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Altera_Forum
Honored Contributor I
781 Views

changing PLL parameters to get desired PLL Implementation

How can I force/override M/N values for the PLLs in Quartus II?

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2 Replies
Altera_Forum
Honored Contributor I
52 Views

There are two methods of doing this that I know of: 

A) You can go to chip editor, select the PLL you want to change the settings of, click on resource property editor, this will bring up the properties of the PLL showing all the specifications such as M and N values, you can go ahead and change these values, after you are done changing these values it will show you all the other specifications effected by this change in blue text and it will also tell you if the settings that you have made will result in stable PLL or not or the setting itself is legal or not. You can save these settings and can run assembler to implement these changes in the PLL. Do not run the whole compilation again. 

 

B) The second way to make the change is to make it in the .v or .vhd file generated by the Megafunction. Turn on the “advanced parameter” option in the PLL Megawizard, then when you generate the PLL, Megawizard will include all the PLL parameters in .V or .VHD file that it generates. You can then go ahead and in the .V or .VHD file and make changes to your M and N counter.
Altera_Forum
Honored Contributor I
52 Views

If you change the M/N values to whatever you want, how do you know the PLL loop will be stable? I thought Quartus had to be used to determine stable loop settings for the PLL? At least that's what Altera support told me.

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