Likewise, because the register has a finite number of possible states, it must eventually enter a repeating cycle. The initial value of the LFSR is called the seed, and because the operation of the register is deterministic, the stream of values produced by the register is completely determined by its current (or previous) state. The only linear function of single bits is xor, thus it is a shift register whose input bit is driven by the exclusive-or (xor) of some bits of the overall shift register value. The maximal sequence consists of every possible state except the '0000' state.Ī linear feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. The XOR gate provides feedback to the register that shifts bits from left to right. Template:Redirect Template:Refimprove Template:No footnotes File:LFSR-F4.GIFĪ 4-bit Fibonacci LFSR with its state diagram.
