Logical Unit Reset Message : X'1C' (I→T); Task Attribute Messages - Fujitsu MBA3073 SERIES Technical Manual

When the TARG is ready to transfer data for a disconnected task for which a TARGET
TRANSFER DISABLE message has been sent, the TARG shall reconnect to the INIT for the task
(via a reselection phase and consecutive message in phases containing an IDENTIFY message,
and an optional SIMPLE message), send a DISCONNECT message, and, if the INIT does not
respond with a MESSAGE REJECT message, generate a bus free phase. This connection serves
to notify the INIT that the task is ready for data transfer. If the INIT rejects the DISCONNECT
message, the TARG may generate a data in or data out phase; otherwise, the INIT may reconnect
to the task as described in the CONTINUE TASK message to perform the data transfer.
INITs should avoid sending the TARGET TRANSFER DISABLE message to the TARG that
have not implemented this message. Such the TARG may not respond as described in this section.
An application client can determine whether a device server implements this message by
examining the (TRANDIS) bit in the standard INQUIRY data.
The application client shall inform the INIT to use the CONTINUE TASK message by issuing a
TARGET TRANSFER DISABLE link control function in the send SCSI command phase.
The HDD does not support this message.
2.3.16 LOGICAL UNIT RESET message : X'1C' (I→T)
When the TARG receives this message normally, it enters the BUS FREE phase.
In case the I_T_L_x nexus has been established with LUN=0, TARG clears all the tasks in the
logical unit and generates UNIT ATTENTION condition for all INITs. Receipt of this message
has no effect on the MODE SELECT parameters and negotiated transfer agreements.
In case the I_T_L_x nexus has been established with non zero LUN or I_T nexus has been
established, TARG clears the task that is currently executed. In this case, there is no effect on the
other tasks.
2.3.17

Task attribute messages

Bit
7
Byte
0
1
The task attribute messages define a queue tag of I/O operation. The TAG field is an unsigned
eight-bit integer to be assigned by the INIT when it issues a command.
When the INIT issues a command using a tagged queuing, the INIT sends the appropriate task
attribute messages immediately after the IDENTIFY message during the same MESSAGE OUT
phase in order to set the queue tag for the I/O operation. If the task attribute messages are not sent,
the I/O operation is treated as an untagged command.
C141-C015
6 5 4
Message Code (X'20', X'21', or X'22')
TAG (X'00'- X'FF')
3 2 1 0
165