Datasheet

217
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
Figure 23-14. Differential measurement range.
ADMUX = 0xFB (ADC3 - ADC2, 1.1V reference, left adjusted result)
Voltage on ADC3 is 300mV, voltage on ADC2 is 500mV.
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 23-2. 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
0
Output Code
0x1FF
0x000
V
REF
Differential Input
Voltage (Volts)
0x3FF
0x200
- V
REF