「Verilog学习笔记」状态机与时钟分频

专栏前言

本专栏的内容主要是记录本人学习Verilog过程中的一些知识点，刷题网站用的是牛客网

状态机写法?

`timescale 1ns/1ns

module huawei7(
	input wire clk  ,
	input wire rst  ,
	output reg clk_out
);

//*************code***********//
	parameter S0 = 0, S1 = 1 , S2 = 2 , S3 = 3 ; 
	reg [2:0] state, nstate ; 

	always @ (posedge clk or negedge rst) 
		if (~rst) state <= 0 ; 
		else state <= nstate ; 

	always @ (*) 
		case (state) 
			S0 : nstate = S1 ; 
			S1 : nstate = S2 ; 
			S2 : nstate = S3 ; 
			S3 : nstate = S0 ; 
			default : nstate = S0 ; 
		endcase

	always @ (posedge clk or negedge rst) 
		if (!rst) clk_out <= 0 ; 
		else if (state == S0) clk_out <= 1 ; 
		else clk_out <= 0 ; 


//*************code***********//
endmodule

不用状态机的写法?

`timescale 1ns/1ns

module huawei7(
	input wire clk  ,
	input wire rst  ,
	output reg clk_out
);

//*************code***********//
	reg [2:0] cnt ; 

	always @ (posedge clk or negedge rst) 
		if (!rst) cnt <= 0 ; 
		else cnt <= cnt == 3 ? 0 : cnt + 1 ; 

	always @ (posedge clk or negedge rst) 
		if (!rst) clk_out <= 0 ; 
		else if (cnt == 0) clk_out <= 1 ; 
		else clk_out <= 0 ; 


//*************code***********//
endmodule