I2C controller core之Bit controller(01)

FPGA proven, AISC proven, I2C controller core from OpenCores

http://opencores.org/project,i2c

Bit-controller

-- Translate simple commands into SCL/SDA transitions
-- Each command has 5 states, A/B/C/D/idle
--
-- start:    SCL  ~~~~~~~~~~~~~~\____
--           SDA  XX/~~~~~~~\______
--                x | A | B | C | D | i
--
-- repstart  SCL  ______/~~~~~~~\___
--           SDA  __/~~~~~~~\______
--                x | A | B | C | D | i
--
-- stop      SCL  _______/~~~~~~~~~~~
--           SDA  ==\___________/~~~~~
--                x | A | B | C | D | i
--
--- write    SCL  ______/~~~~~~~\____
--           SDA  XXX===============XX
--                x | A | B | C | D | i
--
--- read     SCL  ______/~~~~~~~\____
--           SDA  XXXXXXX=XXXXXXXXXXX
--                x | A | B | C | D | i
--

1　　ports declaration

 library ieee;
 use ieee.std_logic_1164.all;
 use ieee.numeric_std.all;

 entity i2c_master_bit_ctrl is
 port (
           clk    : in std_logic;
           rst    : in std_logic;
           nRst   : in std_logic;
           ena    : in std_logic;                     -- core enable signal

           clk_cnt : in unsigned( downto );        -- clock prescale value 
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 --! type unsigned is array (natural range <>) of std_logic

           cmd     : in std_logic_vector( downto );
           cmd_ack : out std_logic;                   -- command completed
           busy    : out std_logic;                   -- i2c bus busy
           al      : out std_logic;                   -- arbitration lost

           din  : in std_logic;
           dout : out std_logic;

           -- i2c lines
           scl_i   : in std_logic;                    -- i2c clock line input
           scl_o   : out std_logic;                   -- i2c clock line output
           scl_oen : out std_logic;                   -- i2c clock line output enable, active low
           sda_i   : in std_logic;                    -- i2c data line input
           sda_o   : out std_logic;                   -- i2c data line output
           sda_oen : out std_logic                    -- i2c data line output enable, active low
 );
 end entity i2c_master_bit_ctrl;

2　　signals declaration

 1 -- architecture
  constant I2C_CMD_NOP    : std_logic_vector( downto ) := "";
  constant I2C_CMD_START  : std_logic_vector( downto ) := "";
  constant I2C_CMD_STOP   : std_logic_vector( downto ) := "";
  constant I2C_CMD_READ   : std_logic_vector( downto ) := "";
  constant I2C_CMD_WRITE  : std_logic_vector( downto ) := "";

  type states is (idle, start_a, start_b, start_c, start_d, start_e,stop_a,stop_b,
                   stop_c, stop_d, rd_a, rd_b, rd_c, rd_d, wr_a, wr_b, wr_c, wr_d);
  signal c_state : states;

  signal iscl_oen, isda_oen : std_logic;     -- internal I2C lines
  signal sda_chk　　　　 : std_logic;  　　　　-- check SDA status (multi-master arbitration)
  signal dscl_oen　　　　: std_logic;  　　　　-- delayed scl_oen signals
  signal sSCL, sSDA　　　: std_logic;  　　　　-- synchronized SCL and SDA inputs
  signal dSCL, dSDA 　　: std_logic;  　　　　 -- delayed versions of sSCL and sSDA
  signal clk_en         : std_logic;  　　　　-- statemachine clock enable
  signal scl_sync, slave_wait : std_logic;   -- clock generation signals
  signal ial            : std_logic;         -- internal arbitration lost signal
  signal cnt            : unsigned( downto ); -- clock divider counter (synthesis)

22 -- block
  signal cSCL, cSDA  : std_logic_vector( downto ); -- capture SDA and SCL
  signal fSCL, fSDA  : std_logic_vector( downto ); -- filter inputs for SCL and SDA
  signal filter_cnt    : unsigned( downto );      -- clock divider for filter
  signal sta_condition : std_logic;          -- start detected
  signal sto_condition : std_logic;          -- stop detected
  signal cmd_stop      : std_logic;          -- STOP command
  signal ibusy         : std_logic;          -- internal busy signal

3　assign outputs

1     -- assign outputs
     scl_o   <= '';
     scl_oen <= iscl_oen;
     sda_o   <= '';
     sda_oen <= isda_oen;