These things can be highly tool specific but in general, the INPUTS have only the overshoot protection of the overshoot protection diodes but the OUTPUTS have the additional protection provided by the CMOS pullup and pulldown devices (even in off state they provide back bias protection). Once again, it depends on how the simulator itself interprets the IBIS model data. regards, jon -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Rakesh Metha Sent: Friday, December 12, 2003 8:01 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] IBIS models - What is the difference between Tri-Out & Tri-In Hi, I am conducting reflection analysis on a PCI based board on the local data bus. There are 4- devices connected to the data bus, a PLX-9054 and 3-Spartan2 fpga's - all with 3.3V I/O's and all bi-directional. I am using the Cadstars SI tool for analysis. I get substantially different results when I use one of the 4-devices as a Driver (Output). and the other 3-are defined as either 1. Tri-Out 2. Tri-In 3. In When I declare any on of the remaing 3 as In/Tri-in the over shoots increase substantially. Please help me by clarifying, what is the difefference between Tri-Out, Tri-In and In. and Which is the prefered one when analysing a bus. with warm regards rakesh mehta ------------------------------------------------------------------ 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 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 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