Input Voltage And Conversion Results - NEC mPD780344 Series User Manual

CHAPTER 12 8-BIT A/D CONVERTER ( µ PD780344, 780344Y SUBSERIES)

12.4.2 Input voltage and conversion results

The relationship between the analog voltage input to the analog input pins (ANI0 to ANI7) and the logical A/D
conversion result (stored in A/D conversion result register 1 (ADCR1)) is shown by the following expression.
V
IN
ADCR1 = INT (
AV
DD
or
AV
(ADCR1 – 0.5) ×
256
where, INT( ): Function which returns integer part of value in parentheses
V : Analog input voltage
AIN
AV : AV
DD DD
ADCR1: A/D conversion result register 1 (ADCR1) value
Figure 12-6 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 12-6. Relationship Between Analog Input Voltage and A/D Conversion Result
A/D conversion result
(ADCR1)
232
× 256 + 0.5)
DD
≤ V < (ADCR1 + 0.5) ×
AIN
pin voltage
255
254
253
3
2
1
0
1 1 3
512 256 512
User's Manual U15798EJ2V0UD
AV
DD
256
2 5 3 507 254
256 512 256 512 256
Input voltage/AV
DD
509 255 511 1
512 256 512