1、设计一个键值显示电路，以DE2板上10个拨动开关(switch)作为输入，代表0-9十个十进制数，用七段数码管显示对应的数值。
module showin7segment(in, seg);
input [9:0] in;
output [6:0] seg;
reg [6:0] seg;
always@ (in)
begin
// seg = {g,f,e,d,c,b,a};
// 0 is on and 1 is off
if (in[9]) seg <= 7'h90;//9
else if (in[8]) seg <= 7'h80;//8
else if (in[7]) seg <= 7'hF8;//7
else if (in[6]) seg <= 7'h82;//6
else if (in[5]) seg <= 7'h92;//5
else if (in[4]) seg <= 7'h99;//4
else if (in[3]) seg <= 7'hB0;//3
else if (in[2]) seg <= 7'hA4;//2
else if (in[1]) seg <= 7'hF9;//1
else seg <= 7'hC0;//0
end
endmodule
2、设计一个流水灯电路，显示方式如下：8个LED先向左依次点亮，循环往复，每个灯亮的持续时间为1秒左右。
module liushuideng(led,clk);
output[7:0] led;
input clk;
reg[8:0] led_r;
reg[25:0] buffer;//中间变量buffer定义为寄存器型
initial
begin led_r=9'b000000001;buffer=0;end
always @(posedge clk)
begin
if(buffer==26'd250)//判别buffer数值为50 000 000时，做输出处理
begin buffer=0;
led_r <= led_r << 1;
if(led_r == 9'd0)
led_r <= 9'b000000001;
end
else buffer=buffer+1;
end
assign led = led_r[7:0];
endmodule
