实现手表的计时功能：

1.具有start启动信号、pause暂停信号，可以自定义其触发机制。

2.具有时间更改接口，可以更改时、分、秒。

3.输出时、分、秒。

Verilog设计

模块端口定义：

module watch1(
    input   wire            clk         ,
    input   wire            rst_n       ,
    input   wire            start       ,   //
    input   wire            pause       ,   //
    input   wire            h_add       ,   //when it is 1, hour   will add 1(when changing the time, the current time do not count)
    input   wire            m_add       ,   //when it is 1, minute will add 1(when changing the time, the current time do not count)
    input   wire            s_add       ,   //when it is 1, second will add 1(when changing the time, the current time do not count)

    output  reg     [4:0]   hour        ,
    output  reg     [5:0]   minute      ,
    output  reg     [5:0]   second           // second+1 per period
);

手表计时使能：

always@(posedge clk or negedge rst_n)
    if(!rst_n) running <= 1'b0;
    else if(pause && start)     //push the keys in the same time, the watch still runs
        running <= 1'b1;//running;keep the state
    else if(pause)     //
        running <= 1'b0;
    else if(start)     //
        running <= 1'b1;
    else ;

或者：

always@(posedge clk or negedge rst_n)
    if(!rst_n) running <= 1'b0;
    else if(start_rise)     //push the key, the watch will run(higher priority)
        running <= 1'b1;
    else if(pause_rise)     //push the key, the watch will stop
        running <= 1'b0;
    // else if(start_fall)     //release the key, the watch will run
    //     running <= 1'b1;
    else ;

小时:

always@(posedge clk or negedge rst_n)
    if(!rst_n) hour <= 'b0;
    else if(h_add) begin
        if(hour == CNT_23)
            hour <= 'b0;
        else
            hour <= hour + 1'b1;
    end
    else if(running & ~m_add & ~s_add ) begin    //when changing the time, the current time do not count
        if(second == CNT_59 && minute == CNT_59) begin
            if(hour == CNT_23)
                hour <= 'b0;
            else
                hour <= hour + 1'b1;
        end
        else ;
    end
    else ;

分钟：

always@(posedge clk or negedge rst_n)
    if(!rst_n) minute <= 'b0;
    else if(m_add) begin
        if(minute == CNT_59)
            minute <= 'b0;
        else
            minute <= minute + 1'b1;
    end
    else if(running & ~s_add & ~h_add ) begin    //when changing the time, the current time do not count
        if(second == CNT_59) begin
            if(minute == CNT_59)
                minute <= 'b0;
            else
                minute <= minute + 1'b1;
        end
        else ;
    end
    else ;

秒：

always@(posedge clk or negedge rst_n)
    if(!rst_n) second <= 'b0;
    else if(s_add) begin
        if(second == CNT_59)
            second <= 'b0;
        else
            second <= second + 1'b1;
    end
    else if(running & ~m_add & ~h_add ) begin    //when changing the time, the current time do not count
        if(second == CNT_59)
            second <= 'b0;
        else
            second <= second + 1'b1;    // second+1 per period
    end
    else ;

仿真波形

时钟进位：

启动&暂停：

或者：

顶层集成

//
module watch_top(
    input   wire            clk         ,
    input   wire            rst_n       ,
    input   wire            start_key   ,   //按键:开始计时(按下按键时均为0)
    input   wire            pause_key   ,   //按键:暂停计时
    input   wire            h_key       ,   //按键:时+1
    input   wire            m_key       ,   //按键:分+1
    input   wire            s_key       ,   //按键:秒+1

    output  wire    [4:0]   hour        ,   //时
    output  wire    [5:0]   minute      ,   //分
    output  wire    [5:0]   second          //秒(每时钟周期+1)
);

// parameter ======================================================

// wire =============================================================
wire start;
wire pause;
wire h_add;
wire m_add;
wire s_add;

// reg =============================================================

// assign =============================================================

// always ==========================================================

// instantiation ======================================================================
//
key_filter u_start_filter(
    .clk        (clk   ),
    .rst_n      (rst_n ),
    .key_in     (start_key),

    .key_flag   ( ),
    .key_out    (start),
    .key_cont   ()
);
key_filter u_pause_filter(
    .clk        (clk   ),
    .rst_n      (rst_n ),
    .key_in     (pause_key),

    .key_flag   ( ),
    .key_out    (pause),
    .key_cont   ()
);
//
key_filter u_h_filter(
    .clk        (clk   ),
    .rst_n      (rst_n ),
    .key_in     (h_key),

    .key_flag   ( ),
    .key_out    (),
    .key_cont   (h_add)
);
key_filter u_m_filter(
    .clk        (clk   ),
    .rst_n      (rst_n ),
    .key_in     (m_key),

    .key_flag   ( ),
    .key_out    (),
    .key_cont   (m_add)
);
key_filter u_s_filter(
    .clk        (clk   ),
    .rst_n      (rst_n ),
    .key_in     (s_key),

    .key_flag   ( ),
    .key_out    (),
    .key_cont   (s_add)
);
//
watch2 u_watch(
    .clk         (clk   ),
    .rst_n       (rst_n ),
    .start       (start ),   //
    .pause       (pause ),   //
    .h_add       (h_add ),   //when it is 1, hour   will add 1
    .m_add       (m_add ),   //when it is 1, minute will add 1
    .s_add       (s_add ),   //when it is 1, second will add 1

    .hour        (hour  ),
    .minute      (minute),
    .second      (second) 
);

endmodule