Nec Corporation

Takuo Nakaki

Hajime Kawamura

Masamichi Kawarabayashi

Takeharu Nemoto

A method designs a logic circuit having a flip-flop which performs an on and off operation in response to a timing clock and a feedback loop. With such a structure, a logic circuit portion which operates in accordance with an enable signal automatically is extracted. Further, the logic circuit portion is formed by the use of a gated clock obtained by gating the timing clock via the enable signal. Thereby, the number of on and off operations of the flip-flop in response to the timing clock can be largely reduced.

Method of changing logic circuit portion into gated clock portion and recording medium storing a program for carrying out the method

A logic circuit design procedure comprises a step of deciding the feasibility of hardware after HDL description and functional verification, and a step of performing logic synthesis of the HDL description which has been determined to be feasible. The feasibility decision step comprises at least a decision on the possibility of spike transfer and a decision on oscillation. The spike transfer check step determines whether at least one of a clock signal and a reset signal of any sequential circuit is output from a combinational circuit. The oscillation check step determines whether an output signal of any combinational circuit is recursively input thereto without passing through a sequential circuit. Only the HDL description which passes the feasibility test is allowed to enter the logic synthesis stage.

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Kanagawa, Japan

Takuo Nakaki