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Contributor
Contributor
7,141 Views
Registered: ‎06-22-2009

GTH line rates

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Hi!

 

I'm a bit confused about the possible line rates for the Virtex-6 GTH transcivers. As written in the GTH user guide the GTH support line rates of

 

• 1.24 Gb/s to 1.397 Gb/s
• 2.48 Gb/s to 2.795 Gb/s
• 4.96 Gb/s to 5.591 Gb/s
• 9.92 Gb/s to 11.182 Gb/s

 

....but I'd like to use the GTH interface at 8.0GBit/s.....    Is this possible or could raise problems?

Why is there no continous range for the GTH transcivers like the GTX transcivers?

 

Thank you a lot!

John

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Xilinx Employee
Xilinx Employee
9,147 Views
Registered: ‎01-03-2008

Re: GTH line rates

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The GTH PLL has a narrow operating frequency range and was designed to meet the 9.92-11.182 Gb/s lines rates.  The other data rates (1/2, 1/4, 1/8) are available as they are simple binary divisions through oversampling.

 

The GTH cannot operate at 8.0 Gb/s.

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7 Replies
Xilinx Employee
Xilinx Employee
9,148 Views
Registered: ‎01-03-2008

Re: GTH line rates

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The GTH PLL has a narrow operating frequency range and was designed to meet the 9.92-11.182 Gb/s lines rates.  The other data rates (1/2, 1/4, 1/8) are available as they are simple binary divisions through oversampling.

 

The GTH cannot operate at 8.0 Gb/s.

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Scholar austin
Scholar
7,133 Views
Registered: ‎02-27-2008

Re: GTH line rates

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i,

 

The ranges specified have been characterized.  The rate you mention, hasn't been checked.  Thus, we can't tell you what bit settings to use (there are many internal bits used to set various parameters), and we can't say anything about performance.  If you wish to play with it, go ahead (no promises, no guarantees).

 

If this is a big market item, and there is a lot of business behind it, then contact your Xilinx FAE, and make the case to have the rate characterized and supported.

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
Scholar austin
Scholar
7,132 Views
Registered: ‎02-27-2008

Re: GTH line rates

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Ed,

 

OK, so by design it can't do 8 Gbs.  I did not know that.

 

Thanks, I thought it was just a matter of characterization.

Austin Lesea
Principal Engineer
Xilinx San Jose
Contributor
Contributor
7,126 Views
Registered: ‎06-22-2009

Re: GTH line rates

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...that's very bad news. Is there absolute no chance to get it running with 8.0 GBit/s? I understand that this setting is out of spec, but even the GTX was working very well at 8.0 GBit/s..... We planned to upgrade to V6, but I didn't expected this pitfall... Thanks a lot! John
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Xilinx Employee
Xilinx Employee
7,115 Views
Registered: ‎01-03-2008

Re: GTH line rates

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> Is there absolute no chance to get it running with 8.0 GBit/s?

 

No chance. 

 

> but even the GTX was working very well at 8.0 GBit/s

 

The V-5 GTX is spec'ed up to 6.5 Gb/s and the V-6 GTX is spec'ed up to 6.6 Gb/s and both used a very different architecture than the V-6 GTH.  If you managed to get a link a 8.0 Gb/s in either V-5 or V-6 it was likely not reliable and certainly would not be in a production environment.

 

The upcoming 7 Series FPGAs will support this line rate.

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Contributor
Contributor
7,110 Views
Registered: ‎06-22-2009

Re: GTH line rates

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> The upcoming 7 Series FPGAs will support this line rate. Thx for the hint.
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Newbie dusan_st
Newbie
6,728 Views
Registered: ‎10-18-2011

Re: GTH line rates

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Can you please tell me if V6 GTH can support GigE (1000Base-X) line rate (1.25Gbps). That protocol is not listed for direct support, but I wonder if some setting can be made in Wizard to make it work? What reference clock frequency would be needed?

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