Hi, A unit with microprocessor based system circuit board is resetting when we plug in emulator port in JTAG port. Using scope we see that CPU reset pin is asserted, hence the reset. We see +5/-3V worth of noise on the signal just by rolling my chair back and forth in front of the emulator. This happens in following scenario: 1. User is sitting on chair, user gets up (doesn't touches the unit) and unit resets. We demonstrated this on three randomly selected units. Sounds ridiculous but it is true OR 2. If we keep solder wires for scoping purposes. It doesn't happen when Unit is enclosed in it's metal housing. Investigated.. a. Reviewed schematics and CPU's reset line is pulled to 3.3V using 1K ohm resistor. b. Physically checked that pull up resistor is in place and is connected with BGA ball of reset pin. c. We checked power monitor chip which can drive reset too..but no issue there. D. Reset line is not going anywhere else other than JTAG port and Power Monitor Chip Brainstormed.. a. Soldering issue due to BGA ? Ruled out as how can soldering issue be on three randomly selected units. b. ESD- Ruled out as per our understanding ESD (air discharge) cannot "arc over" from 2-3 feet distance. Fix:=20 A team member recommended to put a capacitor across resistor. Did that and problem went away. Can anybody explain why it is happening ? Is it noise from Power Supply but how can it defeat a strong pull up ? Thanks, Shiraz Bashir General Electric Healthcare ------------------------------------------------------------------ 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