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CHAPTER 15 A/D CONVERTER
15.4.2 Input voltage and conversion results
The relation between the analog input voltage input to the analog input pins (ANI0 to ANI7) and the A/D conversion
result (the value stored in ADCR) is shown by the following expression.
ADCR = INT ( x 256 + 0.5)
or
(ADCR – 0.5) x ≤ V
IN < (ADCR + 0.5) x
Where, INT( ) : Function which returns integer parts of value in parentheses.
V
IN : Analog input voltage
AVREF0 : AVREF0 pin voltage
ADCR : A/D conversion result register (ADCR)
Figure 15-6 shows the relation between the analog input voltage and the A/D conversion result.
Figure 15-6. Relationships between Analog Input Voltage and A/D Conversion Result
V
IN
AVREF0
AVREF0
256
AVREF0
256
1
512
1
256
3
512
2
256
5
512
3
256
507
512
254
256
509
512
255
256
511
512
1
255
254
253
3
2
1
0
A/D Conversion
Results
(ADCR)
Input Voltage/AV
REF0