PRBS

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PRBS Generator Using VHDLPRBS Generator Using VHDL

Presented By,

Divyesh Patel

&

Alpesh Thesiya

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Pseudo Random Bit Sequence Pseudo Random Bit Sequence (PRBS)(PRBS)

A Pseudorandom bit generator (PRBS) is used to generate a random sequence of 1’s and 0’s

It is a good approach to use a PRBS sequence as a testing driver than a regular pulse wave sequence

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How to construct a PRBSHow to construct a PRBS

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LFSRLFSR

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A linear feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. The only linear functions of single bits are xor and inverse-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.

Types Of LFSR:

Galois Type Fibonacci Type

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Design a 15 bit Pseudo Random Design a 15 bit Pseudo Random Bit Generator / AnalyzerBit Generator / Analyzer

Design a 15bit PRBS serial bit stream at 25MHz

Design a analyzer to check if an error is encountered in the output signal

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DescriptionDescription

Circuit 1: 15 DFF connect in series, the output of the

13th and 15th DFF will connect to a XOR logic gate and feedback to the 1st DFF

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DFF SymbolDFF Symbol

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DFF SchematicDFF Schematic

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Rise and Fall time delayRise and Fall time delay

Rise time delay tR (0 > 1) tR = 7.27ns Fall time delay tf (1 > 0) tf = 4.99ns

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15bit PSRB15bit PSRB

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15bit PSRB schematic15bit PSRB schematic

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15bit PSRB Simulation15bit PSRB Simulation

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ApplicationApplication

Data Encryption/Decryption Digital Signal Processing Wireless Communications Built-in Self Test (BIST) Data Integrity Checksums Data Compression Direct Sequence Spread Spectrum Scrambler/Descrambler Optimized Counters

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ConclusionConclusion

As the PRBS generator using LFSR is easy because of ease of construction from simple electronics circuit, long periods, and very uniformly distributed output. An LFSR is a linear system, leading to fairly easy cryptanalysis.

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THANK YOUTHANK YOU

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