User's Manual

DLT4000 SCSI Interface
8-2 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem
8.2.2 Initiator/Target Operation
The DLT4000 drive does not act as an initiator on the SCSI bus. Therefore, the device
will not do any of the following:
• Generate unsolicited interrupts to the host
• Initiate its own SCSI commands
• Assert bus reset
8.2.3 SCSI IDs and Logical Unit Numbers (LUNs)
The DLT4000 drive with optional medium changer has two logical units. The tape
drive will always appear as LUN 0. The medium changer defaults to appearing as
LUN 1, but may be configured via the MODE SELECT command to any LUN from 0
to 7. Refer to MODE SELECT section in this chapter.
Unsupported LUNs will be treated as follows: If the LUN specified in the IDENTIFY
message is invalid, the DLT4000 drive accepts the Command Descriptor Block
(CDB). There are three cases of what happens next:
1. If the command is INQUIRY, the target returns the INQUIRY data with the
peripheral qualifier set to 011, indicating that the target will never support the
LUN in question.
2. If the command is REQUEST SENSE, the target returns sense data. The sense
key is ILLEGAL REQUEST, with an additional sense code of INVALID Logical
Unit Number.
3. For any other command, the target terminates the command with CHECK
CONDITION status, and generate the above Sense Data.