275
CHAPTER 14 A/D CONVERTER
14.4.2 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 A/D conversion result register (ADCR)) is shown by the following expression.
ADCR = INT ( × 256 + 0.5)
or
(ADCR – 0.5) ×≤ VIN < (ADCR + 0.5) ×
Where, INT( ) : Function which returns integer parts of value in parentheses.
VIN : Analog input voltage
AVREF0 : AVREF0 pin voltage
ADCR : Value of A/D conversion result register (ADCR)
Figure 14-7 shows the relation between the analog input voltage and the A/D conversion result.
Figure 14-7. Relations between Analog Input Voltage and A/D Conversion Result
VIN
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