基于verilog设计一个用于十字路口的交通灯控制器，能显示十字路口东西、南北两个方向的红、黄、绿的指示状态；具有倒计时的功能，用两组数码管作为东西和南北方向的倒计时显示，主干道直行(绿灯)60秒后，左转(绿灯)40秒；支干道直行(绿灯)45秒后，左转(绿灯)30秒，在每次绿灯变成红灯的转换过程中，要亮黄灯5秒作为过渡。黄灯每秒闪亮一次。只考虑直行和左转车辆控制信号灯，右转车辆不受信号灯控制， 南北向车辆与东西向车辆交替方向，同方向等待车辆应先方向直行车辆而后放行左转车辆。

以下是基于verilog的交通灯控制器设计：

module traffic_light(
    input clk, reset,
    output reg [2:0] EW_light, NS_light,
    output reg [3:0] EW_timer, NS_timer
);

parameter EAST_WEST = 2'b00;
parameter NORTH_SOUTH = 2'b01;
parameter STRAIGHT = 1'b0;
parameter LEFT_TURN = 1'b1;
parameter RED = 3'b100;
parameter YELLOW = 3'b010;
parameter GREEN = 3'b001;

reg [1:0] EW_state, NS_state;
reg [3:0] EW_count, NS_count;
reg [2:0] EW_light_next, NS_light_next;
reg [3:0] EW_timer_next, NS_timer_next;

always @(posedge clk) begin
    if (reset) begin
        EW_state <= EAST_WEST;
        NS_state <= NORTH_SOUTH;
        EW_count <= 60;
        NS_count <= 45;
        EW_light_next <= GREEN;
        NS_light_next <= RED;
        EW_timer_next <= EW_count;
        NS_timer_next <= NS_count;
    end else begin
        case (EW_state)
            EAST_WEST: begin
                if (EW_count == 60) begin
                    EW_light_next <= GREEN;
                    EW_timer_next <= EW_count;
                end else if (EW_count == 20) begin
                    EW_light_next <= YELLOW;
                    EW_timer_next <= 5;
                end else if (EW_count == 0) begin
                    EW_light_next <= LEFT_TURN;
                    EW_timer_next <= 40;
                    NS_light_next <= GREEN;
                    NS_timer_next <= NS_count;
                    NS_state <= NORTH_SOUTH;
                end else begin
                    EW_timer_next <= EW_count;
                end
                EW_count <= (EW_count == 0) ? 60 : EW_count - 1;
            end
            NORTH_SOUTH: begin
                if (NS_count == 45) begin
                    NS_light_next <= GREEN;
                    NS_timer_next <= NS_count;
                end else if (NS_count == 15) begin
                    NS_light_next <= YELLOW;
                    NS_timer_next <= 5;
                end else if (NS_count == 0) begin
                    NS_light_next <= LEFT_TURN;
                    NS_timer_next <= 30;
                    EW_light_next <= RED;
                    EW_timer_next <= EW_count;
                    EW_state <= EAST_WEST;
                end else begin
                    NS_timer_next <= NS_count;
                end
                NS_count <= (NS_count == 0) ? 45 : NS_count - 1;
            end
        endcase
    end
end

always @(posedge clk) begin
    EW_light <= EW_light_next;
    NS_light <= NS_light_next;
    EW_timer <= EW_timer_next;
    NS_timer <= NS_timer_next;
end

endmodule

该设计使用了两个状态机，一个控制东西方向的交通灯状态，一个控制南北方向的交通灯状态。在每个状态中，使用计数器进行倒计时，并在计数器达到特定值时切换到下一个状态。同时，使用一个变量记录下一个状态的灯光状态和倒计时时间，以便在计数器达到特定值时进行更新。最后，使用另一个always块将下一个状态的值传递到当前状态。