Quantum 10K II - Manual (Page 349)

Appendix B. SCSI Bus Signal Timing
B–28 Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives
B.8 SUPPORTED SCSI MESSAGES
Following are descriptions of each of the messages supported by the drive. SCSI-3
message names are used. If there is a corresponding SCSI-2 name that is different, it
is shown in parentheses in
ITALICS.
B.8.1 ABORT TASK Message (0Dh) (ABORT TAG)
The drive’s response to an ABORT TASK message depends on the task being
performed when the message arrives. If anything less than an I_T_L_Q nexus is
established, the drive goes to the BUS FREE phase without affecting any tasks or
recording any sense data.
If an I_T_L_Q nexus exists, the drive aborts the current process and goes to the
BUS FREE phase. If the drive does not have a queued or active task for the specified
tag, it goes to the BUS FREE phase. Any pending data, sense data, or status for the
task are cleared. However, neither an Auto Contingent Allegiance condition for the
initiator nor any other tasks are affected and all cached writes are retained. Mode
parameters and reservations established by earlier commands are not affected.
B.8.2 ABORT TASK SET Message (06h) (ABORT)
The ABORT TASK SET message is sent by the initiator to clear any task for the
I_T_x nexus. The drive’s response depends upon the task being performed when the
message arrives.
If only an I_T nexus has been established (that is, a valid IDENTIFY message has
not been received), the drive goes to the BUS FREE phase without affecting any task
or recording any sense data. An exception is if the drive has received a command
during this I_T nexus; the task is aborted as described below.
If an I_T_L nexus exists, the drive aborts all tasks, and goes to the BUS FREE
phase. Any pending data, sense data, or status for the tasks are cleared. However,
an Auto Contingent Allegiance condition for the initiator is not affected and any
cached writes are retained. Mode parameters and reservations established by earlier
commands are not affected.
B.8.3 CLEAR ACA Message (16h)
Since NACA bit = 1 is not supported, SCSI-2 rules for clearing ACA are in effect
and this message is ignored by the drive.
B.8.4 CLEAR TASK SET Message (0Eh)
The CLEAR TASK SET message clears all tasks from all initiators and goes to the
BUS FREE phase. Pending data and status for all processes are discarded. A Unit
Attention condition is generated for all other initiators that had their queue
commands cleared (additional sense code is set to COMMANDS CLEARED BY
ANOTHER INITIATOR).
Previously established conditions, including mode parameters, reservations, and
Auto Contingent Allegiance conditions are not affected. An I_T_L nexus must exist
for the drive to accept this message. After accepting this message, the drive goes to
the BUS FREE phase.