Write short notes on: i) PLA ii) FLASH RAM

i) PLA (Programmable Logic Array)

A Programmable Logic Array (PLA) is a type of programmable logic device (PLD) that uses a two-dimensional array of logic gates to implement digital logic functions. PLAs are often used to implement combinational logic functions, although they can also be used to implement sequential logic functions.

The basic architecture of a PLA consists of a programmable AND array, a programmable OR array, and a set of input and output pins. The AND array is responsible for generating the product terms of the logic function, while the OR array is responsible for generating the final output function. The input pins are used to connect the PLA to the external world, while the output pins are used to drive external devices.

The PLA can be programmed by specifying the values of the AND and OR arrays. This can be done manually using a programming tool, or it can be done automatically using a computer-aided design (CAD) tool.

PLAs have a number of advantages over other types of PLDs. These advantages include:

• High speed: PLAs can operate at very high speeds, making them ideal for use in high-performance applications.
• Low power consumption: PLAs consume very little power, making them ideal for use in portable devices.
• Small size: PLAs are very small, making them ideal for use in applications where space is limited.

ii) FLASH RAM (Flash Random Access Memory)

Flash RAM (Flash Random Access Memory) is a type of non-volatile memory (NVM) that can be programmed and erased in blocks. Flash RAM is used in a wide variety of applications, including USB flash drives, solid-state drives (SSDs), and digital cameras.

Flash RAM is based on the principle of floating-gate transistors. A floating-gate transistor is a type of transistor that has a floating gate between the source and drain terminals. The floating gate can be programmed by applying a voltage to it, which causes electrons to be injected into or removed from the gate. The amount of charge on the floating gate determines the conductivity of the transistor.

Flash RAM is divided into blocks, which are typically 64 kilobytes (KB) or 128 KB in size. Each block can be programmed or erased independently. This allows Flash RAM to be used to store a variety of data, including code, data, and media files.

Flash RAM has a number of advantages over other types of NVM. These advantages include:

• High speed: Flash RAM can be programmed and erased very quickly, making it ideal for use in high-performance applications.
• Low power consumption: Flash RAM consumes very little power, making it ideal for use in portable devices.
• Long lifespan: Flash RAM can be programmed and erased tens of thousands of times, making it very durable.
• Small size: Flash RAM is very small, making it ideal for use in applications where space is limited.