library ieee;
use ieee.std_logic_1164.all;

-- $Id$:

-- here comes later a real i2c interface!

entity sfp_read is

port (
    RST_n               : in  std_logic; -- power up reset from the DS1818
    -- clock input from the DCS board
    CLK                 : in  std_logic; -- 40 MHz
    we                  : in  std_logic;
    addr                : in  std_logic_vector( 3 downto 0);
    din                 : in  std_logic_vector(31 downto 0);
    dout                : out std_logic_vector(31 downto 0);
    -- SFP Module I2C and present
    SFP_PRESENT         : in  std_logic;
    SFP_SCL             : out std_logic;
    SFP_SDA_i           : in  std_logic;
    SFP_SDA_o           : out std_logic;
    SFP_SDA_e           : out std_logic);
end sfp_read;

architecture a of sfp_read is

signal SFP_SCL_i           : std_logic;
signal SFP_SDA_o_i         : std_logic;
signal SFP_SDA_e_i         : std_logic;

begin
    process(clk, rst_n)
    begin
        if rst_n = '0' then
            SFP_SCL_i   <= '0';
            SFP_SDA_o_i <= '0';
            SFP_SDA_e_i <= '0';
            dout <= (others => '0');
        elsif rising_edge(clk) then
            if we = '1' and addr = "0000" then
                SFP_SCL_i   <= din(0);
                SFP_SDA_o_i <= din(1);
                SFP_SDA_e_i <= din(2);
            end if;
            dout <= (others => '0');
            dout(4 downto 0) <= SFP_PRESENT & SFP_SDA_i & SFP_SDA_e_i & SFP_SDA_o_i & SFP_SCL_i;
        end if;
    end process;

    SFP_SCL     <= SFP_SCL_i;
    SFP_SDA_o   <= SFP_SDA_o_i;
    SFP_SDA_e   <= SFP_SDA_e_i;

end;