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dcwang3
Visitor
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Registered: ‎02-06-2019

IBERT Eye Scan Interpretation

I am running the IBERT tutorial for the ZC706 reference design (Zynq 7000) and testing out the eye scan feature. How do you interpret the y-axis (voltage codes) to actual volts when compared to a conventional eye diagram?

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borisq
Xilinx Employee
Xilinx Employee
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Registered: ‎08-07-2007

hi @dcwang3 

 

one vertical code is equal to ~2mV.

Totally vertical 45 codes or 85mV is valid eye height @ BER=1e-12.

 

Thanks,

Boris

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dcwang3
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is the one vertical code equal to ~2mV valid for all eye scans with IBERT across all FPGAs or is it specific to the Zynq 7000?

Can you explain to me how you got the one vertical code equal to ~2mV?
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dcwang3
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Registered: ‎02-06-2019

@borisq 

Would you be able to explain how one vertical code is ~2mV? Do you have an exact conersion rate? I would like to use the eye scan on the receiver to determin my eye height/width margins. 

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gguasti
Xilinx Employee
Xilinx Employee
2,369 Views
Registered: ‎11-29-2007

hello,

One code is "about"  2mV. Being the amplitude of the signal after the equalizers, we do not need to know exactly the code to voltage conversion.

What is important is that the eye mask is expressed in codes as well.

To know your margin at BER=10E-12, please compare the eye amplitude in codes with the eye mask limit that is 45 codes. I.e., if you measure 50 codes, your margin is 5 codes.

 

 

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evgenis1
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Registered: ‎12-03-2007

@dcwang3 ,

You can derive eye scan vertical voltage from RX_EYESCAN_VX_RANGE setting. It's slightly different for GTH, GTX, and GTY transceivers, so check the documentation for the transceiver type you're using. Attached is a screenshot for GTH transceiver. It defaults to 1.5mv/count, and there are max 127 counts (-127..+127). 

 

eye_scan_vertical_resolution.jpg

 

Thanks,

Evgeni

eye_scan_vertical_resolution.jpg
dcwang3
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Registered: ‎02-06-2019

how about the code to mv conversion for the Zynq 7000 GTX? I was looking in UG476 and didn't see a table for the RX_EYESCAN_VS_RANGE.

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borisq
Xilinx Employee
Xilinx Employee
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Registered: ‎08-07-2007

hi @dcwang3 

 

for 7 series GTX, it is fixed to ~2mV. so there is no attribute to change the voltage value.

 

Thanks,

Boris

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dcwang3
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You mentioned the eye mask amplitude for 1e-12 is 45 codes. What is the UI tolerance for the GTH for Zynq UltraScale for 1e-12?

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roym
Moderator
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Registered: ‎07-30-2007

For the zync ultraScale we look for +/- .15 UI (.3 UI total) clearance to say you will have good eye.  If you have this clearance at 10E9 samples or greater we would expect to get a 10E-15 BER over PVT assuming you meet (and continue to meet) all the power and noise specs for the transceiver.




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sujinchalil
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Registered: ‎06-16-2020

From the above discussion my understanding is,

 1 code = 2mV
 1 step = 1 code = 2 mV
Is this the same for kintex ultrascale plus

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