Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

ALTPLL for multiple input frequencies

Hi All, I have an input clock to MAX-10, which could be 2.5MHz, 25MHz, and 250MHz. I need to put a PLL on this input clock (for shifting the input clock by 90 degrees). I don't have...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
8 years ago

Hi, gj_leeson!

I have the same problem: on one pin may be clock 25MHz or 125MHz and I have a pin, which indicates this - 0 for 25 and 1 for 125.

I read altera manuals about altpll_reconfig with several mif-files. I create the same scheme with two ROMs, MUX, pll_reconfig and pll. I create two mif-files from pll wizard for two input clocks.

And my question: how should I configure the pll? The default PLL settings are for 125MHz, because this situation is more difficult for scheme and TimeQuest timing analyzer. Am I right or not?

What would you advise in this case?

Thanks!