174 Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E
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5.2.2.3
Write Extended Command (2Ah)
Table 5.2.2-4. Write Extended Command
Bit
7
6
5
4
3
2
1
0
Byte(s)
0
0
0
1
0
1
0
1
0
1
Logical Unit No.[1]
DPO FUA
RelAdr
0
0
0
[2] [3]
0
0
[4]
2
Logical Block Address (MSB)
[5]
3
Logical Block Address
[5]
4
Logical Block Address
[5]
5
Logical Block Address (LSB)
[5]
6
0
0
0
0
0
0
0
0
7
Transfer Length (MSB)
[6]
8
Transfer Length (LSB)
9
0
0
0
0
0
0 Flag Link [7]
The Write Extended command requests that the disc drive write to the medium the data transferred by the
initiator.
This command is implemented with the disc drive specific parameters listed in Table 5.2.2-4. Refer also to
“Write Caching” section in the individual Product Manual for information on Write Cache Control.
Notes.
[1] In the CDB, the LUN must be zero.
[2] If the Disable Page Out (DPO) bit is set to one, no data is cached. The DPO bit is only meaningful if the
RCD bit of Mode Select Page 8 is set false (Caching enabled).
[3] A force unit access (FUA) bit of one indicates that the write command shall not return GOOD status until
the logical blocks have actually been written on the media. The FUA bit is only meaningful if the WCE bit
of Mode Sense page 8 is true.
[4] A relative address (RelAdr) bit of one indicates that the logical block address field is a two’s complement
displacement. This negative or positive displacement is to be added to the logical block address last
accessed on the logical unit to form the logical block address for this command. This feature is only
available when linking commands. The feature requires that a previous command in the linked group
have accessed a block of data on the logical unit.
A RelAdr bit of zero indicates that the logical block address field specifies the first logical block of the
range of logical blocks to be operated on by this command.
[5] The Logical Block Address specifies the logical block at which the write operation shall begin, if RelAdr bit
is zero. (See description of RelAdr bit).
[6] The Transfer Length specifies the number of contiguous logical blocks of data that shall be transferred. A
Transfer Length of zero indicates no logical blocks shall be transferred. This condition shall not be con-
sidered an error and no data shall be written. Any other value indicates the number of logical blocks that
shall be transferred.
[7] See “Control Byte” paragraph 4.2.6.
