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Chapter 5 SCSI Interface
General SCSI Bus Operation
5
Data Transfer
Initiator/Target
5
Operation
SCSI IDs and
5
LUNs
52
The library supports asynchronous and synchronous data
transfers. The product has both differential and single-ended SCSI
interfaces. Odd parity is generated during all information transfer
phases where the device writes data to the SCSI bus, and checked
during all information transfer phases where data is read from the
bus.
During operations that take significant amounts of time, such as
Move Media commands, the device disconnects from the SCSI bus,
allowing other devices to access the bus. This disconnection is
configurable through the Disconnect-Reconnect Mode Parameters
page.
The library does not act as an initiator on the SCSI bus and will not:
• Generate unsolicited interrupts to the host
• Initiate its own SCSI commands
• Assert bus reset
The library always appears as logical unit number (LUN) LUN 0.
If the LUN specified in the Identify message is invalid, the library
will accept the Command Descriptor Block (CDB). There are three
cases in which this happens:
• If the command is Inquiry, the target will return the inquiry
data with the peripheral qualifier set to 011, indicating that the
target will never support the LUN in question.
• If the command is Request Sense, the target will return sense
data. The sense key will be Illegal Request, with an additional
sense code of Invalid LUN.
• For any other command, the target will terminate the
command with a Check Condition status, and generates the
sense data.
Quantum|ATL PowerStor L200 Series Library User's Guide
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