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CHAPTER 11
A/D CONVERTER
User’s Manual U12790EJ2V0UD
11.4.3 A/D converter operating modes
The A/D converter has the following two modes.
 A/D conversion mode:
In this mode, the voltage applied to the analog input pin selected from ANI0 to
ANI7 is converted into a digital signal. The result of the A/D conversion is stored
in A/D conversion result register 3 (ADCR3), and at the same time, an interrupt
request signal (INTAD) is generated.
 Power-fail comparison mode: The digital value resulting from A/D conversion is compared with the value
assigned to power-fail comparison threshold value register 3 (PFT3). If the result
of the comparison matches the condition set by bit 6 (PFCM3) of power-fail
comparison mode register 3 (PFM3), an interrupt request signal (INTAD) is
generated.
(1) A/D conversion operation mode
When bit 7 (ADCS3) of A/D converter mode register 3 (ADM3) is set to 1, A/D conversion starts on the voltage
applied to the analog input pins specified by bits 0 to 3 (ADS30 to ADS33) of ADS3.
At the end of the A/D conversion, the conversion result is stored in A/D conversion result register 3 (ADCR3)
and the interrupt request signal (INTAD) is generated. After one A/D conversion operation is started and ends,
the next A/D conversion operation starts immediately. The A/D conversion operation con-tinues repeatedly
until new data is written to ADM3.
If data is written to ADCS3 again during A/D conversion, the converter suspends its A/D conversion operation
and starts A/D conversion on the newly written data.
If data with ADCS3 set to 0 is written to ADM3 during A/D conversion, the A/D conversion operation stops
immediately.