Configuration Of A/D Converter - NEC 78K0S/KU1+ User Manual

Figure 9-2 shows the block diagram of A/D converter.
ANI0/P20/TI000
TOH1
ANI1/P21/TI010/
TO00/INTP0
ANI2/X2/P22
ANI3/X1/P23
2
ADS1 ADS0
Analog input
channel specification
register (ADS)
Cautions 1. In the 78K0S/KU1+, V
sure to connect V
2. In the 78K0S/KU1+, V
When using the A/D converter, stabilize V
9.2

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 I/O 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 V
input signal.
(4) Voltage comparator
The voltage comparator compares the sampled analog input voltage and the output voltage of the D/A converter.
150
CHAPTER 9 A/D CONVERTER
Figure 9-2. Block Diagram of A/D Converter
Sample & hold circuit
V
SS
Controller
3
ADCS FR2 FR1 FR0 ADCE
A/D converter mode
register (ADM)
Internal bus
functions alternately as the ground potential of the A/D converter. Be
SS
to a stabilized GND (= 0 V).
SS
functions alternately as the A/D converter reference voltage input.
DD
and V , and generates a voltage to be compared with the analog
DD SS
User's Manual U18172EJ2V0UD
Voltage comparator
Successive
approximation
register (SAR)
A/D conversion result register
(ADCR, ADCRH)
at the supply voltage used (2.7 to 5.5 V).
DD
V
DD
D/A converter
V
SS
INTAD