CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 11

• Manufacturer Part Number: CMX969D5
• Description: MOTIENT/ARDIS RD-LAP MDC4800 Modem
• Manufacturer: MX-COM, Inc.

MOTIENT
4.4.2
The CMX969 Frame Structure in RD-LAP mode is illustrated in Figure 6, and consists of a Frame Preamble
(comprising a 24-symbol Frame Synchronization pattern and Station ID block) followed by one or more
'Header’ blocks, 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.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
Over-air
signal
(symbols)
SM
RD-LAP Mode
/ARDIS
7
0
0
FEC TRELLIS CODING / DECODING
Byte 0
Byte 0
Byte 1
Byte 2
Byte 3
1
1
( ERROR CORRECTION )
SM
SYMBOL
0
2
SYNC
msb
7
RD-LAP
24
7 6 5 4 3 2 1 0
Byte 1
Station ID
System ID
Domain ID
Base ID
CRC0
FRAME
SYNC
0
24
www.mxcom.com Tel: [phone] 744 5050 Fax: [phone]
TM
PREAMBLE
7
FRAME
MDC4800 Modem
Byte 2
1
S
STATION
lsb
ID
0
22
sent first
Figure 6: RD-LAP Over Air Signal Format
'S' : Channel Status Symbol : +3 = Busy
Frame Sync:
Symbol Sync:
7
+3
-1 +1
8
Byte 3
+3
20
9
2
1
S
'000'
10
21
-1 +1
-3
'HEADER'
0
BLOCK
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
Byte 9
Byte 10
Byte 11
69
-3 +3
4-level
symbols
tri-bits
-1 +3
Block:
7 6 5 4 3 2 1 0
+3
69
Header Block
PACKET (1 TO 44 BLOCKS)
(10 bytes)
-3 +3
-3
Address
Control
(2 bytes)
CRC1
7
&
0
0
FRAME
11
All trademarks and service marks are held by their respective companies.
INTERMEDIATE BLOCKS
22 symbols
Byte 0
-3 +3 +3
1
1
-3
INTERLEAVING / DE-INTERLEAVING
+1 = Unknown -1 = Unknown -3 = Idle
2
FEC TRELLIS CODING / DECODING
2
0 7
-1 +1
Byte 1
3
( ERROR CORRECTION )
-3
S
69
4
-3 +3
-3 +3
0
7 6 5 4 3 2 1 0
Intermediate Blocks
5
22 symbols
+3
+3
Data Bytes
(12)
-1
-3
+1
-3 +3
'LAST'
BLOCK
69
S
-3
+3
29 30
CMX969 Advance Information
-3 +1
7
22 symbols
Byte 11
FRAME
SYNC
-3
7 6 5 4 3 2 1 0
NEXT FRAME
(OPTIONAL)
+3
31
64
-3
0
Last Block
'000'
Doc. # 20480211.002
32
65
-1
Data bytes
Pad bytes
(4 bytes)
-3
(0 - 8)
CRC2
(0 - 8)
-3 +1 +3
-3
S
+3
last
+3