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SCSI Commands
5-6
Quantum DLT 4000 Tape Drive
Table 5–2 Command Descriptor Block - Field Descriptions (continued)
Field
Description
Control Field
The Control Field is the last byte of every command descriptor block. Its
format is shown in Figure 5–2 and it contains the Flag and Link bits. Use of
these bits is initiator-dependent. Setting the Link bit = 1 provides an
automatic link to the next command, bypassing the usual ARBITRATION,
SELECTION, and MESSAGE OUT phases that would normally occur between
commands. Other bits in the Control Field are considered to be reserved.
Relative Address
(RelAdr)
Must be 0 (not supported).
Bit
Byte
7
6
5
4
3
2
1
0
5
Vendor Specific
Reserved
Flag
Link
Figure 5–2 Command Descriptor Block Control Field - Data Format
Table 5–3 Command Descriptor Block Control Field - Field Descriptions
Field
Description
Vendor Specific Bits
These bits must be 0.
Flag Bit
The Flag bit is used in conjunction with the Link bit to notify the initiator in
an expedient manner that a command has been completed.
Link Bit
A Link bit set to 1 indicates that the initiator requests continuation of a task
(an I/O process) across two or more SCSI commands.
If the Link bit is 1 and the Flag bit is 0, and the task completes successfully,
the drive continues the task and returns a status of INTERMEDIATE and a
LINKED COMMAND COMPLETE message.
If the Link bit and the Flag bit within a Control word are both set to 1, and
the drive complete a command with a status of INTERMEDIATE, the drive
returns a LINKED COMMAND COMPLETE message (with Flag).
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: ......