Chapter 11 A/D Converter; Functions Of A/D Converter - NEC 78K0 User Manual

11.1 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.
comparative condition has been matched.
ANI0/P20
ANI1/P21
ANI2/P22
ANI3/P23
ANI4/P24
ANI5/P25
ANI6/P26
ANI7/P27
3
ADS2 ADS1 ADS0
Analog input channel
specification register
(ADS)

CHAPTER 11 A/D CONVERTER

Figure 11-1. Block Diagram of A/D Converter
Sample & hold circuit
AV
SS
Controller
ADCS FR2 FR1 FR0
A/D converter mode
register (ADM)
Internal bus
User's Manual U16227EJ2V0UD
INTAD is generated only when a
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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