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e. Block descriptor length
This field indicates the "Block descriptor" length (byte length) which follows
after the header. The "Page descriptor" length is not included in this value.
The HDD always reports X '08' in this field if "0" is specified in the DBD bit
of this command's CDB, and thus indicates that one "Block descriptor" set
follows after the header. When "1" is specified in the DBD bit of the CDB,
the value of this field is X '00'.
(2) Block descriptor
The 8-byte "Block descriptor" indicates the logical attributes of the data format on
the disk media.
a. Data block count
This field indicates the total number of logical data blocks (the block length is
shown in the "Data block length" field) existing in the "User Space" on the
disk media. This value does not include the number of spare sectors reserved
for alternate block processing.
Furthermore, when this command specifies to transfer the "Default" value and
"Variable" value, the value shown in this field is X '000000' (which means the
maximum number of logical data blocks that it is possible to rank in the "User
Space").
b. Data block length
This field indicates the length (byte length) of 1 logical data block on the disk
media.
(3) Page descriptor
The "Page descriptor" is configured from a parameter field which follows a 2-byte
page header, and is divided into units called "Page" for each parameter's functional
attributes. See the description of the MODE SELECT command (Section 4.1.4)
concerning the configuration of each page descriptor and their contents.
a. PS bit
When this bit is "1," the parameter value defined in that "Page descriptor" can
be saved on the disk media, and when it is "0", it indicates that this is a
parameter which cannot be saved to the disk. It is possible to save all the
"Page descriptors" supported by the HDD. However, "1" is always indicated
in this bit for all "Page descriptors" transferred by this command.
172 C141-C013