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Customizing Clock Frequencies

Honored Contributor II



I have a DE2-115 board with an oscillator providing a 50Mhz clock. I was wondering two things: 


1. Can I somehow convert this to a 20 Mhz clock? 

2. Can I use the built-in PLL's to multiply the 50 Mhz to a higher frequency? And if yes, then what sort of maximum frequency can I create? 


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Honored Contributor II



1. This is no problem. Just can use the Megawizard Plug-in manager to add an altera_pll to your quartus project. Just configure your PLL for 50Mhz input and 20Mhz output and it should work fine. 


2. Yes the PLLs can multiply an reference clock. I believe it can go above 1Ghz but you probably want to implement some logic and then the limiting factor is not the clock frequency but meeting the timing constraints for your design. The maximum speed of the logic depends on the what you are implementing and the speed grade of your device. But it is probably around 150-200Mhz. 


I hope that helps.
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