Using External Clock Source in MC9S08QE32

[mahkamehvarza]

I am using an MC9S08QE32 and I need to run the SCI @ 115200 and the PWM @ 125KHz at the same time. I figured that if I use an external 16MHz Crystal all numbers should work out fine. Now I am trying to get it in PE Codewarior but it I am having issues. In fact I just cannot figure out how to set all those timing parameters such that I do not get warnings. Could someone please explain to me how the timing works here?

[marek_neuzil]

Hello,

If you want to use 16MHz external clock source as the source for the FLL you should select the "Auto select" in the Ref. clock divider and DCO mode properties. The Processor Expert select the best divider and multiplier to set the required Internal bus clock. For example you can set 24MHz internal bus clock. See the following screenshot:

In the case of 24MHz bus clock you can use 115200 buadrate of the SCI and also PWM at 125kHz. See also the attached project.

Best Regards,

Marek Neuzil