Hitachi ULTRASTAR 15K450 HUS154530VLF400 - Manual (Page 225)

Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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19.16 READ (10) - (28)
Table 176: READ (10) - (28)
The READ (10) command requests the drive to transfer data to the Initiator. The larger LBA and Transfer Length fields permit
greater quantities of data to be requested per command than with the READ command and are required to access the full LBA
range of the larger capacity drives.
• FUA_NV (Force Unit Access Non-Volatile Cache) may be set to 0 or 1, but is ignored since NV_SUP=0 in Inquiry
Page 86h.
• Transfer length The number of contiguous blocks to be transferred. If the transfer length is zero, the seek occurs, but
no data is transferred. This condition is not considered an error. If read ahead is enabled, a read ahead is started after
the seek completes.
• DPO (Disable Page Out) bit of one indicates that the data accessed by this command is to be assigned the lowest pri-
ority for being written into or retained by the cache. A DPO bit of one overrides any retention priority specified in the
Mode Select Page 8 Caching Parameters. A DPO bit of zero indicates the priority is determined by the retention pri-
ority. The Initiator should set the DPO bit when the blocks read by this command are not likely to be read again in the
near future.
• FUA (Force Unit Access) bit of one indicates that the data is read from the media and not from the cache. A FUA bit
of zero allows the data to be read from either the media or the cache.
• RDPROTECT defines the manner in which protection information read from disk shall be checked during process-
ing of the command. Protection information is stored on disk, and may be transmitted to the drive's internal data buf-
fer and to the initiator with the user data. If the drive is not formatted with protection information, RDPROTECT
must be set to 000b, else Check Condition status will be returned with sense key of Illegal Request and additional
sense code of Invalid Field in CDB.
• RDPROTECT=000b
Protection information is not transmitted to the initiator and is not checked.
RDPROTECT=001b
Byte
Bit
7 6 5 4 3 2 1 0
0 Command Code = 28h
1 RDPROTECT DPO FUA
Rsvd=
0
FUA_
NV
Obso-
lete
2-5
(MSB)
Logical Block Address
(LSB)
6 Reserved = 0
7-8
(MSB) Transfer Length
(LSB)
9 VU = 0 Reserved = 0 FLAG LINK