MMC-2 Opcode Notes

Joerg Schilling schilling at fokus.gmd.de
Wed Jan 6 14:40:58 PST 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* Joerg Schilling <schilling at fokus.gmd.de>
*
>From t10-owner at Symbios.COM Wed Jan  6 23:31:16 1999

>* From the T10 Reflector (t10 at symbios.com), posted by:
>* Ralph Weber <ralphoweber at csi.com>
>*
>During the MMC-2 code import to SPC-2, I also found
>two opcode notes worthy of consideration.

>1) The use of 23h for READ FORMAT CAPACITIES conflicts with
>a vendor specific usage of opcode 23h noted in SPC and SCSI-2.

MMC has even more such conflicts.

-	Mode page 0x2a is used by MMC although it is granted to be 
	vendor uniqe by SCSI-2. Note that the inquiry data of
	actual MMC drives returns a 2 in the response data
	format field which means SCSI-2 compliant. Using a mode page
	0x2a for non vendor specific functions is a violation
	of the SCSI spec for drive that states to return SCSI-2 compliant
	data formats.

	For this reason, it is hard to write software that 
	correctly recognises a MMC drive.

-	Mode page 0x2a is not writable and for this reason does not
	fit into the general SCSI concept. The semantics of mode
	page 0x2a should better placed into a separate SCSI command.

-	The fact that audio data must be supplied in intel byte order
	violates the rules of SCSI and all known protocols in general.
	(All structured data of all known protcols uses motorola
	byte order which is also known as network byte order).

Jörg

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