Seagate ST3285N, Product Manual

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For all mode pages:
•
If the changeable value is 0, the initiator cannot change the bit directly.
If the changeable value is 1, the initiator can change the bit directly.
For example, in the header below, the changeable value for the page
code bits is 0, which means that the page code cannot be changed;
the changeable value of the PS bit is one, which means that the PS
bit can be changed.
•
During the Mode Sense command, the PS (parameter savable) bit
is 1, which means the mode page is saved on the disc. During the
Mode Select command, you must set the PS bit to 0.
•
An X means that the value of the bit cannot be specified. For example,
the default value of bit 0 of byte 1 of page 00
H
(the Operating Page)
cannot be specified because the bit can be either 1 or 0.
All mode pages contain a 2-byte header that contains the page code and
the page length for that particular page. The header is shown below.
Bit
Byte
7 6 5 4 3 2 1 0
0 PS Page code
changeable 1 0 0 0 0 0 0 0
1 Page length
changeable 00
H
Byte 0 During the Mode Sense command, the
PS (parameter savable)
bit is 1, which means the mode page is saved on the disc. During
the Mode Select command, you must set the PS bit to 0.
The page code is the unique code that identifies the page.
Byte 1 The page length is the length, in bytes, of the page.
90 ST3655 Family SCSI Drives Product Manual, Rev. A