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Visitor dcw15
Visitor
155 Views
Registered: ‎02-28-2019

IBERT only running at 1 speed regardless of values chosen.

I'm trying to test a GTP link on an artix-7 currently and cannot get any of the links I am working with to go higher than 0.625gbps, regardless of the values which i put in via the wizard. I have found if I open the properties of on of the links, I can manually change the output divider value which then will change the speed of the link, but this becomes unstable. 

 

Is there a reason why I am being limited to 0.625gbps regardless of the values I choose? Both system clk and refclk are 150MHz.

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3 Replies
Xilinx Employee
Xilinx Employee
125 Views
Registered: ‎11-29-2007

Re: IBERT only running at 1 speed regardless of values chosen.

hello,

This is not expected. Sorry, I will make many questions trying to guide your debug.

  • Is this an evaluation board or your own board?
  • have you tried to measure the REFCLK quality with an oscilloscope? Does the local oscillator meet the phase noise requirements?
  • Are all power rails correct and in range?
  • Are you testing a loopback or a cable connection? (or both)
  • is the PLL locked?
  • cables and connectors are good?
  • Have you tried a different design (not IBERT)?
  • Which Vivado release are you using? 
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Visitor dcw15
Visitor
110 Views
Registered: ‎02-28-2019

Re: IBERT only running at 1 speed regardless of values chosen.

Hi,

 

  • This is our own board
  • I have no tried to measure this - will do so today, but having used the board for multiple months on other builds I doubt this will be the issue
  • Power rails definitely correct as mentioned have been using the board for other work
  • Have tested both internal feedback loop and an external loop
  • PLL is locked
  • All cables other than feedback loop are shopped. The feedback loop cable is of slightly lesser quality, but is confirmed to be working.
  • Have used many other builds on the board, but only now are looking to use GTP comms, had been using something else prior to this.
  • 2016.2

Thanks!

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Xilinx Employee
Xilinx Employee
101 Views
Registered: ‎11-29-2007

Re: IBERT only running at 1 speed regardless of values chosen.

Hello,

If the PCB was proven to work fine in the past I would

1) upgrade to 2018.3

2) make a simpler IBERT, with few (one or two) active channels

 

 

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