Datasheet

228
8018P–AVR–08/10
ATmega169P
ADMUX = 0xFB (ADC3 - ADC2, 1.1V reference, left adjusted result).
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
ADCR = 512 × (300 - 500) / 1100 = -93 = 0x3A3.
ADCL will thus read 0xC0, and ADCH will read 0xD8. Writing zero to ADLAR right adjusts the
result: ADCL = 0xA3, ADCH = 0x03.
Table 22-2. Correlation Between Input Voltage and Output Codes
V
ADCn
Read Code Corresponding Decimal Value
V
ADCm
+ V
REF
0x1FF 511
V
ADCm
+
511
/
512
V
REF
0x1FF 511
V
ADCm
+
510
/
512
V
REF
0x1FE 510
... ... ...
V
ADCm
+
1
/
512
V
REF
0x001 1
V
ADCm
0x000 0
V
ADCm
-
1
/
512
V
REF
0x3FF -1
... ... ...
V
ADCm
-
511
/
512
V
REF
0x201 -511
V
ADCm
- V
REF
0x200 -512