MX919B View Datasheet(PDF) - MX-COM Inc
Part Name
Description
MFG CO.
'MX919B' PDF : 48 Pages View PDF
4-Level FSK Modem Data Pump
Page 13 of 47
MX919B PRELIMINARY INFORMATION
4.3 Binary to Symbol Translation
Although the over-air signal, and therefore the signals at the modem TXOUT and RXIN pins, consists of 4-
level symbols, the raw data passing between the modem and the µC is in binary form. Translation between
binary data and the 4-level symbols is done in one of two ways, depending on the task being performed.
1. Direct way: (simplest form) - converts between 2 binary bits and a single symbol.
SYMBOL
+3
+1
-1
-3
MSB
1
1
0
0
LSB
1
0
0
1
Accordingly, 1 byte = 4 symbols = 8 bits, and one byte translates to four symbols for the T4S and R4S tasks
and six bytes translates to twenty-four symbols for the T24S task described in Section 4.5.2.
Bits:
Symbols:
MSB
7
6
a
send first
5
4
b
3
2
c
LSB
1
0
d
send last
2. FEC way: (more complicated) - essentially translates groups of 3 binary bits to pairs of 4-level
symbols using a Forward Error Correcting coding scheme for the block oriented tasks THB, TIB, TLB,
RHB, and RILB described in Section 4.5.2.
©2001 MX•COM, INC.
www.mxcom.com Tele: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480170.003
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.
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