含有en端和load端的25min倒计时器

`timescale 1ns / 1ps


//16进制
module second(
input wire clk,
output reg sec);
reg [27:0]q1;
always @(posedge clk)
    begin 
        if(q1==50000000)
            begin
                q1<=0;
                sec<=~sec;
             end
    else
        q1<=q1+1;
    end
endmodule


module cnt24(
input wire clk,//秒脉冲信号
input clk2,//标准时钟信号
input clear,
input stop,
output reg [3:0] cnt60_L,
output reg [3:0] cnt60_H,
output reg [3:0] cnt25_mL,
output reg [3:0] cnt25_mH,
output reg carry
    ); 
    initial begin
        cnt60_L=0;
        cnt60_H=0;
        cnt25_mL=5;
        cnt25_mH=2;
    end
    //状态编码
parameter
	[1:0]work=2'b00;
parameter
	[1:0]pause=2'b10;
parameter
	[1:0]reset=2'b01;
reg [1:0]cstate;
reg [1:0]nstate;
reg en,load;
/*
reg [26:0]counter;
wire clk2Hz=0;
//counter 分频计数器
parameter CNT=50000000;
initial counter=0;
always @(posedge clk )

 if (counter==CNT-1)
       counter<=0;
    else counter<=counter+1;
assign clk2Hz=(counter==CNT)?1:0;
  */  
    
//状态转移
always @(posedge clk2 )	
    cstate<=nstate;
	
//次态判断
always @*
   //if(jinwei)
        case(cstate)
            work:
            begin
                if(stop==1)
                    nstate=pause;
                else
                    nstate=work;
            end
       
            pause:         
            begin
                if(clear==1)nstate=reset;
	            else if(stop==1)
	                   nstate=work;
                       else nstate=pause;
            end
            reset:
            begin
            if(stop==1)
            nstate=work;
            else
            nstate=reset;
           end
            default: nstate=reset;
        endcase
   // else
     //   nstate=cstate;

     
     
//次态输出
always @(posedge clk2 )//or posedge rst)
begin
    //else
        case(cstate)
            reset:begin en<=0;load<=1;end
            work:begin en<=1;load<=0;end
            pause:begin en<=0;load<=0;end
            default:begin en<=0;load<=1;end
        endcase
 end
 //clk为秒脉冲信号  clk2为标准时钟信号
    always @(posedge clk)   
    begin
         if(en==0&&load==1)
         begin
         cnt60_L<=0;
         cnt60_H<=0;
         cnt25_mL<=5;
         cnt25_mH<=2;
         end
        if(en==1&&load==0)
        begin
            carry<=0;
            cnt60_L<=cnt60_L-1;
            if(cnt60_L==0)
                begin
                    cnt60_L<=9;
                    cnt60_H<=cnt60_H-1;
                end 
           if(cnt60_H==0 && cnt60_L==0 )
              begin
                   cnt60_L<=9;
                   cnt60_H<=5;
                   cnt25_mL<=cnt25_mL-1;
                   
             end
           if(cnt60_H==0 && cnt60_L==0 && cnt25_mL==0)
              begin
                  cnt60_L<=9;
                  cnt60_H<=5;
                  cnt25_mL<=9;
                  cnt25_mH<=cnt25_mH-1;
              end 
              if(cnt60_H==0 && cnt60_L==0 && cnt25_mL==0 && cnt25_mH==0)
              begin
                  cnt60_L<=0;
                  cnt60_H<=0;
                  cnt25_mL<=5;
                  cnt25_mH<=2;
                  carry<=1;
              end 
         end
         if(en==0&&load==0)
         begin
         cnt60_L<=cnt60_L;
        cnt60_H<=cnt60_H;
        cnt25_mL<=cnt25_mL;
        cnt25_mH<=cnt25_mH;
        end
     end
endmodule



module shumaguan(
input clk,
input rst_n,
input [3:0]sL,
input [3:0]sH,
input [3:0]mL,
input [3:0]mH,
//input [7:0] x,      //等待显示的BCD码
output reg [6:0] a_to_g, //段信号
output reg [3:0] an  //位选信号
);



wire [15:0]x={mH,mL,sH,sL};
//x={H,L};
//时钟分频 计数器
reg [20:0] clkdiv;
always @(posedge clk or negedge rst_n)
begin
	if(!rst_n)
		clkdiv<=21'd0;
	else
		clkdiv<=clkdiv+1;
end
/*利用计数器自动溢出时间，即就是clkdiv从0~11111111111111111111循环计数，
则clk[19]会在0~1之间以5.24ms为时间间隔变化  2^19=524288
（即后19位全0到全1的计数时间）
*/

//bitcnt: 位扫描信号 0~1循环变化 扫描周期 5.24ms    控制总扫描时间不超过10ms，单个数码管显示时间约为5ms
wire  [1:0]bitcnt;
assign bitcnt=clkdiv[20:19];

//an:位选信号产生，高有效
always @(posedge clk or negedge rst_n)
begin 
if(!rst_n)
	an=4'd0;
else
	case(bitcnt)
	2'd0:an=4'b0001;
	2'd1:an=4'b0010;
	2'd2:an=4'b0100;
	2'd3:an=4'b1000;
    endcase
end


//digit 当前带显示的数字
 
 reg [3:0]digit;
always @(posedge clk or negedge rst_n)
begin
if (!rst_n)
	digit=4'd0;
else
	case(bitcnt)
	2'd0:digit=x[3:0];
	2'd1:digit=x[7:4];
	2'd2:digit=x[11:8];
	2'd3:digit=x[15:12];
	
	default:digit=4'd0;
	endcase
end

//a_to_g: 段码信号，共阴极数码管，段码高有效。 7段译码表
always @(posedge clk or negedge rst_n)
begin
if(!rst_n)
	a_to_g=7'b1111111;
else
	case(digit)
	0:a_to_g=7'b1111110;//段码位序由高到低为a-g
	1:a_to_g=7'b0110000;
	2:a_to_g=7'b1101101;
	3:a_to_g=7'b1111001;
	4:a_to_g=7'b0110011;
	5:a_to_g=7'b1011011;
	6:a_to_g=7'b1011111;
	7:a_to_g=7'b1110000;
	8:a_to_g=7'b1111111;
	9:a_to_g=7'b1111011;
	default:a_to_g=7'b1111110;
	endcase
end
endmodule

module edgecheck(
input key1,key2,
input clk,
output Yup1,Yup2
);
reg a1,b1;
always @(posedge clk)
 begin
	a1<=key1;
	b1<=a1;
end
assign Yup1=a1&(~b1);
reg a2,b2;
always @(posedge clk)
 begin
	a2<=key2;
	b2<=a2;
end
assign Yup2=a2&(~b2);
endmodule

module top(
    input wire clk,
    input rst_n,//数码管的显示开关
    input wire clear0,
    input wire stop,
    output wire [6:0]a_to_g,
    output wire [3:0]an
    );
    wire jinwei;
    wire [3:0]sL;
    wire [3:0]sH;
    wire [3:0]mL;
    wire [3:0]mH;
    wire stop1;//使能端   暂停或继续
    wire clear01; //清零端
    
    second U0(
        .clk(clk),
        .sec(jinwei)
    );

    cnt24 U1(
        .clk(jinwei),
        .clk2(clk),
        .clear(clear01),
        .stop(stop1),
        .cnt60_L(sL),
        .cnt60_H(sH),
        .cnt25_mL(mL),
        .cnt25_mH(mH)
        );
        
     shumaguan U2
     (
        .clk(clk),
        .rst_n(rst_n),
        .sL(sL),
        .sH(sH),
        .mL(mL),
        .mH(mH),
        .a_to_g(a_to_g), //段信号
        .an(an) 
     );
  // 开关消除抖动
edgecheck u3(
.key1(clear0),
.key2(stop),
.clk(clk),
//.jinwei(jinwei),
.Yup1(clear01),
.Yup2(stop1)
);
endmodule

备注：本代码由西安交通大学电气工程及其自动化专业教学使用，如有侵权，联系作者删除。 本代码为西安交通大学学生备忘而用。
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