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microwatt/simple_ram_behavioural.vhdl

78 lines
2.1 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use std.textio.all;
library work;
use work.wishbone_types.all;
use work.simple_ram_behavioural_helpers.all;
entity simple_ram_behavioural is
generic (
FILENAME : string;
SIZE : integer
);
port (
clk : in std_ulogic;
rst : in std_ulogic;
wishbone_in : in wishbone_master_out;
wishbone_out : out wishbone_slave_out
);
end simple_ram_behavioural;
architecture behave of simple_ram_behavioural is
type wishbone_state_t is (IDLE, ACK);
signal state : wishbone_state_t := IDLE;
signal ret_ack : std_ulogic := '0';
signal identifier : integer := behavioural_initialize(filename => FILENAME, size => SIZE);
signal reload : integer := 0;
begin
wishbone_process: process(clk)
variable ret_dat: std_ulogic_vector(63 downto 0) := (others => '0');
begin
wishbone_out.ack <= ret_ack and wishbone_in.cyc and wishbone_in.stb;
wishbone_out.dat <= ret_dat;
if rising_edge(clk) then
if rst = '1' then
state <= IDLE;
ret_ack <= '0';
else
ret_dat := x"XXXXXXXXXXXXXXXX";
-- Active
if wishbone_in.cyc = '1' then
case state is
when IDLE =>
if wishbone_in.stb = '1' then
-- write
if wishbone_in.we = '1' then
assert not(is_x(wishbone_in.dat)) and not(is_x(wishbone_in.adr)) severity failure;
report "RAM writing " & to_hstring(wishbone_in.dat) & " to " & to_hstring(wishbone_in.adr);
behavioural_write(wishbone_in.dat, wishbone_in.adr, to_integer(unsigned(wishbone_in.sel)), identifier);
reload <= reload + 1;
ret_ack <= '1';
state <= ACK;
else
behavioural_read(ret_dat, wishbone_in.adr, to_integer(unsigned(wishbone_in.sel)), identifier, reload);
report "RAM reading from " & to_hstring(wishbone_in.adr) & " returns " & to_hstring(ret_dat);
ret_ack <= '1';
state <= ACK;
end if;
end if;
when ACK =>
ret_ack <= '0';
state <= IDLE;
end case;
else
ret_ack <= '0';
state <= IDLE;
end if;
end if;
end if;
end process;
end behave;