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-LAP¥ 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
4 3
System ID
Domain ID
Base ID
Header Block
7 6 4 3
Intermediate Blocks
Last Block
msb
7 6
lsb
0
Byte
Byte
0
1
2
3
4
5
6
7
5
2
1
5
2
1
0
7
6
5
4
3
2
1
0
2 1
7 6 5 4 3 0
0
1
2
3
Data Bytes
(0-8)
--------------
Pad Bytes
(0-8)
Address
&
Control
CRC0
Data Bytes
(12 bytes)
µC binary data stored
in MX929B data block
memory configured as
header, intermediate, or
last block by MX929B
task being executed.
(10 bytes)
8
9
10
11
CRC2
(4 bytes)
CRC1
(2 bytes)
7
0 7
0
7
2
0
7
0 7
0
7
0
Byte 0
Byte 1
Byte 2
Byte 3
Byte 0
Byte 1
Byte 11
'000'
29 30 31 32
'000'
10
8
9
0
0
1
1
2
2
3
4
5
tri-bits
0
1
2
FEC TRELLIS CODING / DECODING
(ERROR CORRECTION)
FEC TRELLIS CODING / DECODING
(ERROR CORRECTION)
4-level
symbols
64 65
0
1
20 21
INTERLEAVING / DE-INTERLEAVING
22 Symbols
22 Symbols
22 Symbols
Block:
S
S
S
Over-air Signal Symbol Frame
Frame
Sync
Station
ID
'Header'
Block
'Last'
Block
S
S
Intermediate Blocks
69
Sync
Sync
(symbols)
24
24
1
22
1
69
69
69
Frame
Preamble
Packet (1 to 44 Blocks)
Frame
Next Frame
(Optional)
S: Channel Status Symbol: +3 = Busy, +1 = Unknown, -1 = Unknown, -3 = Idle
Frame Sync:
-3
-1 +1 -1 +1 -1 +3 -3 +3 -3 -1 +1 -3 +3 +3 -1 +1
-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
©2001 MX-COM, INC.
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Doc. # 20480171.003
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