Control Byte
The
control byte is the
last
byte of every Command Descriptor Block (CDB).
Control
Byte
Format
Bit
Byte
7
I
6
5
I
4
I
3
I
2 1 0
Last
Vend
Unq
= 0
Reserved
Flag
Link
Link. Command linking
is
supported. A Link bit set
to
one (1) indicates
that
the
Initiator
desires an automatic link to
the
next command upon successful completion of
the
current
command. After successful completion of the current command, the Target will
return
a
status
of INTERMEDIATE and will then send one of
the
messages defined by
the
FLAG bit.
Flag. Typically, the FLAG bit is used
to
cause an interrupt in
the
Initiator between linked
commands.
When LINK::: 0 (zero), then FLAG will = 0 (zero).
When LINK
= 1 (one), and FLAG = 0 (zero), the Target will return a LINKED
COMMAND COMPLETE message when the command completes successfully,
When LINK
= 1 (one), and FLAG = 1 (one), the Target will return a LINKED
COMMAND COMPLETE (WITH FLAG) message when
the
command completes
successfully,
Note
For the Mode Select command only, bit 7 of the control byte
is
used
to
enable
(1) or disable
(0) the Write Protect mode. The
WP
bit in the Mode Sense
parameter list header reports
the
Write Protect status:
1
= enabled
o = disabled.
A-2
SCSI
Command
Descriptions
DRAFT
1/18/93 09:58
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