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Adventurer
Adventurer
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Registered: ‎11-18-2017

Implementation setting (or strategy) to meet timing closure,

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Hello.

Is there a Implementation setting (or strategy) in which implementation runs until the timing is met (there is no negative slack or no timing violance).

Thanks for your help.

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Moderator
Moderator
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Registered: ‎11-04-2010

Re: Implementation setting (or strategy) to meet timing closure,

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Hi, @kimjaewon  ,

Yes, the Explore directive has the higher effort level than Default directive and will try different algorithm to get better timing result. 

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Moderator
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Registered: ‎11-04-2010

Re: Implementation setting (or strategy) to meet timing closure,

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Hi, @kimjaewon ,

No. If such Implementation setting exists, the tool will hang in so many situations.

In many situations, the timing violation realted to design should be intervened with source code optimization, correcting constaints...etc.

 

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Registered: ‎01-22-2015

Re: Implementation setting (or strategy) to meet timing closure,

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@kimjaewon 

All implementation strategies try to run until timing closure is achieved.

When implementation cannot achieve timing closure then it is usually (as hongh says) a result of problems with our coding/design.  The messages and the timing analysis reports produced by implementation help us find and correct the problems with our coding/design.

Achieving timing closure is often a difficult part of FPGA work.  When a design fails timing analysis, we often start by opening the implemented design and looking at the timing paths that have the Worst Negative Slack (WNS).

UG906 is a good document about achieving timing closure as is UG1292.

Mark

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Adventurer
Adventurer
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Registered: ‎11-18-2017

Re: Implementation setting (or strategy) to meet timing closure,

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In the (Vivado) Implementation settings, I changed the Options strategy from Vivado Implementation Defaults to Performance_Explore.

Then, after I re-implemented, the negative slacks all disappeared (although the elapsed time increased). 

I guess changing the settings made the difference.

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Moderator
Moderator
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Registered: ‎11-04-2010

Re: Implementation setting (or strategy) to meet timing closure,

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Hi, @kimjaewon  ,

Yes, the Explore directive has the higher effort level than Default directive and will try different algorithm to get better timing result. 

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619 Views
Registered: ‎01-22-2015

Re: Implementation setting (or strategy) to meet timing closure,

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@kimjaewon 

You were lucky this time.  Rarely, timing closure problems can be solved by only changing the implementation settings/strategy.

Mark