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Visitor
Visitor
1,408 Views
Registered: ‎08-07-2017

timing constraint warning

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Hello all,

 

I'm recieving the following warning 

 

 

[Constraints 18-619] A clock with name 'CLK_50M' already exists, overwriting the previous clock with the same name. 

 

 

My XDC contains the following line:

"create_clock -period 20.000 -name CLK_50M [get_ports CLK_50M]"

My question is why? I cannot find any clock with the same name.

 

The main_pll.xdc contains the following line:

 

create_clock -period 20.0 [get_ports clk_in1]

 

 

is this the source of the problem and another related question, is there a need to define a clock constraint if one is already defined by the pll.xdc?

 

Thanks 

 

 

Jake

 

 

 

 

 

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Xilinx Employee
Xilinx Employee
2,136 Views
Registered: ‎09-20-2012

Re: timing constraint warning

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Hi @jkunin

 

If the clock constraint already exists in IP non-ooc XDC then there is no need to write the constraint in top level xdc.

Thanks,
Deepika.
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Moderator
Moderator
1,404 Views
Registered: ‎01-16-2013

Re: timing constraint warning

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@jkunin.

 

Check the following Answer Record:

https://www.xilinx.com/support/answers/59799.html

 

--Syed

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Give Kudos to a post which you think is helpful and reply oriented.

Did you check our new quick reference timing closure guide (UG1292)?
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Visitor
Visitor
1,375 Views
Registered: ‎08-07-2017

Re: timing constraint warning

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Thanks!

How bout my second question. Does a clock constraint even need to be defined if it's already defined in the pll.xdc?
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Xilinx Employee
Xilinx Employee
2,137 Views
Registered: ‎09-20-2012

Re: timing constraint warning

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Hi @jkunin

 

If the clock constraint already exists in IP non-ooc XDC then there is no need to write the constraint in top level xdc.

Thanks,
Deepika.
--------------------------------------------------------------------------------------------
Google your question before posting. If someone's post answers your question, mark the post as answer with "Accept as solution". If you see a particularly good and informative post, consider giving it Kudos (the star on the left)

View solution in original post