Making an ALU in Digital Works 2

Thread Starter


Joined Mar 22, 2010
Hi, This is my first post so I will briefly introduce myself.

My name is Dane and I am in currently in my second semester of study in a Bachelor of I.T.

In one of my subjects I have an assignment which is:

CIRCUIT OPTION 1: 4 function 4-bit ALU (45 marks):
Your 4-bit ALU must implement the following functionality (It is imperative that the bit values for
S1 and S2 in this table correspond exactly to the functions in your circuit):

0 0 Shift A Through (X = A)
0 1 Logical AND (X = A AND B)
1 0 Logical XOR (X = A XOR B)
1 1 Full adder (X = A + B)

In addition your circuit must include:
1. A multiplexor (comprised of a 2 to 4 Decoder and 4 input Selector)
Your circuit must use a separate template to represent each of the following components:
1. Full Adder
2. Logic Unit (Shift A Through, Full Adder, Logical AND, and Logical XOR)
3. 2 to 4 Decoder
4. 4 Input Selector
5. Multiplexor (Contains 2 to 4 Decoder and 4 Input Selector)
6. 1 Bit ALU (Contains Logic Unit and Multiplexor)
7. 4 Bit ALU (contains four 1 Bit ALUs)
Your 4 Bit ALU will consist of four 1 Bit ALUs wired together appropriately. You will be provided
with an interactive test harness circuit into which you can embed (and wire) your 4 Bit ALU
template for testing.

So I have built the full adder, 2 - 4 decoder, Multiplexor. There was a diagram in my notes with what I thought was the logic unit but I dont see the "shifter" in it.

This is my circuit.

Any suggestions/ideas/feedback would be great.