vhdl/lib/radio/nco/src/nco_lut.vhd

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-- Company: 
-- Engineer:
--
-- Create Date:    12:16:14 10/02/05
-- Design Name:    
-- Module Name:    cordic_stage - Behavioral
-- Project Name:   
-- Target Device:  
-- Tool versions:  
-- Description:
--
-- Dependencies:
-- 
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
-- 
--------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;
USE ieee.numeric_std.ALL;

library ieee_proposed;
use ieee_proposed.math_utility_pkg.all;
use ieee_proposed.fixed_pkg.all;

library work;
use work.fixed_util_pkg.all;
use work.nco_pkg.all;

---- Uncomment the following library declaration if instantiating
---- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity nco is
Generic
(
	nbits_wave		: integer := 18;
	nbits_phase		: integer := 16; 
	nbits_lut_depth	: integer := 12; 
	nbits_dither	: integer := 4; 
	nbits_lfsr		: integer := 12; 
	q_phase			: phase_relation_t := phase_90deg;
	has_pipe_reg	: boolean := false;
	has_out_reg		: boolean := false
);
Port
(
	srst		: in std_logic;
	clk			: in std_logic;
	pacc_clr	: in std_logic;
	pacc_inc	: in std_logic;
	freq_in		: in unsigned(nbits_phase-1 downto 0);
	freq_load	: in std_logic;
	phase_in	: in unsigned(nbits_phase-1 downto 0);
	phase_load	: in std_logic;
	phase_out	: out unsigned(nbits_phase-1 downto 0);
	wave_out_i	: out sfixed;
	wave_out_q	: out sfixed;
	out_valid	: out std_logic
);
end nco;

architecture Behavioral of nco is

	COMPONENT wavelut
	Generic
	(
		nbits_wave		: integer;
		nbits_wave_frac	: integer;
		nbits_lut_depth	: integer; 
		q_phase			: phase_relation_t;
		has_out_reg		: boolean
	);
	Port
	(
		clk			: in std_logic;
		rst			: in std_logic;
		addr_valid	: in std_logic;
		addr		: in unsigned(nbits_lut_depth-1 downto 0);
		wave_i_out	: out sfixed;
		wave_q_out	: out sfixed;
		valid_out	: out std_logic
	);
	END COMPONENT;

-------------------------------------------------------------------------------
	constant nbits_wave_frac : integer := nbits_wave;

-------------------------------------------------------------------------------
	constant lfsr_gen_poly : unsigned(nbits_lfsr-1 downto 0) := to_unsigned(lfsr_poly(nbits_lfsr), nbits_lfsr);	-- 24
	
	signal phase : unsigned(nbits_phase-1 downto 0);
	signal freq_in_r : unsigned(nbits_phase-1 downto 0);
	signal phase_in_r : unsigned(nbits_phase-1 downto 0);
	signal lut_addr_d : unsigned(nbits_lut_depth-1 downto 0);
	signal wave_i_d, wave_q_d : sfixed(sproto(nbits_wave, nbits_wave_frac)'high downto sproto(nbits_wave, nbits_wave_frac)'low);
	
	type lfsr_t is array (0 to 1) of unsigned(nbits_lfsr-1 downto 0);
	signal lfsr : lfsr_t;
	signal lfsr_out : unsigned(nbits_dither-1 downto 0);
	signal lut_addr_valid, lfsr_valid, wave_d_valid : std_logic;
	
-------------------------------------------------------------------------------
begin

	wave_out_i <= wave_i_d;
	wave_out_q <= wave_q_d;
	out_valid <= wave_d_valid;

------------------------------------------------------------
	proc_lfsr: process(srst, clk, lfsr, pacc_inc)
	variable lo : unsigned(nbits_dither-1 downto 0);
	begin
		if rising_edge(clk) then
			if srst = '1' then
				lfsr_valid <= '0';
				lfsr_out <= (others => '0'); 
				for i in lfsr'range loop
					lfsr(i) <= to_unsigned(2**i, nbits_lfsr); 
				end loop;	
			else
				lfsr_valid <= '0';
				if pacc_inc ='1' then 
					lfsr_valid <= '1';
					lo := (others => '0'); 
					for i in lfsr'range loop
						if lfsr(i)(lfsr(i)'left) = '1' then
							lfsr(i) <= (lfsr(i)(lfsr(i)'left-1 downto 0) & lfsr(i)(lfsr(i)'left)) xor lfsr_gen_poly;
						else
							lfsr(i) <= lfsr(i)(lfsr(i)'left-1 downto 0) & lfsr(i)(lfsr(i)'left);
						end if;
					end loop;	
					for i in lfsr'range loop
						lo := lo + lfsr(i)(nbits_dither-1 downto 0); 
					end loop;	
	--				lo := lfsr(0)(nbits_dither downto 0); 
					lfsr_out <= lo(nbits_dither-1 downto 0);
				end if;	
			end if;
		end if;
	end process;

------------------------------------------------------------
	proc_phase_accu: process(clk, phase)
	variable phase_accu : unsigned(nbits_phase-1 downto 0);

	begin
		if rising_edge(clk) then 
			if srst = '1' then
				phase_accu := (others => '0');
			else
				phase <= phase_accu + phase_in_r;
				if pacc_clr = '1' then
					phase_accu := (others => '0');
				elsif pacc_inc = '1' then
					phase_accu := phase_accu + freq_in_r;
				end if;	
			end if;	
		end if;
		phase_out <= phase;
	end process;

------------------------------------------------------------
	freq_in_reg: process(srst, clk, freq_load, freq_in)
	begin
		if rising_edge(clk) then
			if srst = '1' then
				freq_in_r <= (others => '0');
			elsif freq_load = '1' then
				freq_in_r <= freq_in;
			end if;
		end if;
	end process;

------------------------------------------------------------
	phase_in_reg: process(srst, clk, phase_load, phase_in)
	begin
		if rising_edge(clk) then
			if srst = '1' then
				phase_in_r <= (others => '0');
			elsif phase_load = '1' then
				phase_in_r <= phase_in;
			end if;
		end if;
	end process;

------------------------------------------------------------
	proc_pipe_reg: process(clk)
	variable lfsr_sum : unsigned(nbits_phase-1 downto 0);
	begin
		if rising_edge(clk) then
			lut_addr_valid <= '0';
			if srst = '1' then
				lfsr_sum := (others => '0');
			elsif lfsr_valid = '1' then
				lut_addr_valid <= '1';
				lfsr_sum := lfsr_out + phase;
			end if;	
		end if;	
		lut_addr_d <= lfsr_sum(nbits_phase-1 downto nbits_phase-nbits_lut_depth);
	end process;
	
------------------------------------------------------------
	inst_wavelut_d: wavelut
	GENERIC MAP
	(
		nbits_wave		=> nbits_wave,
		nbits_wave_frac	=> nbits_wave_frac,
		nbits_lut_depth	=> nbits_lut_depth,
		q_phase			=> q_phase,
		has_out_reg		=> has_out_reg
	)
	PORT MAP
	(
		rst			=> srst,
		clk			=> clk,
		addr_valid	=> lut_addr_valid,
		addr		=> lut_addr_d,
		wave_i_out	=> wave_i_d,
		wave_q_out	=> wave_q_d,
		valid_out	=> wave_d_valid
	);

------------------------------------------------------------
end Behavioral;