22 read (10) command, Read (10) command – Seagate Fibre Channel Interface User Manual
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Fibre Channel Interface Manual, Rev. D
12.22
Read (10) command
The Read (10) command requests that the target transfer data to the initiator. This command is implemented
with the drive-specific parameters shown in Table 172.
This command operates the same as the Read (6) command (see Section 12.21) except that in the CDB for
this command a four-byte logical block address and a two-byte transfer length may be specified.
The data value most recently written in the addressed logical block is returned to the Host.
This command terminates with a Reservation Conflict status if any reservation access conflict (see Section
12.39) exists, and no data is read.
Field definitions (listed alphabetically)
Control
See Control Bytes in Section 11.2.1.6.
DPO (Disable Page Out)
The DPO bit is used to control replacement of logical blocks in the cache memory when the host has information on the
future usage of the logical blocks.
1
The disc drive assigns the logical blocks accessed by this command the lowest priority for being fetched into or
retained by the cache. The host knows 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.
0
The host expects that logical blocks accessed by this command are likely to be accessed again in the near future.
FUA (Force Unit Access)
1
The target accesses the media in performing the command prior to returning Good status. Read commands access
the specified logical blocks from the media (i.e., the data is not directly retrieved from the cache). In the case where
the cache contains a more recent version of a logical block than the media, the logical block is first written to the
media.
0
The target satisfies the command by accessing the cache memory. For read operations, any logical blocks that are
contained in the cache memory are transferred to the initiator directly from the cache memory.
Logical Block Address
The logical block at which the read operation begins, if RelAdr bit is zero (RelAdr function is not supported by drives
described in this manual).
Table 172: Read (10) command (28h)
Bit
Byte
7
6
5
4
3
2
1
0
0
0
0
1
0
1
0
0
0
1
0
0
0
DPO
FUA
0
0
RelAdr
Reserved
2
Logical Block Address (MSB)
3
Logical Block Address
4
Logical Block Address
5
Logical Block Address (LSB)
6
0
0
0
0
0
0
0
0
7
Transfer Length (MSB)
8
Transfer Length (LSB)
9
Control
28h
Table
number