void I2C_start();
void I2C_write(char);
void I2C_delay();
void I2C_stop();
char I2C_read();
void RTC_write(char,char);
char RTC_read(char);

void setup() {
Serial.begin(9600);
RTC_write(0x00,0x28);
RTC_write(0x01,0x59);
RTC_write(0x02,0x23);
while(1)
{
char second=RTC_read(0x00);
char minute=RTC_read(0x01);
char hour=RTC_read(0x02);
Serial.print("Time :");
Serial.print(hour,HEX);
Serial.print("/");
Serial.print(minute,HEX);
Serial.print("/");
Serial.println(second,HEX);
delay(1000);
}
}

void RTC_write(char address,char data)
{
I2C_start();
I2C_write(0xD0);
I2C_write(address);
I2C_write(data);
I2C_stop();
}

char RTC_read(char address)
{
I2C_start();
I2C_write(0xD0);
I2C_write(address);
I2C_start();
I2C_write(0xD1); 
volatile char data=I2C_read();
I2C_stop();
return data;
}

void I2C_start()
{
volatile char *portf_dir=(volatile char*)0x30;
*portf_dir=0x03;
volatile char *portf_out=(volatile char*)0x31;
*portf_out=0x03;
I2C_delay();
*portf_out=0x02;
I2C_delay();
*portf_out=0x00;
}

void I2C_write(char data)
{
volatile char *portf_dir=(volatile char*)0x30;
volatile char *portf_out=(volatile char*)0x31;
char k,a;
for(k=7;k>=0;k--) 
{
a=(data>>k)&0x01;
if(a==1) 
{
*portf_out|=0x01;
}
else 
{
*portf_out&=~0x01;
}
I2C_delay();
*portf_out|=0x02;
I2C_delay();
*portf_out&=~0x02;
}
*portf_dir&=~0x01;
I2C_delay();
*portf_out|=0x02;
I2C_delay();
*portf_out&=~0x02;
*portf_dir|=0x01;
}

char I2C_read()
{
volatile char *portf_dir=(volatile char*)0x30;
*portf_dir&=~0x01;
volatile char *portf_out=(volatile char*)0x31;
volatile char *portf_in=(volatile char*)0x2F;
volatile char k,data=0x00;
for(k=0;k<8;k++) 
{
*portf_out&=~0x02;
I2C_delay();
*portf_out|=0x02;
I2C_delay();
data=(data<<1)|(*portf_in & 0x01);
}
*portf_dir|=0x01;
*portf_out|=0x01;
*portf_out&=~0x02;
I2C_delay();
*portf_out|=0x02;
I2C_delay();
*portf_out=0x00;


return data;
}

void I2C_stop()
{
volatile char *portf_dir=(volatile char*)0x30;
*portf_dir|=0x01;
volatile char *portf_out=(volatile char*)0x31;
*portf_out|=0x02;
I2C_delay();
*portf_out|=0x01;
I2C_delay();

}

void I2C_delay()
{
char i;
for(i=0;i<20;i++);
}

void loop() {
}