Programmable Array Logic vs. Programmable Logic Array

Attribute	Programmable Array Logic	Programmable Logic Array
Structure	AND array followed by OR array	OR array followed by AND array
Programming Technology	Non-volatile	Volatility depends on technology used
Flexibility	Less flexible	More flexible
Complexity	Less complex	More complex
Speed	Slower	Faster

Introduction

Programmable Array Logic (PAL) and Programmable Logic Array (PLA) are two types of programmable logic devices that are commonly used in digital circuit design. While both PAL and PLA serve similar purposes, they have distinct attributes that set them apart from each other. In this article, we will compare the attributes of PAL and PLA to help you understand the differences between these two types of programmable logic devices.

Architecture

One of the key differences between PAL and PLA lies in their architecture. PAL consists of a fixed OR array and a programmable AND array. The OR array is fixed, meaning that the connections between inputs and OR gates are predetermined. On the other hand, PLA consists of both programmable AND and OR arrays, allowing for more flexibility in terms of logic implementation. This difference in architecture gives PLA an advantage in terms of versatility and customization compared to PAL.

Flexibility

When it comes to flexibility, PLA offers more options compared to PAL. Since PLA has both programmable AND and OR arrays, designers have the ability to implement a wide range of logic functions using the same device. This flexibility allows for more efficient use of resources and can lead to more optimized designs. On the other hand, PAL's fixed OR array limits the types of logic functions that can be implemented, making it less flexible compared to PLA.

Complexity

Another factor to consider when comparing PAL and PLA is complexity. PAL devices are generally simpler in terms of design and implementation compared to PLA. This simplicity can be advantageous for certain applications where a straightforward logic implementation is sufficient. However, for more complex logic functions that require a higher degree of customization, PLA is the preferred choice due to its ability to handle more intricate designs. In terms of complexity, PLA offers more capabilities compared to PAL.

Programming

Programming is a crucial aspect of both PAL and PLA devices. PAL devices are typically programmed using a fuse link technology, where connections are made or broken by blowing fuses. This programming method is permanent and irreversible, making it suitable for applications where the logic configuration does not need to be changed frequently. On the other hand, PLA devices are programmed using a memory cell technology, allowing for reprogramming of the device multiple times. This flexibility in programming makes PLA more suitable for applications that require frequent changes to the logic configuration.

Cost

Cost is an important consideration when choosing between PAL and PLA devices. PAL devices are generally more cost-effective compared to PLA due to their simpler architecture and programming technology. This makes PAL a preferred choice for applications where cost is a primary concern. However, for applications that require a higher degree of flexibility and customization, the additional cost of PLA may be justified by the increased capabilities it offers. In terms of cost, PAL is typically more budget-friendly compared to PLA.

Applications

Both PAL and PLA devices find applications in a wide range of industries, including telecommunications, automotive, aerospace, and consumer electronics. PAL devices are commonly used in applications where a simple logic implementation is sufficient, such as in control systems and signal processing. On the other hand, PLA devices are preferred for applications that require more complex logic functions, such as in data processing and digital signal processing. The choice between PAL and PLA depends on the specific requirements of the application and the level of customization needed.