CHAPTER 10 8-BIT A/D CONVERTER (µPD789426 AND 789446 SUBSERIES)
10.5 Cautions Related to 8-Bit A/D Converter
(1) Current consumption in standby mode
In standby mode, the A/D converter stops operation. Stopping conversion (bit 7 (ADCS0) of A/D converter
mode register 0 (ADM0) = 0) can reduce the current consumption.
Figure 10-7 shows how to reduce the current consumption in standby mode.
Figure 10-7. How to Reduce Current Consumption in Standby Mode
AVDD
ADCS0
P-ch
Series resistor string
AVSS
(2) Input range for pins ANI0 to ANI5
Be sure to keep the input voltage at ANI0 to ANI5 within the rating. If a voltage not lower than AVDD or not
higher than AVSS (even within the absolute maximum rating) is input into a conversion channel, the
conversion output of the channel becomes undefined, which may affect the conversion output of the other
channels.
(3) Conflict
<1> Conflict between writing to A/D conversion result register 0 (ADCR0) at the end of conversion and
reading from ADCR0 using instruction
Reading from ADCR0 takes precedence. After reading, the new conversion result is written to ADCR0.
<2> Conflict between writing to ADCR0 at the end of conversion and writing to A/D converter mode register 0
(ADM0) or analog input channel specification register 0 (ADS0)
Writing to ADM0 or ADS0 takes precedence. ADCR0 is not written to. No A/D conversion end interrupt
request signal (INTAD0) is generated.
(4) Conversion result immediately after start of A/D conversion
The first A/D conversion value immediately after A/D conversion has been started is undefined. Poll the
A/D conversion end interrupt request (INTAD0) and drop the first conversion result.
User’s Manual U15075EJ1V0UM00
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NEC [ NEC ]
