Cino FA470 - Manual (Page 241)

Command Descriptions
2-226
Device NAK
(ALL)
Descriptions
Device non-acknowledgement
Device NAK message is used to guarantee the reliability of packet transfers for commands that
have no natural response, such as Action Commands, Set commands. On receiving a bad
command, the scanner will send a Device NAK message to issue a command error including
Opcode error, LRC check digit error and so on. Device NAK may not be disabled.
Packet Format
Prefix Opcode Status Length Parameter(s) LRC Suffix
7Eh 0Eh 00h XXh 00h 00h 00h <Null> 0E 7Eh
1 Byte 3 Bytes 1 Byte 2 Bytes 0 Byte 1 Byte 1 Byte
. Host Requirements
On receiving a bad command, it takes the device about 1 second to clear out the command buffer. So
you are NOT supposed to send other commands during this period of time after receiving the Device
NAK message. Since Device NAK is a device-to-host message, there is no response for this message.
. Opcode Field
The third byte of the Opcode varies according to the error code. It is reserved.
. Parameter(s) Field
Device NAK message takes no parameters, so the Parameter(s) field is null.
. Length
Total size (bytes) of the Parameter(s) field
. LRC
”Opcode” XOR “Status” XOR “Length” XOR “Parameter(s)”