Mike,
We are talking about different things. My point was that the spec should
be definite enough about what is a correct meaning and usage of clock
times.
You are saying that since you do a specific type of simulation
successfully, there is no reason to worry about the accurate definition.
Or did I take it wrong?
Any abstract EDA tool gets a long waveform and clock times output from
Rx DLL. This is to be used to create eye "histograms". Do we need to
formally define the standard way of doing this or remain silent on this
point thus leaving the possibility that the result is implementation
dependent?
The best I can figure out from the spec and our discussion so far is
this:
"EDA tool will use the portion of the waveform from tick_time_N to
(tick_time_N+1UI) to fill the eye histogram. It is allowed that some
portions of the Rx output waveform will be duplicated or missed in the
histogram if the clock times are non equidistant"
or
"the standard way of building the eye histogram from Rx output is not
defined in details and could be implementation specific"
Vladimir
-----Original Message-----
From: Mike Steinberger [mailto:msteinb@xxxxxxxxxx]
Sent: Wednesday, April 14, 2010 11:35 AM
To: Dmitriev-Zdorov, Vladimir
Cc: fangyi_rao@xxxxxxxxxxx; scott@xxxxxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: Re: [ibis-macro] Re: clock_times .... yet again
Vladimir-
If you want to worry about missing or duplicated data, you might want to
consider the case of an odd/even receiver architecture. As you well
know, the IBIS AMI API is based on the assumption that there is a single
data path, and yet we routinely and successfully use IBIS AMI to model
receivers that have two or four data paths. In such cases, the waveform
in each data interval is the waveform at the decision circuit whose
decision is actually going to be used for that data bit. Thus, the
receiver model output waveform and the resulting eye diagram is built up
from segments of waveform that come from different parts of the circuit
altogether.
This all reproduces measured data quite well, so long as the switch in
waveform segments always occurs at the edge of the eye.
Mike S.
Dmitriev-Zdorov, Vladimir wrote:
But here is a minor technical problem: if you do this way, and the
clock times are not equidistant, then some portions of the waveform in
your histogram are counted twice and some could be missing. This is
another Pandora box: what's a definition of an eye histogram built
from waveform and non-equidistant clock times?
Vladimir