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6-1
Tandberg SLR Product Line SCSI Functional Specifications
6.
Message System
The message system allows communication between an
Initiator and the Drive for the purpose of physical path
management. The physical path may be broken and
reestablished several times during the execution of a
SCSI command if the Initiator has granted the Drive the
privilege of disconnection.
The first message sent by the Initiator after the
SELECTION phase has to be either the IDENTIFY, ABORT
TASK SET or TARGET RESET message. The IDENTIFY message
may be immediately followed by other messages. The
IDENTIFY message establishes the physical path for a
particular logical unit specified by the Initiator.
Since the Drive has only one logical unit, the specified
logical unit number should always be zero. The IDENTIFY
message may also grant the Drive disconnection
privilege. If the Drive is allowed to disconnect, it may
do so by transferring a DISCONNECT message and then
release the SCSI-bus (by entering the BUS FREE phase).
The Drive will always at some later stage reestablish
the physical path by reselecting the Initiator. After
the RESELECTION phase, the Drive's first message will be
IDENTIFY. This allows the physical path to be
reestablished for the Drive's specified logical unit
number.
Whenever a physical path to an Initiator that is
utilizing disconnection and reconnection is established,
the Initiator must ensure that the active pointers of
the physical path are equal to the saved pointers for
that particular logical unit number (an implied restore
operation should occur as a result of a reselection).
When the Drive has completed the execution of a SCSI
command (successfully or not) it will signal the
Initiator that it is about to break the physical path
for good (for this selection sequence) by transferring a
TASK COMPLETE message. The Drive will then enter the BUS
FREE phase.
Содержание SLR7-140 PROGRAMMER
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