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从输出时序上看,Moore型状态机属于异步输出状态机,Mealy型状态机属于同步输出状态机。Moore型有限状态机的输出仅为当前状态的函数,这类状态机在输入发生变化后再等待时钟的到来,时钟使状态发生变化时才导致输出的变化;Mealy型有限状态机的输出是当前状态和所有输入信号的函数,它的输出在输入变化后立即发生。从状态机的工作时序图上当然很容易区分出是哪一种状态机,但是对于初学者并不能很容易从VHDL代码上判断,本文的目的就是从VHDL代码和工作时序对这两类状态机进行区分。只有清楚了这两类状态机在VHDL代码上的特点才能够设计出相应的状态机。
From the output timing point of view, Moore-type state machine belongs to the asynchronous output state machine, Mealy-type state machine belongs to the synchronous output state machine. Moore-type finite state machine output is only a function of the current state, such state machine in the input changes wait for the arrival of the clock, the clock changes the state will lead to changes in output; Mealy finite state machine output is the current State, and all input signals, its output occurs immediately after the input changes. Of course, it is very easy to distinguish which state machine is from the working sequence diagram of the state machine, but it is not easy for beginners to judge from the VHDL code. The purpose of this paper is to classify these two types of state machines from VHDL code and working sequence Make a distinction. Only clear the characteristics of these two types of state machine in the VHDL code to be able to design the corresponding state machine.