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IBERT PRBS is no link

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Visitor
Posts: 3
Registered: ‎12-06-2017

IBERT PRBS is no link

hello 

I used IBERT CORE on KC705 (xc7k325tffg900)which id the FPGA kintex 7, to debug the GTX transceiver on display port.

I connected two display ports by cable to make loopback,so I can transfer signal from display port1 to display port2.

I want to see the BER through theses two display ports by using eye scan plots.

Here is my setted parameters on GUI.parameter1.PNG

parameter2.PNG

parameter3.PNG

 

 I found that I can get the link succeed when I chose the loopback model as Near-End PMA/PCS,either PRBS or Fast/Slow Clk via TX and RX Pattern.

But,when I chose loopback model as None ,there is no link unless I select the TX and RX Pattern as Fast/Slow Clk.

link0.PNG

Who can tell me why PRBS can not do(but clk can) the link when I chose loopback model as None,even I connected 2 display ports by cable?

 

THANX

 

 

 

BER2.PNG
Visitor
Posts: 3
Registered: ‎12-06-2017

Re: IBERT PRBS is no link

anyone can help me?

Xilinx Employee
Posts: 328
Registered: ‎07-30-2007

Re: IBERT PRBS is no link

It looks like you have a link but with cable loopback you are probably overdriving the equalization.  Uncheck the DFE checkbox which will switch you to LPM equalization.  Also try lower amplitudes.  If this is not ac coupled it could be a problem?

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Visitor
Posts: 3
Registered: ‎12-06-2017

Re: IBERT PRBS is no link

hi roym

Thanks for your reply.

I have unchecked the DFE and it still doesn't work.

 

What do you mean by lower amplitudes?Is it the TX Diff swing voltage?I changed it for several values, but no effect.

 

And as you said ac coupled ,how can I set this?

 

I've tried another board with ARTIX-7(xc7a200tffg1156),I met the same problems.

2.PNG

1.PNG

Do you have any ideas ?

 

THANX