High-speed merged plane logic function array

Abstract

A programmable logic array includes a plurality of MOS switching devices formed at preselected locations in an array made up of input and output lines and intersecting product term lines. One group of MOS devices constituting the 'AND' plane arranged at the intersections of the input lines and product term lines performs a logic operation on input signals to the array and outputs logic signals onto the product term lines. A second group of MOS devices constituting the 'OR' plane located at the intersections of the output lines and product term lines receives the outputs of the 'AND' plane devices and performs a logic operation on those signals to produce a set of output signals that are presented at the outputs of the array for use by an external device. The merged plane array of the invention advantageously includes dual-gate MOS devices as switching elements to reduce the capacitance on the product term lines and output lines and thereby to increase the operating speed of the array. The input and output lines and related MOS devices of the array rather than being arranged in physically separate and distinct input 'AND' and output 'OR' planes, as in the prior art, are interspersed or merged with one another so as to reduce the amount of interconnect required between the logic array and an external device which provides the inputs to the array and receives the outputs therefrom.