Write And Verify Command (2Eh) - Seagate SCSI Interface Product Manual

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Write and Verify command (2Eh)

The Write and Verify command requests that the target write the data transferred from the initiator to the
medium and then verify that the data is correctly written. The data is only transferred once from the initiator to
the drive.
Table 172: Write and Verify command (2Eh)
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] A Disable Page Out (DPO) bit of one indicates that the target shall assign the logical blocks accessed by
this command the lowest priority for being fetched into or retained by the cache.
The DPO bit is used to control replacement of logical blocks in the cache memory when the host has infor-
mation on the future usage of the logical blocks. If the DPO bit is set to one, the logical blocks accessed by
the command are not likely to be accessed again in the near future and should not be put in the cache
memory nor retained by the cache memory. If the DPO bit is zero, the logical blocks accessed by this
command are likely to be accessed again in the near future.
[3] A Byte Check (BytChk) bit of zero causes the verification to be simply a medium verification (ECC) with no
data comparison. A BytChk bit of one causes a byte-by-byte compare of data written on the peripheral
device and the data transferred from the initiator. If the compare is unsuccessful, the command shall be
terminated with a Check Condition status and the sense key shall be set to Miscompare.
[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 that no logical blocks shall be transferred. This condition shall not be con-
sidered as an error and no data shall be written. Any other value indicates the number of logical blocks
that shall be transferred.
For systems that support disconnection, the drive disconnects during the execution of this command.
[7] See "Control byte," paragraph 4.2.6.
6 5
0 1
0 0
DPO [2]
0 0
0 0
SCSI Interface Product Manual, Rev. J
4 3
0 1
0 0
0 0
0 0
2 1
1 1
0
BYT CHK
RelAdr [4]
[3]
0 0
0 Flag [7] Link [7]
0
0
0