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% (C) 2006 Muthiah Annamalai <muthuspost@gmail.com>
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% Implement book keeping for a Pseudo-Random Binary Sequence ( PRBS )
% also called as a Linear Feedback Shift Register.
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% For the given PRBS in a intial state, compute the PRBS sequence length.
% Length is period of output when the PRBS state is same as
% the start state of PRBS.
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% Example: If you had a PRBS shift register like the diagram
% below with 4 registers we use representation by polynomial
% of [ 1 2 3 4], and feedback connections between [ 1 3 4 ].
% The output PRBS sequence is taken from the position 4.
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% +---+ +----+ +---+ +---+
% | D |----| D |---| D |---| D |
% +---+ +----+ +---+ +---+
% | | |
% \ / /
% [+]---------------+------+
% 1 + 0.D + 1.D^2 + 1.D^3
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% The code to implement this PRBS will be
% prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
% x = prbs_sequence(prbs) %gives 15
%