06-04-2019 11:10 AM
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?
06-05-2019 02:33 AM
one vertical code is equal to ~2mV.
Totally vertical 45 codes or 85mV is valid eye height @ BER=1e-12.
06-05-2019 04:46 AM
06-10-2019 04:39 AM
06-10-2019 08:30 AM
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.
06-10-2019 09:52 AM
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).
11-13-2019 06:36 PM
for 7 series GTX, it is fixed to ~2mV. so there is no attribute to change the voltage value.
05-04-2020 09:15 AM
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.