P6-29 1x4 DeMUX 適用於DE2-70

P6-29 1x4 DeMUX 適用於DE2-70

//-------------------------------------------------------

//4-bit demultiplexer with if...else if...else if...else...

//Filenale : demux_1x4

//-------------------------------------------------------

module demux_1x4(SW, LEDR, LEDG , CLOCK_27 ,KEY );

input  [17:0] SW; // toggle switches

input  [7:0] KEY;     // Push bottom

input  CLOCK_27; //Clock 27MHz , 50Mhz

output [17:0] LEDR; // red  LEDS   

  output [7:0] LEDG; // green LEDs

  

  

//set original program input , output 

    // Port Declarations

//(y, I, S0, S1);

//output [3:0] y;

//input I;

//input S0, S1;    //Selection signals

    

    

    reg  [3:0] y;

    wire I ,S1,S0;

    

    

    //mapping to hardware 

    assign LEDR = SW;

    

    assign I=SW[0]; 

    assign S1=SW[17];

    assign S0=SW[16];

always @ (I or S0 or S1)

begin

if (S1==1'b0)

begin

if (S0==1'b0)

y = {3'b000, I};   //marge 000 with I to y

else

y = {2'b00, I, 1'b0};

end

else

begin 

if (S0==1'b0)

y = {1'b0, I, 2'b00};

else

y = {I, 3'b000};

end

end

assign LEDG[3:0]=y;

endmodule