Feedback Register (feedback shift register) Definition/Meaning:
A shift register, generally consisting of several cells, in which the first
cell has its input supplied by a combinational logic function of the parallel
outputs of several cells and of a possible external input. An
important case is the linear feedback register in which
linear logic is employed for the feedback
function.
The linear feedback register has the effect of deconvolving the
external serial input with the sequence of combinational coefficients (see
convolution). If the external input is regarded as a
polynomial in which powers
of the indeterminate denote succession in time, and if the combinational
coefficients are regarded likewise as a second polynomial, then the linear
feedback register has the effect of dividing the former polynomial by the
latter. When used in coding or in digital signal processing, feedback shift
registers may be binary or q-ary and may be implemented in hardware or software.
When there is no external serial input, the linear feedback
register can be used on its own to generate m-sequences or, with
parallel loading of the shift register with a source word, as an encoder for
simplex codes; either of these applications requires that the
feedback logic coefficients represent a
polynomial that is primitive.
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