Hi David, there are two methods I usually use (but I not really like both of them) Usually Write and Reads are different in high and low levels. So do an = A-B event trigger, e.g. you want to take a Write (measured at the DRAM), = connect a probe to another DQ channel at the controller and set the = level so high only a Write is catched. now you should have another probe = on the DQS at the DRAM to have a B event, and you can create an eye = timing referenced to the DQS for Writes at the DRAM (of course including = trigger jitter of the scope). If you use the clock as B event you should capture DQ and DQS for the = dataeye. Therefore you are missing the bit by bit correlation DQ to DQS = (assuming you are using a RT scope), but without this correlation you = might see the worst case that can happen over a long period of time more = likely! Another way is to check the WE and RAS signal, and do some kind of logic = triggering. regards Hermann -----Urspr=FCngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] = Im Auftrag von Novak David Gesendet: Mittwoch, 28. Juli 2004 05:19 An: si-list Betreff: [SI-LIST] DDR Eye diagrams For measuring DDR eye diagrams, the best location to measure reads is at = =3D the memory controller and the best place to measure writes is at the = =3D DDR. For example, measuring reads at the DDR will show more = reflections =3D than actually seen by the memory controller (I should = mention that I =3D have only series termination). This sounds simple, but I cannot think of a way to make the scope =3D = differentiate between reads and writes. You might suggest that I create = =3D a memory test which only does reads or only does writes. However, my = =3D worst case signals are when the entire system is running. Can anyone tell me how to make the scope trigger only on reads or only = =3D on writes? Thanks, David ------------------------------------------------------------------ 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