Logic Gates - Building an ALU

1  Introduction

1.1  Basic Components

1.2  Bitwise AND

1.3  Bitwise OR

1.4  Addition

1.5  Subtraction

1.6  Overflow Output

1.7  Negative Output

1.8  Zero Output

1.9  Putting It All Together

1.10  Finally

What To Do

To keep things simple, we will build a 4-bit ALU instead of the full 32-bit ALU discussed here. This should give you a taste on how simple digital gates are used in building complex circuits. We will be using Logisim, an excellent educational tool for designing and simulating digital logic circuits, featuring a simple-to-learn interface, hierarchical circuits, wire bundles, and a large component library.



Acknowledgement. This tutorial has been developed by Warren Toomey, PhD. Its original version can be found here.