Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E
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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 I/O process. 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 releas-
ing 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
possibly the last) with a SAVE DATA POINTER - DISCONNECT message sequence.
Identify (80h - FFh)
The IDENTIFY message (Table 3.5.3-1) is sent by either the initiator or the target to establish an I T L nexus.
Table 3.5.3-1. Identify message format
Bit
7
6
5 4 3 2
1
0
Byte
0
Identify DiscPriv LUN-
LUNTRN
TAR
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
disconnecting. A DiscPriv bit of zero specifies that the target shall not disconnect. This bit is not defined and
shall be set to zero when an IDENTIFY message is sent by a target.
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 disc 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 routine, 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 RE-
QUEST SENSE command the disc 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
sending a MESSAGE REJECT message or by returning CHECK CONDITION status. If a CHECK CONDI-
TION 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.
