Wouter van Ooijen wrote:
> I hope PIC-related questions are still allowed ;)

Can't you see we're busy with guitar chords and fictional TV characters!?

But OK, just this once.

> In a 12C509 cicruit (for which I try to find out what the fuses
> setting should be) the crystal is connected between OSC1 and ground
> (without any capacitors). Is this a working way to connect a crystal?

No.  All PICs as far as I know and the 12C509 for sure since I just checked
the datasheet, require the crystal between OSC1 and OSC2 when the PIC is
driving it directly.  The 12C509 has 4 oscillator modes, external RC,
internal, XT crystal, and LP crystal.

Of course you can use external circuitry to run a crystal and then feed the
result into OSC1, but that would be more than just a crystal to ground on
the OSC1 pin.

I suppose if everything is just right you could use external RC mode but pu=
t
a crystal there instead of R-C.  That leaves many questions and and far fro=
m
guaranteed operation, but I could see it maybe working sometimes, especiall=
y
if there is a pullup on OSC1 to Vdd.

In short though, what you are describing doesn't make sense.


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