ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 204

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

204
ATmega325/3250/645/6450
Figure 96. Differential Measurement Range
Table 86. Correlation Between Input Voltage and Output Codes
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.
V
V
V
...
V
V
V
...
V
V
V
ADCn
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
- V
REF
+
+
+
-
-
- V
+ V
1
511
511
510
1
/
/
512
REF
512
REF
/
/
/
512
512
512
V
V
REF
V
REF
V
V
REF
REF
REF
Read Code
0x1FF
0x1FF
0x1FE
...
0x001
0x000
0x3FF
...
0x201
0x200
Output Code
0x3FF
0x1FF
0x000
0x200
0
Corresponding Decimal Value
-511
-512
511
511
510
-1
...
...
1
0
V
REF
Differential Input
Voltage (Volts)
2570A–AVR–09/04