Cautions For A/D Converter; Circuit Configuration Of Series Resistor String - NEC 78K0 User Manual

13.6 Cautions for A/D Converter

(1) Operating current in standby mode
The A/D converter stops operating in the standby mode. At this time, the operating current can be reduced by
clearing bit 7 (ADCS) of the A/D converter mode register (ADM) to 0.
Figure 13-18 shows the circuit configuration of the series resistor string.
Figure 13-18. Circuit Configuration of Series Resistor String
(2) Input range of ANI0 to ANI7
Observe the rated range of the ANI0 to ANI7 input voltage. If a voltage of AV
(even in the range of absolute maximum ratings) is input to an analog input channel, the converted value of that
channel becomes undefined. In addition, the converted values of the other channels may also be affected.
(3) Conflicting operations
<1> Conflict between A/D conversion result register (ADCR) write and ADCR read by instruction upon the end
of conversion
ADCR read has priority. After the read operation, the new conversion result is written to ADCR.
<2> Conflict between ADCR write and A/D converter mode register (ADM) write or analog input channel
specification register (ADS) write upon the end of conversion
ADM or ADS write has priority. ADCR write is not performed, nor is the conversion end interrupt signal
(INTAD) generated.
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CHAPTER 13 A/D CONVERTER
AV
REF
P-ch
Series resistor string
AV
SS
User's Manual U15947EJ2V0UD
ADCS
REF
*
or higher and AV or lower
SS