module led_test(a, b, c, out);

    input a;                    // 輸入信號

    input b;                    // 輸入信號

    input c;                    // 輸入信號

    //output [7:0]out;    // 由于要用到 always 程序塊中，需要聲明為 reg 類型

    // 如果不是 reg 類型則會報錯

    // Error (10137): Verilog HDL Procedural Assignment error at led_test.v(12):

    //    object "out" on left-hand side of assignment must have a variable data type

    output reg [7:0]out;    // 輸出信號

    always@(a, b, c)begin

        case({a, b, c})

            3'b000 : out = 8'b0000_0001;

            3'b001 : out = 8'b0000_0010;

            3'b010 : out = 8'b0000_0100;

            3'b011 : out = 8'b0000_1000;

            3'b100 : out = 8'b0001_0000;

            3'b101 : out = 8'b0010_0000;

            3'b110 : out = 8'b0100_0000;

            3'b111 : out = 8'b1000_0000;

        endcase

    end

endmodule

`timescale 1ns/1ns                // 延時時間單位/仿真精度

module led_test_tb;

    reg a, b, c;

    wire[7:0] out;

    led_test u1(.a(a), .b(b), .c(c), .out(out));    // 將端口(IO口)連接到 led_test 芯片中

    initial begin   

        a = 0; b = 0; c = 0;    // 設(shè)置端口(IO口)的電平狀態(tài)

        #200;

        a = 0; b = 0; c = 1;

        #200;

        a = 0; b = 1; c = 0;

        #200;

        a = 0; b = 1; c = 1;

        #200;

        a = 1; b = 0; c = 0;

        #200;

        a = 1; b = 0; c = 1;

        #200;

        a = 1; b = 1; c = 0;

        #200;

        a = 1; b = 1; c = 1;

        #200;

        $stop;                // 停止執(zhí)行

    end

endmodule

/* 4-16 譯碼器 */

module led_test(a, b, c, d, out);

    input a, b, c, d;

    output reg[15:0] out;

    always@(a, b, c, d)begin

        case({a, b, c, d})

            4'b0000 : out = 16'b0000_0000_0000_0001;

            4'b0001 : out = 16'b0000_0000_0000_0010;

            4'b0010 : out = 16'b0000_0000_0000_0100;

            4'b0011 : out = 16'b0000_0000_0000_1000;

            4'b0100 : out = 16'b0000_0000_0001_0000;

            4'b0101 : out = 16'b0000_0000_0010_0000;

            4'b0110 : out = 16'b0000_0000_0100_0000;

            4'b0111 : out = 16'b0000_0000_1000_0000;

            4'b1000 : out = 16'b0000_0001_0000_0000;

            4'b1001 : out = 16'b0000_0010_0000_0000;

            4'b1010 : out = 16'b0000_0100_0000_0000;

            4'b1011 : out = 16'b0000_1000_0000_0000;

            4'b1100 : out = 16'b0001_0000_0000_0000;

            4'b1101 : out = 16'b0010_0000_0000_0000;

            4'b1110 : out = 16'b0100_0000_0000_0000;

            4'b1111 : out = 16'b1000_0000_0000_0000;

        endcase

    end

endmodule

`timescale 1ns/1ns

module led_test_tb;

    reg a, b, c, d;

    wire[15:0] out;

    led_test u1(.a(a), .b(b), .c(c), .d(d), .out(out));

    initial begin   

        a = 0; b = 0; c = 0; d = 0; #200;

        a = 0; b = 0; c = 0; d = 1; #200;

        a = 0; b = 0; c = 1; d = 0; #200;

        a = 0; b = 0; c = 1; d = 1; #200;

        a = 0; b = 1; c = 0; d = 0; #200;

        a = 0; b = 1; c = 0; d = 1; #200;

        a = 0; b = 1; c = 1; d = 0; #200;

        a = 0; b = 1; c = 1; d = 1; #200;

        a = 1; b = 0; c = 0; d = 0; #200;

        a = 1; b = 0; c = 0; d = 1; #200;

        a = 1; b = 0; c = 1; d = 0; #200;

        a = 1; b = 0; c = 1; d = 1; #200;

        a = 1; b = 1; c = 0; d = 0; #200;

        a = 1; b = 1; c = 0; d = 1; #200;

        a = 1; b = 1; c = 1; d = 0; #200;

        a = 1; b = 1; c = 1; d = 1; #200;

        $stop;

    end

endmodule