Bit Shuffler - use a MUX?

Thread Starter


Joined Mar 4, 2008
Hello, I have a homework question that I have no idea where to start with.
Any advice on how to take apart the question would be useful.

Here it is:

A shorthand notion for representing a group of wires is: A[3:0] which basically means its A3 A2 A1 A0, 4 bits.

Design a circuit that conforms to the following:

Input: A[3:0] - 4 bit input
S - 1 bit input

Output: D[3:0] - 4 bit output

Operation specifics:

If (S=1) then D[3:0] = A[3:0] --> D[3] = A[3], D[2] = A[2] etc

If (S=0) then D[3:0] = A[2:0], 0 --> D[3] = A[2], D[2] = A[1], .. D[0] = 0.

I mean I thought I could use a multiplexer where S is the select button. So, essentially you select the inputs to be equal to the outputs when the Select value is 1.

When select is 0, you shift everything?

Thank you!