MC92314 Datasheet, PDF (32/100 Pages) Motorola, Inc – DVB-T Single Chip Demodulator Application Note

Device Description
Freescale Semiconductor, Inc.
3.2.3.2.3 Generator Polynomials
The Viterbi decoder is designed to decode bit streams encoded using the DVB standard
generator polynomials (171₈, 133₈) as shown in Figure 3-9.
171₈
+
Data In
Data Out
+ _{tion 1338}
a _{Figure 3-9. Generator Polynomials}
form 3.2.3.2.4 Punctured Codes
In ^{The Viterbi decoder is able to decode a basic rate 1/2 convolutional code and the “standard”}
punctured codes for a k=7 constraint length. The punctured maps are shown in the table below.
y _{Specific bits of the original rate 1/2 code sequence are periodically deleted prior to transmission}
r _{according to the entries in the table, where a 0 means that the bit is deleted and a 1 means that}
a _{the bit is transmitted.}
in _{Table 3-3. Deletion Map For Punctured Rate 1/2 Codes}
lim _{Coding Rate}
re 1/2
P _2/3
Puncture Map
1
1
11
10
3/4
110
101
5/6
11010
10101
7/8
1111010
1000101
3.2.3.2.5 Rate Encoding Data Word
The code rate actually being decoded by the decoder is indicated via external pins SR2..SR0
and via the I²C interface.
MOTOROLA
3-14
Single Chip DVB-T Demodulator - Rev. 1.3 (11/30/98)
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