A.4 Commands

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

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 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.

Appendix A-87