本文主要研究数字电路输入和输出端之间的反馈短路故障(feedback bridging fault,简称FBF)及其测试方法.利用一个新的时序机模型提出了一个带有反馈短路故障电路产生振荡或变成一个稳定异步时序电路的充分必要条件.证明了在任何组合电路中,只需两个测试码便能测试出所有可能的初级输入与输出端之间的短路故障.其次,证明了检测固定型故障的测试码(集)也能检测反馈短路故障。同时提出了一个产生完全测试集的方法,它可以同时测试无扇出(fan-out free)电路中的固定型和短路型故障. This paper mainly studies the feedback bridging fault (FBF) between the input and the output of the digital circuit and its testing method.Using a new timing machine model, a circuit with feedback short circuit is proposed to generate oscillation or become a Sufficient and necessary conditions for stabilizing an asynchronous sequential circuit prove that in any combined circuit, only two test patterns are needed to test for all possible short-circuit faults between the primary input and the output.Secondly, it is proved that the detection of fixed faults Test code (set) can also detect feedback short circuit fault. A method of generating a complete test set is also presented, which can test both fixed and short-circuit faults in fan-out free circuits.