Yes, the V/T table curves are shifted back toward t=zero, and it is important that all waveforms of the same direction (for example all [Rising Waveform]s) must be shifted by the same time offset. But people have different conventions with regard to synchronizing the shifting of the typ/min/max corners. Some people determine the smallest lead time, which is usually on the max corner, and take that much out of all three corners. This is easy because you only have to delete some table rows and subtract some offset from all time values, easily accomplished with just a spreadsheet. Some will remove lead time from each corner independently. I would write code to do this before trying it with a spreadsheet, since it sometimes involves resampling the waveform points. Lance Wang presented on one aspect of the overclocking topic at an IBIS summit: http://www.vhdl.org/pub/ibis/summits/feb07/wang.pdf My own observation is that simulators at one time had trouble with IBIS waveforms longer than 1/2 a clock period, but no longer do. Mike -----Original Message----- From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Scott McMorrow Sent: Monday, May 18, 2009 11:17 AM To: g-m@ti.com Cc: ibis-users@server.eda.org; ibis@server.eda.org Subject: [IBIS] Re: [IBIS-Users] Simulating IBIS at the maximum frequency Gowtham Since time is relative in IBIS model simulations, what you do is to normalize the V/T table timing, by shifting the slower corner curves back towards zero. Essentially, you remove any leading static values from the curves, prior to the edge transitions. Scott Gowtham M wrote: > Hello, > > How do we ensure that IBIS model can be correctly simulated at the > highest possible frequency? Suppose, I have a buffer which is expected > to work at 100MHz. Hence, the VT table should be at most 1 / ( 2 * > 100M ) = 5ns wide. > > If the buffer is designed such that it can just meet this requirement > in min (slow) corner. The problem that I am facing is that I cannot > represent all of typ/min/max transitions within this window of 5ns > because of variations in buffer delay across corners. > > How do I create an IBIS model that can be correctly simulated at > 100MHz in such cases? > > Thanks for your help. > > Gowtham > -- Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed(r) is the registered service mark of Teraspeed Consulting Group LLC -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993Received on Mon May 18 10:08:08 2009
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