27.3.4.4 Smart Mode

The TWI interface has a Smart mode that simplifies application code and minimizes the user interaction needed to adhere to the I²C protocol. For TWI Master, Smart mode accomplishes this by automatically sending an ACK as soon as data register TWI.MDATA is read. This feature is only active when the ACKACT bit in TWIn.MCTRLA register is set to ACK. If ACKACT is set to NACK, the TWI Master will not generate a NACK bit followed by reading the Data register.

With Smart mode enabled for TWI Slave (SMEN bit in TWIn.SCTRLA), DIF (Data Interrupt Flag) will automatically be cleared if Data register (TWIn.SDATA) is read or written.