NEC PD78F9488 - Manual (Page 179)

CHAPTER 10 10-BIT A/D CONVERTER
User’s Manual U15331EJ4V1UD
179
Figure 10-4. Basic Operation of 10-Bit A/D Converter
Conversion
time
Sampling
time
Sampling A/D conversion
Undefined
Conversion
result
Conversion
result
A/D converter
operation
SAR
ADCRL0
INTAD0
A/D conversion continues until bit 7 (ADCS0) of A/D converter mode register 0 (ADML0) is reset (0) by software.
If an attempt is made to write to ADML0 or analog input channel specification register 0 (ADS0) during A/D
conversion, the A/D conversion in progress is canceled. In this case, A/D conversion is restarted from the beginning,
if ADCS0 is set (1).
RESET input clears A/D conversion result register 0 (ADCRL0) to 0000H.
10.4.2 Input voltage and conversion result
The relationship between the analog input voltage at the analog input pins (ANI0 to ANI7) and the A/D conversion
result (A/D conversion result register 0 (ADCRL0)) is represented by:
ADCRL0 = INT (
× 1,024 + 0.5)
or
(ADCRL0
− 0.5) × ≤ V
IN
< (ADCRL0 + 0.5) ×
INT( ):
Function that returns the integer part of a parenthesized value
V
IN
: Analog input voltage
AV
DD
: Supply voltage for the A/D converter
ADCRL0: Value in A/D conversion result register 0 (ADCRL0)
Figure 10-5 shows the relationship between the analog input voltage and the A/D conversion result.
V
IN
AV
DD
AV
DD
1,024
AV
DD
1,024