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[/] [tinycpu/] [trunk/] [src/] [blockram.vhd] - Rev 24
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--RAM module --4096*8 bit file --simultaneous write/read support --16 bit or 8 bit data bus --16 bit address bus --On Reset, will load a "default" RAM image library IEEE; use IEEE.STD_LOGIC_1164.ALL; use ieee.std_logic_arith.all; use IEEE.NUMERIC_STD.ALL; use ieee.std_logic_unsigned.all; entity blockram is port( Address: in std_logic_vector(7 downto 0); --memory address WriteEnable: in std_logic_vector(1 downto 0); --write 1 byte at a time option Enable: in std_logic; Clock: in std_logic; DataIn: in std_logic_vector(15 downto 0); DataOut: out std_logic_vector(15 downto 0) ); end blockram; architecture Behavioral of blockram is type ram_type is array (255 downto 0) of std_logic_vector (7 downto 0); signal RAM0: ram_type; --Spartan 3Es don't natively support byte-wide write enables, so we'll just emulate it with 2 banks of RAM signal RAM1: ram_type; signal di0, di1: std_logic_vector(7 downto 0); signal do : std_logic_vector(15 downto 0); begin di0 <= DataIn(7 downto 0) when WriteEnable(0)='1' else do(7 downto 0); di1 <= DataIn(15 downto 8) when WriteEnable(1)='1' else do(15 downto 8); process (Clock) begin if rising_edge(Clock) then if Enable = '1' then if WriteEnable(0)='1' then RAM0(conv_integer(Address)) <= di0; else do(7 downto 0) <= RAM0(conv_integer(Address)) ; end if; if WriteEnable(1)='1' then RAM1(conv_integer(Address)) <= di1; else do(15 downto 8) <= RAM1(conv_integer(Address)); end if; end if; end if; end process; DataOut <= do; end Behavioral;
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