Quantum DLT1/VS80 SCSI, Инструкция по интерфейсу

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Chapter 2: General SCSI Bus Operation
2-2 July 2004 81-81276-01 Rev A01
2.3 SCSI IDs and Logical Unit Numbers
The tape drive has one logical unit number (LUN), which is always LUN 0.
The tape drive treats unsupported LUNs as follows: If the LUN specified in the IDENTIFY message is
invalid, the tape drive accepts the Command Descriptor Block (CDB). The next action is one of the
following three cases:
•
If the command is INQUIRY, the target returns the INQUIRY data with the peripheral qualifier set
to 011, indicating that the target does not support the LUN in question.
•
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.
•
For any other command, the target terminates the command with CHECK CONDITION status and
generates the Sense Data described in item 2.
2.4 UNIT ATTENTION Condition
The tape drive implements Queued Unit Attentions which are maintained separately for each valid
LUN for each Initiator. The host computer creates Unit Attentions under the following conditions:
•
Power-on Reset
•
BUS Reset
•
Bus Drive Reset message
•
Asynchronous media change
•
Mode Parameters changed by another initiator
•
Firmware update completed.
Two queued Unit Attentions are not unusual. For example, powering up a tape drive and loading a data
cartridge create Power Up and Not-ready to Ready Transition Unit Attentions. Since there are a limited
number of Unit Attention buffers, if an initiator does not clear Unit Attentions queued for it, at some
point the tape drive stops generating new Unit Attentions for that I–L combination. However, existing
Unit Attentions remain queued.
A LOAD command does not generate a Unit Attention for the initiator that issued the command since
the transition to Ready is a synchronous event.