Programmable Logic Array

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Programmable Logic Array

A programmable logic array (PLA) is a type of programmable logic device that combines the features of both PALs and ROMs, allowing for greater flexibility and customization in digital circuit design. PLAs use an array of programmable AND and OR gates to implement complex logic functions, providing a faster and more efficient alternative to traditional discrete logic components.

What does Programmable Logic Array mean?

A Programmable Logic Array (PLA) is a type of digital integrated circuit that can be customized to perform a variety of logical functions. It is a programmable hardware device that can be configured to implement any desired logic function. Unlike traditional logic gates, which are fixed in their functionality, PLAs offer the flexibility to modify their logic behavior after fabrication.

PLAs are composed of an array of logic elements (LEs), which are interconnected by a programmable network of wires. Each LE typically consists of a programmable AND plane and a programmable OR plane. In the AND plane, the inputs are combined using AND gates, while in the OR plane, the outputs of the AND gates are combined using OR gates. The configuration of the PLA determines the specific logic function that it implements.

Applications

PLAs are widely used in a variety of applications due to their versatility and programmability. They are commonly employed in:

  • Digital Signal Processing: PLAs can be used to implement complex digital signal processing algorithms in hardware, providing high-speed and low-latency performance.
  • Control systems: PLAs are used in programmable logic controllers (PLCs), which automate industrial processes. They can be configured to perform various control functions, such as sequencing, timing, and Data Acquisition.
  • Prototyping: PLAs can be used for rapid prototyping of digital circuits. They allow engineers to quickly test and verify logic designs before committing to a permanent hardware implementation.
  • Education: PLAs are used in educational settings to demonstrate the principles of digital logic and hardware design.

History

The concept of PLAs was first introduced in 1973 by Stanford University researchers Robert Hartmann and W. Ralph Hellerman. Their research laid the foundation for the development of commercial PLA devices.

During the 1980s, PLAs gained popularity as a cost-effective and Flexible alternative to traditional logic gates. They were widely used in a variety of electronic devices, including personal computers, printers, and Telecommunications equipment.

With the advent of Field-programmable gate arrays (FPGAs) in the 1990s, the use of PLAs declined somewhat. However, PLAs continue to be used in specialized applications where their configurability and low cost are advantages.