89 lines
2.3 KiB
VHDL
89 lines
2.3 KiB
VHDL
-------------------------------------------------------------------------
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-- Project: JCPU, a portable 8-bit RISC CPU written in VHDL
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-- This file: The ROM file for use in your VHDL design
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--
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-- Copyright (C) 2007 J. Ahrensfeld
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--
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-- This program is free software: you can redistribute it and/or modify
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-- it under the terms of the GNU General Public License as published by
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-- the Free Software Foundation, either version 3 of the License, or
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-- (at your option) any later version.
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--
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-- This program is distributed in the hope that it will be useful,
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-- but WITHOUT ANY WARRANTY; without even the implied warranty of
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-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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-- GNU General Public License for more details.
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--
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-- You should have received a copy of the GNU General Public License
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-- along with this program. If not, see <http://www.gnu.org/licenses/>.
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--
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-- For questions and ideas, please contact the author at jens@jayfield.org
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--
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--------------------------------------------------------------------------
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LIBRARY ieee;
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use IEEE.STD_LOGIC_1164.ALL;
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USE ieee.numeric_std.ALL;
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ENTITY ram IS
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Generic
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(
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word_addr_width : integer := 6
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);
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Port
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(
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clk : in STD_LOGIC;
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ce : in STD_LOGIC;
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we : in unsigned(3 downto 0);
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addr : in unsigned(31 downto 0);
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din : in unsigned(31 downto 0);
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dout : out unsigned(31 downto 0)
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);
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END ram;
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ARCHITECTURE behavior OF ram IS
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constant depth : natural := 2**word_addr_width;
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type sram_t is array (0 to depth-1) of unsigned(31 downto 0);
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function sram_clear return sram_t is
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variable result : sram_t;
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begin
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for i in 0 to sram_t'length-1 loop
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result(i) := (others => '0');
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end loop;
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return result;
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end sram_clear;
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signal sram : sram_t := sram_clear;
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BEGIN
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SRAM_RW:
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process(clk)
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variable index : natural range 0 to depth-1;
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begin
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if rising_edge(clk) and ce = '1' then
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index := to_integer(addr(word_addr_width+1 downto 2));
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if we(0) = '1' then
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sram(index)(7 downto 0) <= din(7 downto 0);
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end if;
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if we(1) = '1' then
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sram(index)(15 downto 8) <= din(15 downto 8);
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end if;
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if we(2) = '1' then
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sram(index)(23 downto 16) <= din(23 downto 16);
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end if;
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if we(3) = '1' then
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sram(index)(31 downto 24) <= din(31 downto 24);
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end if;
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dout <= sram(index);
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end if;
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end process;
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end behavior;
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