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Altera_Forum
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14 years ago

How to calculate parameters for reconfigure a pll

Hello, i'm implementing a reconfigurable PLL using an ALTPLL e ALTPLLRECONFIG megafunction. I initialize my PLL with an input freq of 50MHz and only c0 output clock with output freq of 100MHz...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Hi,

i have to reconfigure my pll on Cyclone IV. The PLL have an input frequency of 50MHz. I have some problem when i try to find the M,N,c0 value for low frequency (eg: 100KHz).

If i try to generate a PLL with this frequency from the Megawizard on quartus i obtain this values:M=12, N=1, c0=500. I note that there is also another section of parameters for c0 on the Megawizard page "Cascade TAP Settings (for c0)" with another post-scale counter and its value is 12. My question is: How i can set this post-scale counter through the ALTPLL_RECONFIG to obtain an output frequency of 100KHz ??

Thanks