To get full 20MHz, I would just get a powered oscillator and use EC
mode.  Something like
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=3DX119-ND
 (That one is for 5V supply, you can get 3.3V capable ones as well if
you need)

If you're not concerned with a few milliamps of extra power
consumption and an extra dollar or two of cost, it will probably save
you some headaches.

-n.



On Tue, Jun 17, 2008 at 12:56 PM, Tom=E1s =D3 h=C9ilidhe <toe@lavabit.com> =
wrote:
>
> I'm used to using the 16F684, and I had the following macro for getting
> the greatest speed out of it:
>
>    #define CrankTheSpeed() ((void)(OSCCON |=3D 0b1110000,OSCTUNE =3D 0b11=
11))
>
> I got myself a "Pickit2 Debug Express" today though, and from now on
> I'll be working with the 16F887.
>
> I took a quick glance at the datasheet for the 887 and it tells me that
> the max speed I'll get is 8 MHz if I choose to use internal oscillators.
>
> I want the absolute maximum speed though (so I think that means I use an
> RC circuit to tell it what speed I want).
>
> Could someone please explain to me what pin I put the RC on, what RC
> values to use, what registers to set, etc.?
>
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