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/////////////////////////////////////////////////////////////////////

////                                                             ////

////  WISHBONE revB.2 compliant I2C Master controller Top-level  ////

////                                                             ////

////                                                             ////

////  Author: Richard Herveille                                  ////

////          richard@asics.ws                                   ////

////          www.asics.ws                                       ////

////                                                             ////

////  Downloaded from: http://www.opencores.org/projects/i2c/    ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

////                                                             ////

//// Copyright (C) 2001 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_top.v,v 1.12 2009-01-19 20:29:26 rherveille Exp $

//

//  $Date: 2009-01-19 20:29:26 $

//  $Revision: 1.12 $

//  $Author: rherveille $

//  $Locker:  $

//  $State: Exp $

//

// Change History:

//               Revision 1.11  2005/02/27 09:26:24  rherveille

//               Fixed register overwrite issue.

//               Removed full_case pragma, replaced it by a default statement.

//

//               Revision 1.10  2003/09/01 10:34:38  rherveille

//               Fix a blocking vs. non-blocking error in the wb_dat output mux.

//

//               Revision 1.9  2003/01/09 16:44:45  rherveille

//               Fixed a bug in the Command Register declaration.

//

//               Revision 1.8  2002/12/26 16:05:12  rherveille

//               Small code simplifications

//

//               Revision 1.7  2002/12/26 15:02:32  rherveille

//               Core is now a Multimaster I2C controller

//

//               Revision 1.6  2002/11/30 22:24:40  rherveille

//               Cleaned up code

//

//               Revision 1.5  2001/11/10 10:52:55  rherveille

//               Changed PRER reset value from 0x0000 to 0xffff, conform specs.

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "i2c_master_slave_defines.v"

//module i2c_master_top(

module i2c_master_slave

  (

   wb_clk_i, wb_rst_i, arst_i, wb_adr_i, wb_dat_i, wb_dat_o,

   wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o, wb_inta_o,

   scl_pad_i, scl_pad_o, scl_padoen_o, sda_pad_i, sda_pad_o, sda_padoen_o );

   // parameters

   parameter ARST_LVL = 1'b1; // asynchronous reset level

   parameter [6:0] DEFAULT_SLAVE_ADDR  = 7'b111_1110;

   //

   // inputs & outputs

   //

   // wishbone signals

   input        wb_clk_i;     // master clock input

   input        wb_rst_i;     // synchronous active high reset

   input        arst_i;       // asynchronous reset

   input [2:0]   wb_adr_i;     // lower address bits

   input [7:0]   wb_dat_i;     // databus input

   output [7:0] wb_dat_o;     // databus output

   input        wb_we_i;      // write enable input

   input        wb_stb_i;     // stobe/core select signal

   input        wb_cyc_i;     // valid bus cycle input

   output       wb_ack_o;     // bus cycle acknowledge output

   output       wb_inta_o;    // interrupt request signal output

   reg [7:0]     wb_dat_o;

   reg          wb_ack_o;

   reg          wb_inta_o;

   // I2C signals

   // i2c clock line

   input        scl_pad_i;       // SCL-line input

   output       scl_pad_o;       // SCL-line output (always 1'b0)

   output       scl_padoen_o;    // SCL-line output enable (active low)

   // i2c data line

   input        sda_pad_i;       // SDA-line input

   output       sda_pad_o;       // SDA-line output (always 1'b0)

   output       sda_padoen_o;    // SDA-line output enable (active low)

   //

   // variable declarations

   //

   // registers

   reg [15:0]    prer; // clock prescale register

   reg [ 7:0]    ctr;  // control register

   reg [ 7:0]    txr;  // transmit register

   wire [ 7:0]   rxr;  // receive register

   reg [ 7:0]    cr;   // command register

   wire [ 7:0]   sr;   // status register

   reg [ 6:0]    sladr;  // slave address register   

   // done signal: command completed, clear command register

   wire         done;

   wire         slave_done;

   // core enable signal

   wire         core_en;

   wire         ien;

   wire         slave_en;

   // status register signals

   wire         irxack;

   reg          rxack;       // received aknowledge from slave

   reg          tip;         // transfer in progress

   reg          irq_flag;    // interrupt pending flag

   wire         i2c_busy;    // bus busy (start signal detected)

   wire         i2c_al;      // i2c bus arbitration lost

   reg          al;          // status register arbitration lost bit

   reg          slave_mode;

   //

   // module body

   //

   wire         slave_act;

   // generate internal reset

   wire         rst_i = arst_i ^ ARST_LVL;

   // generate wishbone signals

   wire         wb_wacc = wb_we_i & wb_ack_o;

   // generate acknowledge output signal ...

   always @(posedge wb_clk_i)

     // ... because timing is always honored.    

     wb_ack_o <=  wb_cyc_i & wb_stb_i & ~wb_ack_o;

   // assign DAT_O

   always @(posedge wb_clk_i)

     begin

        case (wb_adr_i) // synopsys parallel_case

          3'b000: wb_dat_o <= prer[ 7:0];

          3'b001: wb_dat_o <=  prer[15:8];

          3'b010: wb_dat_o <=  ctr;

          3'b011: wb_dat_o <=  rxr; // write is transmit register (txr)

          3'b100: wb_dat_o <=  sr;  // write is command register (cr)

          3'b101: wb_dat_o <=  txr; // Debug out of TXR

          3'b110: wb_dat_o <=  cr;  // Debug out control reg

          3'b111: wb_dat_o <=  {1'b0,sladr};   // slave address register

        endcase

     end

   // generate registers

   always @(posedge wb_clk_i or negedge rst_i)

     if (!rst_i)

       begin

          prer  <=  16'hffff;

          ctr   <=   8'h0;

          txr   <=   8'h0;

          sladr <=  DEFAULT_SLAVE_ADDR;

       end

     else if (wb_rst_i)

       begin

          prer  <=  16'hffff;

          ctr   <=   8'h0;

          txr   <=   8'h0;

          sladr <=  DEFAULT_SLAVE_ADDR;

       end

     else

       if (wb_wacc)

         case (wb_adr_i) // synopsys parallel_case

           3'b000 : prer [ 7:0] <=  wb_dat_i;

           3'b001 : prer [15:8] <=  wb_dat_i;

           3'b010 : ctr         <=  wb_dat_i;

           3'b011 : txr         <=  wb_dat_i;

           3'b111 : sladr       <=  wb_dat_i[6:0];

           default: ;

         endcase

   // generate command register (special case)

   always @(posedge wb_clk_i or negedge rst_i)

     if (!rst_i)

       cr <=  8'h0;

     else if (wb_rst_i)

       cr <=  8'h0;

     else if (wb_wacc)

       begin

          if (core_en & (wb_adr_i == 3'b100) )

            cr <=  wb_dat_i;

       end

     else

       begin

          cr[1] <=  1'b0;

          if (done | i2c_al)

            cr[7:4] <=  4'h0;           // clear command bits when done

          // or when aribitration lost

          cr[2] <=  1'b0;             // reserved bits

          cr[0]   <=  1'b0;             // clear IRQ_ACK bit

       end

   // decode command register

   wire sta  = cr[7];

   wire sto  = cr[6];

   wire rd   = cr[5];

   wire wr   = cr[4];

   wire ack  = cr[3];

   wire sl_cont = cr[1];

   wire iack    = cr[0];

   // decode control register

   assign core_en = ctr[7];

   assign ien = ctr[6];

   assign slave_en = ctr[5];

   // hookup byte controller block

   i2c_master_byte_ctrl byte_controller

     (

      .clk      ( wb_clk_i     ),

      .my_addr  ( sladr        ),

      .rst      ( wb_rst_i     ),

      .nReset   ( rst_i        ),

      .ena      ( core_en      ),

      .clk_cnt  ( prer         ),

      .start    ( sta          ),

      .stop     ( sto          ),

      .read     ( rd           ),

      .write    ( wr           ),

      .ack_in   ( ack          ),

      .din      ( txr          ),

      .cmd_ack  ( done         ),

      .ack_out  ( irxack       ),

      .dout     ( rxr          ),

      .i2c_busy ( i2c_busy     ),

      .i2c_al   ( i2c_al       ),

      .scl_i    ( scl_pad_i    ),

      .scl_o    ( scl_pad_o    ),

      .scl_oen  ( scl_padoen_o ),

      .sda_i    ( sda_pad_i    ),

      .sda_o    ( sda_pad_o    ),

      .sda_oen  ( sda_padoen_o ),

      .sl_cont  ( sl_cont       ),

      .slave_en ( slave_en      ),

      .slave_dat_req (slave_dat_req),

      .slave_dat_avail (slave_dat_avail),

      .slave_act (slave_act),

      .slave_cmd_ack (slave_done)

      );

   // status register block + interrupt request signal

   always @(posedge wb_clk_i or negedge rst_i)

     if (!rst_i)

       begin

          al       <=  1'b0;

          rxack    <=  1'b0;

          tip      <=  1'b0;

          irq_flag <=  1'b0;

          slave_mode <=  1'b0;

       end

     else if (wb_rst_i)

       begin

          al       <=  1'b0;

          rxack    <=  1'b0;

          tip      <=  1'b0;

          irq_flag <=  1'b0;

          slave_mode <=  1'b0;

       end

     else

       begin

          al       <=  i2c_al | (al & ~sta);

          rxack    <=  irxack;

          tip      <=  (rd | wr);

          // interrupt request flag is always generated   

          irq_flag <=  (done | slave_done| i2c_al | slave_dat_req |

                          slave_dat_avail | irq_flag) & ~iack;

          if (done)

            slave_mode <=  slave_act;

       end

   // generate interrupt request signals

   always @(posedge wb_clk_i or negedge rst_i)

     if (!rst_i)

       wb_inta_o <=  1'b0;

     else if (wb_rst_i)

       wb_inta_o <=  1'b0;

     else

       // interrupt signal is only generated when IEN (interrupt enable bit 

       // is set)       

       wb_inta_o <=  irq_flag && ien;

   // assign status register bits

   assign sr[7]   = rxack;

   assign sr[6]   = i2c_busy;

   assign sr[5]   = al;

   assign sr[4]   = slave_mode; // reserved

   assign sr[3]   = slave_dat_avail;

   assign sr[2]   = slave_dat_req;

   assign sr[1]   = tip;

   assign sr[0]   = irq_flag;

endmodule