discuss the random logic versus structured logic forms in brief.Ripunjay Tiwari
Ans. A particular style of digital logic design can be described by the random logic. Some integrated logic circuits are placed within a layout in a similar way that small-scale logic chips are placed on a wire-wrap circuit board and then interconnected. A circuit requires various types of small-scale logic function and that too be at irregular places as the result of which the circuit packages and their interconnection wiring appear to have been randomly placed. Infact, the interconnections and probably the package placement were carefully designed for the circuit to function properly. In spite of that, random logic describes digital circuit that lack regularity of circuit function, placement, and interconnection. Alternatively, the term structured logic is used to characterize logic forms that do clearly show regularity in their layout and interconnection.
A widely used measure introduced by Lattin in 1979 is useful in describing the regularity of an integrated circuit design. This measure is defined as the ratio of the total transistor numbers on the chip to the drawn transistor, where total transistors contains all possible ROM and PLA transistor placements. This measure is known as the chip regularity factor. Hence, a design that needs a unique layout for a circuit element and then uses this circuit element n times without change would provide a regularity factor of n. on the other hand, a design with unique layout for each circuit component would provide a regularity factor of only 1. Generally, a higher regularity factor for a given complexity of design represents decreased design and layout costs.
A method to increase the regularity factor and decrease costs is to develop computer programs that produce integrated circuit layouts directly from high-level descriptions of the circuit’s intended function. The term silicon compiler has been used to define such program.