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Appendix A-48
A.4.6 TEST UNIT READY command
The following table shows the normal sequence of the TEST UNIT READY command when used
with this scanner.
Step Bus phase Initiator operation
← →
Target operation
1 BUS FREE Verifies bus free
2 ARBITRATION
Obtains bus-usage
right
3 SELECTION Selects target
→
Drives BSY signal
4 MESSAGE OUT Selects logical unit
→
5 COMMAND
Specifies TEST UNIT
READY (CDB)
→
6 STATUS
←
Reports GOOD status
7 MESSAGE IN
←
Reports message (Command
Complete)
Releases BSY signal
8 BUS FREE
(1) TEST UNIT READY command: COMMAND phase (initiator → target)
The TEST UNIT READY command checks whether a logical unit is ready. This command does not
request self-test. The acknowledgment of this command reported using the status and sense data.
The CDB of this command is shown in the following illustration.
1
Byte 0
2
3
4
5
Operation code X’00’
(Reserved)
(Reserved)
Control byte
7
6
5
4
3
2
1
0
Logical unit number