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Fibre Channel Interface Manual, Rev. D
349
12.72
XDWriteRead (10) command
 
The XDWriteRead (10) command requests that the target xor the data transferred (data-out) with the data on 
the medium and return the resulting xor data (data-in). This is the equivalent to an XDWrite (10) command fol-
lowed by an XDRead (10) command with the same Logical Block Address and Transfer Length. This command 
is only available on transport protocols supporting bidirectional commands.
Field definitions (listed alphabetically)  
  
Control    
See Section 11.2.1.6.
DPO (Disable Page Out)    
1
No data is cached. The DPO bit is only meaningful if the RCD bit of Mode Select Page 8 is set false (caching 
enabled).
Disable Write    
0
The data transferred from the initiator is written to the medium after the xor operation is complete.
1
The data is not written to the medium.
FUA (Force Unit Access)    
1
The Write command does not return Good status until the logical blocks have actually been written on the media. 
the FUA bit is only meaningful if the WCE bit of Mode Sense Page 8 is true.
Logical Block Address    
The starting logical block address of the data to be affected by the xor operation.
Transfer Length    
The number of logical blocks to be transferred to the XDWrite target for the xor operation. It also specifies the number of 
blocks to be written to the medium after the xor operation.
Table 237:  XDWriteRead (10) command (53h)
    Bit
Byte
7
6
5
4
3
2
1
0
0
0
1
0
1
0
0
1
1
1
Reserved
DPO
FUA
Disable 
Write
Reserved
2
3
4
5
(MSB)
Logical Block Address
(LSB)
6
Reserved
7
(MSB)
Transfer Length
8
(LSB)
9
Control
53h
Table 
number