05-译码器

module decoder
(
  input wire in_1,
  input wire in_2,
  input wire in_3,
  output reg [8:0] out
);
 
  // 使用case语句
  // 使用if-else语句
  always@(*)
  begin
    case({in_1,in_2,in_3})
      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;
      default : out = 8'b0000_0001;
    endcase
  end
endmodule

`timescale 1ns/1ns

module tb_decoder();
  reg in_1;
  reg in_2;
  reg in_3;

  wire [7:0] out;
    
  initial begin
    in_1 <= 1'b0;
    in_2 <= 1'b0;
    in_3 <= 1'b0;
  end
   
  initial begin
    $timeformat(-9,0,"ns",6);
    $monitor("@time:%t:in_1=%b,in_2=%b,in_3=%b,out=%b",$time,in_1,in_2,in_3,out);
  end 

 
  always #10 in_1 <= {$random} % 2;
  always #10 in_2 <= {$random} % 2;
  always #10 in_3 <= {$random} % 2;
  
  decoder decoder_inst(
    .in_1 (in_1),
    .in_2 (in_2),
    .in_3 (in_3),
    .out  (out)
  );
  
  
endmodule