I had a similar problem that repeatedly crashed a computer for me (and almost no one else). That turned out to be a problem with rubbing between polyester clothing and the chair fabric. We ultimately solved it by removing that chair from the "terminal" room. - Lynne "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 Andrew Ingraham Sent: Friday, June 02, 2006 8:42 AM To: SI-List Subject: [SI-LIST] Re: Strange resets happening in one of our circuit boards I too have seen similar effects caused by chairs. I spent at least one late night investigating a circuit board and rolling various chairs around the lab floor. The chair was very definitely generating static discharges somewhere (probably in the rollers of the chair) and this was radiating and being picked up by (a) the scope probe leads, (b) my circuit board, and (c) any cables and leads attached to the circuit under test. As I recall, it didn't matter if I wore a wrist strap, while sitting in the chair. The actual arcing was inaudible and invisible to me. If I remember right (it's been some years now), there was some indication that much of the induced noise was common-mode and being converted to differential later. I wonder if a common-mode choke around your JTAG port might help.... I don't remember now whether those chairs had the grounding chains on their bottoms. Some of our lab chairs had about a foot of loose chain dangling underneath that is supposed to lay on the floor, and our labs were supposed to have been built with flooring material that is slightly conductive. (Google "conductive linoleum" and you'll come up with several hits.) While this would prevent the entire chair frame from becoming charged, it probably does nothing to prevent static from accumulating and arcing within the wheels themselves unless they, too, are made with conductive material. I've just come to accept the fact that all chairs (and many other things too, I'm sure) generate occasional random EMI and I'll see it in my lab measurements from time to time. Was it a capacitor across the pull-up resistor that "fixed" your problem, or was it a capacitor from the reset line to ground? If you had noise from the power supply, a capacitor across the pull-up resistor would not have helped. It would be interesting to see if the problem continues with the unit in its metal housing but with the JTAG attached. Regards, Andy > We see +5/-3V worth of noise on the signal just by rolling my chair > back and forth in front of the emulator. ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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