dbufctl_vhd.txt

the MDCT by the VHDL code

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--                                                                            --
--                          V H D L    F I L E                                --
--                          COPYRIGHT (C) 2006                                --
--                                                                            --
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--
-- Title       : DBUFCTL
-- Design      : MDCT Core
-- Author      : Michal Krepa
--
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--
-- File        : DBUFCTL.VHD
-- Created     : Thu Mar 30 22:19 2006
--
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--
--  Description : Double buffer memory controller
--
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library IEEE;
  use IEEE.STD_LOGIC_1164.all;

library WORK;
  use WORK.MDCT_PKG.all;

entity DBUFCTL is	
	port(	  
		clk          : in STD_LOGIC;  
		rst          : in STD_LOGIC;
    wmemsel      : in STD_LOGIC;
    rmemsel      : in STD_LOGIC;
    datareadyack : in STD_LOGIC;
      
    memswitchwr  : out STD_LOGIC;
    memswitchrd  : out STD_LOGIC;
    dataready    : out STD_LOGIC      
		);
end DBUFCTL;

architecture RTL of DBUFCTL is
 
  signal memswitchwr_reg : STD_LOGIC;
  signal memswitchrd_reg : STD_LOGIC;
  
begin

  memswitchwr  <= memswitchwr_reg;
  memswitchrd  <= memswitchrd_reg;
  
  memswitchrd_reg <= rmemsel;

  MEM_SWITCH : process(clk)
  begin
    if clk = '1' and clk'event then
      if rst = '1' then   
        memswitchwr_reg <= '0'; -- initially mem 1 is selected
        dataready       <= '0';
      else
  
        memswitchwr_reg <= wmemsel;
        
        if wmemsel /= memswitchwr_reg then
          dataready <= '1';
        end if;
        
        if datareadyack = '1' then
          dataready <= '0';
        end if;
     
      end if; 
    end if;
  end process;
  
end RTL;
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