.
Clear it to right adjust the ADC result.
The ADLAR bit affects the configuration of the ADC result data registers. Changing this bit affects the ADC data registers
Bit 4, 2, 1, 0 – MUX4, MUX3, MUX2, MUX1, MUX0: ADC Channel Selection Bits
These 4 bits determine which analog inputs are connected to the ADC input. The different setting are shown in
Table 18-5 onBit
7
6
5
4
3210
REFS1
REFS0
ADLAR
MUX4
MUX3
MUX2
MUX1
MUX0
ADMUX
Read/Write
R/W
-
R/W
Initial Value
0
0000
Table 18-4. ADC Voltage Reference Selection
AREFEN
ISRCEN
REFS1
REFS0
Description
1
0
External Vref on AREF pin, Internal Vref is switched off
1
0
1
AVcc with external capacitor connected on the AREF pin
0
1
AVcc (no external capacitor connected on the AREF pin)
1
0
1
0
Reserved
1
0
1
Internal 2.56V reference voltage with external capacitor connected on
the AREF pin
0
x
1
Internal 2.56V reference voltage