[ibis-macro] Re: Eye mask question
- From: "Ward, Richard" <richard.ward@xxxxxx>
- To: "Arpad_Muranyi@xxxxxxxxxx" <Arpad_Muranyi@xxxxxxxxxx>, IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
- Date: Tue, 8 Dec 2009 13:19:45 -0600
Hi Arpad,
Agreed in theory, although...
It's relativity common to see eye ledges or slew issues
on one side of the eye. Centering it may not be the best
fit for the mask. In the hardware world (given no absolute
reference point) it's reasonable to shift the eye w.r.t
the mask and claim a "pass" still.
One could claim the UI edge is the peak of the PDF for the
crossing points and reference the mask to that (or as you
say - the 0.5UI point). But in practice (on the bench), if
compliance can be made with a shift - this is reasonable
too [and isn't the goal of the model to mimic the hardware
test?]
just my $0.02
Regards,
Richard
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Muranyi, Arpad
Sent: Tuesday, December 08, 2009 11:08 AM
To: IBIS-ATM
Subject: [ibis-macro] Re: Eye mask question
Thank you both, Mike and Richard.
Indeed, this is a referencing question. So if I generate
an eye so that the recovered clock ticks are used for each
bit's center then my eye already incorporates the jitter
in the clock ticks (as well as the waveform). Shouldn't
the center of the eye template then be located at 0.5 UI
(instead of an arbitrary best fit location)?
Arpad
============================================================
-----Original Message-----
From: Mike Steinberger [mailto:msteinb@xxxxxxxxxx]
Sent: Tuesday, December 08, 2009 12:56 PM
To: Muranyi, Arpad
Cc: IBIS-ATM
Subject: Re: [ibis-macro] Re: Eye mask question
Arpad-
It seems to me that the timing of an Rx mask is going to depend on who
defined the mask and what they had in mind when they did it. Therefore I
don't think there's any one answer that fits all cases.
One possibility is that the mask would be placed with respect to the
clock ticks or an equivalent estimate of recovered clock timing. That
choice may be appropriate for some industry standard or locally defined
masks. For others, "best fit" might be the appropriate choice. Another
possibility would be something related to an ideal clock recovery, such
as mean or median threshold crossing time (two separate and distinct
possibilities with important differences between them).
In short, "Ask your mask maker."
Mike S.
Muranyi, Arpad wrote:
> Sorry for my poor problem statement...
>
> I mean the output of Rx (as it comes back from
> Rx GetWave), used together with the clock ticks
> from Rx GetWave to formulate the eye.
>
> Arpad
> ================================================
>
> -----Original Message-----
> From: Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
> Sent: Tuesday, December 08, 2009 12:40 PM
> To: Muranyi, Arpad
> Cc: IBIS-ATM
> Subject: Re: [ibis-macro] Eye mask question
>
> Arpad,
>
> Not meaning to be enigmatic here, but what signal(s) are you thinking
> get used to generate the eye diagram, and how?
>
> Todd.
>
> Todd Westerhoff
> VP, Software Products
> SiSoft
> 6 Clock Tower Place, Suite 250
> Maynard, MA 01754
> (978) 461-0449 x24
> twesterh@xxxxxxxxxx
> www.sisoft.com
>
>
>
> Muranyi, Arpad wrote:
>
>> Hello IBIS-AMI experts,
>>
>> This is a question regarding the analysis/evaluation
>> of the results we get back from an AMI simulation.
>>
>> How does the user decide whether the eye is good or bad?
>>
>> Naturally we have this thing called eye mask (template)
>> which we would all be able to drop into the eye without
>> touching any of the waveforms. But where are we trying
>> to position it? Anywhere it fits the best way? Or is
>> it supposed to be positioned at a certain location?
>>
>> Thanks for any feedback in advance,
>>
>> Arpad
>> =========================================================
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