实验模块组成：
（计数器+控制器）可以分开实现，最好一起实现避免接口对接时出错
译码器
实验要求：
在十字路口两个方向各设一组红、绿、黄灯，显示顺序为：南北方向是绿、黄、红灯；东西方向是红、绿、黄灯。
要求红、绿、黄灯的持续时间分别为：10s、7s、3s，东西、南北方向各用一个数码管显示倒计时时间。 当任意方向出现特殊情况时，应优先放行，即使各方向均亮红灯，倒计时停止，且显示数字闪烁。经过规定时间之后，恢复正常运行状态。
//计数器+控制器
module ZTJ(clk,s,count1,count2,led);
parameter s0=6'b010100,s1=6'b001100,s2=6'b100010,s3=6'b100001,s4=6'b100100;
inputclk,s;
output[3:0]count1;
output[3:0]count2;
output[5:0]led;
reg[3:0]count1;
reg[3:0]count2;
reg[5:0]led;
reg[5:0]st;
reg[5:0]jicun;
reg[3:0]i;
always @(posedgeclk)
if(s==0 & led==6'b000000)
begin
led<=s0;
st<=s0;
count1<=4'b0110;
count2<=4'b1001;
end
else if(s==0 & led!=6'b000000)
begin
case(st)
s0:if(count1!=4'b0000) begin led<=s0;count1<=count1-1;count2<=count2-1;end else begin count1<=4'b0010;st<=s1;end
s1:if(count1!=4'b0000) begin led<=s1;count1<=count1-1;count2<=count2-1;end else begin count1<=4'b1001;count2<=4'b0110;st<=s2;end
s2:if(count2!=4'b0000) begin led<=s2;count1<=count1-1;count2<=count2-1;end else begin count2<=4'b0010;st<=s3;end
s3:if(count2!=4'b0000) begin led<=s3;count1<=count1-1;count2<=count2-1;end else begin count1<=4'b0110;count2<=4'b1001;st<=s0;end
default:led<=s4;
endcase
end
else
begin
jicun<=led;
led<=s4;
count1<=count1;
count2<=count2;
i<=i+1;
if(i==4'b1001)
led<=jicun;
end
endmodule
//译码器
module DECL7S(A,LED7S);
input [3:0] A;
output [6:0] LED7S;
reg [6:0] LED7S;
always@(A)
begin
case(A)
4'b0000: LED7S<=7'b0111111;
4'b0001: LED7S<=7'b0000110;
4'b0010: LED7S<=7'b1011011;
4'b0011: LED7S<=7'b1001111;
4'b0100: LED7S<=7'b1100110;
4'b0101: LED7S<=7'b1101101;
4'b0110: LED7S<=7'b1111101;
4'b0111: LED7S<=7'b0000111;
4'b1000: LED7S<=7'b1111111;
4'b1001: LED7S<=7'b1101111;
4'b1010: LED7S<=7'b1110111;
4'b1011: LED7S<=7'b1111100;
4'b1100: LED7S<=7'b0111001;
4'b1101: LED7S<=7'b1011110;
4'b1110: LED7S<=7'b1111001;
4'b1111: LED7S<=7'b1110001;
default:LED7S<=7'b0111111;
endcase
end
endmodule