Subversion Repositories lq057q3dc02

------------------------------------------------------------------------------

-- Copyright (C) 2007 Jonathon W. Donaldson

--                    jwdonal a t opencores DOT org

--

--  This program is free software; you can redistribute it and/or modify

--  it under the terms of the GNU General Public License as published by

--  the Free Software Foundation; either version 2 of the License, or

--  (at your option) any later version.

--

--  This program is distributed in the hope that it will be useful,

--  but WITHOUT ANY WARRANTY; without even the implied warranty of

--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

--  GNU General Public License for more details.

--

--  You should have received a copy of the GNU General Public License

--  along with this program; if not, write to the Free Software

--  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

--

------------------------------------------------------------------------------

--

-- $Id: enab_control.vhd,v 1.1 2008-11-07 00:48:12 jwdonal Exp $

--

-- Description:

--  This file controls ENAB.  ENAB is dependent upon both HSYNCx, VSYNCx, and

--  the number of CLK_LCD cycles that have passed.  ENAB "tells" (i.e.

--  "enables") the shift registers inside the LCD to start accepting data.

--

-- Structure:

--   - xupv2p.ucf

--   - components.vhd

--   - lq057q3dc02_tb.vhd

--   - lq057q3dc02.vhd

--     - dcm_sys_to_lcd.xaw

--     - video_controller.vhd

--       - enab_control.vhd

--       - hsyncx_control.vhd

--       - vsyncx_control.vhd

--       - clk_lcd_cyc_cntr.vhd

--     - image_gen_bram.vhd

--       - image_gen_bram_red.xco

--       - image_gen_bram_green.xco

--       - image_gen_bram_blue.xco

--

------------------------------------------------------------------------------

--

-- Naming Conventions:

--   active low signals                                       "*x"

--   clock signal                                             "CLK_*"

--   reset signal                                             "RST"

--   generic/constant                                         "C_*"

--   user defined type                                        "TYPE_*"

--   state machine next state                                 "*_ns"

--   state machine current state                              "*_cs""

--   pipelined signals                                        "*_d#"

--   register delay signals                                   "*_p#"

--   signal                                                   "*_sig"

--   variable                                                 "*_var"

--   storage register                                         "*_reg"

--   clock enable signals                                     "*_ce"

--   internal version of output port used as connecting wire  "*_wire"

--   input/output port                                        "ALL_CAPS"

--   process                                                  "*_PROC"

--

------------------------------------------------------------------------------

--////////////////////--

-- LIBRARY INCLUSIONS --

--////////////////////--

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.STD_LOGIC_ARITH.ALL;

USE IEEE.STD_LOGIC_UNSIGNED.ALL;

--////////////////////--

-- ENTITY DECLARATION --

--////////////////////--

ENTITY enab_control IS

  generic (

    C_VSYNC_TVS,

    C_CLK_LCD_CYC_NUM_WIDTH,

    C_ENAB_TEP,

    C_ENAB_THE : POSITIVE

  );

  port (

    RSTx,

    CLK_LCD : IN std_logic;

    CLK_LCD_CYC_NUM : IN std_logic_vector(C_CLK_LCD_CYC_NUM_WIDTH-1 downto 0);

    ENAB : OUT std_logic

  );

END ENTITY enab_control;

--////////////////////////--

-- ARCHITECTURE OF ENTITY --

--////////////////////////--

ARCHITECTURE enab_control_arch OF enab_control IS

begin

  ------------------------------------------------------------------

  --  Process Description:

  --    This process enables/disables the ENAB output signal depending

  --    on the value of the pixel/enab cycle counter and the user-defined

  --    timing parameters.

  --  

  --  Inputs:

  --    RSTx

  --    CLK_LCD

  --  

  --  Outputs:

  --    ENAB

  --

  --  Notes:

  --    N/A

  ------------------------------------------------------------------

  ENAB_cntrl_PROC : process( RSTx, CLK_LCD )

  begin

    if( RSTx = '0' ) then

      ENAB <= '0';

    elsif( CLK_LCD'event and CLK_LCD = '1' ) then

      if( CLK_LCD_CYC_NUM >= (C_ENAB_THE - 1) and --start

          CLK_LCD_CYC_NUM < (C_ENAB_THE + C_ENAB_TEP - 1) ) then --stop

        ENAB <= '1'; --active

      else

        ENAB <= '0';

      end if;

    end if;

  end process ENAB_cntrl_PROC;

END ARCHITECTURE enab_control_arch;