> I have just ordered pic 18f452 and 40mhz xtals (without reading the
manual).

Duh!

> do you mean to tell me that I wasted my money on the xtals?

Yes.

> All I need is just a 10MHz xtal?  I don't get it...

The 18 parts contain a phase lock loop that can multiply the oscillator
frequency by 4 for internal use.  The oscillators themselves top out around
20MHz (I don't remember exactly), which is fine because crystals much above
that are difficult to manufacture or are tricky to use because you have to
resonate them at a harmonic.  To run an 18 PIC at 40MHz, you use a 10MHz
oscillator and turn on the 4x PLL.

Once again, there is no substitute for actually reading the manual.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu