Hi, When you use serial termination in general you use 33ohm and that because the buffer output impedance is about 22ohm -> 33+22=3D 55ohm =3D trace characteristic impedance. The very important point that buffer output impedance is about 22ohm only when output change from "0" to "1" (rising edge), when buffer output change from "1" to "0" (falling edge) is about 100ohm. In case of DDR the data changing both on rising and falling edges (double data rate), so impossible to use with serial termination. My opinion that you should use with parallel termination. Edi -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Aric Hadav Sent: Tue, July 13, 2004 6:24 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] DDR point to point termination Hi, I'm designing an embedded system with DDR. I'm using a CPU connected to an=20 on board four 16 bit DDR devices (no DIMM). I have 2 questions though - 1. can I use only a series termination on the data bus (I saw a few AN that=20 state that if the disctance between the controller and the DDR IC's is upto=20 2" its ok). has anyone did it with a 200MHz clock ? 2. since the address and control lines operate in half the data rate and the=20 DDR controller is very lightly loaded (only 4 chips) can I use only series=20 termination for address and control ? has anyone did it with good resaults ? thanks, Aric _________________________________________________________________ Add photos to your messages with MSN 8. Get 2 months FREE*.=20 http://join.msn.com/?page=3Dfeatures/featuredemail ------------------------------------------------------------------ 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