IBM nec pd78p081(a2) User Manual
128
CHAPTER 10 A/D CONVERTER
10.4.2 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)
×
≤
V
IN
< (ADCR + 0.5)
×
Where,
INT( ) : Function which returns integer parts of value in parentheses.
V
IN
: Analog input voltage
AV
REF
: AV
REF
pin voltage
ADCR : Value of A/D conversion result register (ADCR)
Figure 10-6 shows the relation between the analog input voltage and the A/D conversion result.
Figure 10-6. Relations between Analog Input Voltage and A/D Conversion Result
V
IN
AV
REF
AV
REF
256
AV
REF
256
1
512
1
256
3
512
2
256
5
512
3
256
507
512
512
254
256
256
509
512
512
255
256
256
511
512
512
1
255
254
253
3
2
1
0
A/D Conversion
Results
(ADCR)
Results
(ADCR)
Input Voltage/AV
REF