- EPSON Reference Manual Scanner GT-1000, GT-4000, GT-6000, GT-6500, GT-8000, GT-8500, GT-9000, GT-5000, GT-300, ES-300C, ES-600C, ES-800C, ES-1000C, ES-1200C, Action Scanner II, ES-300GS

NAK Abnormal response (negative acknowledge)
Format: B1 B2 B3 B4 B5 A5
ASCII: NAK
Decimal: 21
Hexadecimal: 15
Explanation:
This code is used by the scanner for handshaking. This code indicates
that a command or a parameter was illegal and not accepted by the
scanner.
When the NAK code is returned from the scanner, it means a
command error has occurred in the scanner, and the command was
ignored. To recover from a command error, resend a legal command
or a command followed by a legal parameter.
3-68 Command Reference