MMC - Inquiry Data for ATAPI and USB Drives

Mike Berhan mikeb at
Wed Dec 19 15:55:23 PST 2007

* From the T10 Reflector (t10 at, posted by:
* "Mike Berhan" <mikeb at>
MMC4,5,6 define certain Inquiry bit fields that should be returned for ATAPI
and USB devices.  You can see these values in Table 328 in mmc6r01.pdf.
1.)  Response Data Format
MMC states that the device shall return 0011b.	I am sure this is a typo
going back to MMC-4.  It should be 0010b and would then match SPC and Mt.
2.)  AERC, TrmTsk, NormACA, HiSup
These four bits comprise bits 4-7 of byte 2 of the Inquiry page.  MMC 4, 5,
and 6 define that these four bits should be returned zero for ATAPI and USB
logical units.	Mt. Fuji documents two formats.  One is for SCSI devices,
the other for ATAPI devices.  For ATAPI devices, bits 4-7 are defined as the
"ATAPI Transport Version."  In the Mt. Fuji annex, it goes on to say
"The AERC, TrmTsk and NormACA are in conflict with the current definition of
the INQUIRY data. This
specification specifies the ATAPI Transport version in place of these bits."
Unless I missed something, these two specifications conflict in their
Inquiry definitions for ATAPI devices.	Table 328 in mmc6r01.pdf conflicts
with Table 499 in fuji7r094.pdf.
I have compared the Inquiry pages of 30 ATAPI CD/DVD devices (from old to
new).  All of them follow the Mt. Fuji specification for ATAPI devices.
Should MMC be adjusted to correctly reflect the ATAPI format?
Alternatively, should Mt. Fuji be brought in compliance with SPC?
Mike Berhan
busTRACE Technologies
9700 Village Center Drive
Suite 50-F
Granite Bay, CA  95746
916.773.4554 phone
916.218.6283 fax
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at

More information about the T10 mailing list