EEPW论坛

module key2(clk,rst_n,key,led);
//programmed by haohaolinux
        input clk,rst_n,key;
        output led;
       
        reg key_rst;
        always @(posedge clk or negedge rst_n)
                if(!rst_n)
                        key_rst=1'b1;
                else
                        key_rst=key;
                       
        reg key_rst_r;
        always @(posedge clk or negedge rst_n)
                if(!rst_n)
                        key_rst_r=1'b1;
                else
                        key_rst_r=key_rst;
                       
        //key_an捕捉key的下降沿,当有按键按下时，key_an置高
        wire key_an=key_rst_r & (~key_rst);
       
        //计数，当有按键按下时，从0开始计数。。
        reg [19:0] cnt;
        always@(posedge clk or negedge rst_n)
                if(!rst_n)
                        cnt=20'b0;
                else if(key_an)
                        cnt=20'b0;
                else
                        cnt=cnt+1;
       
        //当计数器满的时候，再次捕捉按键是否被按下，如果被按下，则led_ctrl置高。
        reg low_sw;
        always@(posedge clk or negedge rst_n)
                if(!rst_n)
                        low_sw=1'b1;
                else if(cnt==20'hfffff)
                        low_sw=key;
        reg low_sw_r;
        always@(posedge clk or negedge rst_n)
                if(!rst_n)
                        low_sw_r=1'b1;
                else
                        low_sw_r=low_sw;
                       
        //捕捉low sw的下降沿
        wire led_ctrl=low_sw_r & (~low_sw);      
       
        reg d1;
        always@(posedge clk or negedge rst_n)
                if(!rst_n)
                        d1=0;
                else
                        if(led_ctrl) d1=~d1;
               
  assign led=d1?1:0;

endmodule