Reconfigurable Linear Feedback Shift Register

Abstract

A linear feedback shift register (LFSR) is a shift register in which the feedback, i.e., the linear function of two or more of its previous states also known as taps, is given as a serial input. Due to the feedback connection, the pseudo-random sequences get repeated continuously resulting in a longer period that will be helpful for operations to be performed regularly. LFSR generates various pseudo-random sequences of the same length (repeated after a particular cycle length period) for each polynomial depending on the type of feedback. The maximum length (can be provided by a primitive polynomial) of an LFSR sequence is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2^{\mathrm{n}}-1$</tex> n is the number of flip-flops. This paper proposes a design of reconfigurable LFSR, which takes the seed values externally and can work as Standard, Galois, Complete or Reseeding designs of LFSR, depending on a mode switch in the circuit. The proposed design is implemented and analyzed for polynomials of degree 2 to 11.