My practical textbook asks me to design a full 18×16 barrel shifter on paper. I have tried looking around but cannot seem to figure out what the A×B convention means when describing a barrel shifter.

Online resources describe a barrel shifter in terms of the total number of input/output bits (n) and sometimes also add a max shift capability (k). In most cases I have seen described, n is a power of 2 (2,4,8,16,...) while k is almost always equal to n - 1.

I could simply treat n = 18, k = 16 here and implement a left shift-only, 4 stages of 18 2:1 MUXs each, but that'd be cumbersome and/or incorrect.


I also found it hard to find a concise description of this notation. However, by plugging in some different values for n and k in Google searches for "n x k barrel shifter", I was able to find this PDF, which shows an 8x4 barrel shifter on page 27, where there are 8 inputs and 4 outputs.

I'm not entirely sure what the value of an asymmetric barrel shifter would be, except perhaps just cost savings for a very specific implementation or device. They seem to be hard to find information about.

If you are in a class, I would ask your instructor or TA about what the correct interpretation is. The only resource I can find suggests it's inputs x outputs, but I think inputs x shift capability is a reasonable interpretation as well.

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