Datasheet

CHAPTER 12 10-BIT SUCCESSIVE APPROXIMATION TYPE A/D CONVERTER ( μ PD78F041x only)
User’s Manual U18698EJ1V0UD
304
12.4.2 Input voltage and conversion results
The relationship between the analog input voltage input to the analog input pins (ANI0 to ANI5) and the theoretical
A/D conversion result (stored in the 10-bit A/D conversion result register (ADCR)) is shown by the following
expression.
SAR = INT ( × 1024 + 0.5)
ADCR = SAR × 64
or
( − 0.5) × ≤ V
AIN < ( + 0.5) ×
where, INT( ): Function which returns integer part of value in parentheses
V
AIN: Analog input voltage
AV
REF: AVREF pin voltage
ADCR: A/D conversion result register (ADCR) value
SAR: Successive approximation register
Figure 12-12 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 12-12. Relationship Between Analog Input Voltage and A/D Conversion Result
1023
1022
1021
3
2
1
0
FFC0H
FF80H
FF40H
00C0H
0080H
0040H
0000H
A/D conversion result
SAR ADCR
1
2048
1
1024
3
2048
2
1024
5
2048
Input voltage/AV
REF
3
1024
2043
2048
1022
1024
2045
2048
1023
1024
2047
2048
1
V
AIN
AV
REF
AVREF
1024
AVREF
1024
ADCR
64
ADCR
64