用状态机实现简单的自动售卖机（Verilog）并验证

目录

一、设计要求

二、分析

1、输入输出

（1）input

（2）output

2、状态

3、状态机

三、源代码

1、FSM.v

2、FSM_tb.v

四、仿真波形

一、设计要求

使用FSM实现自动售卖机。FSM的概念可参考：https://blog.csdn.net/qq_42922513/article/details/130828381https://blog.csdn.net/qq_42922513/article/details/130828381售卖机描述：商品为可乐，一瓶可乐5元钱，每次只能投三种人民币中的一种，分别是：1元，2元，5元。当投够5元时，出一瓶可乐，并找零。

二、分析

1、输入输出

（1）input

输入包括：时钟信号clk，低电平复位信号rst_n，投币in_m

clk, rst_n, [3:0] in_m;

（2）output

输出包括：可乐goods，找零out_m

goods, [3:0] out_m;

2、状态

根据售卖机中有多少钱，将状态机共划分为5个状态，分别为：IDLE（0元）、S0（1元）、S1（2元）、S2（3元）、S3（4元）。

3、状态机描述

本文采用mealy型状态机。对各状态采用独热码进行编码，5个状态需要5bit。

三、源代码

1、FSM.v

`timescale 1ns/1nsmodule FSM (input clk,input rst_n,input [3:0] in_m,output reg goods,output reg [3:0] out_m
);reg [4:0] CS, NS;parameter [4:0]IDLE = 'b00001,S0   = 'b00010,S1   = 'b00100,S2   = 'b01000,S3   = 'b10000;//第一always块，同步时序逻辑
always @ (posedge clk or negedge rst_n) beginif (!rst_n)CS <= IDLE;elseCS <= NS;
end//第二always块，组合逻辑
always @ (*) begincase (CS)IDLE:if (in_m == 4'd1)		NS = S0;else if (in_m == 4'd2)	NS = S1;else if (in_m == 4'd5)	NS = IDLE;else					NS = IDLE;S0:if (in_m == 4'd1)		NS = S1;else if (in_m == 4'd2)	NS = S2;else if (in_m == 4'd5)	NS = IDLE;else					NS = S0;S1:if (in_m == 4'd1)		NS = S2;else if (in_m == 4'd2)	NS = S3;else if (in_m == 4'd5)	NS = IDLE;else					NS = S1;S2:if (in_m == 4'd1)		NS = S3;else if (in_m == 4'd2)	NS = IDLE;else if (in_m == 4'd5)	NS = IDLE;else					NS = S2;S3:if (in_m == 4'd1)		NS = IDLE;else if (in_m == 4'd2)	NS = IDLE;else if (in_m == 4'd5)	NS = IDLE;else					NS = S3;default:NS = IDLE;endcase
end//第三always块，同步时序逻辑
always @ (posedge clk or negedge rst_n) beginif (!rst_n) beginout_m <= 'd0;goods <= 'd0;endelse begincase (CS)IDLE: beginout_m <= 'd0;if (in_m == 'd5)    goods <= 'd1;else                goods<= 'd0;endS0: beginout_m <= 'd0;if (in_m == 'd1 || in_m == 'd2) begingoods <= 'd0;out_m <= 'd0;endelse begingoods <= 'd1;out_m <= 'd1;endendS1: beginout_m <= 'd0;if (in_m == 'd1 || in_m == 'd2) begingoods <= 'd0;out_m <= 'd0;endelse begingoods <= 'd1;out_m <= 'd2;endendS2: beginout_m <= 'd0;if (in_m == 'd1) begingoods <= 'd0;out_m <= 'd0;endelse if (in_m == 'd2) begingoods <= 'd1;out_m <= 'd0;endelse begingoods <= 'd1;out_m <= 'd3;endendS3: begingoods <= 'd1;if (in_m == 'd1)		out_m <= 'd0;else if (in_m == 'd2)	out_m <= 'd1;else					out_m <= 'd4;enddefault: begingoods <= 'd1;out_m <= 'd0;endendcaseend
end
endmodule

2、FSM_tb.v

//FSM_tb.v`timescale 1ns/1nsmodule FSM_tb;reg clk;
reg rst_n;
reg [3:0] in_m;
wire [3:0] out_m;
wire goods;FSM u(.clk(clk),.rst_n(rst_n),.in_m(in_m),.goods(goods),.out_m(out_m)
);initial beginrst_n = 'b0;clk = 'b0;#50rst_n = 'b1;
endalways #20 clk = ~clk;initial beginin_m = 0;#50in_m = 'd1;#40in_m = 'd1;#40in_m = 'd1;#40in_m = 'd1;#40in_m = 'd1;#40in_m = 'd2;#40in_m = 'd2;#40in_m = 'd2;#40in_m = 'd5;#40in_m = 'd2;#40in_m = 'd5;#40$stop;
endendmodule

3、FSM_tb.sv

使用system verilog进行随机验证。SV相关基础可参考：System Verilog基础_qq_42922513的博客-CSDN博客https://blog.csdn.net/qq_42922513/article/details/130984574

//FSM_tb.sv
`timescale 1ns/1nsmodule FSM_tb;bit clk;
bit rst_n;
bit [3:0] in_m;
bit [3:0] out_m;
bit goods;FSM u(.clk(clk),.rst_n(rst_n),.in_m(in_m),.goods(goods),.out_m(out_m)
);initial beginrst_n = 'b0;clk = 'b0;#50rst_n = 'b1;
endalways #20 clk = ~clk;class packet;rand bit [3:0] money_in;constraint c{money_in dist{1:=1, 2:=1, 5:=1};}
endclassinitial beginin_m = 0;packet M;M = new();#50repeat(20) beginassert(M.randomize());in_m = M.money_in;$display("******* in_m = %0d********/n", in_m);#40;end#40$stop;
endendmodule

四、仿真波形

1、工具：VIVADO，testbench文件：FSM_tb.v

2、工具：VIVADO，testbench文件：FSM_tb.sv

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