4.4.11READ command

The following table shows the normal sequence of the READ command when used with this scanner.

Step

Bus phase

Initiator operation

¨ Æ

Target operation

 

 

 

 

 

1

BUS FREE

Verifies bus free

 

 

 

 

 

 

 

2

ARBITRATION

Obtains bus>usage

 

 

 

 

right

 

 

 

 

 

 

 

3

SELECTION

Selects target

Æ

 

 

 

 

 

 

 

 

 

 

Drives BSY signal

 

 

 

 

 

4

MESSAGE OUT

Selects logical unit

Æ

 

 

 

 

 

 

5

COMMAND

Specifies READ

Æ

Reads document

 

 

(CDB)

 

 

 

 

 

 

 

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 Æ 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.

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