Subversion Repositories z80soc

-------------------------------------------------------------------------------------------------
-- Z80_Soc (Z80 System on Chip)
--
-- Version history:
-------------------
-- version 0.6 for for Altera DE1
-- Release Date: 2008 / 05 / 21
--
-- Version 0.5 Beta for Altera DE1
-- Developer: Ronivon Candido Costa
-- Release Date: 2008 / 04 / 16
--
-- Based on the T80 core: http://www.opencores.org/projects.cgi/web/t80
-- This version developed and tested on: Altera DE1 Development Board
--
-- Peripherals configured (Using Ports):
--
--	16 KB Internal ROM	Read		(0x0000h - 0x3FFFh)
--	08 KB INTERNAL VRAM	Write		(0x4000h - 0x5FFFh)
-- 	32 KB External SRAM	Read/Write	(0x8000h - 0xFFFFh)
--	08 Green Leds		Out		(Port 0x01h)
--	08 Red Leds			Out		(Port 0x02h)
--	04 Seven Seg displays	Out		(Ports 0x10h and 0x11h)
--	36 Pins GPIO0 		In/Out	(Ports 0xA0h, 0xA1h, 0xA2h, 0xA3h, 0xA4h, 0xC0h)
--	36 Pins GPIO1 		In/Out	(Ports 0xB0h, 0xB1h, 0xB2h, 0xB3h, 0xB4h, 0xC1h)
--	08 Switches			In		(Port 0x20h)
--	04 Push buttons		In		(Port 0x30h)
--	01 PS/2 keyboard 		In		(Port 0x80h)
--	01 Video write port	In		(Port 0x90h)
--
--  Revision history:
--
-- 2008/05/23 - Modified RAM layout to support new and future improvements
--            - Added port 0x90 to write a character to video.
--            - Cursor x,y automatically updated after writing to port 0x90
--            - Added port 0x91 for video cursor X
--            - Added port 0x92 for video cursor Y
--	          - Updated ROM to demonstrate how to use these new resources
--            - Changed ROM to support 14 bit addresses (16 Kb)
--
-- 2008/05/12 - Added support for the Rotary Knob
--            - ROT_CENTER push button (Knob) reserved for RESET
--            - The four push buttons are now available for the user (Port 0x30)
--
-- 2008/05/11 - Fixed access to RAM and VRAM,
--              Released same ROM version for DE1 and S3E
--
-- 2008/05/01 - Added LCD support for Spartan 3E
--
-- 2008/04(21 - Release of Version 0.5-S3E-Beta for Diligent Spartan 3E
--
--	2008/04/17 - Added Video support for 40x30 mode
--
-- 2008/04/16 - Release of Version 0.5-DE1-Beta for Altera DE1
--
-- TO-DO:
-- - Implement hardware control for the A/D and IO pins
-- - Monitor program to introduce Z80 Assmebly codes and run
-- - Serial communication, to download assembly code from PC
-- - Add hardware support for 80x40 Video out
-- - SD/MMC card interface to read/store data and programs
-------------------------------------------------------------------------------------------------
 
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;
 
entity 	TOP_DE1 is
	port(
 
    -- Clocks
    CLOCK_27,                                      -- 27 MHz
    CLOCK_50,                                      -- 50 MHz
    EXT_CLOCK : in std_logic;                      -- External Clock
 
    -- Buttons and switches
    KEY : in std_logic_vector(3 downto 0);         -- Push buttons
    SW : in std_logic_vector(9 downto 0);          -- Switches
 
    -- LED displays
    HEX0, HEX1, HEX2, HEX3                         -- 7-segment displays
			: out std_logic_vector(6 downto 0);
    LEDG : out std_logic_vector(7 downto 0);       -- Green LEDs
    LEDR : out std_logic_vector(9 downto 0);       -- Red LEDs
 
    -- RS-232 interface
    UART_TXD : out std_logic;                      -- UART transmitter   
    UART_RXD : in std_logic;                       -- UART receiver
 
    -- IRDA interface
 
    -- IRDA_TXD : out std_logic;                      -- IRDA Transmitter
    IRDA_RXD : in std_logic;                       -- IRDA Receiver
 
    -- SDRAM
    DRAM_DQ : inout std_logic_vector(15 downto 0); -- Data Bus
    DRAM_ADDR : out std_logic_vector(11 downto 0); -- Address Bus    
    DRAM_LDQM,                                     -- Low-byte Data Mask 
    DRAM_UDQM,                                     -- High-byte Data Mask
    DRAM_WE_N,                                     -- Write Enable
    DRAM_CAS_N,                                    -- Column Address Strobe
    DRAM_RAS_N,                                    -- Row Address Strobe
    DRAM_CS_N,                                     -- Chip Select
    DRAM_BA_0,                                     -- Bank Address 0
    DRAM_BA_1,                                     -- Bank Address 0
    DRAM_CLK,                                      -- Clock
    DRAM_CKE : out std_logic;                      -- Clock Enable
 
    -- FLASH
    FL_DQ : inout std_logic_vector(7 downto 0);      -- Data bus
    FL_ADDR : out std_logic_vector(21 downto 0);     -- Address bus
    FL_WE_N,                                         -- Write Enable
    FL_RST_N,                                        -- Reset
    FL_OE_N,                                         -- Output Enable
    FL_CE_N : out std_logic;                         -- Chip Enable
 
    -- SRAM
    SRAM_DQ : inout std_logic_vector(15 downto 0); -- Data bus 16 Bits
    SRAM_ADDR : out std_logic_vector(17 downto 0); -- Address bus 18 Bits
    SRAM_UB_N,                                     -- High-byte Data Mask 
    SRAM_LB_N,                                     -- Low-byte Data Mask 
    SRAM_WE_N,                                     -- Write Enable
    SRAM_CE_N,                                     -- Chip Enable
    SRAM_OE_N : out std_logic;                     -- Output Enable
 
    -- SD card interface
    SD_DAT : in std_logic;      -- SD Card Data      SD pin 7 "DAT 0/DataOut"
    SD_DAT3 : out std_logic;    -- SD Card Data 3    SD pin 1 "DAT 3/nCS"
    SD_CMD : out std_logic;     -- SD Card Command   SD pin 2 "CMD/DataIn"
    SD_CLK : out std_logic;     -- SD Card Clock     SD pin 5 "CLK"
 
    -- USB JTAG link
    TDI,                        -- CPLD -> FPGA (data in)
    TCK,                        -- CPLD -> FPGA (clk)
    TCS : in std_logic;         -- CPLD -> FPGA (CS)
    TDO : out std_logic;        -- FPGA -> CPLD (data out)
 
    -- I2C bus
    I2C_SDAT : inout std_logic; -- I2C Data
    I2C_SCLK : out std_logic;   -- I2C Clock
 
    -- PS/2 port
    PS2_DAT,                    -- Data
    PS2_CLK : inout std_logic;     -- Clock
 
    -- VGA output
    VGA_HS,                                             -- H_SYNC
    VGA_VS : out std_logic;                             -- SYNC
    VGA_R,                                              -- Red[3:0]
    VGA_G,                                              -- Green[3:0]
    VGA_B : out std_logic_vector(3 downto 0);           -- Blue[3:0]
 
    -- Audio CODEC
    AUD_ADCLRCK : inout std_logic;                      -- ADC LR Clock
    AUD_ADCDAT : in std_logic;                          -- ADC Data
    AUD_DACLRCK : inout std_logic;                      -- DAC LR Clock
    AUD_DACDAT : out std_logic;                         -- DAC Data
    AUD_BCLK : inout std_logic;                         -- Bit-Stream Clock
    AUD_XCK : out std_logic;                            -- Chip Clock
 
    -- General-purpose I/O
    GPIO_0,                                      -- GPIO Connection 0
    GPIO_1 : inout std_logic_vector(35 downto 0) -- GPIO Connection 1	
);
end TOP_DE1;
 
architecture rtl of TOP_DE1 is
 
	component T80se
	generic(
		Mode : integer := 0;	-- 0 => Z80, 1 => Fast Z80, 2 => 8080, 3 => GB
		T2Write : integer := 1;	-- 0 => WR_n active in T3, /=0 => WR_n active in T2
		IOWait : integer := 1	-- 0 => Single cycle I/O, 1 => Std I/O cycle
	);
	port(
		RESET_n	: in std_logic;
		CLK_n		: in std_logic;
		CLKEN		: in std_logic;
		WAIT_n	: in std_logic;
		INT_n		: in std_logic;
		NMI_n		: in std_logic;
		BUSRQ_n	: in std_logic;
		M1_n		: out std_logic;
		MREQ_n	: out std_logic;
		IORQ_n	: out std_logic;
		RD_n		: out std_logic;
		WR_n		: out std_logic;
		RFSH_n	: out std_logic;
		HALT_n	: out std_logic;
		BUSAK_n	: out std_logic;
		A			: out std_logic_vector(15 downto 0);
		DI			: in std_logic_vector(7 downto 0);
		DO			: out std_logic_vector(7 downto 0)
	);
	end component;
 
	component rom
	port (
		Clk	: in std_logic;
		A	: in std_logic_vector(13 downto 0);
		D	: out std_logic_vector(7 downto 0));
	end component;
 
	component Clock_357Mhz
	PORT (
		clock_50Mhz				: IN	STD_LOGIC;
		clock_357Mhz			: OUT	STD_LOGIC);
	end component;
 
	component clk_div
	PORT
	(
		clock_25Mhz				: IN	STD_LOGIC;
		clock_1MHz				: OUT	STD_LOGIC;
		clock_100KHz			: OUT	STD_LOGIC;
		clock_10KHz				: OUT	STD_LOGIC;
		clock_1KHz				: OUT	STD_LOGIC;
		clock_100Hz				: OUT	STD_LOGIC;
		clock_10Hz				: OUT	STD_LOGIC;
		clock_1Hz				: OUT	STD_LOGIC);
	end component;
 
	component decoder_7seg
	port (
		NUMBER		: in   std_logic_vector(3 downto 0);
		HEX_DISP	: out  std_logic_vector(6 downto 0));
	end component;
 
	component ps2kbd
	PORT (	
			keyboard_clk	: inout std_logic;
			keyboard_data	: inout std_logic;
			clock				: in std_logic;
			clkdelay			: in std_logic;
			reset				: in std_logic;
			read				: in std_logic;
			scan_ready		: out std_logic;
			ps2_ascii_code	: out std_logic_vector(7 downto 0));
	end component;
 
	component vram8k
	port (
		address_a		: IN STD_LOGIC_VECTOR (12 DOWNTO 0);
		address_b		: IN STD_LOGIC_VECTOR (12 DOWNTO 0);
		data_a		: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
		data_b		: IN STD_LOGIC_VECTOR (7 DOWNTO 0);
		clock_a		: IN STD_LOGIC ;
		clock_b		: IN STD_LOGIC ;
		wren_a		: IN STD_LOGIC  := '1';
		wren_b		: IN STD_LOGIC  := '1';
		q_a		: OUT STD_LOGIC_VECTOR (7 DOWNTO 0);
		q_b		: OUT STD_LOGIC_VECTOR (7 DOWNTO 0));
	end component;
 
	COMPONENT video
	PORT (	
			CLOCK_25		: IN STD_LOGIC;
			VRAM_DATA	: IN STD_LOGIC_VECTOR(7 DOWNTO 0);
			VRAM_ADDR	: OUT STD_LOGIC_VECTOR(12 DOWNTO 0);
			VRAM_CLOCK	: OUT STD_LOGIC;
			VRAM_WREN	: OUT STD_LOGIC;
			VGA_R,
			VGA_G,
			VGA_B		: OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
			VGA_HS,
			VGA_VS		: OUT STD_LOGIC);
	END COMPONENT;
 
	COMPONENT video_PLL
	PORT
	(
		inclk0		: IN STD_LOGIC  := '0';
		c0			: OUT STD_LOGIC 
	);
	END COMPONENT;
 
	signal MREQ_n	: std_logic;
	signal IORQ_n	: std_logic;
	signal RD_n		: std_logic;
	signal WR_n		: std_logic;
	signal MWr_n	: std_logic;
	signal Rst_n_s	: std_logic;
	signal Clk_Z80	: std_logic;
	signal DI_CPU	: std_logic_vector(7 downto 0);
	signal DO_CPU	: std_logic_vector(7 downto 0);
	signal A		: std_logic_vector(15 downto 0);
	signal One		: std_logic;
 
	signal D_ROM	: std_logic_vector(7 downto 0);
 
	signal clk25mhz		: std_logic;
	signal clk1hz		: std_logic;
	signal clk10hz		: std_logic;
	signal clk100hz		: std_logic;
 
	signal HEX_DISP0	: std_logic_vector(6 downto 0);
	signal HEX_DISP1	: std_logic_vector(6 downto 0);
	signal HEX_DISP2	: std_logic_vector(6 downto 0);
	signal HEX_DISP3	: std_logic_vector(6 downto 0);
 
	signal NUMBER0		: std_logic_vector(3 downto 0);
	signal NUMBER1		: std_logic_vector(3 downto 0);	
	signal NUMBER2		: std_logic_vector(3 downto 0);
	signal NUMBER3		: std_logic_vector(3 downto 0);
 
	signal GPIO_0_buf_in	: std_logic_vector(35 downto 0);
	signal GPIO_1_buf_in	: std_logic_vector(35 downto 0);
 
	signal 	vram_addra		: std_logic_vector(15 downto 0);
	signal 	vram_addrb		: std_logic_vector(12 downto 0);
	signal 	vram_dina		: std_logic_vector(7 downto 0);
	signal 	vram_dinb		: std_logic_vector(7 downto 0);
	signal 	vram_douta		: std_logic_vector(7 downto 0);
	signal 	vram_doutb		: std_logic_vector(7 downto 0);
	signal  vram_wea		: std_logic;
	signal  vram_web		: std_logic;
	signal  vram_clka		: std_logic;
	signal  vram_clkb		: std_logic;
 
	signal vram_douta_reg	: std_logic_vector(7 downto 0);	
	signal VID_CURSOR		: std_logic_vector(15 downto 0);
	signal CURSOR_X		    : std_logic_vector(5 downto 0);
	signal CURSOR_Y		    : std_logic_vector(4 downto 0);
 
	-- PS/2 Keyboard
	signal ps2_read				: std_logic;
	signal ps2_scan_ready		: std_logic;
	signal ps2_ascii_sig		: std_logic_vector(7 downto 0);
	signal ps2_ascii_reg1		: std_logic_vector(7 downto 0);
	signal ps2_ascii_reg		: std_logic_vector(7 downto 0);
 
	signal Z80SOC_VERSION		: std_logic_vector(2 downto 0);   -- "000" = DE1, "001" = S3E
	signal Z80SOC_STACK			: std_logic_vector(15 downto 0);  -- Should be set to top of (RAM Memory - 1)
 
begin
 
	Z80SOC_VERSION <= "000";		-- "000" = DE1, "001" = S3E
	Z80SOC_STACK <= x"FFFE"; 		-- Should be set to top of (RAM Memory - 1)
	Rst_n_s <= not SW(9);
 
	HEX0 <= HEX_DISP0;
	HEX1 <= HEX_DISP1;
	HEX2 <= HEX_DISP2;
	HEX3 <= HEX_DISP3;
 
	-- SRAM control signals
	SRAM_ADDR(15 downto 0) <= A - x"8000" when (A >= x"8000" and MREQ_n = '0');
	SRAM_DQ(7 downto 0) <= DO_CPU when (Wr_n = '0' and MREQ_n = '0' and A >= x"8000") else (others => 'Z');
	SRAM_WE_N <= Wr_n or MREQ_n when A >= x"8000";
	SRAM_OE_N <= Rd_n;
 
	--	VRAM control signals
	vram_addra <= VID_CURSOR when (IORQ_n = '0' and MREQ_n = '1' and A(7 downto 0) = x"90") else
	             (A - x"4000") when (A >= x"4000" and A <= x"5FFF" and MREQ_n = '0' and IORQ_n = '1') else 
				  "ZZZZZZZZZZZZZZZZ";
	vram_wea <= '0' when ((Wr_n = '0' and MREQ_n = '0' and A >= x"4000" and A <= x"5FFF") or (Wr_n = '0' and IORQ_n = '0'  and MREQ_n = '1' and A(7 downto 0) = x"90")) else
	            '1';
	vram_dina <= DO_CPU;
 
	-- Input to Z80
	DI_CPU <= ("00000" & Z80SOC_VERSION) when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A = x"7FDD") else
			Z80SOC_STACK(7 downto 0) when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A = x"7FDE") else
			Z80SOC_STACK(15 downto 8) when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A = x"7FDF") else
			vram_douta when (MREQ_n = '0' and IORQ_n = '1' and Rd_n = '0' and A >= x"4000" and A <= x"5FFF") else
			SRAM_DQ(7 downto 0) when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A >= x"8000") else
			D_ROM when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A < x"4000") else
			SW(7 downto 0) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"20") else
			("0000" & not KEY) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"30") else
			GPIO_0(7 downto 0) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"A0") else
			GPIO_0(15 downto 8) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"A1") else
			GPIO_0(23 downto 16) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"A2") else
			GPIO_0(31 downto 24) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"A3") else
			("0000" & GPIO_0(35 downto 32)) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"A4") else
			GPIO_1(7 downto 0) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"B0") else
			GPIO_1(15 downto 8) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"B1") else
			GPIO_1(23 downto 16) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"B2") else
			GPIO_1(31 downto 24) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"B3") else
			("0000" & GPIO_1(35 downto 32)) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"B4") else
			ps2_ascii_reg when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"80") else
			("00" & CURSOR_X) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"91") else
			("000" & CURSOR_Y) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"92") else
			"ZZZZZZZZ";
 
	-- Process to latch leds and hex displays
	pinout_process: process(Clk_Z80)
	variable NUMBER0_sig	: std_logic_vector(3 downto 0);
	variable NUMBER1_sig	: std_logic_vector(3 downto 0);	
	variable NUMBER2_sig	: std_logic_vector(3 downto 0);
	variable NUMBER3_sig	: std_logic_vector(3 downto 0);
	variable LEDG_sig		: std_logic_vector(7 downto 0);
	variable LEDR_sig		: std_logic_vector(9 downto 0);
	variable GPIO_0_buf_out: std_logic_vector(35 downto 0);
	variable GPIO_1_buf_out: std_logic_vector(35 downto 0);
	begin		
		if Clk_Z80'event and Clk_Z80 = '1' then
		  if IORQ_n = '0' and MREQ_n = '1' and Wr_n = '0' then
			-- LEDG
			if A(7 downto 0) = x"01" then
				LEDG_sig := DO_CPU;
			-- LEDR
			elsif A(7 downto 0) = x"02" then
				LEDR_sig(7 downto 0) := DO_CPU;
			-- HEX1 and HEX0
			elsif A(7 downto 0) = x"10" then
				NUMBER0_sig := DO_CPU(3 downto 0);
				NUMBER1_sig := DO_CPU(7 downto 4);
			-- HEX3 and HEX2
			elsif A(7 downto 0) = x"11" then
				NUMBER2_sig := DO_CPU(3 downto 0);
				NUMBER3_sig := DO_CPU(7 downto 4);
			-- GPIO_0
			elsif A(7 downto 0) = x"A0" then
				GPIO_0_buf_out(7 downto 0)   := DO_CPU;
			elsif A(7 downto 0) = x"A1" then
				GPIO_0_buf_out(15 downto 8)  := DO_CPU;
			elsif A(7 downto 0) = x"A2" then
				GPIO_0_buf_out(23 downto 16) := DO_CPU;
			elsif A(7 downto 0) = x"A3" then
				GPIO_0_buf_out(31 downto 24) := DO_CPU;
			elsif A(7 downto 0) = x"A4" then
				GPIO_0_buf_out(35 downto 32) := DO_CPU(3 downto 0);
			-- GPIO_1
			elsif A(7 downto 0) = x"B0" then
				GPIO_1_buf_out(7 downto 0)   := DO_CPU;
			elsif A(7 downto 0) = x"B1" then
				GPIO_1_buf_out(15 downto 8)  := DO_CPU;
			elsif A(7 downto 0) = x"B2" then
				GPIO_1_buf_out(23 downto 16) := DO_CPU;
			elsif A(7 downto 0) = x"B3" then
				GPIO_1_buf_out(31 downto 24) := DO_CPU;
			elsif A(7 downto 0) = x"B4" then
				GPIO_1_buf_out(35 downto 32) := DO_CPU(3 downto 0);	
			elsif A(7 downto 0) = x"C0" then
				GPIO_0 <= GPIO_0_buf_out;
			elsif A(7 downto 0) = x"C1" then
				GPIO_1 <= GPIO_1_buf_out;
			end if;
		  end if;
		end if;		
		-- Latches the signals
		NUMBER0 <= NUMBER0_sig;
		NUMBER1 <= NUMBER1_sig;
		NUMBER2 <= NUMBER2_sig;
		NUMBER3 <= NUMBER3_sig;
		LEDR(7 downto 0) <= LEDR_sig(7 downto 0);
		LEDG <= LEDG_sig;
	end process;		
 
	-- the following three processes deals with different clock domain signals
	ps2_process1: process(CLOCK_50)
	begin
		if CLOCK_50'event and CLOCK_50 = '1' then
			if ps2_read = '1' then
				if ps2_ascii_sig /= x"FF" then
					ps2_read <= '0';
					ps2_ascii_reg1 <= "00000000";
				end if;
			elsif ps2_scan_ready = '1' then
				if ps2_ascii_sig = x"FF" then
					ps2_read <= '1';
				else
					ps2_ascii_reg1 <= ps2_ascii_sig;
				end if;
			end if;
		end if;
	end process;
 
	ps2_process2: process(Clk_Z80)
	begin
		if Clk_Z80'event and Clk_Z80 = '1' then
			ps2_ascii_reg <= ps2_ascii_reg1;
		end if;
	end process;
 
	cursorxy: process (Clk_Z80)
	variable VID_X	: std_logic_vector(5 downto 0);
	variable VID_Y	: std_logic_vector(4 downto 0);
	begin
		if Clk_Z80'event and Clk_Z80 = '1' then
			if (IORQ_n = '0' and MREQ_n = '1' and Wr_n = '0' and A(7 downto 0) = x"91") then
				VID_X := DO_CPU(5 downto 0);
			elsif (IORQ_n = '0' and MREQ_n = '1' and Wr_n = '0' and A(7 downto 0) = x"92") then
				VID_Y := DO_CPU(4 downto 0);
			elsif (IORQ_n = '0' and MREQ_n = '1' and Wr_n = '0' and A(7 downto 0) = x"90") then
				if VID_X = "100111" then
					VID_X := "000000";
					if VID_Y = "11101" then
						VID_Y := "00000";
					else
						VID_Y := VID_Y + 1;
					end if;
				else
					VID_X := VID_X + 1;
				end if;
			end if;
		end if;
		VID_CURSOR <= x"4000" + ( VID_X + ( VID_Y * "0101000"));
		CURSOR_X <= VID_X;
		CURSOR_Y <= VID_Y;
	end process;
 
	One <= '1';
	z80_inst: T80se
		port map (
			M1_n => open,
			MREQ_n => MREQ_n,
			IORQ_n => IORQ_n,
			RD_n => Rd_n,
			WR_n => Wr_n,
			RFSH_n => open,
			HALT_n => open,
			WAIT_n => One,
			INT_n => One,
			NMI_n => One,
			RESET_n => Rst_n_s,
			BUSRQ_n => One,
			BUSAK_n => open,
			CLK_n => Clk_Z80,
			CLKEN => One,
			A => A,
			DI => DI_CPU,
			DO => DO_CPU
		);
 
	video_inst: video port map (
			CLOCK_25		=> clk25mhz,
			VRAM_DATA		=> vram_doutb,
			VRAM_ADDR		=> vram_addrb,
			VRAM_CLOCK		=> vram_clkb,
			VRAM_WREN		=> vram_web,
			VGA_R			=> VGA_R,
			VGA_G			=> VGA_G,
			VGA_B			=> VGA_B,
			VGA_HS			=> VGA_HS,
			VGA_VS			=> VGA_VS
	);
 
	vram8k_inst : vram8k PORT MAP (
		clock_a	 	=> Clk_Z80,
		clock_b 	=> vram_clkb,	
		wren_a	 	=> not vram_wea, -- inverted logic so code is similar to SRAM and S3E port
		wren_b	 	=> not vram_web, -- not necessary here, because it is always low (read)		
		address_a	=> vram_addra(12 downto 0),
		address_b	=> vram_addrb(12 downto 0),
		data_a	 	=> vram_dina,
		data_b	 	=> vram_dinb,
		q_a	 		=> vram_douta,
		q_b	 		=> vram_doutb
	);
 
	rom_inst: rom
		port map (
			Clk => Clk_Z80,
			A	=> A(13 downto 0),
			D 	=> D_ROM
		);
 
	-- PLL below is used to generate the pixel clock frequency
	-- Uses DE1 50Mhz clock for PLL's input clock
	video_PLL_inst : video_PLL PORT MAP (
		inclk0	 => CLOCK_50,
		c0	 => clk25mhz
	);
 
	clkdiv_inst: clk_div
	port map (
		clock_25Mhz				=> clk25mhz,
		clock_1MHz				=> open,
		clock_100KHz			=> open,
		clock_10KHz				=> open,
		clock_1KHz				=> open,
		clock_100Hz				=> clk100hz,
		clock_10Hz				=> clk10hz,
		clock_1Hz				=> clk1hz
	);
 
	clock_z80_inst : Clock_357Mhz
		port map (
			clock_50Mhz		=> CLOCK_50,
			clock_357Mhz	=> Clk_Z80
	);
 
	DISPHEX0 : decoder_7seg PORT MAP (
		NUMBER			=>	NUMBER0,
		HEX_DISP		=>	HEX_DISP0
	);		
 
	DISPHEX1 : decoder_7seg PORT MAP (
		NUMBER			=>	NUMBER1,
		HEX_DISP		=>	HEX_DISP1
	);		
 
	DISPHEX2 : decoder_7seg PORT MAP (
		NUMBER			=>	NUMBER2,
		HEX_DISP		=>	HEX_DISP2
	);		
 
	DISPHEX3 : decoder_7seg PORT MAP (
		NUMBER			=>	NUMBER3,
		HEX_DISP		=>	HEX_DISP3
	);
 
	ps2_kbd_inst : ps2kbd PORT MAP (
		keyboard_clk	=> PS2_CLK,
		keyboard_data	=> PS2_DAT,
		clock			=> CLOCK_50,
		clkdelay		=> clk100hz,
		reset			=> Rst_n_s,
		read			=> ps2_read,
		scan_ready		=> ps2_scan_ready,
		ps2_ascii_code	=> ps2_ascii_sig
	);
 
	--
	SRAM_DQ(15 downto 8) <= (others => 'Z');
	SRAM_ADDR(17 downto 16) <= "00";
	SRAM_UB_N <= '1';
	SRAM_LB_N <= '0';
	SRAM_CE_N <= '0';
	--
	UART_TXD <= 'Z';
	DRAM_ADDR <= (others => '0');
	DRAM_LDQM <= '0';
	DRAM_UDQM <= '0';
	DRAM_WE_N <= '1';
	DRAM_CAS_N <= '1';
	DRAM_RAS_N <= '1';
	DRAM_CS_N <= '1';
	DRAM_BA_0 <= '0';
	DRAM_BA_1 <= '0';
	DRAM_CLK <= '0';
	DRAM_CKE <= '0';
	FL_ADDR <= (others => '0');
	FL_WE_N <= '1';
	FL_RST_N <= '0';
	FL_OE_N <= '1';
	FL_CE_N <= '1';
	TDO <= '0';
	I2C_SCLK <= '0';
	AUD_DACDAT <= '0';
	AUD_XCK <= '0';
	-- Set all bidirectional ports to tri-state
	DRAM_DQ     <= (others => 'Z');
	FL_DQ       <= (others => 'Z');
	I2C_SDAT    <= 'Z';
	AUD_ADCLRCK <= 'Z';
	AUD_DACLRCK <= 'Z';
	AUD_BCLK    <= 'Z';
	GPIO_0 <= (others => 'Z');
	GPIO_1 <= (others => 'Z');	
end;