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A.4 Commands
Appendix A-87
A.4.11 READ command
The following table shows the normal sequence of the READ 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 READ
(CDB)
→
Reads document
6 DATA IN
←
Transfers image data
7 STATUS
←
Reports GOOD status
8 MESSAGE IN
←
Reports message (Command
Complete)
Releases BSY signal
9 BUS FREE
(1) READ command: COMMAND phase (initiator → target)
The READ command is used by an initiator to request a target for transfer of data. Upon receiving
this command, the target returns scan data to the initiator.
The CDB of this command is shown in the following illustration.