User’s Manual U16899EJ2V0UD
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CHAPTER 12 A/D CONVERTER
12.1 Functions of A/D Converter
The A/D converter converts an analog input signal into a digital value, and consists of up to eight channels (ANI0 to
ANI7) 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
ANI7. Each time an A/D conversion operation ends, an interrupt request (INTAD) is generated.
(2) Power-fail detection function
This function is used to detect a voltage drop in a battery. The A/D conversion result (ADCR register value) and
power-fail comparison threshold register (PFT) value are compared. INTAD is generated only when a
comparative condition has been matched.
Figure 12-1. Block Diagram of A/D Converter
AV
REF
AV
SS
INTAD
ADCS bit
3
ADS2
ADS1
ADS0
ADCS
FR2
FR1
ADCE
FR0
Sample & hold circuit
AV
SS
Voltage comparator
Controller
A/D conversion result
register (ADCR)
Power-fail comparison
threshold register (PFT)
Analog input channel
specification register
(ADS)
A/D converter mode
register (ADM)
PFEN
PFCM
Power-fail comparison
mode register (PFM)
Internal bus
Comparator
ANI0/P20
ANI1/P21
ANI2/P22
ANI3/P23
ANI4/P24
ANI5/P25
ANI6/P26
ANI7/P27
Successive
approximation
register (SAR)
Selector
Tap selector