MMC1 versus MMC2 and higher about IP in format unit parameter list

David Burg dburg at
Mon Jun 27 05:47:59 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* "David Burg" <dburg at>
Dear MMC people,

I observed an inconsistency between MMC1 and higher MMC revisions regarding
the presence of the Initialization Pattern. While it's maybe ok to change
things, I think the legacy section of current MMC document should describe

In MMC1 (r10a for instance), the presence of a IP Descriptor is mandatory,
even if cleared to zeros even if IP bit shall be zero. In MMC2 and later,
the IP Descriptor is present only if IP bit is 1.

Consequently I see in my test devices both behaviors, some devices checking
the format size at an offset of 8 bytes from the beginning of the parameter
list, some devices checking it at offset 12. I even see devices hanging if
they receive a format unit command with only 12 bytes of format unit
parameter list because they don't check how much data is transferred, and
try to read at an illegal address.

Best regards,

David Burg

David Burg
Software Development

Nero AG               phone: +49 (0)7248 928 327 (room line) Internal VoIP
Im Stoeckmaedle 18    fax:   +49 (0)7248 928 299
76307 Karlsbad        email: dburg at

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