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, the function of a PLD is undefined at the time of m ...

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 that was introduced by Monolithic Memories, Inc. (MMI) in March 1978. Introductory advertisement on ...

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-efficien ...

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 semiconductor device fabrication, prefabricated chip with components that are later interconnected into logic devices (e.g. NAN ...

, 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 functions, registers, and the like. These logic functions are simply placed at regular predefined positions and manufactured on a wafer, 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 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 employed for rituals and rites. Masks have been used since antiquity for both ceremonial and practical purposes, ...

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