Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
206
18.17
READ (10) - (28)
Table 174 READ (10) - (28)
Byte
Bit
7 6 5 4 3 2 1 0
0
Command Code = 28h
1
RDPROTECT DPO FUA RSVD=0 FUA_NV Obsolete
2-5
(MSB)
Logical Block Address
(LSB)
6
Reserved = 0
7-8
(MSB)
Transfer Length
(LSB)
9
VU = 0
Reserved = 0
FLAG
LINK
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 priority 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 priority. 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
processing of the command. Protection information is stored on disk, and may be transmitted to the drive's
internal data buffer 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
- Protection information is transmitted to the initiator with the user data
- Logical Block Guard is checked
- Logical Block Application Tag is checked (applies to READ(32) command only)