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CHAPTER 12 A/D CONVERTER
● Clock selector
The clock selector selects the clock to be used to activate A/D conversion while continuous activation is
enabled (ADC2: EXT = 1).
● Analog channel selector
This circuit selects one out of the eight analog inputs.
● Sample hold circuit
This circuit holds the input voltage selected by the analog channel selector. By performing the sample hold
of the voltage input immediately after the activation of A/D conversion, A/D conversion can be performed
without the variance of the input voltage affecting it during A/D conversion (during comparison).
● D/A converter
This generates the voltage that corresponds to the values set in the ADDH and ADDL registers.
● Comparator
This compares the input voltage for which sample hold is performed, with the output voltage of the D/A
converter to determine which is the greater of the two.
● Control circuit
The control circuit has the following function.
• For A/D conversion functions, this circuit determines the values in turn from the MSB in the 10-bit A/D
data register toward the LSB based on the large and small signals from the comparator. When the
conversion is completed, it sets the interrupt request flag bit (ADC1: ADI).
● A/D data register (ADDH and ADDL)
The high-order 2 bits of 10-bit A/D data are stored in the ADDH register. The low-order 8 bits of 10-bit
A/D data are stored in the ADDL register.
The ADDH and ADDL registers have the following function.
• For A/D conversion function, these registers store the results of A/D conversion.
● A/D control register 1 (ADC1)
This register is used to enable and disable functions, select an analog input, check statuses, and control
interrupts.
● A/D control register 2 (ADC2)
This register is used to select an input clock, enable and disable interrupts, select functions, and perform
other activities.
● Interrupts of the A/D converter
When the set conditions are satisfied at the completion of A/D conversion for IRQ8, if an interrupt request
output is enabled (ADC2: ADIE = 1), an interrupt request occurs.