The Digikey xtals are fine - order them for parallel use - these will have
a capacitance displayed in the spec. The accuracy is typically 25 to 30 ppm.

The 18 series use 10 mHz xtals and a builtin PLL to go to 40 mHz, they
don't use a 40 mhz xtal.

You should be able to just swap the xtals. I use 18 pf caps.

If you use a SERIES xtal in this circuit, you will find that the frequency
is high - I have two 20 mHz series xtals that run about 140 ppm high in
frequency.

Don't forget to change the oscillator setup from XT to HS when you go to
the higher frequency xtals.

Larry

At 11:20 AM 4/24/2003 -0500, you wrote:
>Up until now, I've really only played around with a 16F87x using a 4-MHz
>crystal and 2 22 pF ceramic disc caps...
>
>Osc1      Osc2
>|         |    Please excuse the
>|         |    crudeness of this
>|---|0|---|    diagram, but I
>|         |    don't have time
>=== 22pF  ===   to make it to
>|         |    scale...
>|         |
>|_________|
>      |
>     Gnd
>
>I buy el cheapo XTAL's from Digikey, 4 MHz 20 pF Cload.  I'd like to go to
>20 MHz crystals for some 16F87x projects, and the 16C7x5 USB jobs need a 6
>or 24 MHz, and the 18F45x can handle up to a 40 MHz.  Can I basically just
>swap out the 4 MHz with the other part, even if the other part is a Series
>capacitance crystal?  Or do I need to modify it somehow?  Accuracy is
>important to me, but not critical...100 ppm or so is acceptable.  Thanks!
>
>Mike Hord
>
>
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Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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