Control Byte - HP C2488A Technical Reference Manual

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