Editing Programmable Array Logic (section)

==History==
Before PALs were introduced, designers of digital logic circuits would use [[small-scale integration]] (SSI) components, such as those in the [[7400 series]] TTL ([[transistor-transistor logic]]) family; the 7400 family included a variety of logic building blocks, such as gates ([[NOT gate|NOT]], [[NAND gate|NAND]], [[NOR gate|NOR]], [[AND gate|AND]], [[OR gate|OR]]), [[multiplexers]] (MUXes) and demultiplexers (DEMUXes), [[Flip-flop (electronics)|flip-flops]] (D-type, JK, etc.) and others. One PAL device would typically replace dozens of such "discrete" logic packages, so the SSI business declined as the PAL business took off. PALs were used advantageously in many products, such as [[minicomputers]], as documented in [[Tracy Kidder]]'s best-selling book ''[[The Soul of a New Machine]]''.

PALs were not the first commercial programmable logic devices; [[Signetics]] had been selling its [[field programmable logic array]] (FPLA) since 1975. These devices were completely unfamiliar to most circuit designers and were perceived to be too difficult to use. The FPLA had a relatively slow maximum operating speed (due to having both programmable-AND and programmable-OR arrays), was expensive, and had a poor reputation for testability. Another factor limiting the acceptance of the FPLA was the large package, a 600-[[Thou (unit of length)|mil]] (0.6", or 15.24&nbsp;mm) wide 28-pin [[dual in-line package]] (DIP).

The project to create the PAL device was managed by [[John Birkner]] and the actual PAL circuit was designed by [[H. T. Chua]].<ref name=" Birkner 1978">{{Cite journal |last=Birkner |first=John |author-link=John Birkner |title=Reduce random-logic complexity |journal=Electronic Design |volume=26 |issue=17 |pages=98–105 |location=Rochelle, NJ |date=August 16, 1978 |publisher=Hayden Publishing}}</ref> In a previous job (at mini-computer manufacturer [[Computer Automation]]), Birkner had developed a 16-bit processor using 80 standard logic devices. His experience with standard logic led him to believe that user-programmable devices would be more attractive if the devices were designed to replace standard logic. This meant that the package sizes had to be more typical of the existing devices, and the speeds had to be improved. MMI intended PALs to be a relatively low cost (sub $3) part. However, the company initially had severe manufacturing yield problems{{citation needed|date=January 2020}} and had to sell the devices for over $50.{{citation needed|date=January 2020}} This threatened the viability of the PAL as a commercial product, and MMI was forced to license the product line to National Semiconductor.{{citation needed|date=January 2020}} PALs were later "[[second source]]d" by [[Texas Instruments]] and [[Advanced Micro Devices]].