本实验中主要应用了状态机以及减法器的设计原理。在状态连续变化的数字系统设计中，采用状态机的设计思想有利于提高设计效率，增加程序的可读性，减少错误的发生几率。同时，状态机的设计方法也是数字系统中一种最常用的设计方法。一般来说，标准状态机可以分为穆尔（Moore）机和米利（Mealy）机两种。在穆尔机中，其输出仅仅是当前状态值的函数，并且仅在时钟上升沿到来时才发生变化。米利机的输出则是当前状态值、当前输出值和当前输入值的函数。-In this experiment, the application of the design principles of the state machine and the subtractor. In a state of continuous change of the digital system design using the state machine design ideas to improve the design efficiency, increase the readability of the program, reduce the error probability of the occurrence. At the same time, the state machine design is also a digital system, a most commonly used design methods. Generally speaking, the state machine can be divided into two kinds of Moore (Moore) machine, and Miriam (Mealy) machine. Moore machine, the output is only a function of the current state value, and only the arrival of the rising clock edge when the change. The Milligan machine' s output is the current state value, the function of the current output value and the current input values.