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somisetty Community Member Offline Posts: 64	PRBS pattern for eye diagram USB FS driver... Jan 20^th, 2010, 11:37pm hi, i wanted to generate eye diagram for USB FullSpeed Driver to measure jitter.Would any one suggest me,the PRBS pattern,need to use for generating eye diagram? pattern means how may minimum bits required to get any eye pattern...bit time etc... Thanks
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: PRBS pattern for eye diagram USB FS driver... Reply #1 - Jan 21^st, 2010, 7:30am hi, i didn't understand your question, can you reframe it. I mean bit time is the one for which you design enitre transiver and give some junk prbs and get the EYE. Thanks, RAjasekhar.
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somisetty

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Re: PRBS pattern for eye diagram USB FS driver...
Reply #2 - Jan 22^nd, 2010, 2:57am

Thanks for the reply..

I wanted to generate any eye diagram for USB Full Speed Driver.For that i need a prbs.To generate a prbs,i got a perl script which requires the bit-time as input.

USB protocol defines USB FS mode should have 12Mb/s data rate.I calculated the bit time as 83.33nsec.Iam not sure abt �the bit time.can anyone clarify the bit-time?

Thanks

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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #3 - Jan 22^nd, 2010, 3:12am somisetty wrote on Jan 22^nd, 2010, 2:57am: USB protocol defines USB FS mode should have 12Mb/s data rate. I calculated the bit time as 83.33nsec. Correct. See http://www.designers-guide.org/Forum/YaBB.pl?num=1234925581/5#5
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somisetty

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Re: PRBS pattern for eye diagram USB FS driver...
Reply #4 - Jan 25^th, 2010, 12:54am

Thanks for the reply...

I have given USB Full Speed Drivers a PRBS with bit time of 83n and 127bits. As USB Io is a differential output,the out pins shown in the image are DP_OUT ans DM_OUT.

when i generated the Eye diagram for 2 output pins separately with Time base as 83nsec and got the below eye...As you can see the eye is not complete,can any one let me know whats wrong with the simulation ...

Thanks again...

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USB_eye_pattern.pdf

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pancho_hideboo

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Re: PRBS pattern for eye diagram USB FS driver...
Reply #5 - Jan 25^th, 2010, 1:03am

somisetty wrote on Jan 25^th, 2010, 12:54am:

when i generated the Eye diagram for 2 output pins separately with Time base as 83nsec and got the below eye...
As you can see the eye is not complete,can any one let me know whats wrong with the simulation ...

I think you have some mistakes in using function for eyediagram.

What tool do you use for post processing ?

What do you mean by "fs_dp" and "fs_dm" ?

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somisetty Community Member Offline Posts: 64	Re: PRBS pattern for eye diagram USB FS driver... Reply #6 - Jan 25^th, 2010, 1:08am Thanks for the reply.. Iam using the tool CosmosScope by Synopsys... fs_dm and fs_dp are input pins of the drivers and dp_out and dm_out are the outputs of the driver.
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #7 - Jan 25^th, 2010, 1:10am Upload your simulation data as �tr0, fsdb or psf format. If you upload your simulation data, I can verify eyediagram. I think you have some mistakes in using function for eyediagram.
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somisetty Community Member Offline Posts: 64	Re: PRBS pattern for eye diagram USB FS driver... Reply #8 - Jan 25^th, 2010, 2:04am Thanks for the help... pls find the file... "prbs.tr0" in prbs.rar
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pancho_hideboo

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Re: PRBS pattern for eye diagram USB FS driver...
Reply #9 - Jan 26^th, 2010, 1:39am

somisetty wrote on Jan 25^th, 2010, 2:04am:

pls find the file... "prbs.tr0" in prbs.rar

As I expected, there is no issue related to design in your post at all.

Your question is no more than easy usage of very specific vendor's tool.
Please post such questions to Simulator's Board not to Design's Board.

I verified your data("prbs.tr0") by Agilent ADS Post Processing Environment.
I found that a bit rate of your PRBS is 1/83nsec= 12.0482Mbps not 12.0Mbps.

Attached figure is conventional plot from your data("prbs.tr0").

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somisetty_prbs_1.png

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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #10 - Jan 26^th, 2010, 1:50am Attached figure is an eyediagram for "fs_dp".
Back to top	eye_fs_dp.png Kita━━━━━━(ﾟ∀ﾟ)━━━━━━ !!!!! http://www7.plala.or.jp/ungeromeppa/flash/kita.html http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related IP Logged

pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #11 - Jan 26^th, 2010, 1:51am Attached figure is an eyediagram for "fs_dp_out".
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #12 - Jan 26^th, 2010, 1:55am See arguments of function of eye() in attached figure, although this is a function in Agilent ADS Post Processing Environment. Here I set 1/83nsec as Bit Rate(=Symbol Rate). Arguments of function for eyediagram are very simlar, even if you use CosmosScope of Synopsys.
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #13 - Jan 26^th, 2010, 2:00am Of course, I can plot an eyediagram using CosmosScope. Show me your settings for eyediagram in CosmosScope. Attached figure is my result.
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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: PRBS pattern for eye diagram USB FS driver... Reply #14 - Jan 26^th, 2010, 2:03am Attached figure is an eyediagram using another settings.
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