coeff_dpmem.vhd

fir滤波器程序的实现

--===========================================================================--
--                                                                           --
--  S Y N T H E S I Z A B L E    FIR filter   C O R E                        --
--                                                                           --
--  www.opencores.org - January 2000                                         --
--  This IP core adheres to the GNU public license.                          --
--                                                                           --
--  VHDL model of Finite Impulse Response filter                             --
--                                                                           --
--  This model uses dual-port memory for storing coefficients and samples.   --
--  Resolution of coefficients and samples is adjustable. Number of TAPs     --
--  depends on dual-port memory size. This design can be cascaded to         --
--  form FIR filter with even greater number of TAPS.                        --
--                                                                           --
--  Implementation with 16x16 bit fixed point multiplier in Xilinx Virtex    --
--  XCV50-6 runs at 55 MHz and with 256 TAPs can handle frequency            --
--  bandwidth of +-107KHz.                                                   --
--                                                                           --
--  Author: Damjan Lampret, [e-mail]                            --
--                                                                           --
--  TO DO:                                                                   --
--                                                                           --
--   - synthesis with Syplify pending (there are some problems with          --
--     UNSIGNED and BIT_LOGIC_VECTOR types in some units !)                  --
--                                                                           --
--   - testbench                                                             --
--                                                                           --
--   - support for more dual-port memories (currently supported              --
--     Virtex/Spartan2 (generic dual-port memory added but not tested))      --
--                                                                           --
--   - top level "cascade" module for easy cascading several FIR filters     --
--                                                                           --
--   - verification with real application and real coefficients              --
--                                                                           --
--===========================================================================--

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use work.config.all;

entity coeff_dpmem is
    port (
	INPUT  : in STD_LOGIC_VECTOR (COEFF_WIDTH-1 downto 0);
	OUTPUT : out STD_LOGIC_VECTOR (COEFF_WIDTH-1 downto 0);
	REPEAT : out STD_LOGIC;
	LOADING_COEFF : out STD_LOGIC;
	CLK : in STD_LOGIC;
	RST : in STD_LOGIC
    );
end coeff_dpmem;

architecture virtex_blockram of coeff_dpmem is

component RAMB4_S16_S16
    port (
	ADDRA : in UNSIGNED (MAXMEMADDR-1 downto 0);
	ADDRB : in UNSIGNED (MAXMEMADDR-1 downto 0);
	DIA : in STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
	DIB : in STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
--	DOA : out STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
	DOB : out STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
	CLKA : in STD_LOGIC;
	CLKB : in STD_LOGIC;
	ENA : in STD_LOGIC;
	ENB : in STD_LOGIC;
	RSTA : in STD_LOGIC;
	RSTB : in STD_LOGIC;
	WEA : in STD_LOGIC;
	WEB : in STD_LOGIC
    );
end component;

attribute INIT_00 : string;
attribute INIT_00 of virtex_blockram: label is "000100020003000400050006000000000000000000000000000000000000000F";

signal WRITE_ADDR: UNSIGNED (MAXMEMADDR-1 downto 0);
signal WRITE_DATA: STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
signal READ_ADDR: UNSIGNED (MAXMEMADDR-1 downto 0);
signal READ_DATA: STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);
signal RD: STD_LOGIC;
signal WR: STD_LOGIC;
signal GND: STD_LOGIC_VECTOR (MAXMEMWIDTH-1 downto 0);

begin

GND <= (others => '0');
LOADING_COEFF <= WR;
    
OUTPUT (COEFF_WIDTH-1 downto 0) <= READ_DATA (COEFF_WIDTH-1 downto 0);
WRITE_DATA (COEFF_WIDTH-1 downto 0) <= INPUT (COEFF_WIDTH-1 downto 0);
    
coeff_dpmem_ctrl:
process(CLK,RST)
variable counter: UNSIGNED (TAPS downto 0);
begin
	if RST = '1' then
		counter := (others => '0');
		WR <= not COEFF_LOADED_AT_STARTUP;
		RD <= '0';
	elsif rising_edge(CLK) then
		if counter < NUM_TAPS then
			counter := counter + 1;
			REPEAT <= '0';			
		elsif counter = NUM_TAPS then
			counter := (others => '0');
			REPEAT <= '1';
			WR <= '0';
		else
		end if;
		READ_ADDR (MAXMEMADDR-1 downto TAPS) <= (others => '0');
		WRITE_ADDR (MAXMEMADDR-1 downto TAPS) <= (others => '0');
		READ_ADDR (TAPS-1 downto 0) <= counter (TAPS-1 downto 0);
		WRITE_ADDR (TAPS-1 downto 0) <= counter (TAPS-1 downto 0);
	end if;
end process;

virtex_blockram: RAMB4_S16_S16
    port map(
	ADDRA => WRITE_ADDR,
	ADDRB => READ_ADDR,
	DIA => WRITE_DATA,
	DIB => GND,
--	DOA => open,
	DOB => READ_DATA,
	CLKA => CLK,
	CLKB => CLK,
	ENA => WR,
	ENB => RD,
	RSTA => RST,
	RSTB => RST,
	WEA => WR,
	WEB => GND(0)
    );

end virtex_blockram;