I2C Mutli slave issue

[chandu.kurapati]

Hi,

I attached the I2C bus with one master and two slaves, here two slaves are same device address and Master sends the same data to the two slaves.

My question is what happen like this type of I2C communication, two slaves are accepting the same data is it possible in the I2C protocol.

Please can any one explain about it.

Thanks & Regards,

Chandu.Kurapati.

 

[tantalos]

This is possible, i2c uses open drain outputs and two devices can drive the SCL/SDA lines at the same time. The result of this contention will be of course that when one device wants to send a bit HIGH and the other LOW the master will see LOW.
The case of a master device sending data to two slave devices should work because the only situation when two devices will drive the bus at the same time is the acknowledge phase sent by the slave devices.
So when one of the slave devices does not acknowledge the address or the data the master will not notice that.

 

[shaiko]

I2C specifications dictate that every slave on the bus must have a unique address.
2 devices with the same address on the same I2C bus make no sense. You simply won't be able to achieve reliable 2 way communication between master and slaves.

What are you trying to do?
What devices are these?

So when one of the slave devices does not acknowledge the address or the data the master will not notice that.

What tantalos said here is simply impossible.
If both devices have the same address (assuming both are turned on and working properly) there can't be a scenario when one will acknowledge the address while the other won't.

The only way I can see your configuration working - is if both slaves are exactly the same component and both are Rx only.