disk_ctrl.vhd

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	library IEEE;
	use IEEE.STD_LOGIC_1164.ALL;
	use IEEE.numeric_std.all;
	use work.types.all;
	use work.disk.all;

	entity disk_ctrl is
	port ( clk : in std_logic;
	addr : inout byte;
	data : inout byte;
	DMA_req : out std_logic;
	DMA_ack : in std_logic
	);
	end disk_ctrl;

	architecture Behavioral of disk_ctrl is

	constant param_1 : byte := x"FB";
	constant param_2 : byte := x"FC";
	constant param_3 : byte := x"FD";
	constant param_4 : byte := x"FE";

	constant read_cmnd : byte := x"FF";
	constant sector_size : integer := 256;

	signal buff : disk_block;

	signal b_addr : byte;
	signal b_count : byte;
	signal b_offset : byte;
	signal b_length : byte;
	begin

	process (clk)
	type rd_state is ( idle,
	buff_sect,
	wait_DMA,
	transfer_byte,
	inc_byte_counter
	);
	variable state : rd_state := idle;
	variable block_counter : integer := 0;
	variable byte_counter : integer := 0;
	variable block_size : integer := sector_size;
	begin
	if rising_edge (clk) then
	if addr = param_1 then
	b_addr <= data;
	end if;
	if addr = param_2 then
	b_count <= data;
	end if;
	if addr = param_3 then
	b_offset <= data;
	end if;
	if addr = param_4 then
	b_length <= data;
	end if;

	if addr = read_cmnd then
	byte_counter := to_integer(unsigned(b_offset));
	block_counter := 0;
	state := buff_sect;
	end if;
	case state is
	when idle =>
	when buff_sect =>
	buff <= disk_data(to_integer(unsigned(b_addr))+block_counter);
	if block_counter = to_integer(unsigned(b_count)) then
	if to_integer(unsigned(b_length)) /= 0 then
	block_size := to_integer(unsigned(b_length));
	end if;
	end if;
	DMA_req <= '1';
	state := wait_DMA;
	when wait_DMA =>
	if DMA_ack = '1' then
	state := transfer_byte;
	end if;
	when transfer_byte =>
	if byte_counter < block_size then
	data <= buff(byte_counter);
	state := inc_byte_counter;
	else
	DMA_req <= '0';
	if block_counter < to_integer(unsigned(b_count)) then
	block_counter := block_counter + 1;
	byte_counter := 0;
	state := buff_sect;
	else
	addr <= (others => 'Z');
	data <= (others => 'Z');
	block_size := sector_size;
	state := idle;
	end if;
	end if;
	when inc_byte_counter =>
	byte_counter := byte_counter + 1;
	state := transfer_byte;
	end case;
	end if;
	end process;
	end Behavioral;