How to set PLL in CCS

[falcon1877]

Hi everyone, I'm using PIC18F4550. Now, I want to use external crystal with 10MHz. I want to set it at 20MHZ (use PLL). How can I do that in CCS ?

[falcon1877]

:( Please help me

[ckielstra]

First of all, be patient.
Many people on this forum live in a different time zone from you. So when you are awake, they sleep.
Bumping a thread after just 4 hours is annoying. When you annoy people they will not help you.

Then the short answer to your question: You can't because the hardware doesn't support it.
The PLL _must_ get an input frequency of 4MHz. With a 10MHz external crystal this would require a PLL prescaler of 2.5. Impossible.

Study figure 2-1 in the data sheet carefully. Then come back with a configuration that will work.

A hint for you to figure out the CCS fuse settings:
- Check the top of the PIC18F4550.h file. Here are listed all the supported fuse names for this chip.
- In the PICC directory you find the file fuses.txt with a short description of all fuse names.

[Ttelmah]

Also if you search for 4550 fuse settings on the forum, I have in the past posted fairly detailed notes of how the CCS settings work.
The nearest you could get, would be 24MHz.

Best Wishes

[falcon1877]

ok, thanks guys, I'll be more patient next time.