Read Extended - IBM Ultrastar 36LZX Specifications

8.20 READ EXTENDED (28)

Byte
7 6
0
1 Reserved = 0
2 (MSB)
3
4
5
6
7 (MSB)
8
9 VU = 0
Figure 125. Read Extended (28)
The READ EXTENDED command requests the drive to transfer data to the initiator. The larger Logical
Block Address 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.
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 A 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. A FUA 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.
RelAdr Relative Block Address is not supported. Must be set to zero.
Bit
5 4 3
Command Code = 28h
DPO FUA
Logical Block Address
Reserved = 0
Transfer Length
Reserved = 0
Ultrastar 36LZX hard disk drive specifications
2 1 0
Reserved = RelAdr
0 = 0
(LSB)
(LSB)
FLAG LINK
151