P7-18 以function 呼叫function 完成16bit Even Parity checker 適用於DE2-70

P7-18 以function 呼叫function 完成16bit Even Parity checker
適用於DE2-70 

Even 時HEX3..HEX0 Display EVEN (相近於)
Odd  時HEX3..HEX0 Display Odd    (相近於)

//--------------------------------------------------------------------------------
// 16-bit even-parity generator modified from ex.7-2 using function call 
// Filename : even_parity_16.v
//--------------------------------------------------------------------------------
module enev_16f_funcall_fun(SW, LEDR, LEDG , CLOCK_27 ,KEY ,HEX0 ,HEX1 ,HEX2,HEX3 );

input  [17:0] SW; // toggle switches
input  [3:0] KEY;     // Push bottom
input  CLOCK_27; //Clock 27MHz , 50Mhz

output [17:0] LEDR; // red  LEDS   
  output [8:0] LEDG; // green LEDs
    
    output [6:0] HEX0,HEX1,HEX2,HEX3; //7-segment display
    
  
//set original program input , output 
  
//even_parity_16(Din, Pout);
//input [15:0] Din;
//output Pout;

wire [15:0] Din;
reg [6:0] HEX0,HEX1,HEX2,HEX3;
reg [7:0] High_byte;  // Hight byte of input data
reg [7:0] Low_byte;  // Low byte of input data
reg High, Low;      // Parities of high and low byte
reg Pout;        // Parity output

assign LWDR=SW;
assign Din=SW[15:0];  


always @(Din)
     begin
      High_byte = Din[15:8];
     Low_byte = Din[7:0];
 High = even8(High_byte); //Call function even8
 Low = even8(Low_byte);
 Pout = High ^ Low;   //Bitwise xor
     end

always @(Pout)
begin
  case (Pout)
1'b0 : 

 begin 
   
HEX3=7'b0000110;  //e
HEX2=7'b1100011;  //v
HEX1=7'b0000110;  //e
HEX0=7'b0101011;  //n
end


1'b1 : 
 
 begin 
   
HEX3=7'b1111111;  //
HEX2=7'b1000000;  //o
HEX1=7'b0100001;  //d
HEX0=7'b0100001;  //d
end


  default : 
   begin 
HEX3=7'b1111111;  //
HEX2=7'b1111111;  //
HEX1=7'b1111111;  //
HEX0=7'b1111111;  //

       end
       
  endcase

   end



//==========================================
function even8;
  input [7:0] I8;
  begin 
   even8 = even4(I8[7:4]) ^ even4(I8[3:0]);  // xor operation
  end
endfunction


//==========================================
function even4;
  input [3:0] I4;
  begin 
   even4 = ^ I4;  // reduction xor operation
  end
endfunction

endmodule