二位元多工器

module top;

wire[1:0] A, B, OUT;
wire SEL;
system_clock #200 clock1(A[0]);
system_clock #200 clock2(A[1]);
system_clock #100 clock3(B[0]);
system_clock #100 clock4(B[1]);
system_clock #400 clock5(SEL);
mux2 M1(OUT,A,B,SEL);

endmodule

module mux2(OUT, A, B, SEL);
output [1:0] OUT;
input [1:0] A,B;
input SEL;
mux hi (OUT[1], A[1], B[1], SEL);
mux lo (OUT[0], A[0], B[0], SEL);

endmodule

module mux(OUT, A, B, SEL);
output OUT;
input A,B,SEL;
not I5 (sel_n, SEL);
and I6 (sel_a, A, SEL);
and I7 (sel_b, sel_n, B);
or I4 (OUT, sel_a, sel_b);
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($time>1000)$stop;

endmodule