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/////////////////////////////////////////////////////////////////////
////                                                             ////
////  WISHBONE rev.B2 compliant I2C Master byte-controller       ////
////                                                             ////
////                                                             ////
////  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_byte_ctrl.v,v 1.8 2009-01-19 20:29:26 rherveille Exp $
//
//  $Date: 2009-01-19 20:29:26 $
//  $Revision: 1.8 $
//  $Author: rherveille $
//  $Locker:  $
//  $State: Exp $
//
// Change History:
//               $Log: not supported by cvs2svn $
//               Revision 1.7  2004/02/18 11:40:46  rherveille
//               Fixed a potential bug in the statemachine. During a 'stop' 2 cmd_ack signals were generated. Possibly canceling a new start command.
//
//               Revision 1.6  2003/08/09 07:01:33  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 1.5  2002/12/26 15:02:32  rherveille
//               Core is now a Multimaster I2C controller
//
//               Revision 1.4  2002/11/30 22:24:40  rherveille
//               Cleaned up code
//
//               Revision 1.3  2001/11/05 11:59:25  rherveille
//               Fixed wb_ack_o generation bug.
//               Fixed bug in the byte_controller statemachine.
//               Added headers.
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
 
`include "i2c_master_slave_defines.v"
 
module i2c_master_byte_ctrl 
  (
   clk, my_addr, rst, nReset, ena, clk_cnt, start, stop, read, write, ack_in, 
   din, cmd_ack, ack_out, dout, i2c_busy, i2c_al, scl_i, sl_cont, scl_o, 
   scl_oen, sda_i, sda_o, sda_oen,slave_dat_req, slave_en, slave_dat_avail,
   slave_act, slave_cmd_ack
   );
 
 
   //
   // inputs & outputs
   //
   input clk;     // master clock
   input my_addr; // Slave address input
   input rst;     // synchronous active high reset
   input nReset;  // asynchronous active low reset
   input ena;     // core enable signal
   input sl_cont;
   input [15:0] clk_cnt; // 4x SCL
 
   // control inputs
   input 	start;
   input 	stop;
   input 	read;
   input 	write;
   input 	ack_in;
   input [7:0] 	din;
 
   // status outputs
   output       cmd_ack;
   reg 		cmd_ack;
   output       ack_out;
   reg 		ack_out;
   output       i2c_busy;
   output       i2c_al;
   output [7:0] dout;
 
   // I2C signals
   input 	scl_i;
   output 	scl_o;
   output 	scl_oen;
   input 	sda_i;
   output 	sda_o;
   output 	sda_oen;
   input 	slave_en;
   output reg 	slave_dat_req;
   output reg 	slave_dat_avail;
   output reg 	slave_act;
   output reg 	slave_cmd_ack;
   //
   // Variable declarations
   //
 
   // statemachine
   parameter [9:0] ST_IDLE       = 10'b00_0000_0000;
   parameter [9:0] ST_START      = 10'b00_0000_0001;
   parameter [9:0] ST_READ       = 10'b00_0000_0010;
   parameter [9:0] ST_WRITE      = 10'b00_0000_0100;
   parameter [9:0] ST_ACK        = 10'b00_0000_1000;
   parameter [9:0] ST_STOP       = 10'b00_0001_0000;
   parameter [9:0] ST_SL_ACK     = 10'b00_0010_0000;
   parameter [9:0] ST_SL_RD      = 10'b00_0100_0000; 
   parameter [9:0] ST_SL_WR      = 10'b00_1000_0000;
   parameter [9:0] ST_SL_WAIT    = 10'b01_0000_0000;
   parameter [9:0] ST_SL_PRELOAD = 10'b10_0000_0000;
 
 
   reg 		sl_wait;
   // signals for bit_controller
   wire [6:0] 	my_addr;
   reg [3:0] 	core_cmd;
   reg 		core_txd;
   wire 	core_ack, core_rxd;
   wire 	sl_cont;
   // signals for shift register
   reg [7:0] 	sr; //8bit shift register
   reg 		shift, ld;
   reg 		master_mode;
   reg [1:0] 	slave_cmd_out;
   // signals for state machine
   wire 	go;
   reg [2:0] 	dcnt;
   wire 	cnt_done;
   wire 	slave_ack;
 
 
   //Slave signals
   wire 	slave_adr_received;
   wire [7:0] 	slave_adr;
 
 
   reg [1:0] 	slave_cmd;
   //
   // Module body
   //
 
   // hookup bit_controller
   i2c_master_bit_ctrl bit_controller 
     (
      .clk     ( clk      ),
      .rst     ( rst      ),
      .nReset  ( nReset   ),
      .ena     ( ena      ),
      .clk_cnt ( clk_cnt  ),
      .cmd     ( core_cmd ),
      .cmd_ack ( core_ack ),
      .busy    ( i2c_busy ),
      .al      ( i2c_al   ),
      .din     ( core_txd   ),
      .dout    ( core_rxd ),
      .scl_i   ( scl_i    ),
      .scl_o   ( scl_o    ),
      .scl_oen ( scl_oen  ),
      .sda_i   ( sda_i    ),
      .sda_o   ( sda_o    ),
      .sda_oen ( sda_oen  ),
      .slave_adr_received ( slave_adr_received  ),
      .slave_adr  ( slave_adr  ),
      .master_mode (master_mode),
      .cmd_slave_ack (slave_ack),
      .slave_cmd (slave_cmd_out),
      .sl_wait (sl_wait),
      .slave_reset (slave_reset)
      );
 
   reg 		slave_adr_received_d;
   // generate go-signal
   assign go = (read | write | stop) & ~cmd_ack;
 
   // assign dout output to shift-register
   assign dout = sr;
 
   always @(posedge clk or negedge nReset)
     if (!nReset)
       slave_adr_received_d <=  1'b0;
     else
       slave_adr_received_d <=   slave_adr_received;
 
   // generate shift register
   always @(posedge clk or negedge nReset)
     if (!nReset)
       sr <=  8'h0;
     else if (rst)
       sr <=  8'h0;
     else if (ld)
       sr <=  din;	  
     else if (shift)
       sr <=  {sr[6:0], core_rxd};
     else if (slave_adr_received_d & slave_act)
       sr <=  {slave_adr[7:1], 1'b0};
 
 
 
   // generate counter
   always @(posedge clk or negedge nReset)
     if (!nReset)
       dcnt <=  3'h0;
     else if (rst)
       dcnt <=  3'h0;
     else if (ld)
       dcnt <=  3'h7;
 
     else if (shift)
       dcnt <=  dcnt - 3'h1;
 
   assign cnt_done = ~(|dcnt);
 
   //
   // state machine
   //
   reg [9:0] 	c_state; // synopsys enum_state
 
 
 
   always @(posedge clk or negedge nReset)
     if (!nReset)
       begin
	  sl_wait <=  1'b0;
	  core_cmd <=  `I2C_CMD_NOP;
	  core_txd <=  1'b0;
	  shift    <=  1'b0;
	  ld       <=  1'b0;	        
	  cmd_ack  <=  1'b0;
	  c_state  <=  ST_IDLE;
	  ack_out  <=  1'b0;
	  master_mode <=  1'b0;
	  slave_cmd  <=  2'b0;
	  slave_dat_req	<=  1'b0;  
          slave_dat_avail	<=  1'b0;
	  slave_act <=  1'b0;
	  slave_cmd_out <=  2'b0;
	  slave_cmd_ack <=  1'b0;
       end
     else if (rst | i2c_al | slave_reset)
       begin
	  core_cmd <=  `I2C_CMD_NOP;
	  core_txd <=  1'b0;
          shift    <=  1'b0;
          sl_wait  <=  1'b0;
	  ld       <=  1'b0;
	  cmd_ack  <=  1'b0;
	  c_state  <=  ST_IDLE;
	  ack_out  <=  1'b0;
	  master_mode <=  1'b0;
	  slave_cmd  <=  2'b0;
	  slave_cmd_out <=  2'b0;
	  slave_dat_req	<=  1'b0;  
          slave_dat_avail	<=  1'b0;
          slave_act <=  1'b0;
          slave_cmd_ack <=  1'b0;
       end
     else
       begin
	  slave_cmd_out <=  slave_cmd;
	  // initially reset all signals
	  core_txd <=  sr[7];
	  shift    <=  1'b0;
	  ld       <=  1'b0;	      
	  cmd_ack  <=  1'b0;
	  slave_cmd_ack <=  1'b0;
 
	  case (c_state) // synopsys full_case parallel_case
	    ST_IDLE:
	      begin
	         slave_act <=  1'b0;
	         if (slave_en & slave_adr_received & 
		     (slave_adr[7:1] == my_addr )) begin
 
		    c_state  <=  ST_SL_ACK;
		    master_mode <=  1'b0;
		    slave_act <=  1'b1;
		    slave_cmd <=  `I2C_SLAVE_CMD_WRITE;
		    core_txd <=  1'b0;
 
		 end
		 else if (go && !slave_act )
	           begin
	              if (start )
	                begin
	                   c_state  <=  ST_START;
	                   core_cmd <=  `I2C_CMD_START;
	                   master_mode <=  1'b1;
	                end
	              else if (read)
	                begin
	                   c_state  <=  ST_READ;
	                   core_cmd <=  `I2C_CMD_READ;
	                end
	              else if (write)
	                begin
	                   c_state  <=  ST_WRITE;
	                   core_cmd <=  `I2C_CMD_WRITE;
	                end
	              else // stop
	                begin
	                   c_state  <=  ST_STOP;
	                   core_cmd <=  `I2C_CMD_STOP;
 
	                end
 
	              ld <=  1'b1;
	           end
 
	      end
            ST_SL_RD: //If master read, slave sending data
              begin  
		 slave_cmd <=  `I2C_SLAVE_CMD_NOP;      
		 if (slave_ack) begin
		    if (cnt_done) begin
	               c_state   <=  ST_SL_ACK;
	               slave_cmd <=  `I2C_SLAVE_CMD_READ;
	            end
	            else
	              begin
	                 c_state   <=  ST_SL_RD;       
	                 slave_cmd <=  `I2C_SLAVE_CMD_WRITE; 
	                 shift     <=  1'b1;
	              end
		 end
              end       
            ST_SL_WR: //If master write, slave reading data   
              begin
		 slave_cmd <=  `I2C_SLAVE_CMD_NOP;           
		 if (slave_ack)
	           begin
	              if (cnt_done)
	                begin
	                   c_state  <=  ST_SL_ACK;
	                   slave_cmd <=  `I2C_SLAVE_CMD_WRITE;
	                   core_txd <=  1'b0;
	                end
	              else
	                begin
	                   c_state  <=  ST_SL_WR;
	                   slave_cmd <=  `I2C_SLAVE_CMD_READ;
	                end
	              shift    <=  1'b1;
	           end
	      end
            ST_SL_WAIT: //Wait for interupt-clear and hold SCL in waitstate
              begin
                 sl_wait <=  1'b1;
                 if (sl_cont) begin
                    sl_wait <=  1'b0; 
                    ld <=  1'b1;	  
                    slave_dat_req	<=  1'b0;  
                    slave_dat_avail	<=  1'b0;   
                    c_state   <=  ST_SL_PRELOAD;                  
	         end   	               
              end
 
            ST_SL_PRELOAD:           
              if (slave_adr[0]) begin 
	         c_state   <=  ST_SL_RD;
	         slave_cmd <=  `I2C_SLAVE_CMD_WRITE;
	      end 
	      else begin                    
	         c_state  <=  ST_SL_WR;
	         slave_cmd <=  `I2C_SLAVE_CMD_READ;		 
	      end 
 
            ST_SL_ACK:
              begin
		 slave_cmd <=  `I2C_SLAVE_CMD_NOP;  
		 if (slave_ack)  begin
                    ack_out <=  core_rxd;
                    slave_cmd_ack  <=  1'b1;
                    if (!core_rxd) begin // Valid ack recived
                       // generate slave command acknowledge signal if 
		       // succesful transfer	                  
                       c_state   <=  ST_SL_WAIT;	 
	               if (slave_adr[0]) begin // I2C read request
	                  slave_dat_req	<=  1'b1;
	               end 
	               else begin              // I2C write request
	                  slave_dat_avail	<=  1'b1;
	               end
	            end  
	            else begin
	               c_state   <=  ST_IDLE;
	            end 
	         end
	         else begin
	            core_txd <=  1'b0;
	         end
	      end
 
	    ST_START:
	      if (core_ack)
	        begin
	           if (read)
	             begin
	                c_state  <=  ST_READ;
	                core_cmd <=  `I2C_CMD_READ;
	             end
	           else
	             begin
	                c_state  <=  ST_WRITE;
	                core_cmd <=  `I2C_CMD_WRITE;
	             end
 
	           ld <=  1'b1;
	        end
 
	    ST_WRITE:
	      if (core_ack)
	        if (cnt_done)
	          begin
	             c_state  <=  ST_ACK;
	             core_cmd <=  `I2C_CMD_READ;
	          end
	        else
	          begin
	             c_state  <=  ST_WRITE;       // stay in same state
	             core_cmd <=  `I2C_CMD_WRITE; // write next bit
	             shift    <=  1'b1;
	          end
 
	    ST_READ:
	      if (core_ack)
	        begin
	           if (cnt_done)
	             begin
	                c_state  <=  ST_ACK;
	                core_cmd <=  `I2C_CMD_WRITE;
	             end
	           else
	             begin
	                c_state  <=  ST_READ;       // stay in same state
	                core_cmd <=  `I2C_CMD_READ; // read next bit
	             end
 
	           shift    <=  1'b1;
	           core_txd <=  ack_in;
	        end
 
	    ST_ACK:
	      if (core_ack)
	        begin
	           if (stop)
	             begin
	                c_state  <=  ST_STOP;
	                core_cmd <=  `I2C_CMD_STOP;
	             end
	           else
	             begin
	                c_state  <=  ST_IDLE;
	                core_cmd <=  `I2C_CMD_NOP;
 
			// generate command acknowledge signal
	                cmd_ack  <=  1'b1;
	             end
 
	           // assign ack_out output to bit_controller_rxd (contains 
		   // last received bit)
	           ack_out <=  core_rxd;
 
	           core_txd <=  1'b1;
	        end
	      else
	        core_txd <=  ack_in;
 
	    ST_STOP:
	      if (core_ack)
	        begin
	           c_state  <=  ST_IDLE;
	           core_cmd <=  `I2C_CMD_NOP;
 
	           // generate command acknowledge signal
	           cmd_ack  <=  1'b1;
	        end
 
	  endcase
       end
endmodule