Hello, Yan Hang, IBIS and SPICE do not have the same Time=0 reference, due to the way SI tools trigger I/O inputs. This means that there is a time offset between the two waveforms. This offset can be corrected for by simulating the load [Vmeas, Rref, Cref]. This delay offset can then be used to adjust the delay in other simulations. Many SI tools have automated this process. A good paper on this is http://pcdandm.com/cms/content/view/2800/95/. There is also a HyperLynx Application Note, referenced in that paper. Best regards, Lynne "IBIS training when you need it, where you need it." Dr. Lynne Green Green Streak Programs http://www.greenstreakprograms.com 425-788-0412 lgreen22@xxxxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of raj singh Sent: Friday, November 17, 2006 1:34 AM To: yang@xxxxxxxxxx; si-list@xxxxxxxxxxxxx Cc: liuweidong@xxxxxxxxxx Subject: [SI-LIST] Re: Buffer delay Hspice delays should be accurate and in general more than ibis. Better to use ibis only for SI sims and not for timing. regards Raj yan hang <yang@xxxxxxxxxx> wrote: Hi All, Now I do some board timing simulations . I got the hspice = model and ibis model for same buffer. Then I set a test fixture(Ex. Cref=3D15pf,Rref=3D1E6,Vref=3D3.3V),I contrast the simulation result of = buffer dealy using hspice model and ibis model. I found there is a little big diffrence between them. So when translate hspice model to ibis model,how to consider about the buffer deley issue? =20 Should I trust the buffer delay value from ibis model = simulation? Best Regards. Yan Hang Huawei Technology 086-21=A3=AD68644808=A3=AD24043 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu