rofactor.v

基于VHDL语言的一个FFT快速傅里叶变换程序。采用4蝶形算法

/*
 * filename: rofactor.v
 *
 * version: 2007-04-21
 *
 * funciton: 在rof_start出现的下一个时钟,依次输出旋转因子,共
 *     输出256*3个
 *
 */

module	rofactor
(
	rst,
	clk8x,
	rof_start,

	angle

//	,state,
//	cnt256,
//	inc1, inc2, inc3
);

input					rst, clk8x, rof_start;

output	[7:0]			angle;

//output	[1:0]			state;
//output	[7:0]			cnt256;
//output	[5:0]			inc1, inc2, inc3;

reg		[1:0]			state;
reg		[7:0]			cnt256;
wire	[5:0]			inc1, inc2, inc3;

reg		[7:0]			angle;

always @ (posedge clk8x)
begin
	if (rst)
		state <= 2'b0;
	else if (rof_start)
		state <= 2'b01;
	else if	(cnt256 == 255)
		state <= state + 1'b1;

	if (rst)
		cnt256 <= 8'b0;
	else if (state!=0)
		cnt256 <= cnt256 + 1'b1;
end

assign inc1 = cnt256[7:2];
assign inc2 = {cnt256[5:2], 2'b0};
assign inc3 = {cnt256[3:2], 4'b0};

always @ (posedge clk8x)
begin
	if (rst || cnt256[1:0]==3)
		angle <= 8'b0;
	else if (state == 1)
		angle <= angle + inc1;
	else if (state == 2)
		angle <= angle + inc2;
	else if (state == 3)
		angle <= angle + inc3;
	else
		angle <= 8'b0;
end

endmodule