7.3.5.2 Slave Transmitter Mode:

The first byte transmitted by the master is the slave address, with the R/W bit high. The slave acknowledges reception of a valid slave address. The next byte is transmitted by the slave and is the most significant byte of the register indicated by the pointer register. The master acknowledges reception of the data byte. The next byte transmitted by the slave is the least significant byte. The master acknowledges reception of the data byte. The master can terminate data transfer by generating a not-acknowledge bit on reception of any data byte, or by generating a start or stop condition.