Input Voltage And Conversion Results - NEC 78K0 Series User Manual

13.4.2 Input voltage and conversion results

The relationship between the analog input voltage input to the analog input pins (ANI0 to ANI7) and the theoretical
A/D conversion result (stored in the 10-bit A/D conversion result register (ADCR)) is shown by the following
expression.
V
AIN
× 1024 + 0.5)
SAR = INT (
AV
REF
ADCR = SAR × 64
or
ADCR AV
REF
− 0.5) ×
(
64 1024
where, INT( ): Function which returns integer part of value in parentheses
V : Analog input voltage
AIN
AV : AV pin voltage
REF REF
ADCR: A/D conversion result register (ADCR) value
SAR: Successive approximation register
Figure 13-12 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 13-12. Relationship Between Analog Input Voltage and A/D Conversion Result
A/D conversion result
CHAPTER 13 A/D CONVERTER
ADCR AV
≤ V + 0.5) ×
< (
AIN
64 1024
SAR
1023
1022
1021
3
2
1
0
1 1 3
2048 1024 2048
Preliminary User's Manual U17260EJ3V1UD
REF
2 5 3 2043 1022
1024 2048 1024 2048 1024
Input voltage/AV
REF
ADCR
FFC0H
FF80H
FF40H
00C0H
0080H
0040H
0000H
2045 1023 2047 1
2048 1024 2048
317