Message Frame
The Message Frame structure is used by all messages sent with the Azande Protocol.
A message has following parts:
- START and END character.
- ID and SUB ID: Gives the message an unique identity
- PAYLOAD: Holds data from sender.
- CRC: Type 16-CCITT
Frame
Unescaped Frame
Byte# |
0 |
1 |
2 |
3 .. N-3 |
N-2 |
N-1 |
N |
Name |
START |
ID |
SUB ID |
PAYLOAD |
CRC MSB |
CRC LSB |
END |
Value |
0xAA |
[0..255] |
[0..255] |
Optional |
CRC16-CITT |
0xBB |
|
Escaped Frame
Byte# |
0 |
- |
- |
- |
- |
- |
N |
Name |
START |
- |
- |
- |
- |
- |
END |
Value |
0xAA |
Escaped area without any 0xAA or 0xBB |
0xBB |
||||
More information about escaping.
ID and SUB ID
The 2 bytes ID and SUB ID gives the message an unique identity.
Payload
All but the VOID messages have payload, holding data for the receiver.
CRC
Bytes |
Byte # 0 to N-3 |
Type |
CRC16-CCITT |
Seed |
0xFFFF |
Polynomial |
x16 + x12 + x5 + 1 |
START and END characters
The START and END characters frames one message.
Name |
Value |
START |
0xAA |
END |
0xBB |