Seagate SCSI Interface Product Manual page 241

SCSI Interface Product Manual, Rev. J
Table 182: Port Control field
Value Description
00 The target transfers the data using the same port that received the command.
01 The target transfers the data using a different port than that which received the
command.
10 The target transfers the data using one port of the target's choice.
11 The target transfers the data using one or more ports of the target's choice.
[6] The Logical Block Address field specifies the logical block at which the Read operation of the data to be
Xored shall begin.
[7] The Transfer Length field specifies the number of logical blocks that shall be transferred to the XDWrite
Extended target, and to the XPWrite target.
The Xor data transfer to the secondary target is performed using an XPWrite command. The XPWrite
command is sent to the device specified in the secondary address field. The Secondary Logical Block
Address field value is placed in the Logical Block Address field of the XPWrite command. The Transfer
Length Field value is placed in the Transfer Length field of the XPWrite command. The completion status
of the XDWrite Extended command shall not be returned to the initiator until the completion status of the
XPWrite command has been received.
Note. The Xor data transfer to the secondary target may be broken into multiple XPWrite commands. If
this is done, the XDWrite Extended target will need to calculate the logical block addresses and
transfer lengths for the individual XPWrite commands. Also, the completion status of the XDWrite
Extended command shall not be returned to the initiator until the completion status of all XPWrite
commands have been received.
[8] See "Control byte," paragraph 4.2.6.
If the XPWrite command terminates with a Check Condition status and the sense key is not set to Recovered
Error, the XDWrite Extended command shall return Check Condition status.
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