qzheng, Andy is quite correct. When an Ibis model is extracted with only ramps, all of the delay information is lost. The best you can do is to correlate the rising and falling edge rates to the original Hspice, along with the output drive strength, to determine if the extraction was performed correctly. If waveform tables are used in the IBIS model, and if the extraction is performed on the same Spice model that you are comparing with, the edges and delays should be exactly the same provided: 1) the waveform tables have not been normalized to remove leading delay. But even then, the delay relationship between the edges should be maintained. 2) The signal used to stimulate the Ibis model in Hspice has its delay adjusted to triger the driver at the same absolute time as in the orignal Hspice simulation. best regards, scott -- Scott McMorrow Teraspeed Consulting Group LLC 2926 SE Yamhill St. Portland, OR 97214 (503) 239-5536 http://www.teraspeed.com ------------------------------------------------------------------ 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