PIC 18F4550 clock frequency problems

James Boo · Joined: 09 Nov 2006 Posts: 1

I am working with an 18F4550. For the #FUSES, I have selected

#FUSES HS, NOPROTECT, NOLVP, NOBROWNOUT, NOWDT, NOMCLR, NOPUT

With this setting, the PIC is completely unresponsive--it just doesn't work. When I change the #fuses settings to:

#FUSES HS, INTRC, NOPROTECT, NOLVP, NOBROWNOUT, NOWDT, NOMCLR, NOPUT

The PIC works, but the frequency is way too slow for what I need it to do. How do I get it to work at 8MHz frequency?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Here is a test program for the 18F4550 that runs off the internal
oscillator at 8 MHz. I tested this with PCH vs. 3.249 on a PicDem2-Plus
board.

Ttelmah · Guest

Without knowing what type of oscillator you want to use, it'll be a guess. HS, _requires_ an external crystal. If you do not have one, get rid of it. INTRC, implies operation with the internal oscillator.

#FUSES INTRC, NOPROTECT, NOLVP, NOBROWNOUT, NOWDT, NOMCLR, NOPUT
#use delay(clock=8000000)

Should normally give you 8MHz. However on some compilers, you may need to have the line:

setup_oscillator(OSC_8MHZ);

Near the start of the main (the compiler should generate this internally, automatically if the correct 'delay' statement is present, but it is safer to include it yourself).

Best Wishes