Electronics/ALU

Arithmetic and Logic Unit

Introduction

The Arithmetic and Logic Unit are not a single entity, but are actually composed of two separate units whose operation is highly dependent on the Select Input(S).

This input is a one-bit input that will decide whether to route the binary variables to the Arithmetic or to the Logic Circuit.

Arithmetic Unit

Handles basic operations such as Addition and Subtraction. The Multiplication and Division operations are dependent on the basic operations and Bit-Shifting. The Multiply and Divide operations can also be implemented using Hardwired / Microprogrammed Control.

Logic Unit

The Logic unit is a Hardware Unit implemented for performing basic operations such as AND, OR, NAND and NOT. A particular logical operation is selected using a 4:1 Demultiplexer.

The results of all the operations are routed into a data bus for memory addressing.

further reading

• Microprocessor Design/ALU