Hi, James, First, you must decide how Vcc_core will vary with corners. It might vary in the same direction as Vcc_pu, or in the opposite direction, or not at all. SPICE can help you determine the best/worst case combinations (corresponding to IBIS min/max corners). The SPICE input files must have Vcc (Vcc_pu) set the normal way for s2ibnis3. The Vcc_core (1.8V) source must be created, with the desired voltage, before the SPICE files generated by s2ibis3 are simulated. This can not be done using the default s2ibis3 flow. There are two ways to add a Vcc_core voltage source under s2ibis3. One could add the Vcc_core pin to the subckt AND to every call to the subckt, and add a Vcc_core voltage source - this requires editing EVERY SPICE file generated by s2ibis3, running SPICE, then running s2ibis3 model extraction. Alternatively, one could add a Vcc_core voltage source within the subckt - this has the advantage that one does not need to edit the s2ibis3 netlists, except to set the voltage for Vcc_core. I personally prefer the second approach, but either one will work. Best of luck, Lynne PS: Please check my web site for upcoming IBIS training classes. We are willing to arrange classes in additional locations. "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 james cui Sent: Monday, November 27, 2006 7:47 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] About S2ibis2 Hello,ALL thanks Lynne for your help I have another question about S2IBIS2. How can I change ".DC" sweep range to generate Pullup curve,but not change core power? (now) **Pullup curve Vcc=1.8v **core power Vcc=1.8v (I want)**Pullup curve Vcc=3.3v **core power Vcc=1.8v Thanks ------------------------------------------------------------------ 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