SAS 2 - scrambler operation

David Freeman David.Freeman at finisar.com
Thu Jul 19 10:32:50 PDT 2007


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Would it not be easier to have just a free-running scrambler where the
output is muxed into the data stream instead of adding extra logic to
pause the scrambler for primitives. So, yes, Primitive are not
scrambled, however, I would prefer to not have to pause the idle data
generator every time in need to insert a primitive.
Are we expecting to be able to descramble the data and verify that it is
really all zeros?
Regards,
David Freeman
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Stephen
FINCH
Sent: Thursday, July 19, 2007 6:47 AM
To: 'Robert Watson'; t10 at t10.org
Subject: RE: SAS 2 - scrambler operation
I'd like to address the question by use of an example.
In a normal frame (between SOF and EOF or between SOAF and EOAF), the
scrambler is not advanced is a ALIGN primitive is inserted.  In fact,
the scrambler is not be advanced when any primitive is inserted, such as
RRDY or ACK.  Since the TRAIN and TRAIN_DONE patterns consists of TRAIN
and TRAIN_DONE primitives and scrambled data then, by the example above,
the scrambler would not be advanced when the primitive portions of the
patterns are sent.
In section 7.6 it states:
"All data dwords are scrambled. Table 117 lists the scrambling for
different types of data dwords."
In a brief search of SAS-2, I didn't find an explicit statement that
primitives are not scrambled, but they aren't.
Regards,
Steve Finch 
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Robert
Watson
Sent: Wednesday, July 18, 2007 4:19 PM
To: 't10 at t10.org'
Subject: SAS 2 - scrambler operation
6.7.4.2.3.4 Train-SNW defines two training patterns: TRAIN pattern and
TRAIN)DONE pattern. Both are defined as their respective redundant
primitive followed by 58 dwords set to 0x00000000 scrambled and 8b10b
encoded. Furthermore, the scrambler is initialized at the end of RCDT
and is not re-initialized after that.
The question we have is : Does the scrambler pause while sending TRAIN
or TRAIN_DONE primitives; that is, is the dword following the primitive
the scrambler's successor dword to the dword preceding the primitive? Or
does the scrambler run continuously, and TRAIN or TRAIN_DONE is
overlayed on top of scrambler dwords? I would expect the former, but I
don't feel that the current draft (sas2r10) is clear in this regard.
Thanks,
Robert Watson
PMC-Sierra, Inc.



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