module mux_8(addr, in1, in2, in3, in4, in5,in6,in7,in8,mout,ncs);
input [2:0] addr; 
input [3:0] in1,in2,in3,in4,in5,in6,in7,in8;
input ncs; 
output [3:0] mout; 
reg [3:0] mout;
always @(addr or in1 or in2 or in3 or in4 or in5 or in6 or in7 or in8 or ncs)
begin
if(!ncs)
case(addr)
3'b000: mout = in1; 
3'b001: mout = in2;
3'b010: mout = in3;
3'b011: mout = in4; 
3'b100: mout = in5; 
3'b101: mout = in6; 
3'b110: mout = in7; 
3'b111: mout = in8; 
endcase
else
mout = 0;
end
endmodule

`timescale 1ns/1ns
module test;
wire[3:0] mout;
reg [3:0] in1,in2,in3,in4,in5,in6,in7,in8;
reg [2:0] addr; 
reg ncs;
initial
begin
ncs=0; //在初始化模块里将使能信号置为0，让选择器正常工作
in8={$random}%16; //使用系统任务$random产生一个0至15之间的数
in1={$random}%16;
in2={$random}%16;
in3={$random}%16;
in4={$random}%16;
in5={$random}%16;
in6={$random}%16;
in7={$random}%16;
addr=3'b000; 
repeat(5)   //重复下面的语句块5次，赋5次值
begin
#10 in8={$random}%16;
in1={$random}%16;
in2={$random}%16;
in3={$random}%16;
in4={$random}%16;
in5={$random}%16;
in6={$random}%16;
in7={$random}%16;
addr=addr+1;
end
#10 $stop;
end
mux_8 example(.addr(addr),.in1(in1),.in2(in2),.in3(in3),.in4(in4),.in5(in5),.in6(in6),.in7(in7),.in8(in8),.mout(mout),.ncs(ncs));
endmodule