[T10] Questoin about SAS SSC

Harvey Newman harvey.newman at avagotech.com
Fri Oct 23 07:34:21 PDT 2015


Hi Jason,

Your general understanding is correct.  The phy capabilities TX SSC TYPE
bit indicates the SSC type (i.e., center-spreading or down-spreading).
This allowed a product that is connected to optimize the Rx to receive SSC
if they desire. The term "may" indicates it "may or may not" without any
preference. The optimization is optional. If the configuration bits also
indicate operation "with SSC" the requirement is the receiver be compliant
even in the presence of the full SSC deviation advertised by the TX SSC
TYPE bit.   The rules for initiator center-spread and target down-spread
are specified elsewhere in the standard and this is the expected operation.

In the wording of your question, "Is that mean RX should ensure..." you
have used the term should, where in this case in spec language this is a
shall. The term should indicates a flexibility of choice but once you
indicate support for SSC it is a requirement to be fully compliant in the
presence of SSC.  It is the optimization that is optional.

Regards,
Harvey Newman
Avago Technologies



On Thu, Oct 22, 2015 at 11:19 PM, Guojian (F) <guojian111 at hisilicon.com>
wrote:

> Hi,
>
>   I have a question about SAS SSC.
>
>   From the attached Picture, we can see that initiator and target would
> notify each other TX SSC TYPE by transmitting SNW-3 phy capabilities.
>
>   NOTE 13 - The phy’s receiver may use the TX SSC TYPE bit to optimize
> its clock data recovery circuitry (seeSAS-3).
>
>   Is that means RX should ensure it can receive center-spreading SSC or
> down-spreading SSC signal by using received TX SSC TYPE?
>
>
>
>   So, it is possible that initiator transmit center-spreading SSC signal
> and target transmit down-spreading SSC signal. Is that right?
>
>
>
> Thanks and Best Regards!
>
>
>
> Jason Guo
>
>
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>


-- 
Harvey Newman
Avago Technologies
(408) 433-4028
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