Abort Scanning (Can); Normal Response (Ack); Negative Response (Nak) - Epson ES-1000C Reference Manual

2. Abort scanning (CAN)

Usually you send an ESC G command to start scanning and, after the
scanner sends a data block, the computer responds with an ACK code
to confirm the data was received. If the computer sends a CAN code
instead of the ACK code, the scanner cancels scanning and stops
sending data.
The scanner recognizes the CAN code only after it has sent a data
block and is waiting to receive the ACK code from the computer. If
the scanner receives the CAN code when it is waiting to receive a
command, a command error results.
After the scanner cancels scanning, the carriage returns to the home
position. Other scanner settings are not affected by canceling
scanning. Also, scanning does not resume at the position where it was
canceled.

3. Normal response (ACK)

When the scanner receives correct commands or parameters, it sends
this code to the computer as a kind of confirmation.
When sending image data, the computer should send an ACK code to
the scanner after it receives each data block. When scanning in color,
the computer should send an ACK code after each data block for each
color.

4. Negative response (NAK)

When the scanner receives an incorrect command or parameter, it
sends a NAK code. When the scanner sends this code, a command
error also results.
If the scanner returns a NAK code, the previously sent command is
not performed. If you were trying to change a scanner setting, the
previous setting remains in effect.
Command Usage
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