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CHAPTER 12 8-BIT A/D CONVERTER ( µ PD780344, 780344Y SUBSERIES)
12.6 A/D Converter Cautions
(1) Power consumption in standby mode
The A/D converter stops operating in the standby mode. At this time, the power consumption can be reduced
by setting bit 7 (ADCS0) of A/D converter mode register 0 (ADM0) to 0.
Figure 12-11 shows the circuit configuration of the series resistor string.
Figure 12-11. Example of Series Resistor String Circuit Configuration
(2) Input range of ANI0 to ANI7
The input voltages of ANI0 to ANI7 should be within the specification range. In particular, if a voltage higher
than or equal to AV
or lower than or equal to AV
DD
the conversion value of that channel will be undefined and the conversion values of other channels may also
be affected.
(3) Conflicting operations
<1> Conflict between A/D conversion result register 1 (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> Conflict between ADCR1 write and external trigger signal input upon the end of conversion
The external trigger signal is not accepted during A/D conversion. Therefore, the external trigger signal
is not accepted during ADCR1 write.
<3> Conflict between ADCR1 write and A/D converter mode register 0 (ADM0) write or analog input channel
specification register 0 (ADS0) write upon the end of conversion
ADM0 or ADS0 write is given priority. ADCR1 write is not performed, nor is the conversion end interrupt
request signal (INTAD0) generated.
238
AV
DD
P-ch
Series resistor string
AV
SS
is input (even if within the absolute maximum rating range),
SS
User's Manual U15798EJ2V0UD
ADCS0
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