DPO bit in sample CDB
Kevin D Butt
kdbutt at us.ibm.com
Wed Aug 24 10:39:34 PDT 2011
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I stumbled onto bits in the type variable length CDB for long LBA 32-byte
commands that are not defined.
I sent the following note to Ralph:
In SPC-4r31, Table 17 -Typical variable length CDB for long LBA 32-byte
commands in byte 10 bit 4 there is a DPO field and in bit 3 there is a FUA
field. There is no description for what these fields mean. I can search
for FUA and find it being used in multiple places.
When I search for DPO I cannot find a single instance.
His response was that he suspects they are from SBC-3.
Indeed, I can find them defined in SBC-3.
The problem I still have, however, is that they are shown in Table 17 -
Typical variable length CDB for long LBA 32-byte commands but there is not
definition of what the bits mean. While I don't like that the bits aren't
described for the table, the FUA didn't bother me too much, because I
could find it in a search of SPC-4. However, not being able to find the
DPO bit in SPC-4 left me lost and confused. What should be done to remove
that confusion? Should there be a reference to the bits and where they
can be found or should the offending bits be replaced with "device type
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
Data Protection & Retention
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
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