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12.5 A/D Converter Cautions
(1) Current consumption in standby mode
A/D converter stops operating in the standby mode. At this time, current consumption can be reduced by setting
bit 7 (ADCS1) of the A/D converter mode register (ADM1) to 0 to stop conversion.
Figure 12-10 shows how to reduce the current consumption in the standby mode.
Figure 12-10. Example of Method of Reducing Current Consumption in Standby Mode
(2) Input range of ANI0 to ANI4
Keep the input voltage of ANI0 to ANI4 within the rated range. If a voltage outside the rated range is input, the
conversion value of that channel is undefined, and the values of the other channels may also be affected.
(3) Contending operations
<1> Contention between A/D conversion result register (ADCR1) write and ADCR1 read by instruction
upon the end of conversion
ADCR1 read is given priority. After the read operation, the new conversion result is written to ADCR1.
<2> Contention between ADCR1 write and A/D converter mode register (ADM1) write or analog input
channel specification register (ADS1) write upon the end of conversion
ADM1 or ADS1 write is given priority. ADCR1 write is not performed, nor is the conversion end interrupt
signal (INTAD) generated.
<3> If the A/D converter mode register (ADM1) or analog input channel specification register (ADS1) is written
as soon as the A/D conversion end interrupt (INTAD) has occurred, the contents of the A/D conversion
result register (ADCR1) will be undefined.
After an A/D conversion operation has been completed, therefore, read ADCR1 before writing data to ADM
or ADS1.
(4) Starting conversion
The first A/D conversion result after A/D conversion has been started by setting bit 7 (ADCS1) of the A/D
conversion mode register (ADM1) to "1" may differ from the expected value.
Therefore, do not use the first conversion result immediately after A/D conversion has been started.
CHAPTER 12 A/D CONVERTER
AV
REF
P-ch
Series resistor string
AV
SS
Preliminary User's Manual U14581EJ3V0UM00
ADCS1
165
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