multi slave in I2C bus

" If you have both devices on the same bus, you will have to use 100KHz for everything."

So kind of your regular and a quick response.

Yes, As per the specification i bring the clock rate from 400 kHz to 100 kHz by setting the appropriate value in SSPADDR register, the slave doesn't acknowledge to the slave address. I'm am putting I2C_READ module with the initialization. Please verify where the mistake may be.

/*

I2C CLOCK RATE W/BRG
---------------------
FCY FCY*2 BRG VALUE FSCL (2 rollovers of BRG)
--------------------------------------------------------------
10 MHz 20 MHz 19h 400 kHz(1)
10 MHz 20 MHz 20h 312.5 kHz
10 MHz 20 MHz 3Fh 100 kHz
4 MHz 8 MHz 0Ah 400 kHz(1)
4 MHz 8 MHz 0Dh 308 kHz
4 MHz 8 MHz 28h 100 kHz
1 MHz 2 MHz 03h 333 kHz(1)
1 MHz 2 MHz 0Ah 100 kHz
1 MHz 2 MHz 00h 1 MHz(1)

Note 1: The I2C interface does not conform to the 400 kHz I2C specification (which applies to rates greater than
100 kHz) in all details, but may be used with care where higher rates are required by the application.
*/

void i2c_init(void)
{
   TRISC3=1;
   TRISC4=1;

   SSPCON=0x28;
   SSPCON2=00;
   SSPADD=0x28;
}

unsigned char DS1307_READ(unsigned char addr)
{
   unsigned char read_data;
   start();
   write(0xd0);
   //while(!ACKSTAT){}
   write(addr);
   restart();
   write(0xd1);
   check_idle();
   RCEN=1;
   check_idle();
   read_data= SSPBUF;
   check_idle();
   ACKDT=1;
   ACKEN=1;
   stop();
   return read_data;
}

" If you have both devices on the same bus, you will have to use 100KHz for everything."

So kind of your regular and a quick response.

Yes, As per the specification i bring the clock rate from 400 kHz to 100 kHz by setting the appropriate value in SSPADDR register, the slave doesn't acknowledge to the slave address. I'm am putting I2C_READ module with the initialization. Please verify where the mistake may be.

/*

I2C CLOCK RATE W/BRG
---------------------
FCY FCY*2 BRG VALUE FSCL (2 rollovers of BRG)
--------------------------------------------------------------
10 MHz 20 MHz 19h 400 kHz(1)
10 MHz 20 MHz 20h 312.5 kHz
10 MHz 20 MHz 3Fh 100 kHz
4 MHz 8 MHz 0Ah 400 kHz(1)
4 MHz 8 MHz 0Dh 308 kHz
4 MHz 8 MHz 28h 100 kHz
1 MHz 2 MHz 03h 333 kHz(1)
1 MHz 2 MHz 0Ah 100 kHz
1 MHz 2 MHz 00h 1 MHz(1)

Note 1: The I2C interface does not conform to the 400 kHz I2C specification (which applies to rates greater than
100 kHz) in all details, but may be used with care where higher rates are required by the application.
*/

void i2c_init(void)
{
   TRISC3=1;
   TRISC4=1;

   SSPCON=0x28;
   SSPCON2=00;
   SSPADD=0x28;
}

unsigned char DS1307_READ(unsigned char addr)
{
   unsigned char read_data;
   start();
   write(0xd0);
   //while(!ACKSTAT){}
   write(addr);
   restart();
   write(0xd1);
   check_idle();
   RCEN=1;
   check_idle();
   read_data= SSPBUF;
   check_idle();
   ACKDT=1;
   ACKEN=1;
   stop();
   return read_data;
}

"... i bring the clock rate from 400 kHz to 100 kHz by setting the appropriate value in SSPADDR register ..."

Your code is for a Microchip PIC. Since Keil does not provide PIC development tools, this forum is not the place to be posting. You need to take this discussion to the Microchip forum or your compiler vendor's forum. And when you do take it there, please add what oscillator frequency you are running the PIC at (from SSPADD=0x28, I assume it's 16MHz) and you need to show the code for start(), write(), restart(), check_idle(), and stop().

Your code is for a Microchip PIC

Thank you so much Mr Henry

A lot of thanks for your co-operation. Indeed i knew that. But i was so ponder with the mistake and i wanted some body to analise. Some of your questionnaire led me to review the hardware and i took the RTC segment to a separate board other than my working mother board which comprise of few more devices like EEPROM and shift registers. Now i con able to communicate with DS1307 and can reed the subsequent registers as well. But as you know still there is more to do. I will let you know the further growth definitely.

Thanks again.

Thanks Mr Henry

Now its working fine. I hope I'll always find you there in my trouble.

Thank you again