UPD78F0138 NEC, UPD78F0138 Datasheet - Page 267

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

12.6 Cautions for A/D Converter
(1) Operating current in standby mode
(2) Input range of ANI0 to ANI7
(3) Conflicting operations
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 12-18 shows the circuit configuration of the series resistor string.
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.
<1> Conflict between A/D conversion result register (ADCR) write and ADCR read by instruction upon the end
<2> Conflict between ADCR write and A/D converter mode register (ADM) write or analog input channel
of conversion
ADCR read has priority. After the read operation, the new conversion result is written to ADCR.
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.
Figure 12-18. Circuit Configuration of Series Resistor String
AV
AV
REF
SS
CHAPTER 12 A/D CONVERTER
User’s Manual U16228EJ2V0UD
P-ch
Series resistor string
ADCS
REF
or higher and AV
SS
or lower
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