DB929B Datasheet, PDF (15/51 Pages) CML Microcircuits – Full Data Packet Framing

4-Level FSK Modem Data Pump
Page 15 of 50
MX929B PRELIMINARY INFORMATION
4.4 Frame Structure
The MX929B Frame Structure as used in a RD-LAPÂ¥ system is illustrated in Figure 7, and consists of a
Frame Preamble (comprising a 24-symbol Frame Synchronization pattern and Station ID block), followed by a
'Header Block', one or more 'Intermediate Blocks', and a 'Last Block'. Channel Status (S) symbols are
included at regular intervals. The first Frame of any transmission is preceded by a Symbol Synchronization
pattern.
Station ID
msb
lsb
Byte 7 6 5 4 3 2 1 0
0
System ID
1
Domain ID
2
Base ID
3
CRC0
µC binary data stored
in MX929B data block
memory configured as
header, intermediate, or
last block by MX929B
task being executed.
Header Block
Byte 7 6 5 4 3 2 1 0
0
1
2
3
Address
4
&
Control
5
6
(10 bytes)
7
8
9
10
CRC1
11
(2 bytes)
Intermediate Blocks
765 432 10
Data Bytes
(12 bytes)
Last Block
765 432 10
Data Bytes
(0-8)
--------------
Pad Bytes
(0-8)
CRC2
(4 bytes)
7
07
0
7 20
Byte 0 Byte 1 Byte 2 Byte 3
0 12
'000'
8 9 10
tri-bits
7
07
0
Byte 0 Byte 1
0 12 34 5
7
0
Byte 11
'000'
29 30 31 32
FEC TRELLIS CODING / DECODING
(ERROR CORRECTION)
01
4-level
20 21 _symbols
FEC TRELLIS CODING / DECODING
(ERROR CORRECTION)
0 12
64 65
INTERLEAVING / DE-INTERLEAVING
Block:
22 Symbols S 22 Symbols S 22 Symbols S
Over-air Signal
(symbols)
Symbol
Sync
Frame
Sync
S
Station
ID
S
'Header'
Block
24
24 1 22 1 69
Frame
Preamble
Intermediate Blocks
69
69
Packet (1 to 44 Blocks)
Frame
'Last'
Block
69
Frame
Sync
Next Frame
(Optional)
S: Channel Status Symbol: +3 = Busy, +1 = Unknown, -1 = Unknown, -3 = Idle
Frame Sync:
-1 +1 -1 +1 -1 +3 -3 +3 -3 -1 +1 -3 +3 +3 -1 +1 -3 -3 +1 +3 -1 -3 +1 +3
Symbol Sync:
+3 +3 -3 -3 +3 +3 -3 -3 +3 +3 -3 -3 +3 +3 -3 -3 +3 +3 -3 -3 -3 -3 +3 +3
sent first
last
Figure 7: Over-Air Signal Format
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