[SI-LIST] Re: Eye Diagram Question
- From: "Alfred P. Neves" <al.neves@xxxxxxxxxxx>
- To: "'Michael Greim'" <mgreim001@xxxxxxxxx>, "'Richard Feldman'" <Richard.Feldman@xxxxxxxxxxx>
- Date: Fri, 25 Sep 2009 20:47:13 -0700
Can you run a clock pattern at a low frequency (if not, you should be able
to trigger off the clock portion of a compliant character)? Although the
rise/fall time disparity will be evident due to TX having unequal strengths,
there is no ISI to deal with so the reduces the problem a bit.
With low frequency clocks, say 5T patterns you also can more easily see
impact of reflections due to impedance bumps.
Alfred P. Neves `·.¸¸.·´¯`·.. ><((((º>
.¸¸.·´¯`·.¸><((((º>
(503) 718 7172 Office
(503) 679 2429 Mobile
www.wildriversfishing.blogspot.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Michael Greim
Sent: Wednesday, September 23, 2009 2:12 PM
To: Richard Feldman
Cc: Morse, Jeff; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Eye Diagram Question
I think that the outside world and managers are under
the belief that the eyes of the world all look like the
attached. Nice explanation, and attachment I couldn't
find a pic fast enough to match the description. I always
love hearing, can't you just tweak a knob or something
to fix that?
-Mike.
On Wed, Sep 23, 2009 at 3:40 PM, Richard Feldman <
Richard.Feldman@xxxxxxxxxxx> wrote:
> The unsymmetry just means the first half of a driven step (0 to 50%; right
> side of eye)
> slews faster than the second half (50% to 100%; left side of eye). Very
> common with simple plants; a plain RC lowpass step response will have that
> characteristic. Here is the first image example I found by googling:
>
>
http://www.altera.com/products/devices/arria-fpgas/arria-ii-gx/images/eye-di
agram.jpg
>
> Rich
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Morse, Jeff
> Sent: Wednesday, September 23, 2009 12:14 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Eye Diagram Question
>
> Hi,
>
> What would cause an eye digaram to be asymmetric between the left and
> right hand sides? I am looking at an eye that has a left hand side that
> has a very shallow rise/fall to the respective zero and one levels. The
> right hand side has much sharper rise/fall. I understand there are
> frequency dependent losses, but I would *think* that would affect both
> sides of the eye in the same way. I played with preemphasis in the
> driver - but didn't see much effect.
>
> Any ideas what this might be / not be? ISI, reflection, etc?
>
> Thanks,
> Jeff
>
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--
Best Regards,
Michael C. Greim
And all this science they don't understand
Is just my job six days a week.....
We will either find a way or make one -Hannibal
In the middle of every difficulty lies opportunity -Al Einstein
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