As an observation, the digital part of this definition would seem to include such technologies as AGTL+, which is usually a wired-or buss technology (no pullup) but is implemented such that on the rising transition, there is a small "kicker" that drives the active driver as a pullup for 1 cycle and then turns off and lets the wired-or termination drive the line. (although I think this is done in AGTL+ for SI termination issues, but perhaps that is the same as High Frequency content). jon > -----Original Message----- > From: DoraBabu - CTD, Chennai. [mailto:dbabu@xxxxxxxxxxxxxxx] > Sent: Friday, July 05, 2002 9:27 AM > To: lincj@xxxxxxxxxxxxxxxxxxx; hpc@xxxxxxxxxx > Cc: SI_LIST (E-mail) > Subject: [SI-LIST] Re: TO define the "Preemphasis" > > > > > Got it from Xilinx Signal Integrity glossary : > > Pre emphasis is magnitude boosting of high frequency spectral > components > before launching the signal (wave) onto the Transmission > Line. Transmission > Lines embedded in most standard PCB materials (FR4, Rogers > 43xx, Nelco and > Rogers) suffer varying degrees of dispersion and loss in the > 1 gigahertz > spectrum. This is mostly due to conductance losses (leakage > from the copper > trace to any other conducting structure) and Skin Effect. > Dispersion is a > phenomenon whereby spectral components travel at different > velocities. The > waveform looks smeared when it arrives at the receiver. > Both of these "characteristics" play into a diminished and > poorly received > signal. By boosting the high freq. spectral components, the > magnitude of > these components can be diminished as the wave travels through the > Transmission Line, but since it starts out larger than the > lower frequency > components, the composite signal arrives at the receiver > looking the way it > was intended. > > Pre Emphasis is done by simply increasing the maximum amplitude of the > signal for one bit period. If the signal is 1 bit in > duration, the amplitude > is allowed to rise to a value which is some percentage > greater in magnitude. > At this point, if the signal is to stay at the same logic > state, the driver > sends a decreased magnitude signal, or nominal logic level. > Every time a > transition occurrs, the greater magnitude level is used. For > all times after > this that the same level is to be transmitted, the nominal > magnitude is > used. > > --Regards > Dorababu > > -----Original Message----- > From: Miller [mailto:lincj@xxxxxxxxxxxxxxxxxxx] > Sent: Friday, July 05, 2002 5:38 PM > To: hpc@xxxxxxxxxx > Cc: SI_LIST (E-mail) > Subject: [SI-LIST] Re: TO define the "Preemphasis" > > > > You can also check xilinx's Multi-Gigahertz Signaling FAQ > http://www.xilinx.com/xlnx/xil_prodcat_product.jsp?title=si_gigfaq > > Best Regards > > Miller Lin > > > ------------------------------------------------------------------ > 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 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 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 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