2位多工器

这次课程，更深刻理解模拟的意义。

器件的延迟效应与周期的设置应该相互匹配，不然会出现很多复杂的不需要的脉冲。

module top;

wire A0, A1, B0, B1, SEL , NOT_SEL , X , Y , Z, W, OUT0, OUT1;

system_clock #1600clock1(A0);
system_clock #800clock2(A1);
system_clock #400clock3(B0);
system_clock #200 clock4(B1);
system_clock #100 clock5(SEL);

not n1(NOT_SEL, SEL);

and a1(X, A0, SEL);
and a2(Y, A1, SEL);
and a3(Z, B0, NOT_SEL);
and a4(W, B1, NOT_SEL);

or o1(OUT0, X , Z);
or o2(OUT1, Y , W);

endmodule

module system_clock(clk);
parameter PERIOD=100;
output clk;
reg clk;

initial clk=0;

always
 begin
#(PERIOD/2) clk=~clk;
 end

always@(posedge clk)
 if($time>2000)$stop;

endmodule