CHAPTER 10 A/D CONVERTER
User’s Manual U16898EJ3V0UD
158
Figure 10-2 shows the block diagram of A/D converter.
Figure 10-2. Block Diagram of A/D Converter
AV
REF
V
SS
INTAD
2
ADS1
ADS0
V
SS
ANI0/P20
ANI1/P21
ANI2/P22
ANI3/P23
ADCS
FR2
FR1
ADCE
FR0
3
Sample & hold circuit
Voltage comparator
Controller
A/D conversion result register
(ADCR, ADCRH)
Analog input
channel specification
register (ADS)
A/D converter mode
register (ADM)
Internal bus
Successive
approximation
register (SAR)
Selector
D/A converter
Caution In the 78K0S/KA1+, V
SS
functions alternately as the ground potential of the A/D converter. Be
sure to connect V
SS
to a stabilized GND (= 0 V).
10.2 Configuration of A/D Converter
The A/D converter consists of the following hardware.
(1) ANI0 to ANI3 pins
These are the analog input pins of the 4-channel A/D converter. They input analog signals to be converted into
digital signals. Pins other than the one selected as the analog input pin by the analog input channel specification
register (ADS) can be used as input port pins.
(2) Sample & hold circuit
The sample & hold circuit samples the input signal of the analog input pin selected by the selector when A/D
conversion is started, and holds the sampled analog input voltage value during A/D conversion.
(3) D/A converter
The D/A converter is connected between AV
REF
and V
SS
, and generates a voltage to be compared with the
analog input signal.
(4) Voltage comparator
The voltage comparator compares the sampled analog input voltage and the output voltage of the D/A converter.