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Chapter 5 Tutorial
PRBS
4
5
An LFSR is specified by the number of stages it contains and which
stages (“taps”) feed the exclusive-or (XOR) gate(s) that comprise its
feedback network. The PRBS output is taken from the last stage. With
properly chosen taps, an L-stage LFSR produces a repetitive PRBS of
length 2
L
-1. The clocking frequency of the LFSR determines the “bit
rate” of the PRBS.
In the 33500 Series, you can set L to be 7, 9, 11, 15, 20, or 23, resulting in
sequences from 127 to 8,388,607 bits in length.
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