Luping, It is not possible or it might take huge engineering efforts to design/fabricate a board/channel that matches exactly as specified by the compliance channel. The common practice is to have your channel designed as close to the compliance channel but could be slightly worse. If the characteristic of the silicon (jitter, tolerance etc)coming out of this worse channel still meet the spec, then you know you are spec compliant and with margin. Negative dB just means it is loss, you always got loss from passive interconnect. Regards, Wei -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx liuluping 41830 Sent: 2008-1-15 23:33 To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Questions about Compliance interconnect magnitude response and ISI loss in XAUI standard Dear SI-listers: 802.3-2005_section4 Clause 47.4.1 and Figure 47-6 specify the characteristics for a test chanel that is refered to in the clause as a "Compliance Interconnect". The figure gives a S21(limit) line which the transmission magnitude response ,|S21|,of the Compliance Interconnect in dB should smaller than it. In general,channel specifications typically provide a limit line for attenuation,which represents the maximum allowed attenuation value , i.e.the channel attenuation must be less than than the limit line .Losses are usually indicated in dB,and increase positively along the y-axis , However ,we see that this is not the case for Figure 47-6.We also see that the response for a sample compliance interconnect is provided on the plot, and that this response is below the limit line, however the y-axis is labeld in negative dB ,what does this mean?Is it means that the channel with greater loss are considered valid ? Best Regards, Luping Liew CAD/SI Engineer Network Interconnect Research Department Huawei Technologies Co.,Ltd. *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~ Bantian,Longgang,Shenzhen 518129 P.R.C. Tel:+86-755-28972154 28780808 Fax:+86-755-28978853 E-mail:liuluping@xxxxxxxxxx URL:http://www.huawei.com ***************************************************************** This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or em ail immediately and delete it! ***************************************************************** ------------------------------------------------------------------ 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 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 technical documents are available at: http://www.si-list.net 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