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CHAPTER 14 A/D CONVERTER
(7) AVREF0 pin
This pin inputs the A/D converter reference voltage.
It converts signals input to ANI0 to ANI7 into digital signals according to the voltage applied between AV
REF0
and AVSS.
The current flowing in the series resistor string can be reduced by setting the voltage to be input to the AVREF0
pin to AVSS level in standby mode.
Caution A series resistor string of approximately 10 kΩ is connect between the AVREF0 pin and the
AV
SS pin. Therefore, if the output impedance of the reference voltage source is high, this
will result in an active line connected in parallel to the series resistor string between the
AVREF0 pin and the AVSS pin, causing a large reference voltage error.
(8) AV
SS pin
This is a GND potential pin of the A/D converter. Keep it at the same potential as the VSS pin when not using
the A/D converter.
(9) AV
DD pin
This is an A/D converter analog power supply pin. Keep it at the same potential as the V
DD pin when not using
the A/D converter.
14.3 A/D Converter Control Registers
The following three types of registers are used to control the A/D converter.
• A/D converter mode register (ADM)
• A/D converter input select register (ADIS)
• External interrupt mode register 1 (INTM1)
(1) A/D converter mode register (ADM)
This register sets the analog input channel for A/D conversion, conversion time, conversion start/stop and
external trigger.
ADM is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets ADM to 01H.