18F4431 40MHz Crystal frequency

Hi all,

What should I do to operate a 18F4431 at 40MHz?

I tried using a 10MHz crystal with 2x22pF caps with the "HS oscillator, PLL enabled (clock frequency=4XFOSC1)" but it didn't work [I blinked an LED with 1Hz and the timing was all wrong].

I used a 4MHz with the same option but it also gave me the same result.

The pic works fine with a 20MHz crystal at HS mode.

What have I done wrong? Here is the bit configuration that I used

Regards

hi,
You seem to have set the CONFIG ok, are you sure its not your program thats giving the incorrect results for the LED timing.?

E.

EDIT:

I see others are having a similar problem.

https://www.electro-tech-online.com/threads/18f-intrc-pll.31065/

Found this microchip addendum app.

Post your code.

Thank you both for replying. I am using mikroc pro for pic v5.61

What speed does the LED blink?
How does the compiler know what frequency you are operating at?

BTW, the code you posted will produce a 0.5Hz flash.

Mike.