I had this problem when an oscillator with too much jitter was substituted for the originally specified part. Something to check.... Robert D. LaMoreaux -----Original Message----- From: Suresh Subramaniam <ssubram@xxxxxxxxxx> Sent: Sunday, October 24, 2010 11:45 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Ethernet PHY not linking Hello Experts, I am facing the following situation: We have a tri-mode Ethernet PHY on one of our boards. It will reliably link at 10Mbps but fails 100MBps and 1Gbps. The schematics have been verified for correctness and the PHY configuration bits are strapped properly on the board . RESET meets the timing specs defined in the datasheet. The RJ-45 connector has integrated magnetics. The MDI* diff pairs out to the connector are routed on the lower layers in the stackup (the last five layers are reproduced below). Couple of pairs are routed on Sig4 and two other pairs are routed on Sig5. GND SIG4 PWR5 SIG5 GND The traces are about 0.5 inches in length. DVDD is a small plane on SIG4 and powers the core of the chip. AVDD is a small plane on SIG 5 and supplies analog power. PWR5 is a 3.3V power plane (note that the signaling voltage is 2.5V which is on a different layer). The 3.3V power plane is pulled back around the RJ-45 making the MDI* diff pairs without a reference plane on one side for about 100 mils. I understand that the layout is not ideal. But can these deviations from the ideal cause the link to fail at 100Mbps and 1000Mbps. Appreciate any pointers and insights you can offer. Thanks Suresh Subramaniam ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu