(1)REQUEST SENSE command: COMMAND phase (initiator Æ target)
The REQUEST SENSE command requests the sense data that shows the status of a logical unit. On receiving this command, the target sets the units status in the sense data and returns it to the initiator.
The CDB of this command is shown in the following illustration.
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Byte 0 |
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| Operation code X©03 |
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1 |
| Logical unit number |
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| (Reserved) |
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2 |
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| (Reserved) |
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| Allocation length |
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5 |
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| Control |
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a.Allocation length: Byte 4
Specifies the storage area in bytes that the initiator allocates for sense data. If a 0 is set here, sense data is not transferred, but this is not treated as an error. The target terminates the DATA IN phase when it has transferred either the bytes of sense data specified in this field or all of effective sense data.
(2)Sense data: DATA IN phase (target Æ initiator)
The target creates sense data if its status is B©00001 (CHECK CONDITION) or if a BUS FREE error has occurred. This scanner creates sense data when any of the errors described later is encountered.
The sense data on this scanner is shown in the following illustration.
4 $ 30