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为解决铁路信号系统现有安全时钟体系可用度较低的问题,提出了一种三模-单模体系的安全时钟系统,分析了该系统与传统安全时钟体系的可用度问题,理论推导证明了在长期工作条件下该方法与现有设计方法相比,可大幅度提高系统可用度。在此基础上,根据铁路信号系统设计中的特殊要求,提出了其中关键模块——比较模块的设计方法,该方法利用Gray码计数器对时钟频率进行三模冗余,并将频率进行两两比较,其结果送入多数表决器进行时钟有效性判别,为系统提供频率稳定的安全时钟。仿真试验结果表明该设计方法能有效防止时钟频率漂移产生的危险输出。
In order to solve the problem of low availability of existing safety clock system in railway signal system, a safe clock system of three-mode-single-mode system is proposed, and the availability of the system with traditional safety clock system is analyzed. The theoretical derivation proves that Compared with the existing design methods, this method can greatly improve system availability under long-term working conditions. On this basis, according to the special requirements in the design of railway signal system, the design method of the key module-comparison module is put forward. The method uses the Gray code counter to perform the three-mode redundancy on the clock frequency and compares the frequencies one by two , The result is sent to the majority voter to judge the validity of the clock and provide the system with a safe clock with stable frequency. The simulation results show that the design method can effectively prevent the clock frequency drift generated dangerous output.