Release Unit Command; Release Unit Command: Command Phase (Initiator → Target) - Fujitsu Scan Partner 300C Instruction Manual

4.4.2 RELEASE UNIT command

The following table shows the normal sequence of the RESERVE UNIT command when used with this scanner.
Step Bus phase
1 BUS FREE
2 ARBITRATION
3 SELECTION
4 MESSAGE
OUT
5 COMMAND
6 STATUS
7 MESSAGE IN
8 BUSFREE
4.4.2.1 RELEASE UNIT command: COMMAND phase (initiator
The RELEASE UNIT command releases a reserved status. If this command comes from an initiator that has not
declared reservation, the target ignores the command and responds with the GOOD status (the reserved status is
not released).
The CDB of this command is shown in the following illustration.
Byte 0
1
2
3
4
5
(a) TP (third party): Byte 1
Table 4-9
Initiator operation
Verifies bus free
Obtains bus-usage right
Selects target
Selects local unit
Specifies RELEASE
UNIT (CDB)
7 6 5
Logical unit number
RELEASE UNIT command
← ← → →
→
Drives BSY signal
→
→
←
Reports GOOD status
←
Reports message (Command Complete)
Releases BSY signal
4
3
Operation code X'17'
TP
(Reserved)
Control byte
4-21
Target operation
→
target)
2 1
TPID
(Reserved)
0