Specifications

mikroElektronika | Free Online Book | PIC Microcontrollers | Appendix B: Examples
Why are these modes so important? Owing to
the fact that it is almost impossible to make
a stable oscillator which operates over a
wide frequency range, the microcontroller
must know which crystal is connected in
order that it can adjust the operation of its
internal electronics to it. This is why all
programs used for chip loading contains an
option for oscillator mode selection. See
above figure.
Quartz resonator
When a quartz crystal is used for frequency stabilization, the built in oscillator operates at a very precise frequency which
is isolated from changes in temperature and voltage power supply as well. This frequency is normally labelled on the
microcontroller package.
Apart from the crystal, capacitors C1 and C2 must be also connected as per the schematic below. Their capacitance is not
of great importance, therefore, the values provided in the table should be considered as a recommendation rather than a
strict rule.
Ceramic resonator
Ceramic resonator is cheaper, but very similar to quartz by its function and the way of operating. This is why the
schematics illustrating their connection to the microcontroller are identical. However, the capacitor value is a bit
different in this case due to different electric features. Refer to the table.
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