Write Extended Command (2Ah) - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
5.52

Write Extended command (2Ah)

The Write Extended command requests that the drive write to the medium the data transferred by the initiator.
This command is implemented with the drive specific parameters listed in Table 175. Refer also to individual
drive's Product Manual, Volume 1, Write Caching section, for information on Write Cache Control.
Table 175: Write Extended command (2Ah)
Bit 7
Byte
0 0
1 0
Logical Unit Number [1]
2 Logical Block Address (MSB) [5]
3 Logical Block Address [5]
4 Logical Block Address [5]
5 Logical Block Address (LSB) [5]
6 0
7 Transfer Length (MSB) [6]
8 Transfer Length (LSB) [6]
9 0
Notes.
[1] The Logical Unit Number 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 avail-
able 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 note [4]).
[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 consid-
ered 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.
This command operates the same as the Write command (Section 5.49) except that in the CDB for this com-
mand a four byte Logical Block Address and a two byte Transfer Length may be specified.
This command shall be terminated with a Reservation Conflict status if any reservation access conflict (see
Section 5.35) exists, and no data shall be written.
6 5
0 1
0 0
DPO [2]
0 0
0 0
4 3
0 1
FUA [3]
0 0
0 0
2 1
0 1
0 0
RelAdr [4]
0 0
0 Flag [7] Link [7]
219
0
0
0