14 scan, Scan – FUJITSU M3093DG User Manual
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4.4.14 SCAN
The normal SCAN sequence for the scanner is as follows:
Step
Bus phase
Initiator operation
¨Æ
Target operation
1
2
3
4
5
6
7
8
9
Bus Free
(Arbitration)
Selection
(Message Out)
Command
Data Out
Status
Message In
Bus Free
Checks Bus Free
Acquires the right to use the
bus
Selects the target
Selects the logical device
Specifies SCAN (CDB)
Specifies the window ID
Ж
Ж
Ж
Ж
¨
¨
Drives the BSY signal
Specifies reading
Reports GOOD status
Reports message
(Command complete)
Releases the BSY
signal
(1)
SCAN command: Command phase (Initiator to Target)
The SCAN command defines reading method for the scanner.
The command descriptor block (CDB) is as follows:
Byte 0
1
2
3
4
5
Operation code X©1Bπ
Logical unit number
7
6
5
4
3
2
1
0
(Reserved)
Control byte
(Reserved)
Allocation length
f
Transfer length: Byte 4
The transfer length specifies the number of bytes of window data sent during
the DATA OUT phase. A 0 means that no data is transferred. This is not an
error.
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