HP C2246 Technical Reference Manual page 113

Write
Write
The WRITE command requests that the Target write the data transferred by the Initiator to
the media. The Target accepts both the non-extended (6-byte) and extended (10-byte) CDB
formats.
Write (6 .. Byte) Command Descriptor Block (COB)
Bit
Byte
"(
I
6
I
5
I
4
I
3
I
2
I
l
I
0
00
Opcode= OAR
01 Logical Unit Number
I
Logical Block Address (MSB)
02-03 Logical Block Address (LSB=03)
04 Transfer Length
05
Control Byte
Write (10-Byte) Command Descriptor Block (COB)
Bit
Byte
7
I
6
I
5
I
4
I
3
I
2
I
1
I
0
00
Opcode= 2AH
01 Logical Unit Number
I
DPO=O
I
FUA
I
Reserved
I
RelAdr
02-05 (MSB=02) Logical Block Address (LSB=05)
06
Reserved
07-08 (MSB=07)
Transfer Length
(LSB=08)
09
Control Byte
Logical Block Address. This field specifies the logical block at which the write operation will
begin.
FUA (Forced Unit Access). If the FUA bit is set to one (1), the WRITE command will not
return GOOD Status until the logical blocks have actually been written on the media. If the
FUA bit
is
set to zero (0), logical blocks may be transferred directly to cache memory, and
GOOD Status may be returned to the Initiator prior to writing the logical blocks to the media
if the WCE bit in Mode page 08H, byte 02 is set. Any error which occurs after the GOOD
Status is returned as a deferred error and information regarding the error is not reported until
a subsequent command.
RelAdr (Relative Address). A one (1) indicates that the logical block address field is a two's
complement displacement. This negative or positive displacement is to be added to the
logical block address last accessed on the logical unit to form the logical block address for this
command. This feature is available only when linking commands. The feature requires that a
previous command in the linked group has accessed a block of data on the logical unit.
A RelAdr bit of zero (0) indicates that the logical block address field specifies the first logical
block of the range of logical blocks to be operated on by this command.
Transfer Length. This field specifies the number of contiguous logical blocks of data to be
transferred. When using the non-extended (6-byte) CDB format, a Transfer Length of zero
indicates that 256 logical blocks will be transferred. When using the extended (10-byte) CDB
SCSI Command Descriptions A-57