In order to maximize the length of the LFSR, i.e. It has to satisfy several properties - it is expressed as a polynomial modulo 2, meaning all the coefficients must be either 1 or 0.Įxample: a register with taps at positions 11, 10, 7, 3 will have a feedback polynomial: The location and number of the taps is determined by the register's reciprocal characteristic polynomial. Other linear functions can be used as well. This constitutes one step of the feedback shift register. It operates by taking the bits of the inital value (called fill or seed), shifting them one position to the left and replacing the leaving bit with exclusive-or of the leaving bit and bits at special locations in the register called the taps. A simple emulator of a linear-feedback shift register (LFSR).
