pre.vhd

cordic算法的vhdl实现

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--  File: pre.vhd                                        --
--  created : July 09,2001 15:00                         --
--  mail to [e-mail]                          --
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library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.STD_LOGIC_ARITH.all;
use IEEE.STD_LOGIC_SIGNED.all;

entity pre is   
	port (                       
		clk    : in  std_logic;
		x_in   : in  STD_LOGIC_VECTOR (15 downto 0);
		y_in   : in  STD_LOGIC_VECTOR (15 downto 0);
		octant : out STD_LOGIC_VECTOR (2 downto 0);
		x_out  : out STD_LOGIC_VECTOR (15 downto 0);
		y_out  : out STD_LOGIC_VECTOR (15 downto 0)
		);
end pre;

architecture pre of pre is
signal xint,xinta,xintb : std_logic_vector (15 downto 0);
signal yint,yinta,yintb : std_logic_vector (15 downto 0);
signal oct_int          : std_logic_vector (1 downto 0); 

begin                         
	
	process(clk)    
		variable xsign    : std_logic;
		variable ysign    : std_logic;
		variable xyswap   : std_logic;
                variable oct_int1 : std_logic_vector (1 downto 0);
	begin
		if clk'event and clk='1' 
			then
			xinta <=  x_in;
			xintb <= -x_in;
			yinta <=  y_in;
			yintb <= -y_in;
			xsign := xinta(15);
			ysign := yinta(15);
			
                       if ( xsign = '0' and ysign = '0' ) then
                             xint    <= xinta;
                             yint    <= yinta;
                             oct_int <= "00";
                         elsif ( xsign = '1' and ysign = '0') then
                             xint    <= yinta;
                             yint    <= xintb;
                             oct_int <= "01";
                         elsif ( xsign = '1' and ysign = '1' ) then
                             xint    <= xintb;
                             yint    <= yintb;
                             oct_int <= "10";
                         else 
                             xint    <= yintb;
                             yint    <= xinta;
                             oct_int <= "11"; 
                       end if;
 			if xint <= yint then 
 				x_out    <= yint;
 				y_out    <= xint;
 				xyswap   := '1';
 				oct_int1 := oct_int +1;
 			else
 				x_out    <= xint;
 				y_out    <= yint;
 				xyswap   := '0'; 
 				oct_int1 := oct_int;
 			end if;			  
 			
                        octant <= (oct_int1 & xyswap);	   
		end if;		
	end process;
	
end pre;