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PRBS pattern for eye diagram USB FS driver... (Read 248 times)
pancho_hideboo
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #15 - Jan 26th, 2010, 3:11am
 
BTW, why does the flat part around 1.5V exist in output waveform ?
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somisetty
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #16 - Jan 26th, 2010, 9:42pm
 
Thanks a lot for your time and help..

i have few doubts...in the cosmoscope settings of yours ..
you took ideal trigger not the default,would pls let me know why only ideal trigger?
how does start x value be calculated?(10n in the 1st setting and 48n in the 2nd setting..)


Pls find my settings...attached...

Thanks again...

Next time onwards i will take care to post them in simulator broads...
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somisetty
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #17 - Jan 27th, 2010, 12:40am
 
pancho_hideboo wrote on Jan 26th, 2010, 3:11am:
BTW, why does the flat part around 1.5V exist in output waveform ?


hi,

i think it might be due to transmission line...
Thanks
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« Last Edit: Jan 27th, 2010, 2:16am by somisetty »  
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pancho_hideboo
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #18 - Jan 27th, 2010, 3:59am
 
somisetty wrote on Jan 26th, 2010, 9:42pm:
i have few doubts...in the cosmoscope settings of yours ..
you took ideal trigger not the default,would pls let me know why only ideal trigger?
Attached is a function for eyediagram plot in Cadence Post Processing Environment.
You can see arguments of "eyeDiagram()" are almost same as arguments for "Ideal trigger" in CosmosScope.

The following is a function for eyediagram plot in Agilent Post Processing Environment.
http://edocs.soco.agilent.com/display/ads2009/eye%28%29

If you compare these functions from two vendors with eydiagram menu in CosmosScope,
you can understand that "Ideal trigger" is very common function for eyediagram.

somisetty wrote on Jan 26th, 2010, 9:42pm:
how does start x value be calculated?(10n in the 1st setting and 48n in the 2nd setting..)
"Start X value" is used for same purpose as "Delay" in Agilent Post Processing Environment.
I determined 10nsec and 48nsec by balancing right and left in eyediagram.

"Time base" is used for same purpose as "Cycles" in Agilent Post Processing Environment.

Why do you set "Trigger value" as 0 in "Default" ?
I don't think it is proper value.

If you use "Default" and use "fs_dm" as "Ref. signal", you should set 0.5~0.6V as "Trigger value".
Also you had better set relative large value(e.g. 200nsec>>83nsec) as "Time base".

somisetty wrote on Jan 27th, 2010, 12:40am:
pancho_hideboo wrote on Jan 26th, 2010, 3:11am:
BTW, why does the flat part around 1.5V exist in output waveform ?
i think it might be due to transmission line...
I don't think your answer make sense.


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« Last Edit: Jan 28th, 2010, 3:18am by pancho_hideboo »  

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somisetty
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #19 - Jan 31st, 2010, 9:42pm
 
Thanks for your help...
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pancho_hideboo
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Re: PRBS pattern for eye diagram USB FS driver...
Reply #20 - Feb 1st, 2010, 3:45am
 
somisetty wrote on Jan 31st, 2010, 9:42pm:
Thanks for your help...
Apart from your very easy issue which is no more than usage of very specific vendor's tool.
I don't think your answer to the following make sense at all.
somisetty wrote on Jan 27th, 2010, 12:40am:
pancho_hideboo wrote on Jan 26th, 2010, 3:11am:
BTW, why does the flat part around 1.5V exist in output waveform ?
i think it might be due to transmission line...

I think design of your driver is not proper, although I don't know your circuit topology.

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« Last Edit: Feb 1st, 2010, 7:17am by pancho_hideboo »  
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