Historically, they are very likely to be different. The peak to peak amplitude depends on the output impedance of the buffer. In one case, the R to ground the pullup device is active controlling the amplitude of the swing. In the case of R to Vcc the pulldown device is controlling the amplitude. In most cases the pullup and pulldown devices do not have the same DC output impedance so the amplitudes will differ. I have noticed in more modern processes the IV characteristics of the pullup and pulldown better match each other. This gives a more consistent output impedance, independent of state, which makes serial termination easier to do. Tom Dagostino Teraspeed Consulting Group LLC 503-430-1065 tom@xxxxxxxxxxxxx www.teraspeed.com -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jayasree Nayar Sent: Thursday, August 12, 2004 5:37 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Regarding rising waveforms in the IBIS models Hi all, Would like to get your inputs regarding the following questions I have regarding the rising waveforms in an IBIS model: In an IBIS model, for the two rising waveforms , one with V_fixture= 0 and the other with V_fixture =Vcc, should the total swing (difference between the maximum and minimum voltage values) be the same. If so, what could be the reason that there is a difference in the voltge swing between the two rising waveforms. Please advise. Thank you. regards Jayasree -- Binary/unsupported file stripped by Ecartis -- -- Type: text/x-vcard -- File: njy.vcf ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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