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-------------------------------------------------------------------------------------------------
-- Z80 Control Microprocessor
--
-- Version history:
-------------------
-- Version 0.2 Alpha for for Altera DE1
-- Developer: Tyler Pohl
-- Release Date: 2010 / 10 / 01
--
-- 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):
--
--      40 KB Internal ROM              Read            (0x0000h - 0x9FFFh) -- Location 1FFFH will be used to unlock locked RAM in future
--
--  08 KB Shared Memory     Read/Write  (0xA000h - 0xBFFFh)
--
--        Locked Supr1                  (0xC000h - 0xC7FFh)
--                Supr2                                     (0xC800h - 0xCFFFh) 
--        Supr3                         (0xD000h - 0xD7FFh) 
--        Supr4                         (0xD800h - 0xDFFFh) -- Stack starts at DFEA and goes down initialize this in z80 code
--        Supr5                         (0xE000h - 0xE7FFh) 
--        Supr6                                                 (0xE800h - 0xEFFFh) 
--        Lacoked Pram                                  (0xF000h - 0xF7FFh) -- Switched between 5 banks
--        Sram                          (0xF800h - 0xF8FFh) -- Switched between 5 banks
--                Ram                           (0xF900h - 0xFFFFh) -- Switched between 5 banks

--      08 Green Leds                   Out                     (Port 0x01h)
--      08 Red Leds                             Out                     (Port 0x02h)
--      04 Seven Seg displays   Out                     (Ports 0x10h and 0x11h)

--  01 Uart0                            In/Out          (Port 0x24h)

--  01 Rom Switching        Out         (Port 0xDDh)
--  02 Rom Switching        Out         (Port 0xDDh)
--  03 Rom Switching        Out         (Port 0xDDh)

--  00 to 04 Ram Bank Switching  Out         (Port 0xDCh)

-- Future Ports (Registers)
--PRF F0h
--STATS,RTCIN F0h       --Brown Out and Pwr Fail Stat 60Hz
--PFKILL F1h
--RTCRST F2h
--SFTPRT F3h
--MEXPON F4h
--MEXPOFF F5h
--IOXPON F6h
--IOXPOFF F7h
--EPPAGE1 FCh
--EPPAGE2 FDh
--
--  Revision history:
--
-- 2010/10/01 - Modified RAM layout to support new and future improvements
--            - Changed ROM to support 16 bit addresses
--                        - Serial port Recived works under Interrupt -- Load z80test and data ends up on hex display   
--
--
-- Getting Started
        -- Use CII_Starter_USB_API_v1 project to load flash chip - don't forget to erase chip first
        -- Load rom.bin to flash chip starting at address 0
        -- Connect the serial port up to hyperterminal or minicom
        -- Sends data out and displays on hex display
        -- Type chars to send from PC serial port - z80 recieves and displays on hex display under interrupt
--
--
-- TO-DO:
-- - MOST IMPORTANT
-- - Search for this ????? and figure out why it stops the CPU from running 
-- -
-- - Serial communication, to download assembly code from PC
-- - SD/MMC card interface to read/store data and programs
-- - Get Flash Write to Work -- Why does the CPU not run when connecting DO_CPU to the FL_DQ pins ?
-- - Figure out why cpu does not run when having LED, and uart enabled in the Port output section
-- - Get all the memory above.
-- - Get the serial Tx Interrupt to work.
-- - Add registers to uart so baudrate, parity, interrupts can be modified.
-- - Document this project in the form of Microprocessor Datasheets.
-------------------------------------------------------------------------------------------------

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 : out std_logic;                                         -- Write Enable
    FL_RST_N : out std_logic;                                        -- Reset
    FL_OE_N : out std_logic;                                         -- 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 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;
                clock_10sec             : OUT   STD_LOGIC;
                clock_1min              : OUT   STD_LOGIC;
                clock_1hr               : 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 miniUART 
        PORT (
                SysClk   : in  Std_Logic;  -- System Clock
                Reset    : in  Std_Logic;  -- Reset input
                CS_N     : in  Std_Logic;
                RD_N     : in  Std_Logic;
                WR_N     : in  Std_Logic;
                RxD      : in  Std_Logic;
                TxD      : out Std_Logic;
                IntRx_N  : out Std_Logic;  -- Receive interrupt
                IntTx_N  : out Std_Logic;  -- Transmit interrupt
                Addr     : in  Std_Logic_Vector(1 downto 0); -- 
                DataIn   : in  Std_Logic_Vector(7 downto 0); -- 
                DataOut  : out Std_Logic_Vector(7 downto 0)); --     
        END COMPONENT;
        
        
        signal INT_n    : std_logic;
        signal M1_n             : std_logic;
        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 Clk_357Mhz       : 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 AA               : std_logic_vector(21 downto 0);
        
        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 clk10sec         : std_logic;
        --signal clk1min                : std_logic;
        --signal clk1hr         : 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 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)
        

        
        signal uart0_CS                 : std_Logic;
        signal uart0_RD                 : std_Logic;
        signal uart0_WR                 : std_Logic;
        signal uart0_RxInt              : std_Logic;
        signal uart0_TxInt              : std_Logic;
        signal uart0_Addr       : std_Logic_Vector(1 downto 0);
        signal uart0_DataIn     : std_Logic_Vector(7 downto 0);
        signal uart0_DataOut    : std_logic_Vector(7 downto 0);
        signal UartIntVector    : std_logic_Vector(7 downto 0);
        

        --signal FlashReady             : std_logic;
        --signal iDataFlash             : std_logic_Vector(7 downto 0);
        --signal iCMDFlash              : std_logic_Vector(2 downto 0);
        
        --signal FlashAddr      : std_logic_Vector(21 downto 0);
        
        --signal LedBlink                       : std_logic;    
        
        --signal SingleShot             : std_logic;
        
        signal IntVector                : std_logic_Vector(7 downto 0);
        
        
        
        --signal Z80_RAM_ADR    : Std_Logic_Vector(15 downto 0); 
        --signal Z80_RAM_CE     : Std_Logic; 
        --signal Z80_RAM_OE     : Std_Logic;
        --signal Z80_RAM_WE             : Std_Logic; 
                

        --signal Z80_EE_ADR     : Std_Logic_Vector(21 downto 0); 
        --signal Z80_EE_0E      : Std_Logic;
        --signal Z80_EE_WE      : Std_Logic; 
        --signal Z80_EE_CE      : Std_Logic;            

        --signal PFA_IOE            : Std_Logic; 
        --signal PFA_MEX            : Std_Logic;        

        signal LEDRED           : std_logic_Vector(7 downto 0);
        
        
begin
        


        Rst_n_s <= not SW(9);                   -- Switch 9 toggles Reset on z80
        

        HEX0 <= HEX_DISP0;                              -- Move Signal to Output Pins
        HEX1 <= HEX_DISP1;                              -- Move Signal to Output Pins
        HEX2 <= HEX_DISP2;                              -- Move Signal to Output Pins   
        HEX3 <= HEX_DISP3;                              -- Move Signal to Output Pins
        
        -- SRAM control signals
        SRAM_ADDR(15 downto 0) <= A - x"C000" when (A >= x"C000" and MREQ_n = '0');
        SRAM_DQ(7 downto 0) <= DO_CPU when (Wr_n = '0' and MREQ_n = '0' and A >= x"C000") else (others => 'Z');
        SRAM_WE_N <= Wr_n or MREQ_n when A >= x"C000";
        SRAM_OE_N <= Rd_n or MREQ_n when A >= x"C000";  --Rd_n;
        
        -- ???? Why can't this pin be connected to MREQ_n CPU will not run unless its is connected to zero
        SRAM_CE_N <= '0';
        --------------------------------------------------------------------------------------------------

        --1FFFH is used for unlocking ram in future.  Auto lock after one read or write.
        
        -- FLASH control signals        

        --FL_ADDR(15 downto 0) <= A(15 downto 0) when (Clk_Z80 = '1' and A < x"A000");
        FL_ADDR(15 downto 0) <= A(15 downto 0) when (A < x"A000" and MREQ_n = '0');
    --D_ROM(7 downto 0) <=  FL_DQ when (Clk_Z80 = '1' and A < x"A000");
        D_ROM(7 downto 0) <=  FL_DQ when (A < x"A000" and MREQ_n = '0');   
    
    -- ????? Unblock this and CPU will not run
    --FL_DQ <= DO_CPU when (Wr_n = '0' and MREQ_n = '0' and A < x"A000") else (others => 'Z');
    -----------------------------------------------------------
    
    FL_DQ       <= (others => 'Z');     

    FL_WE_N <= Wr_n;              --'1';                -- Write Enable

    FL_OE_N <= Rd_n;    -- Output Enable
    
    FL_CE_N <= MREQ_n when A < x"A000"; -- Chip Enable
            


    
    --Buffer Flash Data Lines
        --D_ROM(0) <= '1' when FL_DQ(0) = '1' else '0';
        --D_ROM(1) <= '1' when FL_DQ(1) = '1' else '0';
        --D_ROM(2) <= '1' when FL_DQ(2) = '1' else '0';
        --D_ROM(3) <= '1' when FL_DQ(3) = '1' else '0';
        --D_ROM(4) <= '1' when FL_DQ(4) = '1' else '0';
        --D_ROM(5) <= '1' when FL_DQ(5) = '1' else '0';
        --D_ROM(6) <= '1' when FL_DQ(6) = '1' else '0';
        --D_ROM(7) <= '1' when FL_DQ(7) = '1' else '0'; 

        
 

        
        -- UART control signals
        uart0_CS <= IORQ_n when (A(7 downto 0) = x"24" and IORQ_n = '0');
        uart0_RD <= Rd_n when (A(7 downto 0) = x"24" and IORQ_n = '0'); 
        uart0_WR <= Wr_n when (A(7 downto 0) = x"24" and IORQ_n = '0'); 
        uart0_Addr <= b"00";
    ----------------------------------------------
    ----------------------------------------------
        --Z80 Interrupt Vectors
        --               IBMVECT
        --0040 AA1C               DW        COMMBOUT    ;CHAN-B TRANSMIT BUFFER EMPTY
        --0042 101B               DW        COMBCLI     ;BSTATUS
        --0044 F21C               DW        COMMBIN     ;BRECEIVE
        --0046 FF1A               DW        COMBCLII    ;BEXTINT
        --0048 281C               DW        COMMAOUT    ;ATRBMTY
        --004A 691C               DW        COMACLI     ;WAS CRTEXINT   ;ASTATUS
        --004C 2F1B               DW        COMMAIN     ;WAS CRTINP     ;ARECEIVE
        --004E 971C               DW        COMACLII    ;WAS CRTEXIN?   ;AEXTINT        
        IntVector(7 downto 0) <= x"4C"  when (IORQ_n = '0' and MREQ_n = '1' and M1_n = '0' and uart0_RxInt = '1');
    ----------------------------------------------------------  
       



        
        -- Depending on bus signals DI_CPU gets loaded with one of these values.  
        -- Note: bus signals change while z80 is executing different instructions.
        -- Input to Z80
        DI_CPU <= 
                        SRAM_DQ(7 downto 0) when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A >= x"C000") else
                        
                        --Input ROM Code
                        D_ROM when (Rd_n = '0' and MREQ_n = '0' and IORQ_n = '1' and A < x"A000") else

                        uart0_DataIn(7 downto 0) when (IORQ_n = '0' and MREQ_n = '1' and Rd_n = '0' and A(7 downto 0) = x"24") else
                        
                        IntVector(7 downto 0) when (IORQ_n = '0' and MREQ_n = '1' and M1_n = '0' and uart0_RxInt = '1') 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 uart0_buf_DataOut: std_logic_vector(7 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
                        -- 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);
                        elsif A(7 downto 0) = x"24" then
                                uart0_buf_DataOut := DO_CPU;            --load data to uart output buffer
                                
                        end if;
                  end if;
                end if;         
                -- Latches the signals
                NUMBER0 <= NUMBER0_sig;
                NUMBER1 <= NUMBER1_sig;
                NUMBER2 <= NUMBER2_sig;
                NUMBER3 <= NUMBER3_sig;
                
                
                -- ???? Unblock this and CPU will not run
                --LEDRED(7 downto 0) <= LEDR_sig(7 downto 0);
                ---------------------------------------------
                
                
                uart0_DataOut <= uart0_buf_DataOut;
        end process;            

        One <= '1';
        z80_inst: T80se
                port map (
                        M1_n => M1_n,       
                        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 => INT_n,           
                        NMI_n => clk1hz,
                        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
                );
                

        clkdiv_inst: clk_div
        port map (
                clock_25Mhz                             => CLOCK_27,
                clock_1MHz                              => open,
                clock_100KHz                    => open,
                clock_10KHz                             => open,
                clock_1KHz                              => open,
                clock_100Hz                             => clk100hz,
                clock_10Hz                              => clk10hz,
                clock_1Hz                               => clk1hz,
                clock_10sec                             => clk10sec,
                clock_1min                              => open,
                clock_1hr                               => open
        );
                
        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
        );

        
        U1 : miniUART PORT MAP ( 
                SysClk   => CLOCK_50,           --: in  Std_Logic;  -- System Clock
                Reset    => Key(0),             --: in  Std_Logic;  -- Reset input
                CS_N     => uart0_cs,           --: in  Std_Logic;
                RD_N     => uart0_Rd,           --: in  Std_Logic;
                WR_N     => uart0_Wr,           --: in  Std_Logic;
                RxD      => UART_RXD,           --: in  Std_Logic;
                TxD      => UART_TXD,           --: out Std_Logic;
                IntRx_N  => uart0_RxInt,                --: out Std_Logic;  -- Received Byte
                IntTx_N  => uart0_TxInt,                --: out Std_Logic;  -- Transmit Buffer Empty
                Addr     => uart0_Addr,         --: in  Std_Logic_Vector(1 downto 0); -- 
                DataIn   => uart0_DataOut,      --: in  Std_Logic_Vector(7 downto 0); -- 
                DataOut  => uart0_DataIn        --: out Std_Logic_Vector(7 downto 0)); --                               
        );              
                




                
        LEDR(0) <= '1' when LEDRED(0) = '1' else '0';
        LEDR(1) <= '1' when LEDRED(1) = '1' else '0';
        LEDR(2) <= '1' when LEDRED(2) = '1' else '0';
        LEDR(3) <= '1' when LEDRED(3) = '1' else '0';
        LEDR(4) <= '1' when LEDRED(4) = '1' else '0';
        LEDR(5) <= '1' when LEDRED(5) = '1' else '0';
        LEDR(6) <= '1' when LEDRED(6) = '1' else '0';
        LEDR(7) <= '1' when LEDRED(7) = '1' else '0';   

        
        
        INT_n <= '0' when uart0_RxInt ='1' else '1'; 
    
    
    -- Block any of these and CPU will not run -- ?????
        LEDG(0) <= uart0_RxInt;
        LEDG(1) <= uart0_TxInt;
        LEDG(5) <= INT_n;
        ------------------------------------------------------
        
        LEDG(6) <= clk10sec;
        LEDG(7) <= clk1hz;
        
        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(21 downto 16) <= b"000000";
    FL_RST_N <= '1';            -- Reset
    
        TDO <= '0';
        I2C_SCLK <= '0';
        AUD_DACDAT <= '0';
        AUD_XCK <= '0';
        -- Set all bidirectional ports to tri-state
        DRAM_DQ     <= (others => 'Z');

        I2C_SDAT    <= 'Z';
        AUD_ADCLRCK <= 'Z';
        AUD_DACLRCK <= 'Z';
        AUD_BCLK    <= 'Z';
        GPIO_0 <= (others => 'Z');
        GPIO_1 <= (others => 'Z');      
end;