The MX PLL3 calculation is generating 208.87793 MHz not 204 MHz. Is this a bug or am I missing something?

KiptonM · ‎2021-12-16

I believe HSE is 24 MHz, DIVM3 is /2 (12 MHz) DIVN3 is X34 (408 MHz) DIVP3 is /2 (204 MHz) But the screen says it is 208.87793.

I thought I knew how the PLL worked. And it is not like this.

I have a screen shot.

TDK · ‎2021-12-16

You have a fractional N set in your PLL. Set it back to 0 to get the expected results.

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TDK · ‎2021-12-16

You have a fractional N set in your PLL. Set it back to 0 to get the expected results.

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PatrickF · ‎2021-12-16

@TDK gives the right answer. 24/2=12MHz, 12MHz*(34+6660/8192) = 417.755859MHz with DIVP3=2 end up to 208.8779297MHz.

Regards.

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KiptonM · ‎2021-12-18

I missed that completely. Thank you.

I do not remember changing it. And do not know why I would.

Thanks again.

Kip