void stop();
 void Ack();
 void Nak();
 void rstart();
 unsigned char arr[32];
main()
{
  for(i=0;i<32;i++)arr[i]=97+i;
mem_rwmany(2,0xa0,0x00); // writes 2 pages to eeprom
mem_seqrdlcdwr(2,0xa0,0x00);  // reads 2 pages n displays on lcd

}


 
void rstart()   // high to low transition of data bus while clock is high
{
 scl=0;
 sda=1;
 scl=1;
 sda=0;
scl=0;
}

void stop()  // low to high transition of data bus while clock is high
{
scl=0;
 sda=0;
 scl=1;
 sda=1;
scl=0;
 }

void Ack()      // generates ack
{
scl=0;
sda = 0;        // should be 0
 scl = 1;
 scl = 0;
 sda=1;  // has to be pulled high again....
}

void Nak()      // generates nak
{
scl=0;
sda = 1;         // shud be 1
 scl = 1;
 scl = 0;
}

// i2c mem code starts

       
void mem_rwmany(unsigned char pages,unsigned char d_add,unsigned char m_add)
// pagewrites 16 bytes to no of pages
{
 unsigned char i,page_count;
 dev_addw=d_add;
 mem_addw=m_add;

 for(i=0;i<pages;i++,page_count++)        // to write all pages*16 (max 2048) locations
  {
  if(page_count==16){ dev_addw+=2; page_count=0; } // after every 16*16=256 locations , dev_add inc by 2 to point to nxt block
   mem_datawr();                                  // write 16 bytes of arr as pagewrite to eeprom
  }
  arr_count=0;

}


void mem_datawr()  // starts the sequence of writing data to eeprom
{
 char i;
 rstart();
 mem_write(dev_addw);        // load dev_add into eeprom
 //if(sda!=0)lcddata('1');
 mem_write(mem_addw);
 for(i=0;i<16;i++,mem_addw++) mem_write(arr[arr_count++]);      // writes contents of arr[16] to eeprom using pagewrite
 
 stop();
 delay(3);
}

       
void mem_write(unsigned char value)
{
 char j;
  bitchar=value;
  for(j=0;j<8;j++)
   {
    scl=0;      // to clock in data
    sda=msbc;
    scl=1;
    bitchar=bitchar<<1;
   }
  scl=0; // to receive ack from eeprom
  scl=1;
  scl=0;
  delay(3);
 
}




void mem_seqrdlcdwr(unsigned char pages,unsigned char d_add,unsigned char m_add)  
// reads seq 32 bytes from eeprom n writes to LCD till no of pages...
{
        char i,j,page_count=0;
        mem_addr=m_add;                                 // for read operation 1st set mem_add=0 so as to refer to 0000 mem location
    dev_addr=d_add;                             // dev_add=A0 as 1st dummy write operation to be performed
       
        matrix=0x0F;

        for(i=0;i<(pages/2);i++,page_count++)     // to read all (pages/2)*32 (max 64*32 = 2048) locations
   {
    if(on_button==0){lcdclr() ; lcdstring("terminating read"); delay(50); break; }
        lcdclr();
        if(page_count==8){ dev_addr+=2;  page_count=0; } // after every 8*32=256 locations , dev_add inc by 2 to point to nxt block
        mem_seqdatard();                                  // read 16 bytes of eeprom into arr_rd[32] as sequential read
                       
        for(j=0;j<32;j++){lcddata(arr[j]); arr[j]=0; }// output 32 bytes of arr_rd to LCD, to clr read array parallely
        delay(100);  
       
   }
}



void mem_seqdatard()   // to read 32 bytes of data using  random +  seq read
{
 unsigned char i;
 rstart();
 mem_write(dev_addr);   // load in dev add
 mem_write(mem_addr);   // load in mem add
 rstart();
 mem_write(dev_addr+1);  // load in mem add +1 to indicate read operation from dat mem location
 
 for(i=0;i<32;i++)
 {
 arr[i]=mem_read();  // read 32 bytes in arr_rd
 if(i<31)Ack();                 // ack till 31 bytes
 else Nak();               // nak at the 32nd byte
 }
 stop();
 mem_addr+=32;                  // inc mem_add by 32 as 32 bytes have been read
 delay(5);
 
}


unsigned char mem_read()        // reads a char from eeprom n returns it
{
 char i;
 bitchar=0;
 scl=0;

 for(i=0;i<8;i++)
 {
  bitchar=bitchar<<1;
  scl=1;         // to clock out data at -ve transition
  scl=0;
  lsbc=sda;
 
 }
 
 return bitchar;
}
 
 
   // mem code ends