Initiator Detected Error - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
Identify (80h - FFh)
The Identify message (Table 4) is sent by either the initiator or the target to establish an I T L nexus.
Table 4. Identify message format
Bit 7
Byte
0 Identify
The Identify bit shall be set to one to specify that this is an Identify message.
A Disconnect Privilege (DiscPriv) bit of one specifies that the initiator has granted the target the privilege of dis-
connecting. A DiscPriv bit of zero specifies that the target shall not disconnect. Those drive models that do not
implement this feature must set this bit to zero. This bit is used in connection with the Disconnect Immediate
(DImm) bit in the Disconnect/Reconnect Mode Page.
Note. If an initiator selects a drive using the SCSI-1 Single Initiator Option, the drive shall not attempt to dis-
connect from that task, regardless of the state of the Disconnect Privilege bit in the Identify message (if
sent).
A logical unit target (LUNTAR) bit of zero specifies that the Identify message is directed to a logical unit. A
LUNTAR bit of one specifies that the Identify message is directed to a target routine that does not involve the
logical unit. This bit is not supported by the drive and will always be interpreted as a 0.
The logical unit number target routine number (LUNTRN) field specifies a logical unit number if the LUNTAR bit
is zero. The LUNTRN field specifies a target routine number if the LUNTAR bit is one. Only the Inquiry and
Request Sense commands are valid for target routines. If a target receives any other command for a target rou-
tine, it shall return Check Condition status and shall set the sense key to Illegal Request.
An invalid LUNTRN field terminates the command with a Check Condition, and in response to a Request
Sense command the drive returns sense data with the sense key set to Illegal Request and the additional
sense code set to Logical Unit Not Supported.
An Identify message is invalid if a reserved bit is set to one or if the LUNTAR bit is set to one and the target
does not implement target routines. A device may respond to an invalid Identify message by immediately send-
ing a Message Reject message or by returning Check Condition status. If a Check Condition status is returned,
the sense key shall be set to Illegal Request and the additional sense code shall be set to Invalid Bits in Identify
Message Field.
If a valid Identify message has not yet been received for the current nexus, the drive returns a Message Reject
message and goes to the Bus Free phase (see Unexpected Disconnect, in Section 3.1.1).
Only one logical unit number or target routine number shall be identified per task. The initiator may send one or
more Identify messages during a connection. A second Identify message with a different value in either the
LUNTAR bit or LUNTRN field shall not be issued before a Bus Free phase has occurred; if a target receives a
second Identify message with a different value in either of these fields, it shall go to Bus Free phase (unex-
pected BUS switch to another task. See the DTDC field of the Disconnect-Reconnect Control Page (Table 91)
for additional controls over disconnection.
An implied Restore Pointers message shall be performed by the initiator prior to the assertion of the ACK sig-
nal on the next phase for an Identify message sent during reconnection.
Initiator Detected Error (05h)
The Initiator Detected Error message is sent from an initiator to inform a target that an error has occurred that
does not preclude the target from retrying the operation. The source of the error may either be related to previ-
ous activities on the SCSI bus or may be internal to the initiator and unrelated to any previous SCSI bus activ-
ity. Although present pointer integrity is not assured, a Restore Pointers message or a disconnect followed by a
reconnect, shall cause the pointers to be restored to their defined prior state.
6 5
DiscPriv LUNTAR
4 3
LUNTRN
2 1
31
0