Input Voltage And Conversion Results; Relationship Between Analog Input Voltage And A/D Conversion Result - NEC 78K0 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 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
AV
REF
(ADCR − 0.5) ×
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 13-9 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 13-9. Relationship Between Analog Input Voltage and A/D Conversion Result
A/D conversion result
(ADCR)
288
CHAPTER 13 A/D CONVERTER
AV
≤ V < (ADCR + 0.5) ×
AIN
1024
SAR
1023
1022
1021
3
2
1
0
1 1 3
2048 1024 2048
User's Manual U15947EJ2V0UD
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