27.3.4.3.1.1 Case S1: Address Packet Accepted - Direction Bit Set

If the R/W direction flag is set, this indicates a master read operation. The SCL line is forced low by the slave, stretching the bus clock. If ACK is sent by the slave, the slave hardware will set the data interrupt flag indicating data is needed for transmit. Data, repeated Start, or Stop can be received after this. If NACK is sent by the slave, the slave will wait for a new Start condition and address match.