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(1) Successive approximation register (SAR)
This register compares the voltage value of the analog input signal with the voltage tap (compare voltage)
value from the series resistor string, and holds the comparison result starting from the most significant bit
(MSB).
When the comparison result has been held down to the least significant bit (LSB) (i.e. when A/D conversion
has been completed), the contents of the SAR register are transferred to the ADA0CRn register.
Remark
n = 0 to 7
(2) A/D conversion result register n (ADA0CRn), A/D conversion result register H (ADA0CRnH)
The ADA0ARn register is a 16-bit register that stores the A/D conversion result. ADA0ARn consist of 8
registers and the A/D conversion result is stored in the higher 10 bits of the ADCRn register corresponding to
analog input. (The lower 6 bits are fixed to 0.)
(3) A/D converter mode register 0 (ADA0M0)
This register specifies the operation mode and controls the conversion operation by the A/D converter.
(4) A/D converter mode register 1 (ADA0M1)
This register sets the conversion time of the analog input signal to be converted.
(5) A/D converter channel specification register (ADA0S)
This register sets the input port that inputs the analog voltage to be converted.
(6) Sample & hold circuit
The sample & hold circuit samples each of the analog input signals sequentially sent from the input circuit and
sends the sampled data to the voltage comparator. This circuit also holds the sampled analog input signal
voltage during A/D conversion.
(7) Voltage comparator
The voltage comparator compares the analog input signal with the output voltage of the series resistor string.
(8) Series resistor string
This series resistor string is connected between AV
the analog input signal.
(9) ANI0 to ANI7 pins
These are analog input pins for the 8 channels of the A/D converter and are used to input analog signals to be
converted into digital signals. Pins other than ones selected as analog input with the ADA0S register can be
used as input ports.
Caution Make sure that the voltages input to ANI0 to ANI7 do not exceed the rated values. In
particular if a voltage higher than AV
channel becomes undefined, and the conversion values of the other channels may also be
affected.
CHAPTER 11 A/D CONVERTER
and AV
REF0
is input to a channel, the conversion value of that
REF0
User's Manual U17031EJ2V0UD
and generates a voltage for comparison with
SS
271
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