Question on Cristal speed with PIC 18F4525

cjusto · Joined: 26 Apr 2006 Posts: 38 Location: Portugal

Hi Forum!

I am using a 18F4525. in the datasheet it is said that "Four Crystal modes, up to 40 MHz".

can i really use a 40MHz crystal?? i ask this because in the oscillator chapter the table for HS Oscillator configuration, the maximum value is 25MHz.

i am using a 4 pins crystal.

i hope someone can give me some tips.

thanks

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

To get the 40Mhz you use a 10Mhz clock and the H4 fuse. That will internally multiply by 4 to get the 40. Also see PLL in the spec sheet. You will also
have to remove the power once it is programmed to get the PLL working.
I think you just remove the power just that one time.

cjusto · Joined: 26 Apr 2006 Posts: 38 Location: Portugal

hi treitmey!!

thanks for the explanation.

cya