Quantum 10K II - Manual (Page 284)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–217
5.47 WRITE (10) Command (2Ah)
The WRITE (10) command requests that the drive write initiator-supplied data to
the medium.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (2Ah)
1 Reserved DPO FUA Reserved RelAdr
2 - 5 Logical Block Address
6 Reserved
7 - 8 Transfer Length
9 Control
Figure 5–107 WRITE (10) Command Descriptor Block — Data Format
Table 5–101 WRITE (10) Command — Field Descriptions
Field Description
DPO Disable Page Out. When the value of the field is 1, the drive tells the
controller to bypass cache as much as possible. The buffers used for the
WRITE data are given a low priority. This bit may be useful if the host CPU is
performing a background copy operation and does not want to wipe out
the drive's cache.
When DPO is 0, the drive tells the controller to cache this WRITE data in a
normal manner.
NOTE: The drive normally assigns a low priority to write caching. Therefore,
the DPO bit in a WRITE command is ignored.
FUA Force Unit Access. When 1, the data must be written on the medium
before GOOD status is returned. When 0, GOOD status may be returned
after the data is fetched from the initiator and before it is written to the
medium. If the WCE (Write Cache Enable) bit on the MODE SELECT
command Caching Page is clear, the FUA bit is ignored and behaves as if it
were always set (that is, if WCE = 0, the controller forces FUA = 1).
Logical Block Address The address of the first logical block where the Write operation will occur.
RelAdr Relative Address. This drive does not support this feature; the field must be
0.
Transfer Length The number of contiguous logical blocks of data to write. The drive returns
CHECK CONDITION status with the correct sense data if the specified
transfer would cause the write operation to extend beyond the Logical
Block Address space.