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Posted by Woody Brison on July 8, 2008, 2:58 pm
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wrote:
> In article
>
> [snip]
>
> > It would appear from these statements that the ANSI standard
> > X3.263-1995 has it wrong. =A0The Scramber cannot issue zeros
> > between frames, it must continue thru its 2047-state sequence.
>
> > How is it all these PHY designers knew to ignore that one
> > specific line of code in the spec? =A0For we put a scope on the
> > twisted pair coming out of the wall, and we could not find an
> > example of an interframe sequence of Idle codes. Whatever brand
> > of PHY is sending this signal, is not following the ANSI spec but
> > instead keeps the LFSR running between frames. As I suspect all
> > of them do.
>
> > Any hints, Rich?
>
> As I am not a Verilog guru, I cannot speak to the meaning or validity of
> the code cited. However, it should be clear that 100BASE-TX does a
> "scramble-AFTER-encode", and that the scrambler is never turned in a
> twisted-pair PHY, except perhaps for test purposes.
>
> Of course, in a fiber medium (100BASE-FX), there is no need for the
> scrambler, as there will be no EMI generated from the fiber pulses.
> Perhaps the cited section of the standard and the code reflect
> 100BASE-FX, rather than -TX?
>
> It is possible that there is a typo in the ANSI standard, but I doubt
> that something this catastrophic would have gone unnoticed this long.
>
> --
> Rich Seifert =A0 =A0 =A0 =A0 =A0 =A0 =A0Networks and Communications Consu=
lting
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 21885 Bear Creek Way
> (408) 395-5700 =A0 =A0 =A0 =A0 =A0 =A0Los Gatos, CA 95033
> (408) 228-0803 FAX
>
> Send replies to: usenet at richseifert dot com
I'm going to proceed with my design, arrange the scrambler to
run all the time. We'll be connecting this to various other
commercial PHYs and we'll see if they play together, that's
the bottom line. I'll keep you posted from time to time.
Least I can do for the help you (all) have been.
Wood
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