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A-61124 March 1999 4-1
4 Scanner — Host Communications
This chapter provides an overview of the communication link
between the scanner and the host system. Communications
between the scanner and the host system occur across a SCSI
bus. The SCSI interface supports two-way command/data
communication between the scanner and the host system. The
SCSI-2 command set is supported.
Host to scanner
communications
The host transmits machine setup information to the scanner
using both the SCSI Define Windows command and the SCSI
Send command. The SCSI Define Windows command is used to
set up image processing parameters such as resolution,
threshold, contrast, etc.
The SCSI Send command transmits scanner-unique commands.
These allow settings of both image processing parameters and
machine configuration. These commands are embedded within
the Send command as data and can be identified by the 2-byte,
scanner-unique command field. A series of scanner-unique
commands may be sent as one data string within a single Send
command.
Scanner to host
communications
The scanner transmits digitized images to the host via the SCSI
interface using the SCSI Read command.
The scanner is capable of transmitting current image processing
setup information using the SCSI Get Windows command.
Additionally, the scanner can transmit both image processing and
configuration information using the SCSI Read command .
SCSI data rates
The
Digital Science
Document Scanner 9500 has a SCSI
controller which is capable of faster SCSI transfer rates. It is
capable of operating at a sustained maximum data transfer rate
of 7 megabytes-per-second. Actual data transfer rate is a function
of the host system configuration.