Robert,
Thank you for your reply.
I agree that it is important to keep with the
rest of the standard.
Section 7.4 defines the idle dwords that
are sent when a link is idle.
“Idle dwords
are vendor-specific data dwords which are scrambled (see 7.6).”
It would seem to me that a precedents has
been set for allowing “vendor-specific” implementation of the “scrambled
training data” dwords between the train primitives.
if this is agreeable with the parties
concerned I would be willing to draft a proposal.
Regards,
David Freeman
Finisar Corp
From: Robert Watson
[mailto:Robert_Watson@pmc-sierra.com]
Sent: Thursday, July 19, 2007 11:55
AM
To: David Freeman; t10@t10.org
Subject: RE: SAS 2 - scrambler
operation
While I agree that it would be easier from
an implementation point of view to overlay the data, it would not seem (to me)
to be in keeping with the rest of the standard, as Stephen illustrates. So I
prefer pausing the scrambler when a primitive is inserted.
For the second question – reception
is vendor specific, I believe; but what is transmitted should be, in my
opinion, well defined.
Thanks,
Robert Watson
PMC-Sierra,Inc.
From:
owner-t10@t10.org [mailto:owner-t10@t10.org] On
Behalf Of David Freeman
Sent: Thursday, July 19, 2007
10:33 AM
To: t10@t10.org
Subject: RE: SAS 2 - scrambler
operation
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@t10.org [mailto:owner-t10@t10.org] On
Behalf Of Stephen FINCH
Sent: Thursday, July 19, 2007 6:47
AM
To: 'Robert Watson'; t10@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@t10.org [mailto:owner-t10@t10.org] On
Behalf Of Robert Watson
Sent: Wednesday, July 18, 2007
4:19 PM
To: 't10@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.