-------------------------------------------------------------------------                                                             --------  WISHBONE revB2 I2C Master Core; bit-controller             --------                                                             --------                                                             --------  Author: Richard Herveille                                  --------          richard@asics.ws                                   --------          www.asics.ws                                       --------                                                             --------  Downloaded from: http://www.opencores.org/projects/i2c/    --------                                                             -----------------------------------------------------------------------------                                                             -------- Copyright (C) 2000 Richard Herveille                        --------                    richard@asics.ws                         --------                                                             -------- This source file may be used and distributed without        -------- restriction provided that this copyright statement is not   -------- removed from the file and that any derivative work contains -------- the original copyright notice and the associated disclaimer.--------                                                             --------     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     -------- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   -------- TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   -------- FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      -------- OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         -------- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    -------- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   -------- GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        -------- BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  -------- LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  -------- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  -------- OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         -------- POSSIBILITY OF SUCH DAMAGE.                                 --------                                                             ---------------------------------------------------------------------------  CVS Log----  $Id: i2c_master_bit_ctrl.vhd,v 1.12 2004/05/07 11:53:31 rherveille Exp $----  $Date: 2004/05/07 11:53:31 $--  $Revision: 1.12 $--  $Author: rherveille $--  $Locker:  $--  $State: Exp $---- Change History:--               $Log: i2c_master_bit_ctrl.vhd,v $--               Revision 1.12  2004/05/07 11:53:31  rherveille--               Fixed previous fix :) Made a variable vs signal mistake.----               Revision 1.11  2004/05/07 11:04:00  rherveille--               Fixed a bug where the core would signal an arbitration lost (AL bit set), when another master controls the bus and the other master generates a STOP bit.----               Revision 1.10  2004/02/27 07:49:43  rherveille--               Fixed a bug in the arbitration-lost signal generation. VHDL version only.----               Revision 1.9  2003/08/12 14:48:37  rherveille--               Forgot an 'end if' :-/----               Revision 1.8  2003/08/09 07:01:13  rherveille--               Fixed a bug in the Arbitration Lost generation caused by delay on the (external) sda line.--               Fixed a potential bug in the byte controller's host-acknowledge generation.----               Revision 1.7  2003/02/05 00:06:02  rherveille--               Fixed a bug where the core would trigger an erroneous 'arbitration lost' interrupt after being reset, when the reset pulse width < 3 clk cycles.----               Revision 1.6  2003/02/01 02:03:06  rherveille--               Fixed a few 'arbitration lost' bugs. VHDL version only.----               Revision 1.5  2002/12/26 16:05:47  rherveille--               Core is now a Multimaster I2C controller.----               Revision 1.4  2002/11/30 22:24:37  rherveille--               Cleaned up code----               Revision 1.3  2002/10/30 18:09:53  rherveille--               Fixed some reported minor start/stop generation timing issuess.----               Revision 1.2  2002/06/15 07:37:04  rherveille--               Fixed a small timing bug in the bit controller.\nAdded verilog simulation environment.----               Revision 1.1  2001/11/05 12:02:33  rherveille--               Split i2c_master_core.vhd into separate files for each entity; same layout as verilog version.--               Code updated, is now up-to-date to doc. rev.0.4.--               Added headers.------------------------------------------- Bit controller section---------------------------------------- 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---- Timing:      Normal mode     Fast mode------------------------------------------------------------------- Fscl         100KHz          400KHz-- Th_scl       4.0us           0.6us   High period of SCL-- Tl_scl       4.7us           1.3us   Low period of SCL-- Tsu:sta      4.7us           0.6us   setup time for a repeated start condition-- Tsu:sto      4.0us           0.6us   setup time for a stop conditon-- Tbuf         4.7us           1.3us   Bus free time between a stop and start condition--library ieee;use ieee.std_logic_1164.all;use ieee.std_logic_arith.all;entity i2c_master_bit_ctrl is	port (		clk    : in std_logic;		rst    : in std_logic;		nReset : in std_logic;		ena    : in std_logic;				-- core enable signal		clk_cnt : in unsigned(15 downto 0);		-- clock prescale value		cmd     : in std_logic_vector(3 downto 0);		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;architecture structural of i2c_master_bit_ctrl is	constant I2C_CMD_NOP    : std_logic_vector(3 downto 0) := "0000";	constant I2C_CMD_START  : std_logic_vector(3 downto 0) := "0001";	constant I2C_CMD_STOP   : std_logic_vector(3 downto 0) := "0010";	constant I2C_CMD_READ   : std_logic_vector(3 downto 0) := "0100";	constant I2C_CMD_WRITE  : std_logic_vector(3 downto 0) := "1000";	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 clk_en, slave_wait : std_logic;          -- clock generation signals	signal ial                : std_logic;          -- internal arbitration lost signal--	signal cnt : unsigned(15 downto 0) := clk_cnt;  -- clock divider counter (simulation)	signal cnt : unsigned(15 downto 0);             -- clock divider counter (synthesis)begin	-- whenever the slave is not ready it can delay the cycle by pulling SCL low	-- delay scl_oen	process (clk)	begin	    if (clk'event and clk = '1') then	      dscl_oen <= iscl_oen;	    end if;	end process;	slave_wait <= dscl_oen and not sSCL;	-- generate clk enable signal	gen_clken: process(clk, nReset)	begin	    if (nReset = '0') then	      cnt    <= (others => '0');	      clk_en <= '1';	    elsif (clk'event and clk = '1') then	      if (rst = '1') then	        cnt    <= (others => '0');	        clk_en <= '1';	      else	        if ( (cnt = 0) or (ena = '0') ) then	          if (slave_wait = '0') then	            cnt    <= clk_cnt;	            clk_en <= '1';	          else	            cnt    <= cnt;	            clk_en <= '0';	          end if;	        else	          if (slave_wait = '0') then	            cnt <= cnt -1;	          end if;	          clk_en <= '0';	        end if;	      end if;	    end if;	end process gen_clken;	-- generate bus status controller	bus_status_ctrl: block	  signal dSCL, dSDA          : std_logic;  -- delayes sSCL and sSDA	  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	begin	    -- synchronize SCL and SDA inputs	    synch_scl_sda: process(clk, nReset)	    begin	        if (nReset = '0') then	          sSCL <= '1';	          sSDA <= '1';	          dSCL <= '1';	          dSDA <= '1';	        elsif (clk'event and clk = '1') then	          if (rst = '1') then	            sSCL <= '1';	            sSDA <= '1';	            dSCL <= '1';	            dSDA <= '1';	          else	            sSCL <= scl_i;	            sSDA <= sda_i;