4-49
This scanner calculates the numbers of X-direction pixels and Y-direction pixels of the image data to be transferred to
the initiator. The scanner performs this calculation by referencing the resolution and area up with the SET WINDOW
command. This data need not be issued if the number of pixels are known 1 the initiator.
The transfer format for this data is shown in the following illustration.
(MSB)
Number of X-direction pixels
(LSB)
(MSB)
Number of Y-direction pixels
(LSB)
(Reserved)
4.4.10
Scan command
The following table shows the normal sequence of the SCAN 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 SCAN (CDB)
→
6
DATA OUT
→
Transfer data
7
STATUS
←
Reports GOOD status
8
MESSAGE IN
←
Reports message (Command Complete)
Releases BSY signal
9
BUS FREE
4.4.10.1
SCAN Command phase (initiator
→
target)
The Scan Command requests the target begin a scan operation. It is required for scanning color image, but not
required for scan B/W image.
Byte 0
3
4
7
8
F