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patocarr
Teacher
Teacher
3,657 Views
Registered: ‎01-28-2008

Directed link change upon link up?

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Hi folks,

 

  My design can succesfully change from 4X Gen1 to Gen2 and viceversa using directed link speed change. I would've thought that upon start, the core will attempt to link at the fastest, widest setting it can, but that's not the case; it always starts in Gen1 mode.

  Why is it not automatically going to Gen2? If this is normal, then my application should attempt a directed link speed change as soon as link goes up. Is this how it's intended to work?

 

Thanks in advance,

-Pat

 

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luisb
Xilinx Employee
Xilinx Employee
4,188 Views
Registered: ‎04-06-2010

Hi Pat,

 

A Gen2 link will always come up at gen1 speeds first.  Take a look at section 4.2.4.8 of the Gen2 specification.  

 

I believe the downstream facing port generally initiates the uptrain to gen2 speeds.  If you're the endpoint, then you probably don't have to do anything because the link partner will initiate.  The core does support initiating the uptrain as an endpoint, but you should be able to rely on the link partner to do this for you.

 

Hope this helps...

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luisb
Xilinx Employee
Xilinx Employee
4,189 Views
Registered: ‎04-06-2010

Hi Pat,

 

A Gen2 link will always come up at gen1 speeds first.  Take a look at section 4.2.4.8 of the Gen2 specification.  

 

I believe the downstream facing port generally initiates the uptrain to gen2 speeds.  If you're the endpoint, then you probably don't have to do anything because the link partner will initiate.  The core does support initiating the uptrain as an endpoint, but you should be able to rely on the link partner to do this for you.

 

Hope this helps...

View solution in original post

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