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Does clock domains of same PLL are considered as single domain for CDC Analysis

Altera_Forum
Honored Contributor II
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Hello everyone, 

 

iam new to CDC analysis. iam using questa 0-ln CDC tool for CDC analysis, and i need to specify clock domains before analysis. I have a design which has altera PLL to produce different clock sources. My doubt is can i consider the two clock outputs (10MHz and 8 MHz) of single PLL as same domain or not ? As the two clocks are emerging from the same PLL source they should possess constant phase relation ship. but still there is possibility of timing violations across clock domain boundary. so can i consider the outputs of single PLL as same domain (inpendent of their individual frequencies) or not ?
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Altera_Forum
Honored Contributor II
406 Views

 

--- Quote Start ---  

Hello everyone, 

 

iam new to CDC analysis. iam using questa 0-ln CDC tool for CDC analysis, and i need to specify clock domains before analysis. I have a design which has altera PLL to produce different clock sources. My doubt is can i consider the two clock outputs (10MHz and 8 MHz) of single PLL as same domain or not ? As the two clocks are emerging from the same PLL source they should possess constant phase relation ship. but still there is possibility of timing violations across clock domain boundary. so can i consider the outputs of single PLL as same domain (inpendent of their individual frequencies) or not ? 

--- Quote End ---  

 

 

no. 

two clocks(different in phase/frequency) can be viewed as synchronous if they have one constant phase relationship at their sampling edges
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