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Observer
Observer
4,297 Views
Registered: ‎04-02-2011

Virtex 7 eye scan is glitchy

I'm running a GTX eye scan test similar to the method used in XAPP1198. The problem I'm seeing is that when transitioning from vertical offset -1 to vertical offset 0, the eye diagram gets "shifted" up. For example, you can see the bottom of the eye forming below the 0 offset, but then once you hit the 0 offset, you start to see the bottom of the eye starting to form again. Here's a sample of one of my GTX to illustrate.Screenshot from 2015-08-13 11:22:55.png

 

I've verified that the correct HORZ_OFFSET, VERT_OFFSET, etc are being written to the DRP port of the transceiver. Has any one seen this before or have any idea why this might be happening? This seems to be happening on all of my transceivers, but the amount of vertical shift that occurs varries. In some cases, it seems to be shifted in the opposite direction.

 

Any ideas would help! Thanks.

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Explorer
Explorer
4,086 Views
Registered: ‎09-19-2010

Hello Samurai,

 

I have had recetly problems with eye scan so I went through the code.

 

In my idea one very good approach to see what is really going on, is to add xil_printf messages to the

write_es_data routine inside your Microblaze design.


Doing so, you can watch exactly at which address in the block memory , which values are written. There you can see the values for total number of samples, error count, vertical and horizontal offsets.

 

Looking at the log of the run, and also comparing it with the dumped txt file, it should be easily possible to find out the source of the issue.