AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 329

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

25.8
25.8.1
7593A–AVR–02/06
ADC Register Description
ADC Multiplexer Selection Register – ADMUX
Table 25-2.
Example 1:
Example 2:
• Bit 7:6 – REFS1:0: Reference Selection Bits
These bits select the voltage reference for the ADC, as shown in
changed during a conversion, the change will not go in effect until this conversion is complete
Bit
Read/Write
Initial Value
V
V
V
...
V
V
V
...
V
V
V
ADCn
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
– ADMUX = 0xED (ADC3 - ADC2, 10x gain, 2.56V reference, left adjusted result)
– Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
– ADCR = 512 * 10 * (300 - 500) / 2560 = -400 = 0x270
– ADCL will thus read 0x00, and ADCH will read 0x9C.
– ADMUX = 0xFB (ADC3 - ADC2, 1x gain, 2.56V reference, left adjusted result)
– Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
– ADCR = 512 * 1 * (300 - 500) / 2560 = -41 = 0x029.
– ADCL will thus read 0x40, and ADCH will read 0x0A.
+ 0.999 V
+ 0.998 V
+ 0.001 V
- 0.001 V
- 0.999 V
- V
Writing zero to ADLAR right adjusts the result: ADCL = 0x70, ADCH = 0x02.
Writing zero to ADLAR right adjusts the result: ADCL = 0x00, ADCH = 0x29.
+ V
REF
REF
/GAIN
REFS1
/GAIN
Correlation Between Input Voltage and Output Codes
R/W
REF
REF
7
0
REF
REF
REF
/GAIN
/GAIN
/GAIN
/GAIN
/GAIN
REFS0
R/W
6
0
ADLAR
R/W
Read code
5
0
0x1FE
0x1FF
0x1FF
0x001
0x000
0x3FF
0x201
0x200
...
...
MUX4
R/W
4
0
Corresponding decimal value
511
511
510
...
1
0
-1
...
-511
-512
MUX3
R/W
3
0
MUX2
R/W
2
0
MUX1
R/W
AT90USB64/128
1
0
Table
MUX0
R/W
0
0
25-3. If these bits are
ADMUX
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