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-- ZPU

--

-- Copyright 2004-2008 oharboe - Øyvind Harboe - oyvind.harboe@zylin.com

-- 

-- The FreeBSD license

-- 

-- Redistribution and use in source and binary forms, with or without

-- modification, are permitted provided that the following conditions

-- are met:

-- 

-- 1. Redistributions of source code must retain the above copyright

--    notice, this list of conditions and the following disclaimer.

-- 2. Redistributions in binary form must reproduce the above

--    copyright notice, this list of conditions and the following

--    disclaimer in the documentation and/or other materials

--    provided with the distribution.

-- 

-- THIS SOFTWARE IS PROVIDED BY THE ZPU PROJECT ``AS IS'' AND ANY

-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

-- PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

-- ZPU PROJECT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

-- INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

-- OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

-- HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

-- STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

-- ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-- 

-- The views and conclusions contained in the software and documentation

-- are those of the authors and should not be interpreted as representing

-- official policies, either expressed or implied, of the ZPU Project.--------------------------------------------------------------------------------

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use ieee.numeric_std.all;

---- Uncomment the following library declaration if instantiating

---- any Xilinx primitives in this code.

--library UNISIM;

--use UNISIM.VComponents.all;

library work;

use work.zpu_config.all;

use work.zpupkg.all;

entity fpga_top is

end fpga_top;

architecture behave of fpga_top is

signal clk : std_logic;

signal  areset                  : std_logic := '1';

component  zpu_io is

  generic (

           log_file:       string  := "log.txt"

          );

  port(

        clk         : in std_logic;

        areset        : in std_logic;

                busy : out std_logic;

                writeEnable : in std_logic;

                readEnable : in std_logic;

                write   : in std_logic_vector(wordSize-1 downto 0);

                read    : out std_logic_vector(wordSize-1 downto 0);

                addr : in std_logic_vector(maxAddrBit downto minAddrBit)

                );

end component;

signal                    mem_busy : std_logic;

signal                    mem_read : std_logic_vector(wordSize-1 downto 0);

signal                    mem_write : std_logic_vector(wordSize-1 downto 0);

signal                    mem_addr : std_logic_vector(maxAddrBitIncIO downto 0);

signal                    mem_writeEnable : std_logic;

signal                    mem_readEnable : std_logic;

signal                    mem_writeMask: std_logic_vector(wordBytes-1 downto 0);

signal                    enable : std_logic;

signal                    dram_mem_busy : std_logic;

signal                    dram_mem_read : std_logic_vector(wordSize-1 downto 0);

signal                    dram_mem_write : std_logic_vector(wordSize-1 downto 0);

signal                    dram_mem_writeEnable : std_logic;

signal                    dram_mem_readEnable : std_logic;

signal                    dram_mem_writeMask: std_logic_vector(wordBytes-1 downto 0);

signal                    io_busy : std_logic;

signal                    io_mem_read : std_logic_vector(wordSize-1 downto 0);

signal                    io_mem_writeEnable : std_logic;

signal                    io_mem_readEnable : std_logic;

signal                    dram_ready : std_logic;

signal                    io_ready : std_logic;

signal                    io_reading : std_logic;

signal                    interruptcounter : unsigned(15 downto 0);

signal                    interrupt : std_logic;

signal break : std_logic;

begin

        zpu: zpu_core port map (

                clk => clk ,

                areset => areset,

                enable => enable,

                in_mem_busy => mem_busy,

                mem_read => mem_read,

                mem_write => mem_write,

                out_mem_addr => mem_addr,

                out_mem_writeEnable => mem_writeEnable,

                out_mem_readEnable => mem_readEnable,

                mem_writeMask => mem_writeMask,

                interrupt => interrupt,

                break  => break);

        ioMap: zpu_io port map (

        clk => clk,

                areset => areset,

                busy => io_busy,

                writeEnable => io_mem_writeEnable,

                readEnable => io_mem_readEnable,

                write   => mem_write,

                read    => io_mem_read,

                addr => mem_addr(maxAddrBit downto minAddrBit)

        );

        dram_mem_writeEnable <= mem_writeEnable and not mem_addr(ioBit);

        dram_mem_readEnable <= mem_readEnable and not mem_addr(ioBit);

        io_mem_writeEnable <= mem_writeEnable and mem_addr(ioBit);

        io_mem_readEnable <= mem_readEnable and mem_addr(ioBit);

        mem_busy <= io_busy;

        -- Memory reads either come from IO or DRAM. We need to pick the right one.

        memorycontrol:

        process(dram_mem_read, dram_ready, io_ready, io_mem_read)

        begin

                mem_read <= (others => 'U');

                if dram_ready='1' then

                        mem_read <= dram_mem_read;

                end if;

                if io_ready='1' then

                        mem_read <= (others => '0');

                        mem_read <= io_mem_read;

                end if;

        end process;

        io_ready <= (io_reading or io_mem_readEnable) and not io_busy;

        memoryControlSync:

        process(clk, areset)

        begin

                if areset = '1' then

                        enable <= '0';

                        io_reading <= '0';

                        dram_ready <= '0';

                    interruptcounter <= to_unsigned(0, 16);

                        interrupt <= '0';

                elsif (clk'event and clk = '1') then

                        enable <= '1';

                        io_reading <= io_busy or io_mem_readEnable;

                        dram_ready<=dram_mem_readEnable;

                        -- keep interrupt signal high for 16 cycles

                    interruptcounter <= interruptcounter + 1;

                        if (interruptcounter < 16) then

                                report "Interrupt asserted!" severity note;

                                interrupt <='1';

                        else

                                interrupt <='0';

                        end if;

                end if;

        end process;

        -- wiggle the clock @ 100MHz

        clock : PROCESS

           begin

                        clk <= '0';

                   wait for 5 ns;

                        clk <= '1';

                   wait for 5 ns;

                   areset <= '0';

        end PROCESS clock;

end behave;