
SIMPLE SERIAL INTERFACE
63
CMD_NACK
Description: Negative acknowledgment of received packet
Packet Format
Length
Opcode
Message
Source
Status
Cause
Checksum
0x05
0XD1
Field Descriptions
Field Name
Format
Size
Description
Length
Length of message
(not including
checksum).
1 Byte
Length Field
Opcode
0xD1
1 Byte
Identifies this opcode type.
Message Source
0 = Reader
4 = Host
1 Byte
Identifies where the message
is coming from.
Status
Bit 0: Retransmit
Bit 1-7: Unused
1 Byte
Identifies the transmission
status.
Unused bits must be set to 0.
Cause
Reason Cause
1 Byte
Identifies the reason the
NACK occurred:
0 = Reserved
1 = (RESEND) Checksum
failure
2 = (BAD_CONTEXT)
Unexpected or Unknown
message
3 = Reserved
4 = Reserved
5 = Reserved
6 = (DENIED) Host Directive
Denied
7 = Reserved
8 = Reserved
9 = Reserved
Checksum
2's complement
sum of message
contents excluding
checksum.
2 Byte
Checksum of message.
Содержание Dragon D151
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