PLD,CPLD and FPGA

PLD and FPGA:

A logic device is an electronic component that performs a defined function that is decided at the time of its manufacture and will never change. For example, a not gate always inverts the logic level of the input signal and does/cannot do anything else.

On the other hand, Programmable Logic Devices (PLD) are those components that do not have a specific function associated with them. These can be configured to perform a certain function by the user as needed and can be changed to perform some other function at a later time, i.e. they are reconfigurable. All of these PLDs are programmable using device programs that transfer the Boolean logic pattern to the programmable device.

However, the amount of flexibility offered depends on its type.

Types of programmable logic devices

Programmable Logic Array (PLA)

This device consists of sets of programmable AND gates and OR gates that must be configured by the user to obtain the output.

Programmable Array Logic (PAL)

PALs use an array of OR gates with fixed logic, while an array of AND gates that can be programmed according to user requirements. As a result, these devices express the output as a combination of inputs in the form of a sum of products.

Generic Logic Array (GLA)

These devices had similar properties to PALs, plus they were electrically erasable and reprogrammable.

Complex Programmable Logic Device (CPLD)

CPLDs are denser than PALs and consist of a large number of programmable logic elements. The interconnection between these macrocells must be established by the user.

Here the logic elements that establish the sum of product are combined to form structures in order to reduce the number of input-output (IO) pins. CPLDs are preferred to implement designs based on combinational logic.

Field Programmable Gate Array (FPGA)

FPGAs are based on gate array technology.

These devices consist of configurable logic blocks (CLBs) along with an interconnect matrix that sits in between.