Subversion Repositories z80soc

-- Z80SoC for Altera DE1
-- Ronivon Candido Costa
--
-- 2010 - 02 - 17 Update
-- Changed the entity to include signals for the char memory
-- The char memory is a dual port ram memory, and now
--     the char paterns can be modified by software.
-- 
--
library IEEE; 
use  IEEE.STD_LOGIC_1164.all; 
use  IEEE.STD_LOGIC_ARITH.all;
use  IEEE.STD_LOGIC_UNSIGNED.all;
 
ENTITY video is
        PORT(   CLOCK_25                : IN STD_LOGIC;
                        VRAM_DATA               : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
                        VRAM_ADDR               : OUT STD_LOGIC_VECTOR(13 DOWNTO 0);
                        VRAM_CLOCK              : OUT STD_LOGIC;
                        VRAM_WREN               : OUT STD_LOGIC;
                        CRAM_DATA               : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
                        CRAM_ADDR               : OUT STD_LOGIC_VECTOR(10 DOWNTO 0);
                        CRAM_WEB                : OUT STD_LOGIC;
                        VGA_R,
                        VGA_G,
                        VGA_B                   : OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
                        VGA_HS,
                        VGA_VS                  : OUT STD_LOGIC);
END video;

ARCHITECTURE A OF video IS

    use work.z80soc_pack.all;
        
        -- Added for VDU support
        constant vid_width                      : std_logic_vector := "001010000"; -- 80 columns
        signal Clock_video                      : std_logic;
        signal VGA_R_sig                        : std_logic_vector(3 downto 0);
        signal VGA_G_sig                        : std_logic_vector(3 downto 0);
        signal VGA_B_sig                        : std_logic_vector(3 downto 0);
        signal pixel_row_sig            : std_logic_vector(9 downto 0);
        signal pixel_column_sig         : std_logic_vector(9 downto 0);
        signal pixel_clock_sig          : std_logic;
        signal char_addr_sig            : std_logic_vector(7 downto 0);
        signal font_row_sig                     : std_logic_vector(2 downto 0);
        signal font_col_sig                     : std_logic_vector(2 downto 0);
        signal pixel_sig                        : std_logic;
        signal video_on_sig                     : std_logic;
        
        constant sv1                            : integer := 3 + pixelsxchar - 1;
        constant sv2                            : integer := 9 + pixelsxchar - 1;
        constant cv1                            : integer := 0 + pixelsxchar - 1;
        constant cv2                            : integer := 2 + pixelsxchar - 1;
        signal fix                                      : integer;
                
COMPONENT VGA_SYNC
        PORT(   clock_25Mhz                                             : IN    STD_LOGIC;
                        red, green, blue                                : IN    STD_LOGIC_VECTOR(3 DOWNTO 0);
                        red_out, green_out, blue_out    : OUT   STD_LOGIC_VECTOR(3 DOWNTO 0);
                        horiz_sync_out, vert_sync_out, 
                        video_on, pixel_clock                   : OUT   STD_LOGIC;
                        pixel_row, pixel_column                 : OUT   STD_LOGIC_VECTOR(9 DOWNTO 0));
END COMPONENT;
        
BEGIN
        
        VGA_R_sig <= "0000";
        VGA_G_sig <= "0000";
        VGA_B_sig <= pixel_sig & pixel_sig & pixel_sig & pixel_sig;
        
        -- Fonts ROM read
        -- Picks next letter for a 80 Columns x 30 Lines display
        VRAM_WREN <= '1';
        VRAM_CLOCK <= pixel_clock_sig;
        VRAM_ADDR <= pixel_row_sig(sv2 downto sv1) * conv_std_logic_vector(vid_cols,7) + pixel_column_sig(sv2 downto sv1);

        -- Fonts RAM read
        -- Takes the letter, calculates the position in the char memory to get the pixel pattern
        -- Plot the pixel in the video
        -- Using pixel_row(3 downto 1) has the effect of "shifting" (multiplying by 2)
        -- This will plot 2 pixels on video for every pixel defined on char memory
        CRAM_WEB <= '1';
        CRAM_ADDR <= VRAM_DATA & pixel_row_sig(cv2 downto cv1);
        fix <= 1 when pixelsxchar = 2 else 2;
        pixel_sig <= CRAM_DATA (CONV_INTEGER(NOT (pixel_column_sig(cv2 downto cv1) - fix)))  when 
                    ( (pixel_row_sig < (pixelsxchar * 8 * vid_lines)) and (pixel_column_sig < (pixelsxchar * 8 * vid_cols)) ) else 
                '0';
                        
        vga_sync_inst: VGA_SYNC 
                port map (
                        clock_25Mhz                     => CLOCK_25,
                        red                                     => VGA_R_sig,
                        green                           => VGA_G_sig,
                        blue                            => VGA_B_sig,
                        red_out                         => VGA_R,
                        green_out                       => VGA_G,
                        blue_out                        => VGA_B,
                        horiz_sync_out          => VGA_HS,
                        vert_sync_out           => VGA_VS,
                        video_on                        => video_on_sig,
                        pixel_clock                     => pixel_clock_sig,
                        pixel_row                       => pixel_row_sig,
                        pixel_column            => pixel_column_sig
        );
                
END A;