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Anonymous
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How to make Place & Route tool go over fixed constraints ?

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Hi,

 

I fixed in the ucf file a constraint to a path ( 10 ns for example). I get a violation timing of (-1 ns ). then I relax my constraints ( 12 ns instead of 10 ns). I was waiting that the Place and Route Tool is able to perform this constraint with a margin

of + 1 ns. However It is not the case. the margin is about few ps ( + 8 ps). My feeling is that Xilinx tool when It attempts the fixed constraints does not optimize more that It.

 

My Questions is : there is an option to PAR tool to optimize timing even when It attempts the constraints fixed in the ucf file ?

 

Regards,

Hicham 

 

   

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Professor
Professor
6,383 Views
Registered: ‎08-14-2007

Re: How to make Place & Route tool go over fixed constraints ?

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No.

 

The constraints imply that the time you entered is what is required and therefore there is no

additional value to optimizing that path further.  This is actually the desirable behavior since

continuing to optimize the already met constraints requires more run time and could result

in poorer performance of other paths.  Meeting the constraint with no margin still means that

the design should work under all operating conditions and still meet the constraint.  If you want

more margin you need to adjust you constraint.  For example in your case you could ask for

11 ns instead of 12.

 

Regards,

Gabor

-- Gabor

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Professor
Professor
6,384 Views
Registered: ‎08-14-2007

Re: How to make Place & Route tool go over fixed constraints ?

Jump to solution

No.

 

The constraints imply that the time you entered is what is required and therefore there is no

additional value to optimizing that path further.  This is actually the desirable behavior since

continuing to optimize the already met constraints requires more run time and could result

in poorer performance of other paths.  Meeting the constraint with no margin still means that

the design should work under all operating conditions and still meet the constraint.  If you want

more margin you need to adjust you constraint.  For example in your case you could ask for

11 ns instead of 12.

 

Regards,

Gabor

-- Gabor

View solution in original post

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Anonymous
Not applicable
5,134 Views

Re: How to make Place & Route tool go over fixed constraints ?

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Thank you for your answer.  It 's what I want to know.

 

Regards,

Hicham 

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