Cautions For A/D Converter - NEC 78K0 User Manual

(8) Conversion time
This expresses the time since sampling has been started until digital output is obtained.
The sampling time is included in the conversion time in the characteristics table.
(9) Sampling time
This is the time the analog switch is turned on for the analog voltage to be sampled by the sample & hold circuit.

11.6 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 11-18 shows the circuit configuration of series resistor string.
Figure 11-18. 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.
CHAPTER 11 A/D CONVERTER
Sampling
time
Conversion time
AV
REF
P-ch
Series resistor string
AV
SS
User's Manual U16227EJ2V0UD
ADCS
or higher and AV
REF
or lower
SS
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