P7-20 以任務呼叫函數及任務完成16bit Comparator 適用於DE2-70

P7-20 以任務呼叫函數及任務完成16bit Comparator
適用於DE2-70 

//------------------------------------------------
// 16-bit Comparator using 4-bit-comparator task & 
// 4-bit-comparator function
// filename: compare16.v
//------------------------------------------------
module comp_16_t_tf(SW, LEDR, LEDG , CLOCK_27 ,KEY ,HEX0 ,HEX1 ,HEX2,HEX3 ,HEX4 );

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 [7:0] LEDG; // green LEDs
    
    output [6:0] HEX0,HEX1,HEX2,HEX3,HEX4; //7-segment display
    
// set original program input , output 

// ( A, B, Yout );
// input [15:0] A ; //16-bit input A and B
// input [15:0] B ;
// output [2:0] Yout;
// Yout[2]=1'b1 -->Great than,
// Yout[1]=1'b1 --> Equal, and 
    //Yout[0]=1'b1 -->Less than

reg [15:0] A,B ; //16-bit input A and B
//set SW17=1 then A input , SW=0 Then B input , Enable is KEY[0] 


reg [7:0] A8bit; // 4-bit data in input A
reg [7:0] B8bit; // 4-bit data in input B
reg [2:0] Yout ;
  
reg [6:0] HEX0,HEX1,HEX2,HEX3,HEX4;


assign LEDR=SW;
assign LEDG[3]=KEY[3];


always @( negedge KEY[3] )  //Setting A or B value
begin 
                       
if (SW[17]) 
A<=SW[15:0];   //SW17=1 then Setting A value
else
B<=SW[15:0];   //SW17=0 then Setting B value
     end


always @( A or B )
begin
A8bit = A[15:8] ; 
B8bit = B[15:8] ;
compare8( A8bit , B8bit , Yout );
if( Yout == 3'b010 ) // A[15:12] == B[15:12]
begin
   A8bit = A[7:0] ;
       B8bit = B[7:0] ;
       compare8( A8bit , B8bit , Yout ) ;
     
         end
end
//=================================
always @( Yout )
    begin
case (Yout)
3'b010 : 

 begin 
   
HEX4=7'b0000110;  //e
HEX3=7'b0011000;  //q
HEX2=7'b1100011;  //u
HEX1=7'b0000110;  //e
HEX0=7'b1000111;  //l
end


3'b100 : 
 
 begin 
HEX4=7'b0000010;  //g
HEX3=7'b0001101;  //r
HEX2=7'b0000110;  //e
HEX1=7'b0001000;  //a
HEX0=7'b0000111;  //t
 end

3'b001 :  
 begin 
HEX4=7'b1111111;  //
HEX3=7'b1000111;  //L
HEX2=7'b0000110;  //e
HEX1=7'b0010010;  //s
HEX0=7'b0010010;  //s
 end



  default : 
   begin 
HEX4=7'b1111111;  //
HEX3=7'b1111111;  //
HEX2=7'b1111111;  //
HEX1=7'b1111111;  //
HEX0=7'b1111111;  //

       end
       
  endcase

end

//=================================
// Task for a 8-bit comprator
task compare8 ;
 input [7:0] I_A ;  //4-bit input I_A and I_B
 input [7:0] I_B ;
 output [2:0] S ;  //S[2]=1'b1 -->Great than, S[1]=1'b1 --> Equal, and 
                   //S[0]=1'b1 -->Less than

 reg [3:0] A4bit;
 reg [3:0] B4bit;
  

 begin
A4bit=I_A[7:4];
B4bit=I_B[7:4];
compare4_T(A4bit,B4bit,S);   //Call Task

if(  S == 3'b010) // Equal )

begin 

A4bit=I_A[3:0];
B4bit=I_B[3:0];
S=compare4_F(A4bit,B4bit); //Call Function

end
 

 end
endtask
//

//===================================
// Task for a 4-bit comprator
//===================================

task compare4_T ;

 input [3:0] I_A ;  //4-bit input I_A and I_B
 input [3:0] I_B ;
 output [2:0] S ;  //S[2]=1'b1 -->Great than, S[1]=1'b1 --> Equal, and 
                   //S[0]=1'b1 -->Less than
 begin
if( I_A > I_B )
S = 3'b100 ; // Great than
else if( I_A == I_B )
      S = 3'b010 ; // Equal
else
 S = 3'b001 ; // Less than  

 end
endtask

//===================================
// Function for a 4-bit comprator
//===================================

function [2:0] compare4_F;

 input [3:0] I_A ;  //4-bit input I_A and I_B
 input [3:0] I_B ;
 // output [2:0] S ;  //S[2]=1'b1 -->Great than, S[1]=1'b1 --> Equal, and 
                     //S[0]=1'b1 -->Less than
 begin
if( I_A > I_B )
compare4_F = 3'b100 ; // Great than
else if( I_A == I_B )
compare4_F = 3'b010 ; // Equal
else
compare4_F = 3'b001 ; // Less than  

 end
endfunction
//

endmodule