Henrik, You suspect the right things. Your big problem is that you don't have much of anything for a defined=20 return path, so it is composed from your other signals. You need a lot=20 more than two grounds at either end of a wide bus. Why not borrow IDE133=20 cables with interleaved grounds. Your signaling rates are similar to=20 theirs, and those connectors are plentiful and cheap. Your signals are pretty slow, so you will only need to terminate if the=20 path is over abut 8cm. Books that could help you immensely: "High Speed Digital Design", Johnson and Graham "Signal Integrity Simplified", Bogatin Good luck. Steve. At 11:13 PM 10/27/2005 +0200, Henrik Gild wrote: >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 >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: > //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