Input Voltage And Conversion Results - NEC mPD780973 Series Preliminary User's Manual

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.
V
IN
ADCR1 = INT (
AV
REF
or
AV
REF
(ADCR1 – 0.5) ×
256
where, INT( ) : Function which returns integer part of value in parentheses
V : Analog input voltage
IN
AV : AV
REF REF
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
A/D conversion result
(ADCR1)
CHAPTER 13 A/D CONVERTER
× 256 + 0.5)
≤ V < (ADCR1 + 0.5) ×
IN
pin voltage
255
254
253
3
2
1
0
1 1 3 2
512 256 512 256
AV
REF
256
5 3 507 254 509
512 256 512 256 512
Input voltage/AV
REF
255 511 1
256 512
157