Subversion Repositories two_dimensional_fast_hartley_transform

/**********************************************************************
 * File  : signed_mult_const_asic.v
 * Author: Ivan Rezki
 * email : irezki@gmail.com
 * Topic : RTL Core
 * 		  2-Dimensional Fast Hartley Transform
 *
 *
 * Function: Signed Multiplier - constant sqrt(2) = 1.41421
 * 1.41421*a = (256*1.41421)*a/256 = 362.03776*a/256 = 362*a/256
 * product = 362*a/2^8
 *
 * RIGHT TO USE: This code example, or any portion thereof, may be
 * used and distributed without restriction, provided that this entire
 * comment block is included with the example.
 *
 * DISCLAIMER: THIS CODE EXAMPLE IS PROVIDED "AS IS" WITHOUT WARRANTY
 * OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
 * TO WARRANTIES OF MERCHANTABILITY, FITNESS OR CORRECTNESS. IN NO
 * EVENT SHALL THE AUTHOR OR AUTHORS BE LIABLE FOR ANY DAMAGES,
 * INCLUDING INCIDENTAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF THE
 * USE OF THIS CODE.
 **********************************************************************/
 
module signed_mult_const_asic (
	rstn,
	clk,
	valid,
	a,
	p
);
 
parameter		N = 8;
input			rstn;
input			clk;
input			valid;
input  [N-1:0] a; // variable - positive/negative
output [N  :0] p; // product output
 
// FHT constant
//wire [8:0] mult_constant; // always positive
//assign mult_constant = 9'd362;
parameter mult_constant = 9'd362;
 
reg [N-1:0] a_FF;
always @(posedge clk)
if		(!rstn) a_FF <= #1 0;
else if (valid)	a_FF <= #1 a;
 
// Convert into 2's complement if (a_FF) is negative
wire [N-1:0] b;
assign b = a_FF[N-1] ? {~a_FF[N-1:0] + {{N-1{1'b0}},1'b1} } : a_FF[N-1:0];
 
// Multiply 2 positive numbers 
// b[N-2:0] * mult_constant[8:0]
// output result mult_wo_sign
// N-2+1 - number of (b) bits
// 8+1   - number of mult_constant bits
// N-2+1+8+1 - number of bits on the output
// = N+8 = [N+7:0]
wire [N+7:0] mult_wo_sign; // mult without sign
assign mult_wo_sign = b[N-2:0]*mult_constant;
 
// Divided by 256 - [N+7-8:0] = [N-1:0]
wire [N-1:0] div256; // divided 256
assign div256 = mult_wo_sign >> 8;
 
assign p = a_FF[N-1] ? 
					{1'b1,{~div256[N-1:0] + {{N-1{1'b0}},1'b1}} } : 
					{1'b0,  div256[N-1:0]}
					;
endmodule
 
// Update Log:
// 27 Jul. 2011
// wire [8:0] mult_constant replaced by parameter