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microwatt/fpga/pp_soc_memory.vhd

108 lines
2.9 KiB
VHDL

-- The Potato Processor - A simple processor for FPGAs
-- (c) Kristian Klomsten Skordal 2014 - 2015 <kristian.skordal@wafflemail.net>
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use std.textio.all;
use work.pp_utilities.all;
--! @brief Simple memory module for use in Wishbone-based systems.
entity pp_soc_memory is
generic(
MEMORY_SIZE : natural := 4096; --! Memory size in bytes.
RAM_INIT_FILE : string
);
port(
clk : in std_logic;
reset : in std_logic;
-- Wishbone interface:
wb_adr_in : in std_logic_vector(log2(MEMORY_SIZE) - 1 downto 0);
wb_dat_in : in std_logic_vector(63 downto 0);
wb_dat_out : out std_logic_vector(63 downto 0);
wb_cyc_in : in std_logic;
wb_stb_in : in std_logic;
wb_sel_in : in std_logic_vector( 7 downto 0);
wb_we_in : in std_logic;
wb_ack_out : out std_logic
);
end entity pp_soc_memory;
architecture behaviour of pp_soc_memory is
type ram_t is array(0 to (MEMORY_SIZE / 8) - 1) of std_logic_vector(63 downto 0);
impure function init_ram(name : STRING) return ram_t is
file ram_file : text open read_mode is name;
variable ram_line : line;
variable temp_word : std_logic_vector(63 downto 0);
variable temp_ram : ram_t := (others => (others => '0'));
begin
for i in 0 to (MEMORY_SIZE/8)-1 loop
exit when endfile(ram_file);
readline(ram_file, ram_line);
hread(ram_line, temp_word);
temp_ram(i) := temp_word;
end loop;
return temp_ram;
end function;
signal memory : ram_t := init_ram(RAM_INIT_FILE);
attribute ram_style : string;
attribute ram_style of memory : signal is "block";
attribute ram_decomp : string;
attribute ram_decomp of memory : signal is "power";
type state_type is (IDLE, ACK);
signal state : state_type;
signal read_ack : std_logic;
begin
wb_ack_out <= read_ack and wb_stb_in;
memory_0: process(clk)
begin
if rising_edge(clk) then
if reset = '1' then
read_ack <= '0';
state <= IDLE;
else
if wb_cyc_in = '1' then
case state is
when IDLE =>
if wb_stb_in = '1' and wb_we_in = '1' then
for i in 0 to 7 loop
if wb_sel_in(i) = '1' then
memory(to_integer(unsigned(wb_adr_in(wb_adr_in'left downto 3))))(((i + 1) * 8) - 1 downto i * 8)
<= wb_dat_in(((i + 1) * 8) - 1 downto i * 8);
end if;
end loop;
read_ack <= '1';
state <= ACK;
elsif wb_stb_in = '1' then
wb_dat_out <= memory(to_integer(unsigned(wb_adr_in(wb_adr_in'left downto 3))));
read_ack <= '1';
state <= ACK;
end if;
when ACK =>
if wb_stb_in = '0' then
read_ack <= '0';
state <= IDLE;
end if;
end case;
else
state <= IDLE;
read_ack <= '0';
end if;
end if;
end if;
end process;
end architecture behaviour;