Epson GT-6500 EN - Manual (Page 40)

Execution Commands
Execution commands tell the scanner to send back data to the
computer.
Use execution commands to begin image data transfer from the
scanner to the computer, to obtain the scanner ID and status, and to
obtain information on the current scanner settings.
1. Start scanning (ESC G)
Upon receiving this command, the scanner begins scanning and
sending image data to the computer. The scanner sends image data in
data blocks that consist of one or more lines.
After the computer receives a complete data block, it should send an
ACK code to the scanner to confirm receipt.
When the scanner receives the ACK code, it begins sending the next
data block.
This process is repeated over and over to continue sending data.
However, the computer should not send an ACK code after the final
data block.
To determine the final data block, refer to the status information block
at the beginning of each data block. See
page 2-28 for details on the status information block.
ESC G and other commands
The ESC G command begins scanning based on the current scanner
settings. Make sure you use the other commands to make your desired
settings before sending the ESC G command.
2-2 Command Usage