The digital integrated scheme is a microelectronic product made by means of methods of integrated technologies (more often of semi-conductor origin), concluded in an independent body and carrying out the certain function of discrete signals transformation. The nomenclature let out by the industry digital integrated schemes is extensive enough and, consequently, functions of transformation sold by them are varied. The elementary transformations over digital signals are carried out by integrated schemes, which bare the name of logical elements. Combinatorial digital equipment is the system output waveforms of which at some point of timework are unequivocally defined only by the signals operating at the same point in time on its input. In combinatorial digital equipment there are no elements of memory, therefore output waveforms of such equipment are formed and kept only during the term of entrance.
Combinatorial digital equipment can be applied in performance of the variety of logical and arithmetic transformations over input waveforms and are used as encrypt or, decoders, register, multiplexers and other functional units.
Generally designed combinatorial digital equipment maybe presented in the form of a black box, having certain amount of inputs and another amount of outputs, it is not the point. But nevertheless it is initially known about black box as a required algorithm of its functioning, i.e. character of communication between input waveforms and output waveforms (reactions). Proper engineering results in defining of optimum (at some point) structures (scheme) of combinatorial digital equipment or a black box realised on the set basis of logical elements. In other words, combinatorial digital equipment engineering implies scheme foundation of combinatorial structure which comply with the functioning algorithm provided that the scheme of combinatorial would be realised with the help of logical element of a full given functional set and since the required functioning algorithm may be realised with the help of different schemes of different schemes, it should be selected optimum scheme, like the one with the smallest number of apparatus expenses, i.e. minima; number of logical elements or integral schemes.
Work of any combinatorial digital equipment with one output maybe described by logical expression or system of logical expressions, if that equipment has the same number of outputs. In other words, every piece of equipment with one output or its every output of multi output combinatorial digital equipment biunique is conformed to logical expression in which letters conform to input variables, and signs on operations – logical elements, carrying out those operations. Similar logical expressions are called the equations of communication combinatorial digital equipment`s "input-output". In these conditions simplification of their schemes results in minimization of the logical expressions appropriating these systems.
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