# Created by Octave 3.2.3, Tue Jan 05 12:00:36 2010 EST <mandrake@n3.mandriva.com>
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prbs_generator
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 (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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 (C) 2006 Muthiah Annamalai <muthuspost@gmail.

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prbs_iterator
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# type: string
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 (C) 2006 Muthiah Annamalai <muthuspost@gmail.com>
 
 This function generates the output bits from the PRBS
 state, for the number of iterations specified.

 First argument is the PRBS structure obtained from prbs_generator.
 PRBS iterations is specified in the second argument.
 PRBS start state is taken from the prbs.sregs.

 Second argument of the output is PRBS structure with a new
 state. This allows usage like: 
 
 [ seq, prbs ] =  prbs_iterator( prbs, niterations );
 
 while the state of the PRBS is updated.
 
 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 will be 
 prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
 x = prbs_iterator(prbs,15)
 
 See Also: This function is to be used along with functions 
 prbs_iterator, prbs_generator and prbs_sequence.
 

# name: <cell-element>
# type: string
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 (C) 2006 Muthiah Annamalai <muthuspost@gmail.

# name: <cell-element>
# type: string
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prbs_sequence
# name: <cell-element>
# type: string
# elements: 1
# length: 936
 
 (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.
 
 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.
 
 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 will be 
 prbs=prbs_generator([1 3 4],{[1 3 4]},[1 0 1 1]);
 x = prbs_sequence(prbs) #gives 15
 

# name: <cell-element>
# type: string
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 (C) 2006 Muthiah Annamalai <muthuspost@gmail.

