On Wed, 3 Dec 2003, Olin Lathrop wrote:

> Prasad, Satyaprakash (Consultant) wrote:
> > What is difference between the LP, XT, and HS oscillator modes?
>
> Pretty much just what the manual says they are.
>
> > Can anyone please explain me the "EXTRC External Resistor/Capacitor
> > with
> > CLKOUT" oscillator mode?
>
> Probably.  There always seems to be a misguided person here who tries to
> help people that are too lazy to read the manual.  Not me though.

  I'l give a shot. The PIC micro family have at least two type of external
oscillators. The R oscillators and the RC oscillators. If things are very
clear for the R oscillators (just one resistor from the oscin pin to
ground), there aren't too simple for RC oscillators because the oscin pin
have a self capacitance of about 5...10pF. My tests shows a tipical value
of 7 pF for 4 or 5 different PICmicros in PDIP package. So you may see
that and RC oscillator may work wery good without any capacitor or with
much smaller capacitor value than data sheet mention.


>
> > What will happen if an external RC clock of higher prescribed
> > frequency is used?
>
> Microchip won't guarantee the PICs operation.
>
> > Will the software completely halt or unexpected behavior could
> > be expected?
>

  unexpected behavior it's a common thing to all electronical components.
That's why MTBF was invented, to have an excuse... :)

best,
Vasile

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