I2C PCA9564: simple question

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Joined Apr 1, 2008
In this particular chip (probably with all I2C chips), whenever you send a byte of information over the line, you expect an acknowledge back from the receiver.

Does this come over the SDA line or the SCL line of the bus? Thanks in advance.


Joined Feb 24, 2006
It comes back on the SDA line. It is an open collector, so multiple devices can be connected together. Anybody can pull it low, and the pullup resistor takes it high as long as nobody is pulling it low. If a device is lonely, there will be no ACK pulse.