Javier Puiggros wrote:
> Hi everybody, I' am new at Piclist an I am starting a rf project with
> rfpic 509AG. The mcu part is working fine but I have a 12 Mhz crystal
> at XTAL pin and I only see 5V. If I look at CLOCKOUT I can see some
> oscillation at 3 MHz but only 0,2-0,5 volts over DC (2 V app).

Is the oscillator mode set to HS?  Anything over 4MHz requires HS mode.

> I use a
> series cap 22 pf connecting crystal to ground.

Huh?  "Series" and "to ground" sound mutually exclusive in this context.
The crystal should be connected directly between the two oscillator pins.
Each side of the crystal should have one of the 22pF caps connected to it.
The other ends of both caps go to ground.

> My question is about
> the crystal type, because in the datasheet I read that I need a
> colpitts crystal, is a special kind?

For proper accuracy, you need a crystal specified for parallel resonance.
These will be specified with a capacitance value in catalogs, whereas series
resonant crystals will usually say "series".


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