🎲 电子骰子

// Electronic Dice - 电子骰子
// 8-bit LFSR伪随机数, 按键掷骰1-6
module dice(
    input  wire       clk,     // 50MHz
    input  wire       rst,
    input  wire       roll,    // 掷骰按键
    output reg  [2:0] face,    // 骰子面值 1-6
    output reg        rolling  // 掷骰中
);

// 8-bit LFSR, feedback polynomial: x^8 + x^6 + x^5 + x^4 + 1
reg [7:0] lfsr;
wire feedback;

assign feedback = lfsr[7] ^ lfsr[5] ^ lfsr[4] ^ lfsr[3];

// LFSR runs continuously
always @(posedge clk or posedge rst) begin
    if (rst) begin
        lfsr <= 8'hAC;  // Non-zero seed
    end else begin
        lfsr <= {lfsr[6:0], feedback};
    end
end

// Roll debounce and edge detection
reg roll_d1, roll_d2, roll_d3;
wire roll_edge = roll_d2 && !roll_d3;

always @(posedge clk or posedge rst) begin
    if (rst) begin
        roll_d1 <= 1'b0;
        roll_d2 <= 1'b0;
        roll_d3 <= 1'b0;
    end else begin
        roll_d1 <= roll;
        roll_d2 <= roll_d1;
        roll_d3 <= roll_d2;
    end
end

// Roll duration counter
reg [3:0] roll_cnt;

always @(posedge clk or posedge rst) begin
    if (rst) begin
        face    <= 3'd1;
        rolling <= 1'b0;
        roll_cnt <= 4'd0;
    end else begin
        if (roll_edge && !rolling) begin
            rolling  <= 1'b1;
            roll_cnt <= 4'd10;  // Roll for 10 cycles
        end

        if (rolling) begin
            // Map LFSR to 1-6 during rolling
            face <= (lfsr[2:0] % 3'd6) + 3'd1;
            if (roll_cnt > 4'd0) begin
                roll_cnt <= roll_cnt - 4'd1;
            end else begin
                rolling <= 1'b0;
                // Final result
                face <= (lfsr % 6) + 1;
            end
        end
    end
end

endmodule