If the simulator is telling you the truth then you should be disappointed in the driver not the simulator (or maybe the receiver for having such a harsh undershoot rule). I know how this can be frustrating. Even though, as you say, the trace is very short, it might not be short compared to the rise time of your signal. To reduce undershoot in a point to point topology, you should make the source Z of the driver equal the T-line Z (Zo). If it does then a signal is launched that is 50% of its final value, it hits the load and doubles to a perfect 100%, reflects back to the source and gets absorbed - because Zsource =3D Zo. To make Zsource =3D Zo ,as you mention, you can add a series resistor, = or go to a weaker driver. Rereading your email (before I hit send) I have one other point I'd like to mention. You mention that the problem is with the PPC part (power PC processor?). I have noticed that many of the Freescale processors have very very fast edges. I've seen 3.3V IO on Freescale's PowerQUICC processor family have rise times of 100ps. What's sad, is that these same IO have a Clk-to-Q of 4ns (why does an IO need a 100ps rise time with a prop time of 4ns????). Very frustrating - it causes so many noise problems. I've been complaining to Freescale about this for years. So check your rise time of the driver. Is it really fast? If it is, then it is causing your problem...that combined with Xilinx's very strict under/overshoot rules. Regards, Jim Peterson Honeywell -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of crr1231@xxxxxxx Sent: Tuesday, July 08, 2008 8:23 PM To: Aubrey_Sparkman@xxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Virtex -5 PCI ibis file and simulation I am using PCI (33MHz). The simulator says that my problem is with undershoot but I'm thinking that the model isn't very good. It is a point to point trace and very short (PPC to V5). I don't have room on the board for series resistors and don't realy want to go down that path. I'm dissapointed that the simulator (ICX) and the ibs model for the V5 is showing what it does. The only way I can reduce the undershoot is to insert the V5 with a fast-6mA driver in place of the PPC IO. Any other suggestions are welcomed. Thanks, Charlene -----Original Message----- From: Aubrey_Sparkman@xxxxxxxx To: weirsi@xxxxxxxxxx; crr1231@xxxxxxx Cc: si-list@xxxxxxxxxxxxx; cradtke@xxxxxxxxxxxxxxx Sent: Tue, 8 Jul 2008 1:13 pm Subject: [SI-LIST] Re: Virtex -5 PCI ibis file and simulation Charlene, You didn't say whether you were using PCI or PCI-X, but my memory says both PCI and PCI-X specs allowed HUGE amounts of over and undershoot. PCI-66 was often the worst case. Are you sure you violate the *shoot specs? The spec allows so much, I've only ever seen this once. Steve is right that series resistors can reduce the *shoots but that takes a lot of resistors and they can kill your setup time if you have a long link or several loads. Aubrey Sparkman=3D20 Enterprise Engineering Signal Integrity Team=3D20 Dell, Inc.=3D20 Aubrey_Sparkman@xxxxxxxx=3D20 (512) 723-3592=3D20 "The single biggest problem in communication is the illusion that it has taken place." -- George Bernard Shaw -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Tuesday, July 08, 2008 2:42 PM To: crr1231@xxxxxxx Cc: si-list@xxxxxxxxxxxxx; cradtke@xxxxxxxxxxxxxxx Subject: [SI-LIST] Re: Virtex -5 PCI ibis file and simulation PCI is so old that this could be a real problem. I don't believe Xilinx does anything to particularly slow down V5 outputs when set for PCI I/O. External resistors should take care of the problem. Steve. crr1231@xxxxxxx wrote: > I was wondering if anyone else in the community has been able to implement (in simulation and in Hardware) PCI at 3.3v on the virtex 5 device (point to point between processer and FPGA). It seems that the V5 model that I am using responds the same whether I use 3.3V or 3.0V and gives the same over and undershoot regardless of trace length using the PCI models in the ibis file. According to my questionable simulations, overshoot is within range but undershoot is out by 300mV. My concern is that the sim is somewhat accurate, in hardware - the input diodes will not be able to clamp and the device will be damaged (over time). If anyone has successfully used an ibis model ( I am using the 1136 package), would you mind emailing it to me? > With much appreciation, > Charlene > > > ------------------------------------------------------------------ > 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.net > > List archives are viewable at: =3D20 > //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 > =3D20 > > > =3D20 -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882=3D20 California office (866) 675-4630 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax=3D20 Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ------------------------------------------------------------------------ ------------------------------ Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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.net List archives are viewable at: =3D20 //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 =3D20 ------------------------------------------------------------------ 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.net List archives are viewable at: =20 //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 =20 ------------------------------------------------------------------ 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.net List archives are viewable at: =20 //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 =20 ------------------------------------------------------------------ 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.net 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