Todd,pk-pk jitter for good CDRs is designed to be around +/- 0.05 UI at a 10^-12 confidence interval. Deterministic jitter transfer and multiplication in the CDR loop will be added on top of this. CDR jitter can easily approach +/- 0.1 UI at a 10^-12 confidence interval under stress testing.
+/-10% is a reasonable number. Shortest period is 0.9 UI. Longest period is 1.1 UI.
Scott Todd Westerhoff wrote:
Vladimir, What is the magnitude of the effect you're talking about? 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 -----Original Message----- From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Dmitriev-Zdorov, Vladimir Sent: Wednesday, April 14, 2010 4:06 PM To: Mike Steinberger Cc: fangyi_rao@xxxxxxxxxxx; scott@xxxxxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx Subject: [ibis-macro] Re: clock_times .... yet again Mike,I question the practical relevance of your concern about missing orduplicated waveform points at the edge of an eye diagram. Perhaps the brief answer is that superimposing disconnected or overlapped waveform pieces may cause distortions of the jitter PDF that accumulates at eye edges. I'm not ready to discuss the numbers but the approach does not seem technically clean. In particular, it cannot correctly account for peak to peak jitter. Vladimir -----Original Message-----From: Mike Steinberger [mailto:msteinb@xxxxxxxxxx] Sent: Wednesday, April 14, 2010 1:51 PMTo: Dmitriev-Zdorov, Vladimir Cc: fangyi_rao@xxxxxxxxxxx; scott@xxxxxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx Subject: Re: [ibis-macro] Re: clock_times .... yet again Vladimir- The short answer is that your second statement is correct and always has beenI question the practical relevance of your concern about missing or duplicated waveform points at the edge of an eye diagram. It is certainly mathematically possible that there could be missing or duplicated waveform samples at the edge of an eye diagram. When this happens, how will it affect the results of the analysis? And if it doesn't affect the results of the analysis, is it worth discussing?"the standard way of building the eye histogram from Rx output is not defined in details and could be implementation specific"Mike S. Dmitriev-Zdorov, Vladimir wrote:Mike, We are talking about different things. My point was that the specshouldbe 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 accuratedefinition.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 onthispoint 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 AMTo: 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 wanttoconsider the case of an odd/even receiver architecture. As you well know, the IBIS AMI API is based on the assumption that there is asingledata path, and yet we routinely and successfully use IBIS AMI to modelwaveformreceivers that have two or four data paths. In such cases, thein 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 builtupcircuitfrom segments of waveform that come from different parts of thealtogether. This all reproduces measured data quite well, so long as the switch inwaveform 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 waveforminyour 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--------------------------------------------------------------------- IBIS Macro website : http://www.eda.org/pub/ibis/macromodel_wip/ IBIS Macro reflector: //www.freelists.org/list/ibis-macro To unsubscribe send an email: To: ibis-macro-request@xxxxxxxxxxxxx Subject: unsubscribe
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