Altera Viterbi Compiler - Manual (Page 19)

Viterbi IP Core Functional Description
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2014.12.15
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Decoder
The Viterbi decoder can be a continuous or block decoder.
The continuous decoder processes a number of symbols greater than the traceback length. When the
decoder traces back the number of bits (traceback length), it delivers output bits. This behavior changes
when you assert the end of packet (EOP) signal. The decoder then switches to block decoding, starting
traceback from the last symbol or state. The
tr_init_state
signal indicates the end state that starts the
traceback operation. For block decoding Altera recommends you indicate the end state of the tail bits
(usually zero) and set the
tb_type
signal to 1.
Convolutional Encoder
The viterbi IP core convolutional encoder.
Figure 3-1: Convolutional Encoder
L = 5, N = 2 and polynomials GA = 19 and GB = 29. GA in decimal is 19, which is equal to 10011 in
binary. The most significant bit of the binary representation is the connection at the input data bit; the
least significant bit (LSB) represents the connection at the end of the shift register chain. The XOR
function implements the modulo-2 adding operation
RR
Port
MSB
LSB
ga_xor
gb_xor
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