FSM

Introduction

In the digital circuit system, the finite state machine is a very important sequential logic circuit module, which has a very important role in the design of digital systems.

Finite state machine refers to a sequential logic circuit whose output depends on the past input part and the current input part. Generally speaking, in addition to the input part and the output part, the finite state machine also contains a set of registers with a "memory" function. The function of these registers is to remember the internal state of the finite state machine. They are often called state registers. In the finite state machine, the next state of the state register is not only related to the input signal, but also related to the current state of the register, so the finite state machine can be considered as a combination of combinational logic and register logic. Among them, the function of register logic is to store the internal state of the finite state machine; and the combinational logic can be divided into two parts: secondary state logic and output logic. The function of the secondary state logic is to determine the next state of the finite state machine and the function of the output logic Is to determine the output of the finite state machine.

In practical applications, designers often divide them into two types, Moore-type finite-state machines and Mealy-type finite-state machines, depending on whether the finite state machine uses input signals. 1 The output signal of the Moore finite state machine is only related to the current state, that is, the output of the Moore finite state can be regarded as a function of the current state. 2 The output signal of Mealy type finite state machine is not only related to the current state, but also related to all input signals, that is, the output of Mealy type finite state machine can be regarded as a function of the current state and all input signals.