二位元多工器 行為模式

module top; 

wire A0,A1,B0,B1,OUT1,OUT2;

wire SEL;

system_clock #50 clock1(SEL); 

system_clock #100 clock2(A0);

system_clock #200 clock3(A1);

system_clock #400 clock4(B0);

system_clock #800 clock5(B1);

mux_behavioral mux1 (OUT1,OUT2,A0,A1,B0,B1,SEL);

endmodule 

module mux_behavioral(OUT1,OUT2,A0,A1,B0,B1,SEL);

 output OUT1,OUT2;

 input A0,A1,B0,B1,SEL;

 wire  A0,A1,B0,B1,SEL;

 reg   OUT1,OUT2;

always @(A0 or A1 or B0 or B1 or SEL)

 begin

   OUT1 = (A0 & SEL)|(B0 & ~SEL );

   OUT2 = (A1 & SEL)|(B1 & ~SEL );

 end

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