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 | 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 03:06:43 2007
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