3-8线译码器

//3-8线译码器
module cy4(input[2:0] E,//输入端口声明
           input[2:0] A,//输入端口声明
           output reg[7:0]Y//输出端口声明
          );
always @(A,E)
if(E == 3'b111)        
   begin
     case(A)
      3'b000: Y <= 8'b1111_1110;
      3'b001: Y <= 8'b1111_1101;
      3'b010: Y <= 8'b1111_1011;
      3'b011: Y <= 8'b1111_0111;
      3'b100: Y <= 8'b1110_1111;
      3'b101: Y <= 8'b1101_1111;
      3'b110: Y <= 8'b1011_1111;
      3'b111: Y <= 8'b0111_1111;
     default: Y <= 8'b1111_1111;
     endcase
   end
else;
endmodule 

测试脚本代码：
`timescale 1 ns/ 1 ps
module cy4_vlg_tst();
reg [2:0] A;
reg [2:0] E;
wire [7:0] Y;
cy4 i1 (
.A(A),
.E(E),
.Y(Y)
);
initial
begin
E = 3’b111;

1000;

A = 3’b000;

100;

A = 3’b001;

100;

A = 3’b010;

100;

A = 3’b011;

100;

A = 3’b100;

100;

A = 3’b101;

100;

A = 3’b110;

100;

A = 3’b111;

100;

$stop;$display(“Running testbench”);
end
endmodule