Scott, Regarding your second area of concern that you stated "FET switch crosstalk", exactly what parasitic capacitance in the substrate are you referring to? I am aware of gate to substrate capacitance, and source/drain junction capacitance, what are you referring to? Thank You, Chris Jakubiec Sun Microsystems Scott McMorrow wrote: > > All, > > From previous work I performed on the PCI-X bus, the noise > specification was rather ill-defined. Package-level noise was never > even included or anticipated in the budgets. This is a bad thing. > > There are two areas that are of most concern for PCI-X. > > 1) Package crosstalk. Since the bus is not terminated, reflected > reverse crosstalk can become quite significant and one of the most > dominant factors in noise margining. You'll need to perform > measurements designed to isolate SSO noise from package crosstalk. This > can be done by knowing the layout of the package and selecting a set of > adjacent signals to switch in three ways. > a) switch only the center line as a base line measurement > b) switch all signals simultaneously in the same direction for even > mode crosstalk > c) switch all neigbors to the center signal in the opposite > direction as the center for even mode crosstalk. > With these sets of measurements (since the remainder of the drivers on > the bus are quiescent) you will see package crosstalk quite clearly. > > 2) FET switch crosstalk. If you are using a hot-swap design with FET > switches, be very very careful. FET switches have significant crosstalk > between channels that is caused by parasitic capacitance in the > substrate. Packages for these devices usually have large ground > inductance which does not effectively ground out the substrate > parasitics. As a results, you literally see what amounts to simultaneous > switching crosstalk between the channels. This can be quite high, and > in some systems will be the dominant noise. And, since the switch > placement varies from design to design, and the bus is not terminated, > this noise can reflect all over the place and be quite problematic > > regards, > > scott > > Grist, Robert wrote: > > >Also make sure you are not viewing signal conditions during tri-state > >conditions. Noise during this time is not important. > > > > > >-----Original Message----- > >From: Gregory R Edlund [mailto:gedlund@xxxxxxxxxx] > >Sent: Wednesday, October 15, 2003 10:03 AM > >To: swldstn@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx > >Subject: [SI-LIST] Re: PCI and PCI-X bus noise > > > > > >Steve, > > > >I applaud your efforts in making quiet line measurements on PCI/X. This > >is > >an important part of the SI verification process but a difficult one > >because you need to have control over bus patterns, be able to trigger > >on > >the pattern of interest, and verify the switching state of the > >neighboring > >lines. In my opinion, it's well worth the effort to isolate crosstalk > >and > >SSN from reflections as much as possible. Do this by switching only one > >bit on the bus (reflection), all bits (SSN), and a small number of > >aggressors around your quiet line (crosstalk). > > > >The other thing that you can do to determine whether or not you're in > >trouble is to attempt to place the noise events in time relative to the > >input clock at the receiver chip. You will need to scope both the quiet > >line and the clock as close to the die pad as possible. Construct a > >setup > >and hold window around the clock using what you know about clock skew > >and > >the PCI/X timing specs. Do your noise events fall within this window? > >What if your drive chip speeds up or slows down? > > > >I see from my (old) copy of the PCI-X spec that you have 825 mV of noise > >margin to work with on the low level, assuming Vcc =3D 3.3 V. They = > >break > >out > >reflections, crosstalk, and input reference offset but not SSN. I guess > >I > >would have broken out crosstalk, SSN, and input reference offset and > >left > >reflections as part of propagation delay. At any rate, you'll need to > >look > >at your 1.2 V and determine how much of it is crosstalk and SSN that can > >occur inside the setup and hold window. > > > >Greg Edlund > >Senior Engineer > >Signal Integrity > >IBM Engineering and Technology Services > >3605 Hwy. 52 N, Dept. HDC > >Rochester, MN 55901 > >gedlund@xxxxxxxxxx > > > > > > > >Msg: #11 in digest > >Date: Tue, 14 Oct 2003 13:49:36 -0400 > >From: swldstn@xxxxxxxxxxxx > >Subject: [SI-LIST] PCI and PCI-X bus noise > > > >To all, > > > >In doing some targeted simultaneous switching noise > >data patterns on a PCI and PCI-X bus we see total > >noise of between 0.5 to 1.2 volts depending on bus > >configurations. This voltage is the sum of ground bounce > >ringback, reflections, etc when looking at a quiet > >high or low pin. At this time its hard to separate > >out the source of the noise. The device under test is > >part we have designed. > > > >Is anyone willing to share their experience or point > >me to some published information on PCI and PCI/X? > > > >Any help is appreciated. Thanks in advance. > > > >Steve Waldstein > >swldstn@xxxxxxxxxxxx > > > > > > > >------------------------------------------------------------------ > >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: =20 > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages=20 > >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 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 > > > > > > > > > > -- > 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 > ------------------------------------------------------------------ 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