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10.1 Function of A/D Converter
The A/D converter converts an analog input signal into a digital value, and consists of up to four channels (ANI0 to
ANI3) with a resolution of 10 bits.
The A/D converter has the following two functions.
(1) 10-bit resolution A/D conversion
10-bit resolution A/D conversion is carried out repeatedly for one channel selected from analog inputs ANI0 to
ANI3. Each time an A/D conversion operation ends, an interrupt request (INTAD) is generated.
(2) Power-fail detection function
This function is to detect a voltage drop in a battery. The values of the A/D conversion result (ADCR register
value) and power-fail comparison threshold register (PFT) are compared. INTAD is generated only when a
comparative condition has been matched.
ANI0/P20
ANI1/P21
ANI2/P22
ANI3/P23
2
ADS1
ADS0
Analog input channel
specification register
(ADS)
182
CHAPTER 10 A/D CONVERTER
Figure 10-1. Block Diagram of A/D Converter
Sample & hold circuit
AV
SS
Controller
ADCS
FR2
FR1
FR0
A/D converter mode
register (ADM)
Internal bus
Preliminary User's Manual U16846EJ1V0UD
Voltage comparator
Successive
approximation
register (SAR)
A/D conversion result
register (ADCR)
ADCE
PFEN PFCM
ADCS bit
Comparator
Power-fail comparison
threshold register (PFT)
Power-fail comparison
mode register (PFM)
AV
REF
AV
SS
INTAD
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