157
CHAPTER 13 A/D CONVERTER
13.4.2 Input voltage and conversion results
The relation between the analog input voltage input to the analog input pins (ANI0 to ANI4) and the A/D conversion
result (stored in the A/D conversion result register (ADCR1)) is shown by the following expression.
ADCR1 = INT (
V
IN
×
256 + 0.5)
AV
REF
or
(ADCR1 – 0.5)
×
AV
REF
≤
V
IN
< (ADCR1 + 0.5)
×
AV
REF
256 256
where,
INT( )
: Function which returns integer part of value in parentheses
V
IN
: Analog input voltage
AV
REF
: AV
REF
pin voltage
ADCR1 : A/D conversion result register (ADCR1) value
Figure 13-7 shows the relation between the analog input voltage and the A/D conversion result.
Figure 13-7. Relation between Analog Input Voltage and A/D Conversion Result
255
254
253
3
2
1
0
A/D conversion result
(ADCR1)
1
512
1
256
3
512
2
256
5
512
3
256
507
512
254
256
509
512
255
256
511
512
1
Input voltage/AV
REF
Содержание mPD780973 Series
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