User Manual

SCSI Commands Reference Manual, Rev. J 380
www.seagate.com Parameters for direct access devices
5.3.4 Mode parameter block descriptors
5.3.4.1 Mode block descriptors overview
If the device server returns a mode parameter block descriptor, it shall return a short LBA mode parameter block descriptor (see
5.3.4.2) in the mode parameter data in response to:
a) a MODE SENSE (6) command; or
b) a MODE SENSE (10) command with the LLBAA bit set to zero.
If the device server returns a mode parameter block descriptor and the number of logical blocks is greater than FFFFFFFFh, it
may return a long LBA mode parameter block descriptor (see 5.3.4.3) in the mode parameter data in response to a MODE SENSE
(10) command with the LLBAA bit set to one.
If the application client sends a mode parameter block descriptor in the mode parameter list, it shall send a short LBA mode
parameter block descriptor (see 5.3.4.2) for a MODE SELECT (6) command.
If the application client sends a mode parameter block descriptor in the mode parameter list, it may send a long LBA mode
parameter block descriptor (see 5.3.4.3) for a MODE SELECT (10) command.
Support for the mode parameter block descriptors is optional. The device server shall establish a unit attention condition with
the additional sense code of MODE PARAMETERS CHANGED (see SPC-5 and SAM-5) when the block descriptor values are
changed.
5.3.4.2 Short LBA mode parameter block descriptor
Table 363 defines the block descriptor for direct-access block devices used:
a) with the MODE SELECT (6) and MODE SENSE (6) commands, and
b) with the MODE SELECT (10) and MODE SENSE (10) commands when the LONGLBA bit is set to zero in the mode parameter
header
(see 5.3.3).
A device server shall respond to a MODE SENSE command (see 3.12) by reporting the number of logical blocks specified in the
NUMBER OF LOGICAL BLOCKS field sent in the last MODE SELECT command that contained a mode parameter block descriptor.
If no MODE SELECT command with a mode parameter block descriptor has been received then the current number of logical
blocks shall be returned. To determine the number of logical blocks at which the logical unit is currently formatted, the
application client shall use the READ CAPACITY command (see 3.20) rather than the MODE SENSE command.
On a MODE SENSE command, the device server may return a value of zero indicating that it does not report the number of
logical blocks in the short LBA mode parameter block descriptor.
On a MODE SENSE command, if the number of logical blocks on the medium exceeds the maximum value that is able to be
specified in the NUMBER OF LOGICAL BLOCKS field, the device server shall return a value of FFFFFFFh.
Table 363 Short LBA mode parameter block descriptor
Bit
Byte
7 6 5 4 3 2 1 0
0 (MSB)
NUMBER OF BLOCKS. . .
3 (LSB)
4 Reserved
5 (MSB)
LOGICAL BLOCK LENGTH. . .
7 (LSB)