| Hazards pulses are undesirable short pulses in digital circuits, it mainly caused by transmission delays of circuit elements. Hazards in digital circuits not only may cause errors operation, but also consume power, and add to the computation time. Therefore it is very important to detect and eliminate hazards in circuit designs.This paper investigates the hazards in binary circuits and multivalued circuits respectively. For the hazards resulted from the Single Input Change(SIC-hazard), this paper introduces the techniques for detecting and eliminating hazards by algebraic and K-map's means in binary circuits and multivalued circuits respectively. A new method for design hazard-free binary circuits is proposed for SIC-hazard, in this paper it mainly depends on a new rule for simplification of logic function using K-maps. For the hazards resulted from the Double Input Change(DIC-hazard), a detailed analysis is presented in binary circuits and multivalued circuits respectively. For the hazards resulted from the Multiple Input Change(MIC-hazard) in binary circuits, this paper introduces the four-valued mode of signal behavior, and the method of hazard detection for binary circuits which is based on signal behavior is proposed. In comparison with the traditional method of hazard detection, this method has advantages of direct and being capable of detecting both static and dynamic hazards. Gate freezing is an innovative technique for hazard-free circuits design. The method is based on the idea of transforming some selected high-glitching gates into modified devices, called F-Gates, that are able to filter out spurious transitions whenever a proper control signal is activated. According to the idea of gate freezing , the designs of the logic cells : F-Nand-gate and F-Nor-gate are presented, and then a new kind of RS flip-flop based on F-Gates is proposed. This kind of RS flip-flop not only has correct logic functions, but also eliminates hazards, and reduces the power dissipation.
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