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467 Views
Registered: ‎01-29-2019

Scope/Waveform Eye Diagram

Hi,

I am using a GTP transceiver on an AC701 and I am trying to run eye scans through Matlab using a modified version of xapp1198.

I am able to collect the correct data and display the results for a statistical eye. However, I was wondering what the configuration for the GTP is that supports the scope/waveform eye diagram. It is mentioned throughout the documentation but I cannot seem to get a result so far.

Thank you

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5 Replies
Xilinx Employee
Xilinx Employee
438 Views
Registered: ‎10-19-2011

Re: Scope/Waveform Eye Diagram

Hi @jamesgabauer_og ,

we do not provide code for a waveform or scope display.
But several customers implemented something like it.
You would probably need to make use of the ARMed branch of the eye scan state machine and apply the trigger at the right point with using periodic data.

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424 Views
Registered: ‎01-29-2019

Re: Scope/Waveform Eye Diagram

Hi,

Thank you for the quick response. Is there anywhere I can look to for direction on this, I have found the documentation to be a little confusing. I think one of the main things I have had trouble with is what rdata and sdata actually represent, are they segments of the bit stream? measures from an ADC? I think understanding exactly what those 40 bit values represent would help a lot.

From what you are saying it sounds like I would need to be implementing a test pattern to be sent over the interface for a scope view, is that right?

Thank you again for your help

James

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Xilinx Employee
Xilinx Employee
409 Views
Registered: ‎10-19-2011

Re: Scope/Waveform Eye Diagram

Hi @jamesgabauer_og ,

rdata and sdata are described at the bottom of page 151 and top of page152 in ug482.
Also look at the description for ES_ERRDET_EN on page 155.

So rdata always contains 80bit of consecutive data sampled with the data sampler at the time of trigger.
And sdata contains either the error information for these 80bits or the sampled data of the scan sampler at the same time.

You can only use one offset point at the same time. To scan a waveform you would need to repeat that measurement at different offsets over the same waveform segment. So you need to know at what time to trigger to catch the same sequence.

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385 Views
Registered: ‎01-29-2019

Re: Scope/Waveform Eye Diagram

Ok, that does make a lot of sense for rdata and sdata. I feel like I should have realised that when I read it.

I still don't fully understand how this is meant to work or why I would need t be using the ARMed state but I will keep looking into it.

Thank you again for your help

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348 Views
Registered: ‎01-29-2019

Re: Scope/Waveform Eye Diagram

One last thing

UG482 suggests that I need to unmask a single bit of sdata and accumulate errors on the previous cycles data. I have not done this but I have gotten what resembles an eye diagram by getting sdata and rdata from a qualifier. I don't see how the error accumulation would help in this case because if errdet_en is disabled this won't actually be accumulating errors 

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