[SI-LIST] Re: Eye Diagram Question

  • From: Michael Greim <mgreim001@xxxxxxxxx>
  • To: Richard Feldman <Richard.Feldman@xxxxxxxxxxx>
  • Date: Wed, 23 Sep 2009 16:11:47 -0500

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-diagram.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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