Subversion Repositories iota_pow_vhdl

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

entity spi_slave is

        port

        (

                clk : in std_logic;

                reset : in std_logic;

                mosi : in std_logic;

                miso : out std_logic;

                sck : in std_logic;

                ss : in std_logic;

                data_rd : in std_logic_vector(31 downto 0);

                data_wr : out std_logic_vector(31 downto 0);

                data_wren : out std_logic

        );

end spi_slave;

architecture behv of spi_slave is

signal sync_mosi : std_logic_vector(1 downto 0);

signal sync_sck : std_logic_vector(1 downto 0);

signal sync_ss : std_logic_vector(1 downto 0);

begin

        process(clk)

        variable cnt : integer range 0 to 32 := 0;

        variable iwren : std_logic;

        variable i_miso : std_logic;

        variable i_shiftregister : std_logic_vector(31 downto 0);

        begin

                if rising_edge(clk) then

                        if reset='1' then

                                cnt := 0;

                                data_wren <= '0';

                                iwren := '0';

                        else

                                iwren := '0';

                                sync_mosi <= sync_mosi(0) & mosi;

                                sync_sck <= sync_sck(0) & sck;

                                sync_ss <= sync_ss(0) & ss;

                                case sync_ss is

                                        when "11" =>

                                                i_shiftregister := data_rd;

                                                cnt := 0;

--                                              i_flip := '0';

                                        when "10" =>

                                                miso <= i_shiftregister(31);

                                        when "01" =>

                                                cnt := 0;

                                                iwren := '1';

                                                data_wr <= i_shiftregister;

                                        when "00" =>

                                                case sync_sck is

                                                        when "01" =>

                                                                i_shiftregister := i_shiftregister(30 downto 0) & sync_mosi(0);

                                                                cnt := cnt + 1;

                                                        when "10" =>

                                                                miso <= i_shiftregister(31);

                                                        when others =>

                                                end case;

                                        when others =>

                                end case;

                                data_wren <= iwren;

                        end if;

                end if;

        end process;

end behv;