categoryselect.v

encoder jpeg project

/*******************************************************************/
/*	This module implements the category selection circuit 	 */
/*	of the Entropy encoder 				 			 */
/*******************************************************************/

module categoryselect(	Coefficient, 
                        RunlengthIn, 
				DCin, 
				ACin, 
				EOBin, 
                        EOB2in, 
				ZRLin, 
				Clock,
				Reset, 
				Enable, 
				Category, 
				CoefficientOut, 
				RunLengthOut, 
				DCOut, 
				ACOut, 
				EOBOut, 
				EOB2out, 
				ZRLOut
		    	  );

//                    MODULE INPUTS
input [11:0] 	Coefficient;	// Coefficient from ZRLC stage
input [3:0] 	RunlengthIn;	// Run length from ZRLC stage
input 		Clock; 		// Clock signal
input			Reset;		// Low asserted System-wide reset
input			DCin; 		// DC status signal
input			ACin; 		// AC status signal
input			EOBin; 		// EOB status signal
input			ZRLin; 		// ZRL status signal
input			EOB2in; 		// BlkEnd status signal
input			Enable;		// System-wide enable signal

//                    MODULE OUTPUTS
output 		DCOut; 		// DC status signal out
output		ACOut; 		// AC status signal out
output		EOBOut; 		// EOB status signal out	
output		ZRLOut; 		// ZRL status signal out
output		EOB2out;		// BlkEnd status signal out
output [10:0] 	CoefficientOut;	// Coefficient output
output [3:0] 	RunLengthOut; 	// Run length output
output [3:0]	Category;		// Evaluated category

reg 			DCOut; 
reg			ACOut; 
reg			EOBOut; 
reg			ZRLOut; 
reg			EOB2out;
reg [10:0] 		CoefficientOut;
reg [3:0] 		RunLengthOut; 
reg [3:0]		Category;


// clocked always block implementing assignments to registers.
always @(posedge Clock or negedge Reset)
	begin
	if(!Reset)
		begin
            CoefficientOut <= 0;
    		RunLengthOut <= 0;
            DCOut <= 0;
            ACOut <= 0;
        	EOBOut <= 0;
        	ZRLOut <= 0;
        	EOB2out <= 0;
		end
      else if(Enable)
		begin
    		CoefficientOut <= Coefficient;
    		RunLengthOut <= RunlengthIn;
    		DCOut <= DCin;
        	ACOut <= ACin;
        	EOBOut <= EOBin;
        	ZRLOut <= ZRLin;
        	EOB2out <= EOB2in;

//The following if-else block models a 2:1 multiplexer.  The nested 
//if else statements within the if-else block models the priority   
//encoders for generating the category from the coefficient.  The 
//first set of if-else statements model an active-low input encoder 
//for negative coefficients.  The second set of if-else statements 
//model an active high input encoder for positive coefficients.

        	if (Coefficient [11] == 1'b1)
        		begin
            	if(Coefficient [10] == 1'b0)
                		Category <= 11;
            	else if(Coefficient [9] == 1'b0)
                		Category <= 10;
            	else if(Coefficient [8] == 1'b0)
                		Category <= 9;
            	else if(Coefficient [7] == 1'b0)
                		Category <= 8;
            	else if(Coefficient [6] == 1'b0)
                		Category <= 7;
            	else if(Coefficient [5] == 1'b0)
                		Category <= 6;
            	else if(Coefficient [4] == 1'b0)
                		Category <= 5;
            	else if(Coefficient [3] == 1'b0)
                		Category <= 4;
            	else if(Coefficient [2] == 1'b0)
                		Category <= 3;
            	else if(Coefficient [1] == 1'b0)
                		Category <= 2;
            	else if(Coefficient [0] == 1'b0)
                		Category <= 1;
            	else
                		Category <= 0;
        		end
        	else
        		begin
            	if(Coefficient [10] == 1'b1)
                		Category <= 11;
            	else if(Coefficient [9] == 1'b1)
                		Category <= 10;
            	else if(Coefficient [8] == 1'b1)
                		Category <= 9;
            	else if(Coefficient [7] == 1'b1)
                		Category <= 8;
            	else if(Coefficient [6] == 1'b1)
                		Category <= 7;
            	else if(Coefficient [5] == 1'b1)
                		Category <= 6;
            	else if(Coefficient [4] == 1'b1)
                		Category <= 5;
            	else if(Coefficient [3] == 1'b1)
                		Category <= 4;
            	else if(Coefficient [2] == 1'b1)
                		Category <= 3;
            	else if(Coefficient [1] == 1'b1)
                		Category <= 2;
            	else if(Coefficient [0] == 1'b1)
                		Category <= 1;
            	else
                		Category <= 0;
        		end
  		end
	end
endmodule