// --------------------------------------------------------------------
// Copyright (c) 2005 by Terasic Technologies Inc. 
// --------------------------------------------------------------------
//
// Permission:
//
//   Terasic grants permission to use and modify this code for use
//   in synthesis for all Terasic Development Boards and Altrea Development 
//   Kits made by Terasic.  Other use of this code, including the selling 
//   ,duplication, or modification of any portion is strictly prohibited.
//
// Disclaimer:
//
//   This VHDL or Verilog source code is intended as a design reference
//   which illustrates how these types of functions can be implemented.
//   It is the user's responsibility to verify their design for
//   consistency and functionality through the use of formal
//   verification methods.  Terasic provides no warranty regarding the use 
//   or functionality of this code.
//
// --------------------------------------------------------------------
//           
//                     Terasic Technologies Inc
//                     356 Fu-Shin E. Rd Sec. 1. JhuBei City,
//                     HsinChu County, Taiwan
//                     302
//
//                     web: http://www.terasic.com/
//                     email: support@terasic.com
//
// --------------------------------------------------------------------
//
// Major Functions:i2c controller
//
// --------------------------------------------------------------------
//
// Revision History :
// --------------------------------------------------------------------
//   Ver  :| Author            :| Mod. Date :| Changes Made:
//   V1.0 :| Joe Yang          :| 05/07/10  :|      Initial Revision
// --------------------------------------------------------------------
module I2C_Controller (
	CLOCK,
	I2C_SCLK,//I2C CLOCK
 	I2C_SDAT,//I2C DATA
	I2C_DATA,//DATA:[SLAVE_ADDR,SUB_ADDR,DATA]
	GO,      //GO transfor
	END,     //END transfor 

	ACK,      //ACK
	RESET
);
	input  CLOCK;
	input  [31:0]I2C_DATA;	
	input  GO;
	input  RESET;	
 	inout  I2C_SDAT;	
	output I2C_SCLK;
	output END;	
	output ACK;


reg SDO;
reg SCLK;
reg END;
reg [31:0]SD;
reg [6:0]SD_COUNTER;

wire I2C_SCLK=SCLK | ( ((SD_COUNTER >= 4) & (SD_COUNTER <=39))? ~CLOCK :0 );
wire I2C_SDAT=SDO?1'bz:0 ;

reg ACK1,ACK2,ACK3,ACK4;
wire ACK=ACK1 | ACK2 |ACK3 |ACK4;

//--I2C COUNTER
always @(negedge RESET or posedge CLOCK ) begin
if (!RESET) SD_COUNTER=6'b111111;
else begin
if (GO==0) 
	SD_COUNTER=0;
	else 
	if (SD_COUNTER < 41) SD_COUNTER=SD_COUNTER+1;	
end
end
//----

always @(negedge RESET or  posedge CLOCK ) begin
if (!RESET) begin SCLK=1;SDO=1; ACK1=0;ACK2=0;ACK3=0;ACK4=0; END=1; end
else
case (SD_COUNTER)
	6'd0  : begin ACK1=0 ;ACK2=0 ;ACK3=0 ;ACK4=0 ; END=0; SDO=1; SCLK=1;end
	//start
	6'd1  : begin SD=I2C_DATA;SDO=0;end
	6'd2  : SCLK=0;
	//SLAVE ADDR
	6'd3  : SDO=SD[31];
	6'd4  : SDO=SD[30];
	6'd5  : SDO=SD[29];
	6'd6  : SDO=SD[28];
	6'd7  : SDO=SD[27];
	6'd8  : SDO=SD[26];
	6'd9  : SDO=SD[25];
	6'd10 : SDO=SD[24];	
	6'd11 : SDO=1'b1;//ACK

	//SUB ADDR
	6'd12  : begin SDO=SD[23]; ACK1=I2C_SDAT; end
	6'd13  : SDO=SD[22];
	6'd14  : SDO=SD[21];
	6'd15  : SDO=SD[20];
	6'd16  : SDO=SD[19];
	6'd17  : SDO=SD[18];
	6'd18  : SDO=SD[17];
	6'd19  : SDO=SD[16];
	6'd20  : SDO=1'b1;//ACK

	//DATA
	6'd21  : begin SDO=SD[15]; ACK2=I2C_SDAT; end
	6'd22  : SDO=SD[14];
	6'd23  : SDO=SD[13];
	6'd24  : SDO=SD[12];
	6'd25  : SDO=SD[11];
	6'd26  : SDO=SD[10];
	6'd27  : SDO=SD[9];
	6'd28  : SDO=SD[8];
	6'd29  : SDO=1'b1;//ACK

	//DATA
	6'd30  : begin SDO=SD[7]; ACK3=I2C_SDAT; end
	6'd31  : SDO=SD[6];
	6'd32  : SDO=SD[5];
	6'd33  : SDO=SD[4];
	6'd34  : SDO=SD[3];
	6'd35  : SDO=SD[2];
	6'd36  : SDO=SD[1];
	6'd37  : SDO=SD[0];
	6'd38  : SDO=1'b1;//ACK

	
	//stop
    6'd39 : begin SDO=1'b0;	SCLK=1'b0; ACK4=I2C_SDAT; end	
    6'd40 : SCLK=1'b1; 
    6'd41 : begin SDO=1'b1; END=1; end 

endcase
end



endmodule
