Figure 5-2 Command Descriptor Block Control Field - Data Format - Quantum DLT 8000 Product Manual

SCSI Commands
Table 5–2 Command Descriptor Block — Field Descriptions (continued)
Field
Control Field
Relative Address (RelAdr)
Bit 7
Byte
5 Vendor Specific
Figure 5–2 Command Descriptor Block Control Field — Data Format
Table 5–3 Command Descriptor Block Control Field — Field Descriptions
Field
Vendor Specific Bits
Flag Bit
Link Bit
5-6
Description
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.
Must be 0 (not supported).
6 5 4
Description
These bits must be 0.
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.
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 completes a command with a status of
INTERMEDIATE, the drive returns a LINKED COMMAND
COMPLETE message (with Flag).
Quantum DLT 8000 Tape System
3 2
Reserved
1 0
Flag Link