Logic simulator using small capacity memories for storing logic states, connection patterns, and logic functions

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United States of America Patent

PATENT NO 4782440
SERIAL NO

06761281

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Abstract

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A logic simulator for simulating operation of a logic circuit is provided with gates divisible into successive levels according to a connection pattern between the gates. A pattern memory (16) memorizes the connection pattern as a bit sequence representative of direct connections between each gate of each level to the gates of a preceding level. A function memory (17) memorizes logic functions of the respective gates. Responsive to input logic states of each level, the bit sequence for the gates of the level under consideration, and the logic functions of the respective gates of that level, a calculator (25) calculates output logic states of that level as input logic states of a succeeding level successively for the gates of the level in question. For a higher speed of simulation, the logic circuitry may be divided into a predetermined number of gate groups, each consisting of gates of the successive levels. Each of the pattern and the function memories is divided into parts for the respective gate groups. In order to make the logic simulator have a further reduced memory capacity, the gates of each preceding level may be classified into gate blocks. A block specifier is additionally used. Under the circumstances, it is sufficient that each bit sequence should represent direct connections to the gate blocks. The calculator is supplied with the output logic states of each gate block.

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Patent Owner(s)

Patent OwnerAddress
NEC CORPORATION 33-1 SHIBA 5-CHOME MINATO-KU TOKYO JAPANNot Provided

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Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Nomizu, Nobuyoshi Tokyo, JP 2 95
Sasaki, Tohru Tokyo, JP 168 3850

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