CHAPTER 10 A/D CONVERTERUser’s Manual U16898EJ3V0UD158Figure 10-2 shows the block diagram of A/D converter.Figure 10-2. Block Diagram of A/D ConverterAVREFVSSINTAD2ADS1 ADS0VSSANI0/P20ANI1/P21ANI2/P22ANI3/P23ADCS FR2 FR1 ADCEFR03Sample & hold circuitVoltage comparatorControllerA/D conversion result register(ADCR, ADCRH)Analog inputchannel specificationregister (ADS)A/D converter moderegister (ADM)Internal busSuccessiveapproximationregister (SAR)SelectorD/A converterCaution In the 78K0S/KA1+, VSS functions alternately as the ground potential of the A/D converter. Besure to connect VSS to a stabilized GND (= 0 V).10.2 Configuration of A/D ConverterThe A/D converter consists of the following hardware.(1) ANI0 to ANI3 pinsThese are the analog input pins of the 4-channel A/D converter. They input analog signals to be converted intodigital signals. Pins other than the one selected as the analog input pin by the analog input channel specificationregister (ADS) can be used as input port pins.(2) Sample & hold circuitThe sample & hold circuit samples the input signal of the analog input pin selected by the selector when A/Dconversion is started, and holds the sampled analog input voltage value during A/D conversion.(3) D/A converterThe D/A converter is connected between AV REF and VSS , and generates a voltage to be compared with theanalog input signal.(4) Voltage comparatorThe voltage comparator compares the sampled analog input voltage and the output voltage of the D/A converter.
