Universal logic module with arithmetic capabilities

a logic module and universal technology, applied in the field of universal logic modules, can solve problems such as inflexibility of existing logic cells

Inactive Publication Date: 2004-03-02
ALTERA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This embodiment of the present invention can realize all Boolean functions of three or fewer variables by assigning the three (or fewer) variables, their complements and the constants 0 and 1 to the five input terminals. Furthermore, this circuit is capable of realizing the carry output of a full adder at a secondary output without any additional circuitry. The ULM, therefore, does not require reconfiguring programmable elements to change its logic functions and is capable of implementing a full adder with carry output. Accordingly, the ULM of the present invention provides a small and versatile combinational circuit for use in PLDs.

Problems solved by technology

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

Method used

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  • Universal logic module with arithmetic capabilities
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Embodiment Construction

A universal logic module (ULM) is a combinatorial logic circuit that can produce a set of multi-variable logic functions by only manipulating the application of variables to its several input terminals. The number of all possible unique logical functions of three variables (or less) is given by the expression [2**(2**3)], which is equal to [2**8] or 256. It has long been known that if both true and complements of all input variables as well as the resulting output function are available, the number of nondegenerate (or canonical forms of) three-variable logic functions can be reduced to ten. That is, all Boolean functions of three variables, x, y and z, can be converted into one of ten functions f(x,y,z) by some combination of inverting the inputs, inverting the output, and permuting the inputs.

FIG. 1 shows a logic diagram of the three-variable ULM of the present invention. The ULM includes two 4:1 multiplexers 100 and 102, whose singular outputs feed two data inputs of a 2:1 multip...

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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...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G06F7/00G06F7/575G06F7/48
CPCG06F7/00G06F7/575
Inventor VEENSTRA, KERRY S.
Owner ALTERA CORP
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