--===========================================================================--
-- --
-- vdu8.vhd - Synthesizable Colour Video Display Unit for System09 --
-- --
--===========================================================================--
--
-- File name : vdu8.vhd
--
-- Purpose : Implements a text based Colour Video Display Unit for System09
-- Supports 2KByte Text buffer and 2KByte Attribute memory
-- Displays 80 characters across by 25 character rows
-- Characters are 8 pixels across x 16 lines down.
-- Character attribute bita for foreground and backgrond colour
-- 1 bit for each Blue Green and Red signal
-- Supports 2 x 8 chunky graphics character mode.
-- Uses Generic arguments for setting the video synchronization timing.
--
-- Dependencies : ieee.std_logic_1164
-- ieee.numeric_std
--
-- Uses : ram_2k (ram2k_b16.vhd) 2KByte Character & Attribute buffer
-- char_rom (char_rom2k_b16.vhd) 2KByte Character Generator ROM
--
-- Author : John E. Kent
--
-- Email : dilbert57 at the domain opencores.org
--
-- Web : http://opencores.org/project,system09
--
-- Description : Display Timing:
-- 800 pixels / line
-- 446 lines / frame
-- None interlaced
-- 25MHz pixel clock implies
-- 31.25 KHz line rate
-- 70.067 Hz frame rate
-- Timing settable by generics.
--
-- Display Size:
-- 80 characters across
-- 25 characters down.
--
-- Character Size:
-- 8 horizontal pixels across
-- 16 vertical scan lines down (2 scan lines/row)
--
-- Registers:
-- Base + 0 ASCII character register
-- Writing to this register writes an 8 bit byte
-- into the text buffer at the specified cursor position
-- Text Mode: ASCII Character (0 to 127)
-- Chunky Graphics Mode: B0 B1 (0 to 255)
-- B2 B3
-- B4 B5
-- B6 B7
-- Base + 1 Attibute bit (0 to 255)
-- Writing to the register writes an 8 bit byte
-- into the attribute buffer at the specified cursor position
-- B7 - 0 => Text Mode / 1 => Chunky Graphics Mode
-- B6 - 1 => Character Background Blue
-- B5 - 1 => Character Background Green
-- B4 - 1 => Character Background Red
-- B3 - 1 => Character Background & Foreground Alternates
-- B2 - 1 => Character Foreground Blue
-- B1 - 1 => Character Foreground Green
-- B0 - 1 => Character Foreground Red
-- Base + 2 Cursor Horizontal Position (0 to 79)
-- Base + 3 Cusror Vertical Position (0 to 24)
-- Base + 4 Vertical Scroll Offset (0 to 24)
-- Scrolls the display up by the specified number of character rows
--
-- Video Timing :
--
-- Horizontal 800 Pixels/ 25MHz Pixel Clock = 32usec Line period = 31.25 KHz Line Frequency
-- /--------------------------\_____________/---------------\______________/
-- 640 Pixels Display 16 Pixel FP 96 Pixel HS 48 Pixel BP
--
-- VGA_CLK_FREQ : integer := 25000000; -- HZ
-- VGA_HOR_FRONT_PORCH : integer := 16; -- PIXELS 0.64us (0.94us)
-- VGA_HOR_SYNC : integer := 96; -- PIXELS 3.84us (3.77us)
-- VGA_HOR_BACK_PORCH : integer := 48; -- PIXELS 1.92us (1.89us)
-- VGA_PIX_PER_CHAR : integer := 8; -- PIXELS 0.32us
-- VGA_HOR_CHARS : integer := 80; -- CHARACTERS 25.6us
--
-- Vertical 446 Lines * 32 usec Line rate = 14.272ms Frame Period = 70.07Hz Frame frequency
-- /---------------------------\____________/---------------\______________/
-- 400 Line Display 10 Line FP 2 Line VS 34 Line BP
--
-- VGA_VER_FRONT_PORCH : integer := 10; -- LINES 0.320ms
-- VGA_VER_SYNC : integer := 2; -- LINES 0.064ms
-- VGA_VER_BACK_PORCH : integer := 34; -- LINES 1.088ms
-- VGA_LIN_PER_CHAR : integer := 16; -- LINES 0.512ms
-- VGA_VER_CHARS : integer := 25; -- CHARACTERS 12.8ms
--
-- Copyright (C) 2003 - 2010 John Kent
--
-- 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 3 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, see <http://www.gnu.org/licenses/>.
--
--===========================================================================--
-- --
-- Revision History --
-- --
--===========================================================================--
--
-- Version Author Date Changes
--
-- 0.1 John Kent 2004-09-03 Initial release
--
-- 0.2 Bert Cuzeau 2007-01-16 Modified by for compliance and code cleanliness
-- The effort is not over.
-- There are still signal initialized, which is BAD.
--
-- 0.3 John Kent 2007-02-07 Added generics for VGA Timing
--
-- 0.4 John Kent 2010-07-03 Added GPL notice.
-- Updated description.
-- Rearranged Video Timing
--
Library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
--Library unisim;
-- use unisim.vcomponents.all;
--* @brief Synthesizable Colour Video Display Unit for System09
--*
--* @author Bert Cuzeau and John E. Kent
--* @version 0.4 from 2010-07-03
Entity vdu8 is
generic(
VGA_CLK_FREQ : integer := 25000000; -- HZ
VGA_HOR_CHARS : integer := 80; -- CHARACTERS 25.6us
VGA_HOR_CHAR_PIXELS : integer := 8; -- PIXELS 0.32us
VGA_HOR_FRONT_PORCH : integer := 16; -- PIXELS 0.64us
VGA_HOR_SYNC : integer := 96; -- PIXELS 3.84us
VGA_HOR_BACK_PORCH : integer := 48; -- PIXELS 1.92us
VGA_VER_CHARS : integer := 25; -- CHARACTERS 12.8ms
VGA_VER_CHAR_LINES : integer := 16; -- LINES 0.512ms
VGA_VER_FRONT_PORCH : integer := 10; -- LINES 0.320ms
VGA_VER_SYNC : integer := 2; -- LINES 0.064ms
VGA_VER_BACK_PORCH : integer := 34 -- LINES 1.088ms
);
port(
--+ control register interface
vdu_clk : in std_logic; -- 12.5/25 MHz CPU Clock
vdu_rst : in std_logic;
vdu_cs : in std_logic;
vdu_rw : in std_logic;
vdu_addr : in std_logic_vector(2 downto 0);
vdu_data_in : in std_logic_vector(7 downto 0);
vdu_data_out : out std_logic_vector(7 downto 0);
--+ vga port connections
vga_clk : in std_logic; -- 25MHz clock
vga_red_o : out std_logic;
vga_green_o : out std_logic;
vga_blue_o : out std_logic;
vga_hsync_o : out std_logic;
vga_vsync_o : out std_logic
);
end vdu8;
--* @brief Implements a text based Colour Video Display Unit for System09
--*
--* Supports 2KByte Text buffer and 2KByte Attribute memory.
--* Displays 80 characters across by 25 character rows.
--* Characters are 8 pixels across x 16 lines down.
--* Character attribute bits for foreground and backgrond colour.
--* 1 bit for each Blue Green and Red signal.
--* Supports 2 x 8 chunky graphics character mode.
--* Uses Generic arguments for setting the video synchronization timing.
--*
--* @author Bert Cuzeau and John E. Kent
--* @version 0.4 from 2010-07-03
Architecture RTL of vdu8 is
--
-- Synchronisation constants
--
-- Displayed Characters per row
constant HOR_DISP_CHR : integer := VGA_HOR_CHARS;
-- Last horizontal pixel displayed
constant HOR_DISP_END : integer := (HOR_DISP_CHR * VGA_HOR_CHAR_PIXELS) - 1;
-- Start of horizontal synch pulse
constant HOR_SYNC_BEG : integer := HOR_DISP_END + VGA_HOR_FRONT_PORCH;
-- End of Horizontal Synch pulse
constant HOR_SYNC_END : integer := HOR_SYNC_BEG + VGA_HOR_SYNC;
-- Last pixel in scan line
constant HOR_SCAN_END : integer := HOR_SYNC_END + VGA_HOR_BACK_PORCH;
-- Displayed Characters per Column
constant VER_DISP_CHR : integer := VGA_VER_CHARS;
-- last row displayed
constant VER_DISP_END : integer := (VER_DISP_CHR * VGA_VER_CHAR_LINES) - 1;
-- start of vertical synch pulse
constant VER_SYNC_BEG : integer := VER_DISP_END + VGA_VER_FRONT_PORCH;
-- end of vertical synch pulse
constant VER_SYNC_END : integer := VER_SYNC_BEG + VGA_VER_SYNC;
-- Last scan row in the frame
constant VER_SCAN_END : integer := VER_SYNC_END + VGA_VER_BACK_PORCH;
signal horiz_sync : std_logic := '1';
signal vert_sync : std_logic := '1';
signal cursor_on_v : std_logic;
signal cursor_on_h : std_logic;
signal video_on_v : std_logic := '0';
signal video_on_h : std_logic := '0';
signal h_count : std_logic_vector(9 downto 0) := (others=>'0');
signal v_count : std_logic_vector(8 downto 0) := (others=>'0'); -- 0 to VER_SCAN_END
signal blink_count : std_logic_vector(22 downto 0):= (others=>'1');
--
-- Character generator ROM
--
signal char_addr : std_logic_vector(10 downto 0);
signal char_data_out : std_logic_vector(7 downto 0);
--
-- Control Registers
--
signal reg_character : std_logic_vector(7 downto 0);
signal reg_colour : std_logic_vector(7 downto 0);
signal reg_hcursor : std_logic_vector(6 downto 0); -- 80 columns
signal reg_vcursor : std_logic_vector(4 downto 0); -- 25 rows
signal reg_voffset : std_logic_vector(4 downto 0); -- 25 rows
--
-- Video Shift register
--
signal vga_shift : std_logic_vector(7 downto 0);
signal vga_fg_colour : std_logic_vector(2 downto 0);
signal vga_bg_colour : std_logic_vector(2 downto 0);
signal cursor_on : std_logic;
signal cursor_on1 : std_logic;
signal video_on : std_logic := '0';
signal video_on1 : std_logic := '0';
signal video_on2 : std_logic := '0';
--
-- vga character ram access bus
--
signal col_addr : std_logic_vector(6 downto 0) := (others=>'0'); -- 0 to 79
signal row_addr : unsigned(5 downto 0) := (others=>'0'); -- 0 to 49 (25 * 2 -1)
signal col1_addr : std_logic_vector(6 downto 0) := (others=>'0'); -- 0 to 79
signal row1_addr : unsigned(5 downto 0) := (others=>'0'); -- 0 to 49 (25 * 2 - 1)
signal hor_addr : std_logic_vector(6 downto 0) := (others=>'0'); -- 0 to 79
signal ver_addr : std_logic_vector(6 downto 0) := (others=>'0'); -- 0 to 124
signal vga0_cs : std_logic;
signal vga0_rw : std_logic;
signal vga1_cs : std_logic;
signal vga1_rw : std_logic;
signal vga2_cs : std_logic;
signal vga2_rw : std_logic;
signal vga_cs : std_logic;
signal vga_rw : std_logic;
signal vga_addr : std_logic_vector(10 downto 0) := (others=>'0'); -- 2K byte character buffer
signal vga_data_out : std_logic_vector(7 downto 0);
signal attr_data_out : std_logic_vector(7 downto 0);
--
-- Character write handshake signals
--
signal req_write : std_logic; -- request character write
signal ack_write : std_logic;
--* Block Ram Character gen
component char_rom
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (10 downto 0);
data_in : in std_logic_vector (7 downto 0);
data_out : out std_logic_vector (7 downto 0)
);
end component;
component ram_2k
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (10 downto 0);
data_in : in std_logic_vector (7 downto 0);
data_out : out std_logic_vector (7 downto 0)
);
end component;
begin
--* instantiate Character generator ROM
vdu_char_rom : char_rom port map(
clk => vga_clk,
rst => vdu_rst,
cs => '1',
rw => '1',
addr => char_addr,
data_in => "00000000",
data_out => char_data_out
);
--* Character buffer RAM
char_buff_ram : ram_2k port map(
clk => vga_clk,
rst => vdu_rst,
cs => vga_cs,
rw => vga_rw,
addr => vga_addr,
data_in => reg_character,
data_out => vga_data_out
);
--* Attribute buffer RAM
attr_buff_ram : ram_2k port map(
clk => vga_clk,
rst => vdu_rst,
cs => vga_cs,
rw => vga_rw,
addr => vga_addr,
data_in => reg_colour,
data_out => attr_data_out
);
--* CPU Write interface
vga_cpu_write : process(vdu_clk, vdu_rst)
begin
if vdu_rst = '1' then
reg_character <= "00000000";
reg_colour <= "00000111";
reg_hcursor <= "0000000";
reg_vcursor <= "00000";
reg_voffset <= "00000";
req_write <= '0';
elsif vdu_clk'event and vdu_clk = '0' then
if (vdu_cs = '1') and (vdu_rw = '0') then
case vdu_addr is
when "000" =>
reg_character <= vdu_data_in;
req_write <= '1';
when "001" =>
reg_colour <= vdu_data_in;
when "010" =>
reg_hcursor <= vdu_data_in(6 downto 0);
when "011" =>
reg_vcursor <= vdu_data_in(4 downto 0);
when others =>
reg_voffset <= vdu_data_in(4 downto 0);
end case;
else
if (req_write = '1') and (ack_write = '1') then
req_write <= '0';
else
req_write <= req_write;
end if;
end if;
end if;
end process;
--* CPU Read interface
vga_cpu_read : process(vdu_addr, vdu_cs,
reg_character, reg_colour,
reg_hcursor, reg_vcursor, reg_voffset)
begin
case vdu_addr is
when "000" =>
vdu_data_out <= reg_character;
when "001" =>
vdu_data_out <= reg_colour;
when "010" =>
vdu_data_out <= "0" & reg_hcursor;
when "011" =>
vdu_data_out <= "000" & reg_vcursor;
when others =>
vdu_data_out <= "000" & reg_voffset;
end case;
end process;
--* Video memory access
vga_addr_proc : process(vga_clk, vdu_rst)
begin
if vdu_rst = '1' then
vga0_cs <= '0';
vga0_rw <= '1';
row_addr <= "000000";
col_addr <= "0000000";
--
vga1_cs <= '0';
vga1_rw <= '1';
row1_addr <= "000000";
col1_addr <= "0000000";
--
vga2_cs <= '0';
vga2_rw <= '1';
ver_addr <= "0000000";
hor_addr <= "0000000";
--
vga_cs <= '0';
vga_rw <= '1';
vga_addr <= "00000000000";
elsif vga_clk'event and vga_clk = '0' then
--
-- on h_count = 0 initiate character write.
-- all other cycles are reads.
--
case h_count(2 downto 0) is
when "000" => -- pipeline character write
vga0_cs <= req_write;
vga0_rw <= '0';
col_addr <= reg_hcursor(6 downto 0);
row_addr <= unsigned("0" & reg_vcursor(4 downto 0)) + unsigned("0" & reg_voffset(4 downto 0));
when others => -- other 6 cycles free
vga0_cs <= '1';
vga0_rw <= '1';
col_addr <= h_count(9 downto 3);
row_addr <= unsigned("0" & v_count(8 downto 4)) + unsigned("0" & reg_voffset(4 downto 0));
end case;
--
-- on vga_clk + 1 round off row address
--
vga1_cs <= vga0_cs;
vga1_rw <= vga0_rw;
if row_addr < VER_DISP_CHR then
row1_addr <= row_addr;
else
row1_addr <= row_addr - VER_DISP_CHR;
end if;
col1_addr <= col_addr;
--
-- on vga_clk + 2 calculate vertical address
--
vga2_cs <= vga1_cs;
vga2_rw <= vga1_rw;
ver_addr <= std_logic_vector(unsigned("00" & row1_addr(4 downto 0)) + unsigned(row1_addr(4 downto 0) & "00"));
hor_addr <= col1_addr;
--
-- on vga_clk + 3 calculate memory address
--
vga_cs <= vga2_cs;
vga_rw <= vga2_rw;
vga_addr <= std_logic_vector(unsigned("0000" & hor_addr) + unsigned(ver_addr & "0000"));
end if;
end process;
--* Video shift register
vga_shift_proc : process( vga_clk, vdu_rst)
begin
if vdu_rst = '1' then
ack_write <= '0';
video_on2 <= '0';
video_on <= '0';
cursor_on <= '0';
vga_bg_colour <= "000";
vga_fg_colour <= "111";
vga_shift <= "00000000";
vga_red_o <= '0';
vga_green_o <= '0';
vga_blue_o <= '0';
-- Put all video signals through DFFs to elminate any delays that cause a blurry image
elsif vga_clk'event and vga_clk = '0' then
-- Character Data valid on 1 count
if h_count(2 downto 0) = "000" then
if (req_write = '1') and (ack_write = '0') then
ack_write <= '1';
elsif (req_write = '0') and (ack_write = '1') then
ack_write <= '0';
else
ack_write <= ack_write;
end if;
video_on2 <= video_on1;
video_on <= video_on2;
cursor_on <= (cursor_on1 or attr_data_out(3)) and blink_count(22);
vga_fg_colour <= attr_data_out(2 downto 0);
vga_bg_colour <= attr_data_out(6 downto 4);
if attr_data_out(7) = '0' then
vga_shift <= char_data_out;
else
case v_count(3 downto 2) is
when "00" =>
vga_shift(7 downto 4) <= vga_data_out(0) & vga_data_out(0) & vga_data_out(0) & vga_data_out(0);
vga_shift(3 downto 0) <= vga_data_out(1) & vga_data_out(1) & vga_data_out(1) & vga_data_out(1);
when "01" =>
vga_shift(7 downto 4) <= vga_data_out(2) & vga_data_out(2) & vga_data_out(2) & vga_data_out(2);
vga_shift(3 downto 0) <= vga_data_out(3) & vga_data_out(3) & vga_data_out(3) & vga_data_out(3);
when "10" =>
vga_shift(7 downto 4) <= vga_data_out(4) & vga_data_out(4) & vga_data_out(4) & vga_data_out(4);
vga_shift(3 downto 0) <= vga_data_out(5) & vga_data_out(5) & vga_data_out(5) & vga_data_out(5);
when others =>
vga_shift(7 downto 4) <= vga_data_out(6) & vga_data_out(6) & vga_data_out(6) & vga_data_out(6);
vga_shift(3 downto 0) <= vga_data_out(7) & vga_data_out(7) & vga_data_out(7) & vga_data_out(7);
end case;
end if;
else
vga_shift <= vga_shift(6 downto 0) & '0';
end if;
--
-- Colour mask is
-- 7 6 5 4 3 2 1 0
-- X BG BB BR X FG FB FR
--
if vga_shift(7) = (not cursor_on) then
vga_red_o <= video_on and vga_fg_colour(0);
vga_green_o <= video_on and vga_fg_colour(1);
vga_blue_o <= video_on and vga_fg_colour(2);
else
vga_red_o <= video_on and vga_bg_colour(0);
vga_green_o <= video_on and vga_bg_colour(1);
vga_blue_o <= video_on and vga_bg_colour(2);
end if;
end if;
end process;
--* Sync generator & timing process
--* Generate Horizontal and Vertical Timing Signals for Video Signal
vga_sync : process(vga_clk)
begin
if vga_clk'event and vga_clk = '0' then
--
-- H_count counts pixels (640 + extra time for sync signals)
--
-- Horiz_sync -----------------------------__________--------
-- H_count 0 640 659 755 799
--
if unsigned(h_count) = HOR_SCAN_END then
h_count <= (others=>'0');
else
h_count <= std_logic_vector(unsigned(h_count) + 1);
end if;
--
-- Generate Horizontal Sync Signal using H_count
--
if unsigned(h_count) = HOR_SYNC_BEG then
horiz_sync <= '0';
elsif unsigned(h_count) = HOR_SYNC_END then
horiz_sync <= '1';
else
horiz_sync <= horiz_sync;
end if;
--
-- V_count counts rows of pixels
-- 400 lines + extra time for sync signals
-- 25 rows * 16 scan lines
--
-- Vert_sync ---------------------------------_______------------
-- V_count 0 400 413 414 444
--
if (unsigned(v_count) = VER_SCAN_END) and (unsigned(h_count) = HOR_SCAN_END) then
v_count <= "000000000";
elsif unsigned(h_count) = HOR_SYNC_END then
v_count <= std_logic_vector(unsigned(v_count) + 1);
end if;
--
-- Generate Vertical Sync Signal using V_count
--
if unsigned(v_count) = VER_SYNC_BEG then
vert_sync <= '0';
elsif unsigned(v_count) = VER_SYNC_END then
vert_sync <= '1';
else
vert_sync <= vert_sync;
end if;
-- Generate Video on Screen Signals for Pixel Data
if unsigned(h_count) = HOR_SCAN_END then
video_on_h <= '1';
elsif unsigned(h_count) = HOR_DISP_END then
video_on_h <= '0';
else
video_on_h <= video_on_h;
end if;
if unsigned(v_count) = VER_SCAN_END then
video_on_v <= '1';
elsif unsigned(v_count) = VER_DISP_END then
video_on_v <= '0';
else
video_on_v <= video_on_v;
end if;
if h_count(9 downto 3) = reg_hcursor(6 downto 0) then
cursor_on_h <= '1';
else
cursor_on_h <= '0';
end if;
if (v_count(8 downto 4) = reg_vcursor(4 downto 0)) then
cursor_on_v <= '1';
else
cursor_on_v <= '0';
end if;
-- cursor_on is only active when on selected character
blink_count <= std_logic_vector(unsigned(blink_count) + 1);
end if;
end process;
-- video_on is high only when RGB data is displayed
vga_hsync_o <= horiz_sync;
vga_vsync_o <= vert_sync;
video_on1 <= video_on_H and video_on_V;
cursor_on1 <= cursor_on_h and cursor_on_v;
--
-- Here to look up character ROM
-- This will take one clock cycle
-- and should be performed on h_count = "111"
--
char_addr(10 downto 4) <= vga_data_out(6 downto 0);
char_addr(3 downto 0) <= v_count(3 downto 0);
end RTL;