Seagate SCSI Interface Product Manual page 44

30 SCSI Interface Product Manual, Rev. J
Clear Task Set (0Eh)
The target shall go to the Bus Free phase following successful receipt of the Clear Task Set message. The tar-
get shall perform an action equivalent to receiving a series of Abort Task Set messages from each initiator. All
tasks from all initiators in the task set for the specified logical unit shall be cleared from the task set. All execut-
ing tasks shall be halted. The medium may have been altered by partially executed commands. All pending
status and data for that logical unit for all initiators shall be cleared. No status or ending message shall be sent
for any of the outstanding tasks. A unit attention condition shall be generated for all other initiators with tasks
that either had been executing or were queued in a task set for execution for that logical unit. When reporting
the Unit Attention condition the additional sense code shall be set to Task Set Cleared by Another Initiator.
Task Complete (00h)
The Task Complete message is sent from a target to an initiator to indicate that the execution of a command (or
series of linked commands) has terminated and that valid status has been sent to the initiator. After success-
fully sending this message, the target shall go to the Bus Free phase by releasing BSY. The target shall con-
sider the message transmission to be successful when it detects the negation of ACK for the Task Complete
message with the ATN signal false.
Note. The command may have been executed successfully or unsuccessfully as indicated in the status.
Continue Task (12h)
The Continue Task message is sent from the initiator to the target to reconnect to a task. This message shall
be sent in the same Message Out phase as the Identify message.
Implementors Note: Thus the Message Out phase following Selection phase consists of the Identify, Task
Attribute (if any), and Continue Task messages.
The purpose of the Continue Task message is to distinguish a valid initiator reconnection from an incorrect ini-
tiator reconnection (see Section 4.10).
If the target expects a significant delay before it will be ready to continue processing the reconnected task, it
may attempt to free the SCSI bus by sending a Disconnect message to the initiator. The initiator may reject the
disconnection attempt by responding with Message Reject message.
It is an error for the initiator to send this message on an initial connection (i.e., there is no task for the nexus)
and the target shall go to the Bus Free phase (see unexpected disconnect in Section 3.1.1).
Initiators should avoid sending this message to targets which have not implemented this message. Such tar-
gets may not respond as described in this section. An initiator can determine whether a target implements this
message by examining the TrnDis bit in the standard Inquiry data (see Table 49).
Disconnect (04h)
The Disconnect message is sent from a target to inform an initiator that the present connection is going to be
broken (the target plans to disconnect by releasing the BSY signal), but that a later reconnect will be required
in order to complete the current task. This message shall not cause the initiator to save the data pointer. After
successfully sending this message, the target shall go to the Bus Free phase by releasing the BSY signal. The
target shall consider the message transmission to be successful when it detects the negation of the ACK signal
for the Disconnect message with the ATN signal false.
Targets which break data transfers into multiple connections shall end each successful connection (except pos-
sibly the last) with a Save Data Point–Disconnect message sequence.