RE: [802.3ae] WIS test Pattern PRBS Generator Polynomial
I have no idea what concepts are being floated regarding the 2**31 PRBS,
why it is required for 64/66 testing, and why it will be required for WIS, or
whether it will be optional in all cases. I scanned the serial-PMD email and saw
nothing definitive.
Regarding the current implementation,
I'm not sure why the PRBS generator polynomial is not specifically specified for
802.3ae. The idea that it be tied to a specification in another forum through
two layers of documents seems impractical. And, O.150 says that the specified
polynomial MAY be used to generate a 2**23-1 sequence.
802.3ae specifies that it be reset every frame, inverted every frame, but not
what polynomial to use. Seems inconsistant. And, if ITU decides to recommend
another polynomial, do we really want to change all WIS hardware?
Bruce
> -----Original Message-----
> From: Tom Alexander [mailto:Tom_Alexander@xxxxxxxxxxxxxx]
> Sent: Monday, February 04, 2002 12:29 PM
> To: Nepple, Bruce; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: [802.3ae] WIS test Pattern PRBS Generator Polynomial
>
>
> Hi, Bruce,
>
> I think you have a point. To the best of my knowledge, the
> polynomial to be used is as specified in O.150.
>
> I think it might be useful to the reader if we had a
> (non-normative, superseded by O.150 in case of conflict)
> statement that provided the polynomial itself as well as the
> PRBS length. If you could submit such a comment against the
> next draft, that would be very useful. Ditto for the 2**31 -
> 1 polynomial.
>
> Cheers,
>
> - Tom
>
> -----Original Message-----
> From: Nepple, Bruce [mailto:bnepple@xxxxxxxxxxxxxxxxxxx]
> Sent: Monday, February 04, 2002 11:43 AM
> To: stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: [802.3ae] WIS test Pattern PRBS Generator Polynomial
>
>
> Ouch --- I missed that comment. Thanks for pointing it out.
> My issue was that there are MANY 2**23-1 polynomials. Which one
> specifically is preferred or required was not specified, and there
> was no comment indicating that the choice was implementation
> dependent or to be determined in the future.
>
> Bruce
>
> > -----Original Message-----
> > From: Tom Alexander [mailto:Tom_Alexander@xxxxxxxxxxxxxx]
> > Sent: Monday, February 04, 2002 9:36 AM
> > To: Nepple, Bruce; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> > Subject: RE: [802.3ae] WIS test Pattern PRBS Generator Polynomial
> >
> >
> > Bruce,
> >
> > The PRBS for the mixed-frequency test pattern indeed uses a
> > 2**23 -1 polynomial. This is explicitly described in the WIS
> > clause (see lines 39-41 and 47-48 of page 397, lines 9-13 of
> > page 398, and Figure 50-13 (payload field) on page 398). All
> > these refer to Draft 4.0.
> >
> > Note that in the next draft of the WIS spec, there is a new
> > (optional) additional test pattern introduced, as per the
> > resolution of Comment #72 against Draft 4.0; this pattern
> > uses a 2**31 -1 polynomial.
> >
> > Thanks,
> >
> > - Tom Alexander
> > WIS Scribe
> >
> >
> > -----Original Message-----
> > From: Nepple, Bruce [mailto:bnepple@xxxxxxxxxxxxxxxxxxx]
> > Sent: Friday, February 01, 2002 9:36 PM
> > To: stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> > Subject: [802.3ae] WIS test Pattern PRBS Generator Polynomial
> >
> >
> > I could find no definition of the WIS test Pattern PRBS
> > generator polynomial in Clause 50 (or any other clause, for
> > that matter). I did find a reference to O.172 and in O.172 I
> > found a reference to O.150, and in O.150 I found a definition
> > for a 2**23 -1 length PRBS. (Section 5.6). Is that the
> > required generator for WIS? Is there a reason that it is not
> > specified? Or, did I just manage to overlook it in the
> > specification? (wouldn't be the first time).
> >
> > O.150 Section 5.6 specifies a 23 stage shift register with
> > taps from stage 23 and stage 18 added (mod-2) and applied to
> > the first stage. (I'd call it a x**23 + x**18 + 1 generator
> > with input data = 0, but I'm not a math dude)
> >
> > Bruce
> >
>