Work Flow of ADC in PIC16F877A

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This is the 10-bit Successive Approximation block diagram.

  1. A sample and hold circuit to acquire the input voltage, Vin.
  2. A voltage comparator that compares Vin to the DAC output. It outputs the comparison result to the successive approximation register (SAR).
  3. A successive approximation register designed to supply approximated digital code of Vin to the internal DAC.
  4. An internal reference DAC that supplies the comparator with an analog voltage equivalent of the digital code supplied by the SAR.
  5. A register ADRES to store the ADC result upon-end of-conversion(EOC).