User Manual

SCSI Commands Reference Manual, Rev. J 382
www.seagate.com Parameters for direct access devices
5.3.4.3 Long LBA mode parameter block descriptor
Table 364 defines the block descriptor for direct-access block devices used with the MODE SELECT (10) command and MODE
SENSE (10) command when the LONGLBA bit is set to one in the mode parameter header (see 5.3.3).
A device server shall respond to a MODE SENSE command (see 3.11 and 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 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 long LBA mode parameter block descriptor.
If the logical unit does not support changing its capacity by changing the NUMBER OF LOGICAL BLOCKS field using the MODE
SELECT command (see 3.10), the value in the NUMBER OF LOGICAL BLOCKS field is ignored. If the device supports changing its
capacity by changing the NUMBER OF LOGICAL BLOCKS field, then the NUMBER OF LOGICAL BLOCKS field is interpreted as
follows:
Table 364 Long LBA mode parameter block descriptor
Bit
Byte
7 6 5 4 3 2 1 0
0
(MSB)
NUMBER OF LOGICAL BLOCKS
. . .
7
(LSB)
8
Reserved
. . .
11
12
(MSB)
LOGICAL BLOCK LENGTH
. . .
15
(LSB)