Design of Arithmetic Logic Unit Realized by Programmable Logic Device and VHDL Language

Last Update Time: 2023-03-13 13:31:05

Introduction

Programmable logic devices and VHDL are widely used in digital design and implementation of arithmetic logic units. Programmable logic devices, sometimes called "PLDs" or "Programmable Logic Units (PLUs)", provide an alternate architecture for implementation of logic systems. They require less space in the system and offer an efficient way to create custom logic systems. VHDL is an acronym for VHSIC (very high speed integrated circuit) Hardware Description Language. It is a language used to describe digital logic systems, replacing the combination of schematic diagrams and instructions used earlier.

Programmable Logic Devices

Programmable logic devices (PLDs) consist of several basic elements that can be connected to create Boolean functions. Each of these elements is a programmable universal logic gate or switch which can be programmed to create any arbitrary combination of logic functions. PLDs are organized as a matrix of logic gates and enable highly parallel operation. This makes them ideally suited for complex arithmetic problems. Compared to traditional integrated circuits, PLDs can offer better performance and higher speed. They are also much less expensive because they can be produced in large volumes and require less wiring and fewer components than an integrated circuit. This makes them an attractive choice for many digital design engineers.

VHDL Syntax and Structure

VHDL stands for Very High-Speed Integrated Circuit (VHSIC) Hardware Description Language. It is a very powerful language with a specific syntax and structure, which makes it easier for the programmer to write code and for the design to be interpreted correctly by the EDA tools. VHDL consists of two basic components: objects and data types. Objects are the basic building blocks of VHDL, comprising elements such as entity, architecture, process, signal and port. Data types are the basic data types used for programmable logic. Most common types include Boolean, Integer, Real, Character and others. The syntax of VHDL is also specific and makes it easier to write and understand. A typical VHDL program has the following structure:

    1. Information section: It includes comments and other information used to identify the program.

    2. Declaration section: It contains the declarations of variables, functions and data types used in the program.

    3. Architecture section: It includes the actual architecture of the model written in the program.

    4. Statement section: It contains the procedural statements of the model.

How to Design ALU with PLDs and VHDL

Arithmetic Logic Units (ALUs) are an important part of any processor architecture. They are responsible for executing arithmetic and logic operations on data words. ALU designs can be very complex, but with the help of programmable logic devices and VHDL, it is possible to create a design for an ALU in a relatively short time frame. The first step in creating an ALU is to determine the requirements. This will help you to decide which operations are required in the ALU and determine the data paths. Next, the data paths and operations must be implemented in VHDL. This includes the design of the logic gates, the logic functions and the control logic. PLDs can be used to implement the logic functions, while VHDL can be used to define the control logic. Finally, the ALU must be tested and verified. This is done by writing testbenches in VHDL to simulate the ALU and verify it is working correctly. Once the design is verified, it can be implemented on an FPGA to create the actual ALU.

Conclusion

Programmable Logic Devices and VHDL can be used to design Arithmetic Logic Units. PLDs offer an alternative to traditional ICs and enable highly parallel operations. VHDL provides a language to describe digital logic systems and create the control logic. The design and implementation of an ALU can be done relatively quickly using PLDs and VHDL.