Interfacing with I2C (EEPROM) chip.

Dear all,

I am using Altera Stratix II board.I need to implement I2C interface.

I have connected the I2C (AT24C04 EEPROM) to the board using 2 pins namly sda and scl.

Now My Problem is :

say for write operation ,I need to send device address , word address and data , three things.

I am showing the code below for that.

input clk_50;

inout scl ;

inout sda ;

output int_ack_device ,int_ack_word ,int_ack_data;

reg int_ack_device ,int_ack_word ,int_ack_data,exit_flag;

reg [7:0] clk_count ; //used to generate i2c clock scl

reg out_scl_s1,out_scl_s2,out_scl_s3,out_scl_s4;

reg [7:0] device_address ;

reg [7:0] word_address ;

reg [7:0] data ;

reg [5:0] state ;//making state = 1 to enter into the state machine .

reg out_sda ;

OPNDRN SDA1 (.in(out_sda ), .out(sda));

assign scl = out_scl_s4 ;

//module to derive out_scl_s4 from clk_50.

always @( out_scl_s4)

begin

if ((exit_flag == 0))

begin

case(state)

6'b000001: //generating start condition. state 1

begin

# 7500 out_sda <= 1'b0 ;

state <= 6'b000010 ;

end

6'b000010: //putting device address on bus

begin

out_sda <= device_address[7]; //1

state <= 6'b000011;

end

6'b000011:

begin

out_sda <= device_address[6]; //0

state <= 6'b000100;

end

6'b000100:

begin

out_sda <= device_address[5]; //1

state <= 6'b000101;

end

6'b000101:

begin

out_sda <= device_address[4]; //0

state <= 6'b000110;

end

6'b000110:

begin

out_sda <= device_address[3]; //0

state <= 6'b000111;

end

6'b000111:

begin

out_sda <= device_address[2]; //0

state <= 6'b001000;

end

6'b001000:

begin

out_sda <= device_address[1]; //0

state <= 6'b001001;

end

6'b001001: // putting read/write (R/!W) bit on sda

begin

out_sda <= device_address[0]; //0 w

state <= 6'b001010 ;

end

6'b001010: // value on out_sda should come from i2c device.

begin

int_ack_device <= out_sda ; //0

state <= 6'b001011 ;

end

6'b001011:

begin

out_sda <= word_address[7]; // 1 //this bit is set to one.

state <= 6'b001100 ;

end

First ack which i am receiving in int_ack_device is proper.My problem is that when in state 6'b001011: I apply 1 to out_sda.it doesnt go high at all .I am using signaltap tool for seeing the signal.

I think problem lies in holding scl line by slave.

Relevant warnings are :

Warning: Following 4 pins have nothing, GND, or VCC driving datain port -- changes to this connectivity may change fitting results

Info: Pin int_ack_device has GND driving its datain port

Info: Pin int_ack_word has GND driving its datain port

Info: Pin int_ack_data has GND driving its datain port

Info: Pin sda has GND driving its datain port /* how to remove this warning ??? */

I am seeking for help in this regard.please help.

-Thanks & Regards

Tushar