Discrete Logic Device vs. PLD

Attribute	Discrete Logic Device	PLD
Functionality	Performs basic logic functions	Programmable to perform complex logic functions
Flexibility	Fixed functionality	Flexible and reprogrammable
Cost	Lower cost	Higher cost
Size	Individual components	Integrated circuit
Speed	Slower	Faster

Introduction

When it comes to designing digital circuits, engineers have a variety of options to choose from. Two common choices are discrete logic devices and programmable logic devices (PLDs). Both have their own set of attributes and advantages, which make them suitable for different applications. In this article, we will compare the attributes of discrete logic devices and PLDs to help you understand which one might be the best fit for your project.

Discrete Logic Devices

Discrete logic devices are individual electronic components that perform specific logic functions, such as AND, OR, and NOT gates. These devices are typically made up of transistors, diodes, and resistors, and are used to build simple logic circuits. Discrete logic devices are non-programmable, meaning their functionality is fixed and cannot be changed once they are manufactured. This makes them ideal for applications where a specific logic function is required and will not change over time.

One of the key advantages of discrete logic devices is their simplicity. Since they are designed for specific logic functions, they are easy to understand and implement in a circuit. Discrete logic devices are also known for their reliability and robustness, as they are less prone to failure compared to more complex integrated circuits. Additionally, discrete logic devices are often more cost-effective than programmable alternatives, making them a popular choice for simple logic applications.

However, one of the limitations of discrete logic devices is their lack of flexibility. Once a circuit is built using discrete logic devices, it is difficult to modify or reconfigure without physically changing the components. This can be a drawback in applications where the logic requirements may change over time or where rapid prototyping is necessary. In these cases, engineers may opt for programmable logic devices instead.

Programmable Logic Devices (PLDs)

PLDs are integrated circuits that can be programmed to perform a wide range of logic functions. These devices typically consist of an array of programmable logic gates, such as AND, OR, and XOR gates, as well as programmable interconnects that allow for flexible routing of signals. PLDs can be reprogrammed multiple times, making them ideal for applications where the logic requirements may change or where rapid prototyping is necessary.

One of the key advantages of PLDs is their flexibility. Engineers can easily modify the functionality of a circuit by reprogramming the PLD, without the need to physically change any components. This makes PLDs ideal for applications where the logic requirements are not fixed or where the design needs to be iterated upon quickly. Additionally, PLDs are often more space-efficient than discrete logic devices, as they can pack a large number of logic functions into a single integrated circuit.

However, one of the drawbacks of PLDs is their complexity. Programming a PLD requires specialized software and knowledge of hardware description languages, such as VHDL or Verilog. This can be a barrier for engineers who are not familiar with these tools or who are used to working with discrete logic devices. Additionally, PLDs are typically more expensive than discrete logic devices, especially for low-volume production runs.

Comparison

When comparing discrete logic devices and PLDs, it is important to consider the specific requirements of the project. Discrete logic devices are best suited for applications where a fixed logic function is required, and where simplicity, reliability, and cost-effectiveness are important factors. On the other hand, PLDs are ideal for applications where flexibility, reconfigurability, and space efficiency are key considerations.

• Discrete Logic Devices:
  • Simple and easy to understand
  • Reliable and robust
  • Cost-effective for simple logic functions
  • Lack flexibility and reconfigurability
• PLDs:
  • Flexible and reconfigurable
  • Space-efficient for complex logic functions
  • Require specialized programming tools and knowledge
  • More expensive than discrete logic devices

In conclusion, both discrete logic devices and PLDs have their own set of attributes and advantages, which make them suitable for different applications. By understanding the strengths and limitations of each type of device, engineers can make an informed decision on which one to use for their project.