migrating to pic18f452 from 16f877a

[skimask]

Are you saying that you've actually had a 40MHz xtal or resonator directly work with one of these (18Fxx2) PICs (which would contradict the maximum Datasheet figures)?

Yep, 40Mhz Xtal w/ 33pf cap's right next to OSC1&2 with a bit of a ground plane around the whole thing. Wasn't too reliable though. I'd touch practically anywhere the board and the PIC would lock up. That's when I read the rest of the datasheet (DS39564C) and found what you were saying about the 25Mhz earlier and fixed the whole thing.

As far as the 55Mhz goes, that was a 13.824Mhz oscillator, and using the 4xPLL, but that was also running the chip on 6.5v.

And this was the same chip that did 40Mhz with the external crystal. My guess is that this particular 18F452 chip was 'perfect', if not better, from the factory...a once in a lifetime good deal for me...not the norm obviously...

[sougata]

Hi,

Almost all of my 18F452 designs are based on x4 PLL mode. That is I use a 10MHz crystal and get a 40MHz Fosc. They have never let me down.