A simple programmable logic device (SPLD) is a

programmable logic device A programmable logic device (PLD) is an electronic component used to build reconfigurable digital circuits. Unlike digital logic constructed using discrete logic gates with fixed functions, a PLD has an undefined function at the time of man ...

with complexity below that of a complex programmable logic device (CPLD). The term commonly refers to devices such as

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

s, PLAs and

GAL Gal may refer to: People Surname * Gál, a Hungarian surname * Andreas Gal (born 1976), German programmer * Dani Gal (born 1975), Israeli video artist * Dean Gal (born 1995), Israeli footballer * Edward Gal (born 1970), Dutch dressage rider * G ...

Basic description

Simple programmable logic devices (SPLD) are the simplest, smallest and least-expensive forms of programmable logic devices. SPLDs can be used in boards to replace standard logic components (AND, OR, and NOT gates), such as 7400-series TTL. They typically comprise 4 to 22 fully connected macrocells. These macrocells typically consist of some combinatorial logic (such as AND OR gates) and a flip-flop. In other words, a small

Boolean logic In mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variables are the truth values ''true'' and ''false'', usually denoted 1 and 0, whereas in ...

equation can be built within each macrocell. This equation will combine the state of some number of binary inputs into a binary output and, if necessary, store that output in the flip-flop until the next clock edge. Of course, the particulars of the available logic gates and flip-flops are specific to each manufacturer and product family. But the general idea is always the same. Most SPLDs use either fuses or non-volatile memory cells (

EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power ...

EEPROM EEPROM (also called E2PROM) stands for electrically erasable programmable read-only memory and is a type of non-volatile memory used in computers, usually integrated in microcontrollers such as smart cards and remote keyless systems, or as ...

Flash Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...

, and others) to define the functionality. These devices are also known as: * Programmable array logic (PAL) * Generic array logic (GAL) * Programmable logic arrays (PLA) * Field-programmable logic arrays (FPLA) * Programmable logic devices (PLD)

Advantages

PLDs are often used for address decoding, where they have several clear advantages over the 7400-series TTL parts that they replaced: One chip requires less board area, power, and wiring than several do. The design inside the chip is flexible, so a change in the logic does not require any rewiring of the board. Rather, simply replacing one PLD with another part that has been programmed with the new design can alter the decoding logic.

References

{{cite book , url= https://www.safaribooksonline.com/library/view/introduction-to-digital/9780470900550/chap1-sec007.html , first= Mohammed , last= Ferdjallah , date= 2011 , title= Introduction to Digital Systems: Modeling, Synthesis, and Simulation Using VHDL , chapter= 1.7 Simple Programmable Logic Devices , isbn= 9780470900550 , publisher= John Wiley & Sons , website= Safari Books online Gate arrays