Proposal to obsolete Flag bit in Control byte of CDB

Bob Snively Bob.Snively at Ebay.Sun.COM
Mon Nov 9 08:37:00 PST 1998

* From the T10 (formerly SCSI) Reflector (t10 at, posted by:
* Bob Snively <Bob.Snively at Ebay.Sun.COM>

Document T10/98-241r0 entitled "Obsoleting the flag bit in the control byte"
proposes that SAM-2 and FCP-2 treat the flag bit as obsolete.

There are no present known users of or uses for the flag bit in any
system.  Those few implementors that have supported it have no applications
that exploit their implementations and it remains practically untested.

This is true for parallel SCSI, FC serial SCSI and IEEE 1394 SCSI.

This is your warning that unless a reason to propogate the definition
of this bit into the new documents is identified, that they will
be made obsolete in SAM-2, FCP-2, and all future documents.

See the enclosed text.

Bob Snively			     Phone:	  (510) 574-9051
Sun Microsystems Computer Company      
Mail Stop NWK 04-104
901 San Antonio Road	             E-mail: bob.snively at
Palo Alto, CA 94303

-----------------  Text of 98-241r0  ----------------------------

As part of the development of FCP-2 and SAM-2, the Flag bit has been
identified as a function that is now obsolete.  I propose that we
formally make the flag bit obsolete.

In FCP-2, the control bit is implicitly included in section 7.1.3 which
describes the CDB and in section 4.2 and Annex A section A.1.6 which
describe command linking.  FCP-2 will explicitly say that the Flag bit in the
CDB control field shall be obsolete in FCP-2 implementations.

In SAM-2, section 5.1.2, the Flag bit in the CDB control field shall be made
obsolete.  This requires the following changes to be made:

	Bit 0 of Table 12 is made reserved.
	The flag bit shall be removed from the list in the second paragraph
	of 5.1.2.  The following additional sentence shall be placed at the end
	of that paragraph:
		"The Flag bit is obsolete in SAM-2."
	All additional descriptions of the Flag bit and of the protocols
	enabled by the Flag bit shall be removed.
	All descriptions and occurrences of the service response Linked
	Command Complete (with Flag) shall be removed.  These
	occur in 3.1.15, 3.4, 5.0, 5.1.2, 5.2, 5.4, and 5.5.2.

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