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CHAPTER 11 A/D CONVERTER
r Note on interrupt requests
The interrupt request flag bit (ADC1: ADI) is not set if A/D conversion is reactivated (ADC1: AD
= "1") at the same time as the previous A/D conversion completes, or if the sense function is
reactivated (ADC1: AD = "1") at the same time as the comparison condition is satisfied.
r Error
The smaller the AVR - AVSS, the greater the error would become relatively.
r Turn-on sequence for A/D converter power supply and analog inputs
Always apply the A/D converter power supply (AVCC, AVSS) and analog inputs (AN0 to AN3) at
the same time or after turning on the digital power supply (VCC).
Similarly, when power supply is turned off, always turn off the A/D converter power supply
(AVCC, AVSS) and analog inputs (AN0 to AN3) at the same time or before turning off the digital
power supply (VCC).
Take care that AVCC, AVSS, and the analog inputs do not exceed the digital power supply
voltage when turning the A/D converter power supply on or off.
r Conversion time
A/D conversion function conversion time and sense function comparison time are affected by
the clock mode, oscillator frequency, and main clock speed (speed shift function).
r Continuous activation input clock
The 8/16-bit timer/counter output, which can be selected for continuous activation (ADC2: EXT
= 1), is affected by the clock mode and speed shift function. The timebase timer output, which
can also be selected, is not affected by the speed shift function, but the timebase timer output
cannot be used in subclock mode because the main clock (which drives the timebase timer) is
stopped in that mode.
Note also that the cycle time is affected (for one cycle) when the
timebase timer is cleared.