Barrel Shifter

What Does Barrel Shifter Mean?

A barrel shifter is a specialized digital electronic circuit with the purpose of shifting an entire data word by a specified number of bits by only using combinational logic, with no sequential logic used. The simplest way of achieving this is by using a series of multiplexers where one output is connected to the input of the next multiplexer in the chain, in a specific manner that depends on the amount of shift specified.


Techopedia Explains Barrel Shifter

Barrel shifters are specialized electronic circuits used to shift the bits of binary data and often employed by embedded digital signal processors and other general-purpose processors in order to manipulate data. Data shifting is required for various low-level data applications such as floating-point arithmetic operations, bit indexing and variable-length coding. A barrel shifter is able to complete the shift in a single clock cycle, giving it a great advantage over a simple shifter which can shift n bits in n clock cycles. It is used in conjunction with a processor’s arithmetic logic unit (ALU) or otherwise embedded in the ALU itself.

A barrel shifter is able to shift the bits of binary data by moving it from one multiplexer to the next, with the supported number of bits dictated by how many multiplexers are used.

The formula for determining how many multiplexers are required is n log2(n) where n is the number of bits supported. So for an 8-bit barrel shifter the calculation is 8 × log2(8) = 8 × 3 = 24.


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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…