Input Voltage And Conversion Results - NEC mPD178054 Series User Manual

10.4.2 Input voltage and conversion results

The relationship between the analog input voltage input to the analog input pins (ANI0 to ANI5) and the A/D
conversion result (the value stored in A/D conversion result register 3 (ADCR3) is shown by the following expression.
V
IN
ADCR3 = INT (
V
DD
or
V
(ADCR3 – 0.5) ×
256
Remark INT( ): Function which returns integer parts of value in parentheses.
V : Analog input voltage
IN
V : V
DD DD
ADCR3: A/D conversion result register 3 (ADCR3) value
Figure 10-6 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 10-6. Relationship Between Analog Input Voltage and A/D Conversion Result
255
254
A/D conversion
253
results (ADCR3)
138
CHAPTER 10 A/D CONVERTER
× 256 + 0.5)
DD
≤ V < (ADCR3 + 0.5) ×
IN
pin voltage
3
2
1
0
1 1 3 2 5
512 256 512 256 512
User's Manual U15104EJ2V0UD
V
DD
256
3 507 254 509 255
256 512 256 512 256
Input voltage/V
DD
511
1
512