Message System - Tandberg Data SLR7-140 PROGRAMMER Manual

6.

Message System

The message system
Initiator and the Drive for the purpose of physical path
management. The
reestablished several times during the execution of a
SCSI command if the Initiator has granted the Drive the
privilege of disconnection.
The first message
SELECTION phase has to be either the IDENTIFY, ABORT
TASK SET or TARGET RESET message. The IDENTIFY message
may be immediately
IDENTIFY message establishes the physical path for a
particular logical
Since the Drive has only one logical unit, the specified
logical unit number should always be zero. The IDENTIFY
message may also
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
reestablished for
number.
Whenever a physical
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
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.
6-1 Tandberg SLR Product Line SCSI Functional Specifications
allows communication
physical path
sent by the
followed by
unit specified
grant the
allows the physical
the Drive's specified
path to an
or not)
between
may be broken
Initiator after
other messages.
by the Initiator.
Drive disconnection
path to
logical
Initiator that
it will signal
an
and
the
The
be
unit
is
the