倒计时显示的交通灯求大神指点错误水平入门级入门

ti

module TL(clk,dig,seg,en,led);
input clk;
input en;
output [7:0] dig,seg;
output [2:0] led;
reg [2:0] led_r;
reg [7:0] dig_r,seg_r;
reg [7:0] disp_dat;
reg [24:0] count;
reg [7:0] red,yellow,green;
reg [7:0] num;
reg sec;
reg [1:0] cnt;
assign dig = dig_r;
assign seg = seg_r;
assign led = led_r;//定义段
always@(posedge clk)
begin
count = count + 1'b1;
if(count == 25'd24000000)
begin
   count =25'd0;
   sec = ~sec;
end
end//秒信号产生
always@(en)
begin
if(!en)
   red <= 8'd30;
   yellow <= 8'd5;
   green <= 8'd20;
end//使能赋值
initial
begin
cnt <= 2'b0;
end
always @ (negedge sec)

begin
case (cnt)
   0:begin num <= red ;begin
if(num>1)
   begin
   if(num[3:0] == 0)
      begin
      num[3:0] <= 4'b1001;
      num[7:4]<=num[7:4]-4'b0001;
      end
   else num[3:0]<=num[3:0]-4'b0001;
end
end
led_r <= 5;cnt <= 1;end
   1:begin num <= yellow;begin
if(num>1)
   begin
   if(num[3:0] == 0)
      begin
      num[3:0] <= 4'b1001;
      num[7:4]<=num[7:4]-4'b0001;
      end
   else num[3:0]<=num[3:0]-4'b0001;
end led_r <= 3; cnt <= 2;end end
   2:begin num <= green;
begin
if(num>1)
   begin
   if(num[3:0] == 0)
      begin
      num[3:0] <= 4'b1001;
      num[7:4]<=num[7:4]-4'b0001;
      end
   else num[3:0]<=num[3:0]-4'b0001;
end led_r <= 6;cnt <= 0;end end
default: led_r <= 3;
endcase
end//点亮交通灯+倒计时赋值

always@(posedge clk)
begin
case (count[17:15])
   3'd0:disp_dat = num[3:0];
   3'd1:disp_dat = num[7:4];
default disp_dat = 4'ha;
endcase
case (count [17:15])
3'd0:dig_r = 8'b11111110;
3'd2:dig_r = 8'b11111101;
3'd3:dig_r = 8'b11111011;
3'd4:dig_r = 8'b11110111;
3'd5:dig_r = 8'b11101111;
3'd6:dig_r = 8'b11011111;
3'd7:dig_r = 8'b10111111;
3'd8:dig_r = 8'b01111111;
endcase
end
always@(posedge clk)
begin
case (disp_dat)
4'h0:seg_r = 8'hc0;
4'h1:seg_r = 8'hf9;
4'h2:seg_r = 8'ha4;
4'h3:seg_r = 8'hb0;
4'h4:seg_r = 8'h99;
4'h5:seg_r = 8'h92;
4'h6:seg_r = 8'h82;
4'h7:seg_r = 8'hf8;
4'h8:seg_r = 8'h80;
4'h9:seg_r = 8'h90;
4'ha:seg_r = 8'hbf;
default: seg_r = 8'hff;
endcase
   if((count[17:15] == 3'd2)&sec)
   seg_r = 8'hff;
end//数码管显示
endmodule
芯片是EPM7064AELI44-7N
求指点，勿喷。。。
问题是：下载之后，功能是led灯亮的时间相同，且数码管全部亮，一直闪烁