![]() ![]() The Galois register shown has the same output stream as the Fibonacci register in the first section. Note that the internal state of the LFSR is not necessarily the same. To generate the same output stream, the order of the taps is the counterpart (see above) of the order for the conventional LFSR, otherwise the stream will be in reverse. When the output bit is one, the bits in the tap positions all flip (if they are 0, they become 1, and if they are 1, they become 0), and then the entire register is shifted to the right and the input bit becomes 1. The effect of this is that when the output bit is zero all the bits in the register shift to the right unchanged, and the input bit becomes zero. The new output bit is the next input bit. The taps, on the other hand, are XOR'd with the output bit before they are stored in the next position. In the Galois configuration, when the system is clocked, bits that are not taps are shifted one position to the right unchanged. Named after the French mathematician Évariste Galois, an LFSR in Galois configuration, which is also known as modular, internal XORs as well as one-to-many LFSR, is an alternate structure that can generate the same output stream as a conventional LFSR (but offset in time). ![]()
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