设计思路：使用fpga模拟双向红绿灯，也就是模拟实际路上红绿灯每个灯的亮灭程度：比如第一个红灯亮时，第二个灯的绿灯就亮，然后接着第二个灯的绿灯转为黄灯并闪烁时，第一个红灯转为绿灯，第二个灯转为红灯，依此类推。。。。。
设计思路图如下：
如上图所示，在0到1s时为空闲状态，在1s到4s时，是下方的绿灯和上方的红灯同时亮，在4s到5s时，下方的绿灯改为黄灯，并控制黄灯闪烁（可以更为真实的模拟红绿灯的状态），同时上方的红灯继续亮，在第5s到第8s时，上方的红灯改为绿灯，下方的黄灯改为红灯，在第8s到第9s时，上方的绿灯改为黄灯并控制黄灯闪烁，而下方的红灯保持不变。
伪代码如下：
parameter DELAY_CNT_MAX = 225000000 - 1; //9秒
parameter one_times = 25000000 - 1; //1秒
parameter four_times = 75000000 - 1 + 25000000; //4秒
parameter five_times = 75000000 + 25000000 + 25000000 - 1; //5秒
parameter seven_times = 75000000 + 2500000 + 25000000 + 25000000 + 25000000 - 1; //7秒
parameter eigtht_times = 75000000 + 25000000 + 75000000 + 25000000 - 1; //8秒
parameter nine_times = DELAY_CNT_MAX; //9秒
reg one_times_flag ;
reg four_times_flag ;
reg five_times_flag ;
reg seven_times_flag ;
reg eigtht_times_flag ;
reg nine_times_flag ;
reg [31:0]times_cnt;
always@(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
begin
times_cnt <= 0;
end
else if(times_cnt == DELAY_CNT_MAX)
times_cnt <= 0;
else
times_cnt <= times_cnt + 1'b1;
parameter S0 = 8'b0000_0001;
parameter S1 = 8'b0000_0010;
parameter S2 = 8'b0000_0100;
parameter S3 = 8'b0000_1000;
parameter S4 = 8'b0001_0000;
reg [7:0]state;
always@(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
begin
one_times_flag <= 0;
four_times_flag <= 0;
five_times_flag <= 0;
seven_times_flag <= 0;
eigtht_times_flag <= 0;
nine_times_flag <= 0;
state <= S0;
end
else
begin
case(state)
S0:
begin
one_times_flag <= 1'b1;
if(times_cnt == one_times)
state <= S1;
end
S1:
begin
if(times_cnt == four_times)
begin
one_times_flag <= 0;
four_times_flag <= 1'b1;
state <= S2;
end
end
S2:
begin
if(times_cnt == five_times)
begin
four_times_flag <= 0;
five_times_flag <= 1'b1;
state <= S3;
end
end
S3:
begin
if(times_cnt == eigtht_times)
begin
five_times_flag <= 0;
eigtht_times_flag <= 1'b1;
state <= S4;
end
end
S4:
begin
if(times_cnt == nine_times)
begin
eigtht_times_flag <= 0;
nine_times_flag <= 1'b1;
state <= S0;
end
end
default:
begin
one_times_flag <= one_times_flag ;
four_times_flag <= four_times_flag ;
five_times_flag <= five_times_flag ;
seven_times_flag <= seven_times_flag ;
eigtht_times_flag <= eigtht_times_flag;
nine_times_flag <= nine_times_flag ;
end
endcase
reg [2:0] led_left; // 3个LED的亮灭状态
reg [2:0] led_right; // 3个LED的亮灭状态
always@(posedge i_clk or negedge i_rst_n)
begin
if(!i_rst_n)
begin
led_left <= 0;
led_right <= 0;
end
else
begin
if(one_times_flag)
begin
led_left <= 3'b100;
led_right <= 3'b100;
end
else if(four_times_flag)
begin
led_left <= 3'b100;
led_right <= 3'b010;
end
else if(five_times_flag)
begin
led_left <= 3'b010;
led_right <= 3'b001;
end
else if(eigtht_times_flag)
begin
led_left <= 3'b001;
led_right <= 3'b001;
end
end
end
reg [23:0]cnt;
reg flag1;
reg flag2;
always @(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
cnt <= 0;
else if(cnt == one_times / 6)
cnt <= 0;
else
cnt <= cnt + 1'b1;
always @(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
flag1 <= 0;
else if(led_left[0] == 1'b1)
begin
if(cnt == one_times / 6)
flag1 <= 1'b1;
else
flag1 <= 0;
end
always @(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
flag2 <= 0;
else if(led_right[1] == 1'b1)
begin
if(cnt == one_times / 6)
flag2 <= 1'b1;
else
flag2 <= 0;
end
reg led_3_temp;
always @(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
led_3_temp <= 0;
else if(led_right[1] == 1'b1)
begin
if(flag2 == 1'b1)
led_3_temp <= ~led_3_temp;
else
led_3_temp <= led_3_temp ;
end
always @(posedge i_clk )
begin
if(led_3_temp == 1'b1)
led1_rgb <= 48'hFFFF_8FFF_0000;
else
led1_rgb <= 48'b0;
end
reg led_1_temp;
always @(posedge i_clk or negedge i_rst_n)
if(!i_rst_n)
led_1_temp <= 0;
else if(led_left[0] == 1'b1)
begin
if(flag1 == 1'b1)
led_1_temp <= ~led_1_temp;
else if(flag1 == 0)
led_1_temp <= led_1_temp;
end
always @(posedge i_clk)
begin
if(led_1_temp == 1'b1)
led3_rgb <= 48'hFFFF_8FFF_0000;
else
led3_rgb <= 48'b0;
end
//根据led对应位的高低电平，指定LED灯的颜色输出
assign led0_rgb = (led_right[0] == 1'b1) ? 48'hFFFF_0000_0000 : 48'b0; // 输出RED颜色给LED0
//assign led1_rgb = (led_right[1] == 1'b1) ? 48'hFFFF_FFFF_0000 : 48'b0; // 输出YELLOW颜色给LED1 !!!
assign led2_rgb = (led_right[2] == 1'b1) ? 48'h0000_FFFF_0000 : 48'b0; // 输出GREEN颜色给LED2
//assign led3_rgb = (led_left[0] == 1'b1) ? 48'hFFFF_FFFF_0000 : 48'b0; // 输出YELLOW颜色给LED3 !!!
assign led4_rgb = (led_left[1] == 1'b1) ? 48'h0000_FFFF_0000 : 48'b0; // 输出GREEN颜色给LED4
assign led5_rgb = (led_left[2] == 1'b1) ? 48'hFFFF_0000_0000 : 48'b0; // 输出RED颜色给LED5