Gate array: Difference between revisions

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A '''gate array''' or '''uncommitted logic array''' ('''ULA''') is an approach to the design and manufacture of [[application-specific integrated circuit]]s (ASICs). A gate array circuit is a prefabricated silicon chip circuit with no particular function in which [[transistor]]s, standard [[NAND]] or [[NOR]] [[logic gate]]s, and other [[active device]]s are placed at regular predefined positions and manufactured on a [[wafer (electronics)|wafer]], usually called a '''master slice'''. Creation of a circuit with a specified function is accomplished by adding a final surface layer or layers of metal interconnects to the chips on the master slice late in the manufacturing process, joining these elements to allow the function of the chip to be customised as desired. This layer is analogous to the copper layer(s) of a [[printed circuit board]] ([[Printed circuit board|PCB]]).

Gate array master slices are usually prefabricated and stockpiled in large quantities regardless of customer orders. The design and fabrication according to the individual customer specifications may be finished in a shorter time compared with [[standard cell]] or [[full custom]] design. The gate array approach reduces the [[Photomask|mask]] 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 gate array products manufactured on the same [[die]] size. Gate Arrays were the predecessor of the more advanced Structured ASIC; unlike Gate Arrays, Structured ASICs tend to include predefined or configurable memories and/or analog blocks. Structured ASICs are still sold by companies such as ChipX, Inc.