HDLbits 12-hour clock 问题解答参考

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题目要求：

Create a set of counters suitable for use as a 12-hour clock (with am/pm indicator). Your counters are clocked by a fast-running clk, with a pulse on ena whenever your clock should increment (i.e., once per second).

reset resets the clock to 12:00 AM. pm is 0 for AM and 1 for PM. hh, mm, and ss are two BCD (Binary-Coded Decimal) digits each for hours (01-12), minutes (00-59), and seconds (00-59). Reset has higher priority than enable, and can occur even when not enabled.

The following timing diagram shows the rollover behaviour from 11:59:59 AM to 12:00:00 PM and the synchronous reset and enable behaviour.

大意：复位时设置时间为12:00:00 AM（即PM=0），hh、mm、ss为BCD (Binary-Coded Decimal)两位，分别代表小时(01-12)、分钟(00-59)、秒(00-59)。Reset的优先级高于enable。

要点：PM在11:59:59实现反转，ss为59时mm开始计时，mm、ss均为59，hh开始计时（第一遍设计出错，应把8位的hh、mm、ss各分为2个4位）

代码：

复制代码

module top_module(
    input clk,
    input reset,
    input ena,
    output pm,
    output [7:0] hh,
    output [7:0] mm,
    output [7:0] ss); 
    reg [3:0] hh1,hh0,mm1,mm0,ss1,ss0;

always@(posedge clk)begin//ss
      if(reset)begin
      ss0<='b0;
      end
        else if(!reset&&ena==1'd1)begin//reset=0,ena=1
      if(ss0==4'd9)begin
        ss0<=4'd0;
      end
        else begin
        ss0<=ss0+1'd1;
      end
    end
    end
    always@(posedge clk)begin
      if(reset)begin
      ss1<='b0;
      end
      else if(!reset&&ena==1'd1)begin
        if(ss1==4'd5&&ss0==4'd9)begin
        ss1<=4'd0;
      end
      else if(ss0==4'd9)begin
      ss1<=ss1+1'd1;
      end
    end
    end
    //mm0--------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            mm0<='d0;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&ss1==4'd5&&ss0==4'd9)begin//xx:x9:59,mm0归零
            mm0<='d0;
        end
            else if(ss0==4'd9&&ss1==4'd5)begin//xx:xx:59,进位至mm0，开始计时
            mm0<=mm0+1'd1;
        end
    end
    end
    //mm1-------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            mm1<='d0;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//xx:59:59,分钟位归零
            mm1<=4'd0;
        end
            else if(ss0==4'd9&&ss1==4'd5&&mm0==4'd9)begin//xx:x9:59,mm1开始计时
            mm1<=mm1+1'd1;
        end
    end
    end
    //hh0----------------------------
    always@(posedge clk)begin
         if(reset)begin
             hh0<=4'd2;
         end
            else if(!reset&&ena==1'd1)begin
                if(hh0==4'd9&&mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//09:59:59,跳转到10:00:00
             hh0<=4'd0;
         end
                else if(hh1==4'd1&&hh0==4'd2&&mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//12:59:59跳转到01:00:00
             hh0<=4'd1;
         end
                else if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//xx:59:59小时开始计时
             hh0<=hh0+1'd1;
         end
     end
     end
    //hh1---------------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            hh1<=4'd1;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh0==4'd9)begin//09:59:59进位10:00:00
            hh1<=4'd1;
        end
            else if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh1==4'd1&&hh0==4'd2)begin//12:59:59跳转至01:00:00
            hh1<=4'd0;
        end
    end
    end
    always@(posedge clk)begin
        if(reset)begin
            pm<='b0;//复位要求12:00:00AM
        end
        if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh0==4'd1&&hh1==4'd1)begin//每次到11:59:59时PM翻转
            pm<=~pm;
        end
    end
    //---------------------------------------------------------------------
    assign hh={hh1,hh0};
    assign mm={mm1,mm0};
    assign ss={ss1,ss0};

endmodule

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module top_module(
    input clk,
    input reset,
    input ena,
    output pm,
    output [7:0] hh,
    output [7:0] mm,
    output [7:0] ss); 
    reg [3:0] hh1,hh0,mm1,mm0,ss1,ss0;

    always@(posedge clk)begin//ss
      if(reset)begin
      ss0<='b0;
      end
        else if(!reset&&ena==1'd1)begin//reset=0,ena=1
      if(ss0==4'd9)begin
        ss0<=4'd0;
      end
        else begin
        ss0<=ss0+1'd1;
      end
    end
    end
    always@(posedge clk)begin
      if(reset)begin
      ss1<='b0;
      end
      else if(!reset&&ena==1'd1)begin
        if(ss1==4'd5&&ss0==4'd9)begin
        ss1<=4'd0;
      end
      else if(ss0==4'd9)begin
      ss1<=ss1+1'd1;
      end
    end
    end
    //mm0--------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            mm0<='d0;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&ss1==4'd5&&ss0==4'd9)begin//xx:x9:59,mm0归零
            mm0<='d0;
        end
            else if(ss0==4'd9&&ss1==4'd5)begin//xx:xx:59,进位至mm0，开始计时
            mm0<=mm0+1'd1;
        end
    end
    end
    //mm1-------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            mm1<='d0;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//xx:59:59,分钟位归零
            mm1<=4'd0;
        end
            else if(ss0==4'd9&&ss1==4'd5&&mm0==4'd9)begin//xx:x9:59,mm1开始计时
            mm1<=mm1+1'd1;
        end
    end
    end
    //hh0----------------------------
    always@(posedge clk)begin
         if(reset)begin
             hh0<=4'd2;
         end
            else if(!reset&&ena==1'd1)begin
                if(hh0==4'd9&&mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//09:59:59,跳转到10:00:00
             hh0<=4'd0;
         end
                else if(hh1==4'd1&&hh0==4'd2&&mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//12:59:59跳转到01:00:00
             hh0<=4'd1;
         end
                else if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5)begin//xx:59:59小时开始计时
             hh0<=hh0+1'd1;
         end
     end
     end
    //hh1---------------------------------------------------
    always@(posedge clk)begin
        if(reset)begin
            hh1<=4'd1;
        end
        else if(!reset&&ena==1'd1)begin
            if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh0==4'd9)begin//09:59:59进位10:00:00
            hh1<=4'd1;
        end
            else if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh1==4'd1&&hh0==4'd2)begin//12:59:59跳转至01:00:00
            hh1<=4'd0;
        end
    end
    end
    always@(posedge clk)begin
        if(reset)begin
            pm<='b0;//复位要求12:00:00AM
        end
        if(mm0==4'd9&&mm1==4'd5&&ss0==4'd9&&ss1==4'd5&&hh0==4'd1&&hh1==4'd1)begin//每次到11:59:59时PM翻转
            pm<=~pm;
        end
    end
    //---------------------------------------------------------------------
    assign hh={hh1,hh0};
    assign mm={mm1,mm0};
    assign ss={ss1,ss0};




endmodule