Wolfram Language & System 11.0 (2016)|Legacy Documentation

This is documentation for an earlier version of the Wolfram Language.
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ShiftRegisterSequence

gives a complete maximum-length sequence for a size n linear-feedback shift register.

ShiftRegisterSequence[{n,{tap1,tap2,}}]
gives the complete sequence for a linear-feedback shift register with size n and taps at positions tapi.

ShiftRegisterSequence[poly]
gives the sequence for a linear-feedback shift register with feedback polynomial poly.

ShiftRegisterSequence[{n,{tap1,tap2,},f}]
gives the sequence for a shift register with feedback function f.

ShiftRegisterSequence[spec,s]
gives the first s elements of the shift register sequence.

ShiftRegisterSequence[spec,init,s]
gives the shift register sequence starting from state init.

Details and OptionsDetails and Options

• uses a particular linear-feedback shift register of size n that gives a maximum-length sequence. When possible, a shift register with three taps is used (corresponding to a trinomial). In general, the shift register used is the one whose specification is lexically smallest.
• ShiftRegisterSequence[{n,{tap1,tap2,}}] starts from the initial state {1,0,0,0,}, then at each step first takes the sum mod 2 of the values at the positions tapi, then shifts all values to the left, placing the sum on the right and using this as an element of the output.
• In ShiftRegisterSequence[{n,{tap1,tap2,},f}], the result at each step is obtained by applying f to the list of values from the position tapi.
• The default for f is effectively Mod[Total[#],2]&.
• ShiftRegisterSequence[{n,taps}] gives the same complete sequence as ShiftRegisterSequence[Total[x^(taps-1)]+x^n], though the sequence may start from a different point.
• In ShiftRegisterSequence[poly,init,s], init can be either a list of values of length n or a polynomial whose coefficients correspond to these values.
• ShiftRegisterSequence[spec,init,All] gives the complete sequence of length .
• ShiftRegisterSequence[spec,All] is equivalent to ShiftRegisterSequence[spec].
• ShiftRegisterSequence has the following options:
•  Method Automatic the shift register updating method to use Modulus 2 the modulus to assume
• ShiftRegisterSequence[n,Modulus->p] gives a maximum-length sequence with elements from 0 to .
• Possible settings for the Method option include:
•  "Fibonacci" use conventions suitable for explicit taps "Galois" use conventions suitable for polynomials Automatic use Fibonacci for explicit taps and Galois for polynomials
• Different settings for the Method option affect the initial conditions for a maximum-length sequence but do not affect the overall sequence of states it contains.

ExamplesExamplesopen allclose all

Basic Examples  (3)Basic Examples  (3)

Generate a maximal-length shift register sequence for a register of size 6:

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Generate the sequence from a shift register with taps 6, 2, 1:

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Use a shift register with the nonlinear feedback function BitOr:

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