Mindeo FS580 - Cmd_Nak

78
5-4 CMD_NAK
Description: Negative acknowledgment of received packet
Packet Format
Length
Opcode
Status
Cause
Checksum
0x04
0x4E
Field Descriptions
Field Name
Format
Size
Description
Length
0x04
1 Byte
Length Field
Opcode
0x4E
1 Byte
Identifies the opcode type.
Status
Bit 0: Identifies transmit status
Bit 6-1: Unused
Bit 7: Command source
1 Byte
Bit 0:
0=First time packet is sent
1= Subsequent transmission attempts
Bit 7:
0=Command is from the scanner
1=Command is from the host
All unused bits recommend to be set to 0.
Cause
Reason code
1 Byte
Identifies the reason the NAK occurred:
01＝NAK_OVERFLOW(Data Overflow, with
baud rate of 115200b/s)
02＝NAK_RESEND(Checksum failure)
04＝NAK_BAD_CONTEXT(Unexpected or
unknown message)
08＝NAK_DENIED(Host denies executing the
require of Opcode)
40＝NAK_NO_PARA (The parameter requests
to be changed doesn’t exist)
80＝NAK_OUT_OF_RANGE(The parameter
requests to be changed exceeds the
range)
Checksum
2's complement sum of message
contents excluding checksum.
2 Byte
Checksum of message.
This message is sent when the received packet fails the checksum verification or some error occurred
while handling the message.
ACK/NAK handshaking can be disabled, but this is not recommended.
It is not necessary to respond to a valid ACK or NAK message.