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SCSI Commands
Quantum DLT 4000 Tape Drive
5-5
Table 5–2 Command Descriptor Block - Field Descriptions
Field
Description
Operation Code
The operation code specifies the command being requested. The list of
supported SCSI commands and their operation codes are contained in Table
5-1.
Logical Unit Number The Logical Unit Number contains the number of the device being
addressed. It must be set to 0. The Logical Unit Number is ignored if the
Command Descriptor Block is preceded by an IDENTIFY Message.
Logical Block
Address
The 6-byte READ, SEEK, and WRITE Command Descriptor Blocks contain a
21-bit Logical Block Address. The 10-byte READ, SEEK, and WRITE Command
Descriptor Blocks contain a 32-bit Logical Block Address.
Commands that require additional parameter data specify the length of the
Logical Block Address that is needed. See the specific command descriptions
for more detailed information.
Relative Addressing indicates a technique used to determine the next Logical
Block Address to be operated on. The drive does not support Relative
Addressing. It defaults to a value of 0, which specifies that the Logical Block
Address specifies the first logical block of a range of logical blocks to be
operated on by the command.
Transfer Length
The transfer length field normally specifies the number of blocks to be
transferred between the initiator and the drive. For several commands, the
transfer length indicates the number of bytes (not blocks) to be sent. For
these commands, this field may be identified by a different name.
Parameter List
Length
The Parameter List Length is used to specify the number of bytes sent during
the DATA OUT phase. This field is typically used for parameters that are sent
to a drive (for example, mode, diagnostic, and log parameters). A parameter
list length of 0 indicates that no data is to be transferred.
Allocation Length
The Allocation Length field specifies the number of bytes that the initiator
has allocated for returned data. The Allocation Length is used to limit the
amount of data returned to the initiator.
An Allocation Length of 0 indicates that no data is to be transferred from the
drive to the initiator. The drive terminates the DATA IN phase when the
specified number of bytes have been transferred to the initiator or when all
available data has been transferred, whichever is less.
Summary of Contents for DLTtape DLT 4000
Page 1: ...DLT 4000 Tape Drive Product Manual November 10 2003 81 60043 04 ...
Page 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued ...
Page 6: ......
Page 24: ...About This Manual Quantum DLT 4000 Tape Drive xxiv ...
Page 62: ...Hardware Implementation 2 28 Quantum DLT 4000 Tape Drive ...
Page 100: ...Messages 4 12 Quantum DLT 4000 Tape Drive ...
Page 264: ...SCSI Commands 5 164 Quantum DLT 4000 Tape Drive ...
Page 274: ...Appendix B EEPROM Resident Bugcheck and Event Logs B 6 Quantum DLT 4000 Tape System ...
Page 280: ...Appendix C Updating the Firmware C 6 Quantum DLT 4000 Tape Drive ...
Page 298: ...Index Index 6 Quantum DLT4000 Tape Drive ...
Page 299: ......