>> W Atmedze 128 opcja CKOPT włącza tryb pracy generatora kwarcowego
>> Rail-to-rail, oczywiście ze wskazaniem na "very noisy environment".
>
> A nie jest to opcja sprzetowego zalaczenia pojemnosci? Nigdy nie uzywalem ale
ksiazki mowia co innego niz twierdzisz.
>
> By programming the CKOPT Fuse, the user can enable internal capacitors on XTAL1 and
XTAL2, thereby removing the need for external capacitors.The internal capacitors have
a nominal value of 36pF.

no zajrzałem do datasheeta Atmega 128A

Na stronie 39 stoi :

"XTAL1 and XTAL2 are input and output, respectively, of an inverting
amplifier which can be configured
for use as an On-chip Oscillator, as shown in Figure 8-2. Either a
quartz crystal or a
ceramic resonator may be used. The CKOPT fuse selects between two
different Oscillator
Amplifier modes. When CKOPT is programmed, the Oscillator output will
oscillate will a full railto-
rail swing on the output. This mode is suitable when operating in a very
noisy environment or
when the output from XTAL2 drives a second clock buffer. This mode has a
wide frequency
range. When CKOPT is unprogrammed, the Oscillator has a smaller output
swing. This reduces
power consumption considerably. This mode has a limited frequency range
and it can not be
used to drive other clock buffers.

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Gdzieniedzie spotkałem się też z tą informacją o kondensatorach.
No to ale co - nie wierzyć producentowi ?