## What is an LFSR

A linear-feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. We can use this type of functions in many application such as counters, crypto, ber-meter, CRC generation, scrambling/descrambling algorithm, test application and so on

An LFSR of length N can generate 2^N-1 different states where the values look like pseudo-random values.

There are two different types of LFSR implementation the FIBONACCI and the GALOIS implementation as in Figure1. The LFSR implementations are equivalent.

If we are implementing the LFSR in hardware, the Galois implementation is much more efficient since use two input XOR function and the XOR function is implemented between two consecutive registers. Read More