microwatt/fpga/main_bram_caravel.vhdl

library ieee;
use ieee.std_logic_1164.all;

library work;

entity main_bram is
    generic(
        WIDTH        : natural := 64;
        HEIGHT_BITS  : natural := 11;
        MEMORY_SIZE  : natural := (8*1024);
        RAM_INIT_FILE : string
        );
    port(
        clk  : in std_logic;
        addr : in std_logic_vector(HEIGHT_BITS - 1 downto 0) ;
        di   : in std_logic_vector(WIDTH-1 downto 0);
        do   : out std_logic_vector(WIDTH-1 downto 0);
        sel  : in std_logic_vector((WIDTH/8)-1 downto 0);
        re   : in std_ulogic;
        we   : in std_ulogic
        );
end entity main_bram;

architecture behaviour of main_bram is
    component RAM_512x64 port (
        CLK : in std_ulogic;
        WE  : in std_ulogic_vector(7 downto 0);
        EN  : in std_ulogic;
        Di  : in std_ulogic_vector(63 downto 0);
        Do  : out std_ulogic_vector(63 downto 0);
        A   : in std_ulogic_vector(8 downto 0)
    );
    end component;

    signal sel_qual: std_ulogic_vector((WIDTH/8)-1 downto 0);

    signal obuf : std_logic_vector(WIDTH-1 downto 0);
begin
    assert WIDTH = 64;
    -- Do we have a log2 round up issue here?
    assert HEIGHT_BITS = 10;
    assert MEMORY_SIZE = (4*1024);

    sel_qual <= sel when we = '1' else (others => '0');

    memory_0 : RAM_512x64
        port map (
            CLK  => clk,
            WE   => sel_qual(7 downto 0),
            EN   => re or we,
            Di   => di(63 downto 0),
            Do   => obuf(63 downto 0),
            A    => addr(8 downto 0)
            );

    -- The wishbone BRAM wrapper assumes a 1 cycle delay
    memory_read_buffer: process(clk)
    begin
        if rising_edge(clk) then
            do <= obuf;
        end if;
    end process;
end architecture behaviour;