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Re: [802.3ae]802.3ae PRBSs are upside down

"Nepple, Bruce" wrote:

> <snip>
> My issue is that when you apply this to the PRBS23 (which is reset every frame),
> you end up with incompatible payloads in WIS test mode.  This means that if
> test equipment vendors build in patterns (not required by the specification),
> they need to have all the combinations of inverted and delayed available.
> Seems unnecessary.  It's not really important how it is done, just so it
> is specified consistantly and everyone does it the same way.

The PRBS in the WIS test pattern is separate from the PRBS31 we are discussing
for both clause 49 and 50.

The WIS test pattern was designed specifically for bit based BERT testers. This
test pattern will not work in any other kind of tester because the payload PRBS
is reset and truncated every frame. The PRBS23 is specified in accordance
O.172 (Annex A.2) which references O.150 for the PRBS23 pattern.

From O.150, the PRBS23 has the inverter for (what we call) the normal frame, and
does not have the inverter for (what we call) the inverted frame. In retrospect, I
see that there is no real advantage in inverting the entire SPE, only inverting
the CID would have been sufficient. It's one of those things where there is no
compelling argument to change it.

Is that the answer you were looking for?

Tim Warland  P. Eng.
Applications Engineer
Quake Technologies   (613)270-8113 ext 2311

Tough Times don't last, tough people do