Hello Kevin, Thanx for this info.Which simulator you are using. Regards Akhilesh -----Original Message----- From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Kevin Ko Sent: Thursday, May 17, 2007 10:37 PM To: Akhilesh CHANDRA; 'Todd Westerhoff'; ibis@eda-stds.org Cc: Akhilesh CHANDRA Subject: RE: [IBIS] How we can model startup time in IBIS. Akhilesh, The simulator that I used to have, XTK/Quad, has an offset parameter called "time to Vm". The simulated delay numbers are added or substracted, depending on whether it's a positve or negative offset, to give you the delay that you needed to match your spice sim delay or start time. This can be done in post-processing as well, just an extra step for you. It is a lot easier that trying to adjust the load reference to "match" your spice delay requirement. regards, kevin --- Akhilesh CHANDRA <akhilesh.chandra@st.com> wrote: > hello Todd, > > Thanx for this important info. I have one doubt. > > According to paragraph 3 "IBIS simulations are always compared to a > simulation of a "reference load", because the comparison to the > standard load simulation normalizes out the start time of the model". > > In my case cell delay is 300ps while it's startup time is 3ns. How > it's normalizes when I use standard load. > > Regards > Akhilesh > > -----Original Message----- > From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On > Behalf Of Todd Westerhoff > Sent: Tuesday, May 15, 2007 6:48 PM > To: ibis@server.eda-stds.org > Subject: RE: [IBIS] How we can model startup time in IBIS. > > Akhilesh, > > If you or your customers are correlating simulation results in IBIS to > a transistor level equivalent, it's important to understand that "time > 0" in an IBIS model is arbitrary. There's no guarantee that an IBIS > and transistor model simulated side by side will produce outputs at > the same time, and "shifting" the IBIS result in time to get > correlation is completely legal. > > Bonnie's article made this same point. She mentioned that a > transistor model includes the delay through the buffer, while the IBIS > model represents the output behavior but not necessarily the model's intrinsic delay. > > This is the reason IBIS simulations are always compared to a > simulation of a "reference load", because the comparison to the > standard load simulation normalizes out the start time of the model. > > If you're looking to use SI simulations to derive an interconnect > delay for plugging back into a timing analysis, you should ALWAYS be > normalizing your SI simulations to a reference load. The startup time > of the model gets subtracted out in this case, and you should end up > with the same number for the interconnect delay whether you use the transistor or IBIS model. > > Some would argue that transistor level simulations don't need to be > normalized; I would disagree. It's true that you can define specific > timing and SI strategies where normalization of transistor level SI > simulations isn't required; but most people aren't running analysis > under those conditions. > > Todd. > > Todd Westerhoff > VP, Software Products > SiSoft > 6 Clock Tower Place, Suite 250 > Maynard, MA 01754 > (978) 461-0449 x24 > twesterh@sisoft.com > www.sisoft.com > > -----Original Message----- > From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of > Akhilesh CHANDRA > Sent: Tuesday, May 15, 2007 1:53 AM > To: 'Dunbar, Tony'; ibis@eda-stds.org > Cc: Akhilesh CHANDRA > Subject: RE: [IBIS] How we can model startup time in IBIS. > > Hello Tony, > > Thanx for your reply. Initial delay is not important for SI > simulations but if it's missing in our model then it's difficult to > match spice and IBIS results also few customers use these models for > delay calculation if I don't support this startup time then customer > have only 300ps delay while in silicon it's 3.3ns. > > Regards > Akhilesh > > -----Original Message----- > From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On > Behalf Of Dunbar, Tony > Sent: Monday, May 14, 2007 10:22 PM > To: ibis@server.eda-stds.org > Subject: RE: [IBIS] How we can model startup time in IBIS. > > Hi Akhilesh, > > I've pondered this for a little while and all I can come up with is to > ask why is this an important or even relevant functional detail to be > included in a signal integrity simulation, presuming it is a signal > integrity simulation you are wanting to do? > > An "initial delay" can be incorporated into the stimulus of some SI > simulators but that is really intended to provide for driver-to-driver > skew, whereas your brief description refers to "startup". > > Regards, > Tony > > -----Original Message----- > From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On > Behalf Of Akhilesh CHANDRA > Sent: Monday, May 14, 2007 4:18 AM > To: ibis@server.eda-stds.org > Cc: Akhilesh CHANDRA > Subject: [IBIS] How we can model startup time in IBIS. > > > > Hello Experts, > > I am doing IBIS model of an IO operating at 800MHZ frequency. It > have startup time of 3nsec. After 3ns design gives output of 800mhz > frequency. If I model this time in waveform database of IBIS models > the I have over clocking issue and design is not work at this high > frequency. Can you help me to model this startup time. Is anyone make IBIS model of such designs. > > Regards > Akhilesh > > > -- > 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 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 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 > === message truncated === ____________________________________________________________________________ ________ Looking for earth-friendly autos? 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Autos' Green Center. http://autos.yahoo.com/green_center/ -- 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 Thu May 17 22:07:53 2007
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