Universal logic module with arithmetic capabilities

Abstract

A universal logic module for use in a programmable logic device, capable of generating all logical functions of three variables or less. The universal logic module also implements a full adder with carry propagation.

Description

BACKGROUND OF THE INVENTIONThis invention relates in general to electronic circuits for generation of combinatorial logic. More particularly, this invention relates to a universal logic module for use in programmable logic devices (PLDs).A logic cell is the fundamental building block of a PLD. Each logic cell typically includes a logic array section to implement combinatorial ("sum of the products") logic and a register to provide for sequential logic. When combined together in large numbers inside a PLD, they facilitate implementation of complex combinatorial as well as sequential logic. Therefore, versatility and cell size are among the more important considerations in design of logic cells for PLDs.There exist differing approaches to implementing the combinatorial logic section of a PLD logic cell. One approach employs electrically programmable read only memory (EPROM) elements to implement a programmable AND array that is followed by fixed OR logic. Another method of implementin...

AI Technical Summary

Benefits of technology

The present invention provides a small and versatile logic module (ULM) that can realize all boolean functions of three or fewer variables. It also includes a separate output that can realize the carry output of a full adder. The ULM is programmable and does not require reconfiguration to change its logic functions. It is a compact and efficient tool for use in programmable logic devices (PLDs).

Problems solved by technology

Furthermore, existing logic cells tend to be inflexible when implementing frequently occurring specialized functions.

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