Macrocell arrays in PLDs

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 ...

s, such as

programmable array logic Programmable Array Logic (PAL) is a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. (MMI) in March 1978. Introductory advertisement on PAL (Pro ...

and complex programmable logic devices, typically have a macrocell on every output pin.

Macrocell arrays in ASICs

A macrocell array is an approach to the design and manufacture of

ASIC An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-effici ...

s. Essentially, it is a small step up from the otherwise similar

gate array A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a prefabricated chip with components that are later interconnected into logic devices (e.g. NAND gates, flip-flops, etc.) accord ...

, but rather than being a prefabricated array of simple logic gates, the macrocell array is a prefabricated array of higher-level logic functions such as flip-flops,

ALU ALU, Alu or alu may refer to: Computing and science ;Computing *Arithmetic logic unit, a digital electronic circuit ;Biology * Alu sequence, a type of short stretch of DNA *'' Arthrobacter luteus'', a bacterium Organizations * Abraham Lincoln ...

functions, registers, and the like. These logic functions are simply placed at regular predefined positions and manufactured on a

wafer A wafer is a crisp, often sweet, very thin, flat, light and dry biscuit, often used to decorate ice cream, and also used as a garnish on some sweet dishes. Wafers can also be made into cookies with cream flavoring sandwiched between them. They ...

, usually called master slice. Creation of a circuit with a specified function is accomplished by adding metal interconnects to the chips on the master slice late in the manufacturing process, allowing the function of the chip to be customised as desired. Macrocell array master slices are usually prefabricated and stockpiled in large quantities regardless of customer orders. The fabrication according to the individual customer specifications may be finished in a shorter time compared with standard cell or

full custom Full-custom design is a methodology for designing integrated circuits by specifying the layout of each individual transistor and the interconnections between them. Alternatives to full-custom design include various forms of semi-custom design, s ...

design. The macrocell array approach reduces the

mask A mask is an object normally worn on the face, typically for protection, disguise, performance, or entertainment and often they have been employed for rituals and rights. Masks have been used since antiquity for both ceremonial and pra ...

costs since fewer custom masks need to be produced. In addition manufacturing test tooling lead time and costs are reduced since the same test fixtures may be used for all macrocell array products manufactured on the same die size. Drawbacks are somewhat low density and performance than other approaches to ASIC design. However this style is often a viable approach for low production volumes. A standard cell library is sometimes called a "macrocell library"."ASIC Macro Cells"

References

{{DEFAULTSORT:Macrocell Array Gate arrays