On Aug 10, 2017, at 23:12, Luke Kenneth Casson Leighton <[email protected]> wrote: > > On Fri, Aug 11, 2017 at 12:37 AM, Richard Wilbur > <[email protected]> wrote: > >> On Wed, Aug 9, 2017 at 7:23 AM, Luke Kenneth Casson Leighton >> <[email protected]> wrote: >>> next set... >>> >>> wiggles.jpg is the layer 6 length-matching area: HX2N/P is the one >>> that's the longest, it snakes back on itself. i length-matched all 3 >>> signal pairs to 56.413, and left the CK lines at 57.134 just to give >>> the tiniest bit of delay (TI recommendations iirc). >> >> Very nicely done! 57.134mm - 56.413mm = 721um >> => T(delay) = 721um / 150um/ps = 4.8ps > >> That is a very tiny delay!
I would need to do more research to make a meaningful recommendation. Sorry for bringing up a topic I wasn't prepared to discuss intelligently. Let's go with what you've done. According to my calculations you could get away without any inter-pair skew compensation on the board whatsoever and still meet the HDMI specification for the transmitter budget. What you have done regarding inter-pair skew compensation reserves nearly all of the transmitter inter-pair skew budget from the HDMI standard for the connector and the rest of the system. This will serve to accommodate less than optimal inter-pair skew imposed by the cable and/or receiver. >> Now that we have achieved such close >> synchronization, I'm suggesting we go for the next goal where we >> design a certain amount of inter-pair skew into the layout for >> purposes of lowering the strength of our synchronized pulsing data >> lines to a more diffuse chatter. > > *deep breath*.... aaaaaaaa! :) > > well.... that actually happens for the majority of the length in the > middle (starting layer 6) > > but.... if i simply *take out* the intermediary wiggles on layer 6.... Ill-founded proposal for which I don't presently have the time to improve. >>> no - not even enough space to do 5.1mil / 5.0 clearance... just... too >>> much. >> >> I understand. We might end up with more room--see discussion below. > > which has probably been truncated... Turns out we don't have the room to change the trace width or spacing without having a deleterious effect on impedance. _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
