The 4 VT curves tell the simulator how the pulldown transistor turns off and the pullup device turns on for a rising waveform and how the pullup device turns off and the pulldown device turns on. When using just ramp data the time relationship of turn-off and turn-on is not known. Tom Dagostino Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC 2926 SE Yamhill St. Device Modeling Division Portland, OR 97214 13610 SW Harness Lane Beaverton, OR 97008 http://www.teraspeed.com 503-430-1065 tom@xxxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jack W.C. Lin Sent: Thursday, January 23, 2003 5:34 PM To: 'arpad.muranyi@xxxxxxxxx'; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Question on IBIS: rising/falling waveform - How complete waveform created? Hi Muranyi: In theoretical, if we have pull up and pull down I-V curve (HIGH and LOW curve) plus rise/fall time (ramp), the simulator should can create a waveform. But this waveform will not the same as the waveform which is created by simulator when include pull up, pull down, 4 sets V-T tables. I can't understand that if we have I-V curve and ramp info, why we should have 4 sets V-T tables? Can you explain more about the roles of V-T tables? How to help simulator to create more accurate waveform? I can't understand what you said " Mathematically, if you have a complementary buffer i.e. it has a pullup and a pulldown, with four waveforms in the IBIS model you can set up two equations with two unknowns for each edge (rise/fall) and solve for the unknowns which are the coefficients vs. time for the pullup and pulldown." Thanks Jack -----Original Message----- From: Muranyi, Arpad [mailto:arpad.muranyi@xxxxxxxxx] Sent: Friday, January 24, 2003 12:18 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Question on IBIS: rising/falling waveform - How complete waveform created? This is to answer Jack's and Adeel's questions about how waveforms are used in IBIS. To give an intuitive answer, you can think of waveforms as percentage vs. time tables. They are telling the simulator is how to scale the IV curves as a function of time as the buffer turns on/off. Mathematically, if you have a complementary buffer i.e. it has a pullup and a pulldown, with four waveforms in the IBIS model you can set up two equations with two unknowns for each edge (rise/fall) and solve for the unknowns which are the coefficients vs. time for the pullup and pulldown. Since the IV curve is a function of the pad voltage, the load of the actual simulation doesn't have to be the same as the R_fixture that was used for the waveform tables in the IBIS model. The actual simulation waveform will adjust to the loading conditions. I hope this helps to understand how the IBIS model works in simulators. Arpad Muranyi Intel Corporation =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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