Question regarding K28.6

Elliott, Robert (Server Storage) Elliott at
Thu Oct 11 17:38:54 PDT 2007

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert (Server Storage)" <Elliott at>
K28.6 is not a valid control character in SATA; that's precisely why it is
used by SAS.
While an expander is in an STP connection and is forwarding dwords from SAS
to SATA, if it receives an invalid dword or an ERROR primitive on the SAS
side, it needs to forward something to SATA.  Rather than just hide the
existence of the error and transmit an ALIGN (or try to forward the 10-bit
patterns through as-is), it transmits a K28.6 based primitive called
SATA_ERROR.  This is treated by the SATA device as an invalid dword since it
contains an invalid control character.	The SATA device thus responds the
same as if the error had occurred on the SATA physical link itself.
Rob Elliott, elliott at
Hewlett-Packard Industry Standard Server Storage Advanced Technology
> -----Original Message-----
> From: owner-t10 at [mailto:owner-t10 at] On Behalf
> Of Marian Lakov
> Sent: Thursday, October 11, 2007 3:58 PM
> To: t10 at; T-13Test at
> Subject: Question regarding K28.6
> * From the T10 Reflector (t10 at, posted by:
> * "Marian Lakov" <Marian_Lakov at>
> *
> Hi All,
> I need a clarification regarding K28.6 control character.
> According to SAS (2r10) it will indicate a SATA_ERROR if used
> in SATA link and has no meaning in SAS:
> Table 75 - Control character usage
> First character  Usage in SAS physical links	Usage in SATA
> physical links
> of a dword
> K28.3 	   Primitives used only inside	All primitives
> except ALIGN
>		   STP connections
> K28.5 	   ALIGN and most primitives	ALIGN
>		   defined in this standard
> K28.6 	   Not used			SATA_ERROR
> The corresponding  part of the ATA-8 AST does not define
> K28.6 as a valid control character:
> Table 21 - Valid control characters
> Name	       Description
> K28.3        Occurs only at byte 0 of all primitives except for
>	       the ALIGN primitive
> K28.5        Occurs only at byte 0 of the ALIGN primitive
> Is K28.6 a valid control character for SATA and which part of
> the ATA standard describes its usage?
> Thanks,
> Marian
> ________________________
> Marian Lakov
> Systems Engineer
> Xyratex
> 1804 Centre Point Circle, Suite #112
> Naperville, IL 60563
> Office:  630-364-7600
> Fax:	    630-364-7601
> marian_lakov at
> *
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