How to make screen without color and image if no pen points it in VHDL for a VmodTFT?

Code VHDL - [expand]
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
--use IEEE.unsigned.ALL;
 
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;
 
library digilent;
use digilent.video.ALL;
 
-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
library UNISIM;
use UNISIM.VComponents.all;
 
entity TFTCtl is
   Port (
        CLK_I : in STD_LOGIC;
        CLK_180_I : in STD_LOGIC;
        RST_I : in STD_LOGIC;
        
        X_I: in integer;
        Y_I: in integer;
        Z_I: in STD_LOGIC_VECTOR (11 downto 0);
        WE_I : in std_logic;
        WR_CLK : in std_logic;
        
        R_O : out  STD_LOGIC_VECTOR (7 downto 0);
        G_O : out  STD_LOGIC_VECTOR (7 downto 0);
        B_O : out  STD_LOGIC_VECTOR (7 downto 0);
        DE_O : out  STD_LOGIC;
        CLK_O : out  STD_LOGIC;
        DISP_O : out  STD_LOGIC;
        BKLT_O : out  STD_LOGIC; --PWM backlight control
        VDDEN_O : out STD_LOGIC;
        
        MSEL_I : in STD_LOGIC_VECTOR(3 downto 0) -- Mode selection
    );
end TFTCtl;
 
architecture Behavioral of TFTCtl is
    constant CLOCKFREQ : natural := 9; --MHZ
    constant TPOWERUP : natural := 1; --ms
    constant TPOWERDOWN : natural := 1; --ms
    constant TLEDWARMUP : natural := 200; --ms
    constant TLEDCOOLDOWN : natural := 200; --ms
    constant TLEDWARMUP_CYCLES : natural := natural(CLOCKFREQ*TLEDWARMUP*1000);
    constant TLEDCOOLDOWN_CYCLES : natural := natural(CLOCKFREQ*TLEDCOOLDOWN*1000);
    constant TPOWERUP_CYCLES : natural := natural(CLOCKFREQ*TPOWERUP*1000);
    constant TPOWERDOWN_CYCLES : natural := natural(CLOCKFREQ*TPOWERDOWN*1000); 
 
    signal waitCnt : natural range 0 to TLEDCOOLDOWN_CYCLES := 0;
    signal waitCntEn : std_logic;
 
   type state_type is (stOff, stPowerUp, stLEDWarmup, stLEDCooldown, stPowerDown, stOn); 
   signal state, nstate : state_type := stPowerDown;
 
    signal cntDyn: integer range 0 to 2**28-1;
    signal VtcHCnt: integer;
    signal VtcVCnt: integer;
    signal VtcRst, VtcVde, VtcHs, VtcVs : STD_LOGIC;
    signal int_Bklt, int_De, clkStop : std_logic := '0';
    signal int_R, int_G, int_B : std_logic_vector(7 downto 0);
    
    signal reg_X, reg_Y : natural;
    signal reg_WE : std_logic;
 
    --video ROM data and address bus
    constant FB_COLOR_DEPTH : natural := 2;
 
    signal vram_data, reg_wrdata: std_logic_vector (FB_COLOR_DEPTH-1 downto 0);
    signal vram_addr, vram_wraddr : INTEGER range 0 to H_480_272p_AV*V_480_272p_AV-1;
    type vramt is array (0 to H_480_272p_AV*V_480_272p_AV-1) of 
        std_logic_vector (FB_COLOR_DEPTH-1 downto 0);
    signal vram : vramt := (others => (others => '0'));
    signal vram_we : std_logic;
    attribute RAM_STYLE : string;
    attribute RAM_STYLE of vram: signal is "BLOCK";
begin
 
----------------------------------------------------------------------------------
-- Video Timing Controller
-- Generates horizontal and vertical sync and video data enable signals.
----------------------------------------------------------------------------------
    Inst_VideoTimingCtl: entity digilent.VideoTimingCtl PORT MAP (
        PCLK_I => CLK_I,
        RSEL_I => R480_272P, --VmodTFT Resolution only
        RST_I => VtcRst,
        VDE_O => VtcVde,
        HS_O => VtcHs,
        VS_O => VtcVs,
        HCNT_O => VtcHCnt,
        VCNT_O => VtcVCnt
    );
    VtcRst <= '0';
    
----------------------------------------------------------------------------------
-- VRAM address counter
----------------------------------------------------------------------------------
process (CLK_I)
begin
    if Rising_Edge(CLK_I) then
        --delay DE to account for VRAM registered output delay
        int_De <= VtcVde;
        
        if (VtcRst = '1') then
            vram_addr <= 0;
        else
            if (VtcVde = '1') then
                if (vram_addr = H_480_272p_AV*V_480_272p_AV-1) then
                    vram_addr <= 0;
                else
                    vram_addr <= vram_addr + 1;
                end if;
            end if;
        end if;
    end if;
end process;
 
process (WR_CLK)
begin
   if Rising_Edge(WR_CLK) then
        if (X_I >= 0 and X_I < H_480_272p_AV and
             Y_I >= 0 and Y_I < V_480_272p_AV) then
            vram_we <=  WE_I;
        else
            vram_we <= '0';
        end if;
        vram_wraddr <= (Y_I)*H_480_272p_AV + X_I;
        --color intensity based on touch pressure
        if (Z_I < x"200") then
            reg_wrdata <= "11";
        elsif (Z_I < x"300") then
            reg_wrdata <= "10";
        else
            reg_wrdata <= "01";
        end if;
   end if;
end process;
 
----------------------------------------------------------------------------------
-- VRAM registered output
----------------------------------------------------------------------------------
process (CLK_I)
begin
    if Rising_Edge(CLK_I) then
        vram_data <= vram(vram_addr);
    end if;
end process;
 
process (WR_CLK)
begin
   if Rising_Edge(WR_CLK) then
      if (vram_we = '1') then
            vram(vram_wraddr) <= reg_wrdata;
        end if;
   end if;
end process;
 
----------------------------------------------------------------------------------
-- Screen divided into Red, Green and Blue-only thirds
----------------------------------------------------------------------------------
int_R <= vram_data & "000000" when VtcHCnt < H_480_272p_AV/3 else
                (others => '0');
int_G <= vram_data & "000000" when VtcHCnt >= H_480_272p_AV/3 and VtcHCnt < H_480_272p_AV*2/3 else
                (others => '0');
int_B <= vram_data & "000000" when VtcHCnt >= H_480_272p_AV*2/3 else
                (others => '0');
 
----------------------------------------------------------------------------------
-- Backlight intensity control
----------------------------------------------------------------------------------  
    Inst_PWM: entity digilent.PWM 
    generic map (
        C_CLK_I_FREQUENCY => 9, -- in MHZ
        C_PWM_FREQUENCY => 25000, -- in Hz
        C_PWM_RESOLUTION => 3
    )
    PORT MAP(
        CLK_I => CLK_I,
        RST_I => '0',
        PWM_O => int_Bklt,
        DUTY_FACTOR_I => MSEL_I(2 downto 0)
    );
 
----------------------------------------------------------------------------------
-- LCD Power Sequence
----------------------------------------------------------------------------------  
--LCD & backlight power 
VDDEN_O <= '0' when state = stOff or state = stPowerDown else
                '1';
--Display On/Off signal
DISP_O <=   '0' when state = stOff or state = stPowerUp or state = stPowerDown else
                '1';
--Interface signals
DE_O <= '0' when state = stOff or state = stPowerUp or state = stPowerDown else
                int_De;
R_O <= (others => '0') when state = stOff or state = stPowerUp or state = stPowerDown else
                int_R;
G_O <= (others => '0') when state = stOff or state = stPowerUp or state = stPowerDown else
                int_G;
B_O <= (others => '0') when state = stOff or state = stPowerUp or state = stPowerDown else
                int_B;
--Clock signal
clkStop <=  '1' when state = stOff or state = stPowerUp or state = stPowerDown else
                '0';
--Backlight adjust/enable
BKLT_O <=   int_Bklt when state = stOn else
                '0';
--Wait States
waitCntEn <= '1' when (state = stPowerUp or state = stLEDWarmup or state = stLEDCooldown or state = stPowerDown) and (state = nstate) else
                    '0';
                    
   SYNC_PROC: process (CLK_I)
   begin
      if (CLK_I'event and CLK_I = '1') then
         state <= nstate;
      end if;
   end process;             
 
   NEXT_STATE_DECODE: process (state, waitCnt, MSEL_I)
   begin
      nstate <= state;
      case (state) is
         when stOff =>
            if (MSEL_I(3) = '1' and RST_I = '0') then
               nstate <= stPowerUp;
            end if;
            when stPowerUp => --turn power on first
                if (waitCnt = TPOWERUP_CYCLES) then
               nstate <= stLEDWarmup;
            end if;
         when stLEDWarmup => --turn on interface signals
            if (waitCnt = TLEDWARMUP_CYCLES) then
               nstate <= stOn;
            end if;
         when stOn => --turn on backlight too
                if (MSEL_I(3) = '0' or RST_I = '1') then
                    nstate <= stLEDCooldown;
                end if;
            when stLEDCooldown =>
            if (waitCnt = TLEDCOOLDOWN_CYCLES) then
               nstate <= stPowerDown;
            end if;
            when stPowerDown => --turn off power last
                if (waitCnt = TPOWERDOWN_CYCLES) then
                    nstate <= stOff;
                end if;
      end case;      
   end process;
----------------------------------------------------------------------------------
-- Wait Counter
----------------------------------------------------------------------------------  
    process(CLK_I)
    begin
        if Rising_Edge(CLK_I) then
            if waitCntEn = '0' then
                waitCnt <= 0;
            else
                waitCnt <= waitCnt + 1;
            end if;
        end if;
    end process;
 
----------------------------------------------------------------------------------
-- Clock Forwarding done right
----------------------------------------------------------------------------------
    Inst_ODDR2_MCLK_FORWARD : ODDR2
   generic map(
      DDR_ALIGNMENT => "NONE", -- Sets output alignment to "NONE", "C0", "C1" 
      INIT => '0', -- Sets initial state of the Q output to '0' or '1'
      SRTYPE => "SYNC") -- Specifies "SYNC" or "ASYNC" set/reset
   port map (
      Q => CLK_O, -- 1-bit output data
      C0 => CLK_I, -- 1-bit clock input
      C1 => CLK_180_I, -- 1-bit clock input
      CE => '1',  -- 1-bit clock enable input
      D0 => '1',   -- 1-bit data input (associated with C0)
      D1 => '0',   -- 1-bit data input (associated with C1)
      R => clkStop, -- 1-bit clock reset
      S => '0'     -- 1-bit set input
   );   
end Behavioral;