I would first start with your scope probe. How long is the ground wire? = It needs to be as short as possible, perhaps even shorter than that. If = possible, try an active fet probe. Scope probe ground inductance has = caused many a person to go chasing their tale. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Henrik Gild Sent: Thursday, October 27, 2005 5:14 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] quenching ugly spikes? Hi! As a hobby I'm designing an Ethernet/USB board for those Atari computer enthusiasts who are still active. My board sits on top of an accelerator board containing an MC68060 and a couple of CPLDs, connecting to my = board through two 2.54mm (0.100") 2x25 pin connectors (one for data lines and = one for address/control). My problem is that I get really ugly signals from = the accelerator board. They are supposed to be 3.3V signals but I see spikes = all the way up to 6V on the address lines and the data lines start off with = a small 2V top, then down to -1V and finally up to a 5.5V spike before settling at 3.3V after a total of 18ns. I assume that these symptoms are caused by two things: 1) There are no series resistors on any lines on the accelerator board, = and the data lines are as long as 22cm (about 8.5"). The rise times are somewhere in the 2-3ns region, so I suppose the lack of series = termination is not a good thing. I have series resistors on my board and when my = board drives the signals they look much nicer. 2) There are only two ground pins at each end of both connectors, in = total four per connector. The lack of nearby ground pins for the data and = address lines isn't good either? What do you think I can do about this? I've tried terminating using = diodes (though only 1N4148) but that didn't change anything. I'm thinking of = using chokes on the lines. Could that be a good solution? Both my board and the accelerator board are four layer boards with = dedicated=20 ground and power layers. I hope you can help me out! :) Thanks! /Henrik Gild=E5 ------------------------------------------------------------------ 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: =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 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