% % (C) 2006 Muthiah Annamalai <muthuspost@gmail.com> % % Implement book keeping for a Pseudo-Random Binary Sequence ( PRBS ) % also called as a Linear Feedback Shift Register. % % Given a polynomial create a PRBS structure for that polynomial. % Now all we need is to just create this polynomial and make it work. % polynomial must be a vector containing the powers of x and an optional % value 1. eg: x^3 + x^2 + x + 1 must be written as [3 2 1 0] % all the coefficients are either 1 or 0. It generates only a Binary ... % sequence, and the generator polynomial need to be only a binary % polynomial in GF(2). % % connections, contains a struct of vectors where each vector is the % connection list mapping its vec(2:end) elements to the vec(1) output. % % 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. % % +---+ +----+ +---+ +---+ % | D |----| D |---| D |---| D | % +---+ +----+ +---+ +---+ % | | | % \ / / % [+]---------------+------+ % 1 + 0.D + 1.D^2 + 1.D^3 % % The code to implement this PRBS with a start state of [1 0 1 1] % will be: % % prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]); % x = prbs_sequence(prbs) %gives 15 % % prbs_iterator( prbs, 15 ) %15 binary digits seen % [ 1 1 0 1 0 1 1 1 1 0 0 0 1 0 0 ] % % See Also: This function is to be used along with functions % prbs_iterator, and prbs_sequence. %

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