About IPLL

[zy]

Hello kef ！

I am using XET256 ,I have some promblem about IPLL.

when  fOSC=16MHz, I have two plans for count fVCO ,first SYNDIV=4；REFDIV=1 then fVCO=80M; second YNDIV=24 ；REFDIV=7 ,then fVCO=100M,if the first one is better then the second one because there are explains in document "Use lowest possible fVCO/fREF ratio (SYNDIV value). Use highest possible REFCLK frequency fREF". The the second plan unsafe?

I also want to know how to use FM0 and FM1,and why to use them? 

Thank you for your continued support.

[kef]

Hello

You should address your questions not only for me, but for whole forums community.

Regarding your question, try using this SW to calculate IPLL settings http://cache.freescale.com/files/microcontrollers/doc/user_guide/S12XEIPLLCUGSW.zip

Enabling frequency modulation may help passing EMI tests. Google for spread spectrum modulation.

[zy]

Thank you very much