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).
Содержание DLTtape DLT 4000
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Страница 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued ...
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Страница 24: ...About This Manual Quantum DLT 4000 Tape Drive xxiv ...
Страница 62: ...Hardware Implementation 2 28 Quantum DLT 4000 Tape Drive ...
Страница 100: ...Messages 4 12 Quantum DLT 4000 Tape Drive ...
Страница 264: ...SCSI Commands 5 164 Quantum DLT 4000 Tape Drive ...
Страница 274: ...Appendix B EEPROM Resident Bugcheck and Event Logs B 6 Quantum DLT 4000 Tape System ...
Страница 280: ...Appendix C Updating the Firmware C 6 Quantum DLT 4000 Tape Drive ...
Страница 298: ...Index Index 6 Quantum DLT4000 Tape Drive ...
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