34.6.2.5.3 Receiving and Transmitting Data Packets

After the I²C client receives an address packet, it responds according to the direction either by waiting for the data packet to be received or by starting to send a data packet by writing to DATA.DATA. When a data packet is received or sent, INTFLAG.DRDY is set. After receiving data, the I²C client sends an acknowledge according to CTRLB.ACKACT.

Case 1: Data received

INTFLAG.DRDY is set and SCL is held low, pending software interaction.

Case 2: Data sent

When a byte transmission is successfully completed, the INTFLAG.DRDY Interrupt flag is set. If NACK is received, indicated by STATUS.RXNACK = 1, the I²C client must expect a stop or a repeated start to be received. The I²C client must release the data line to allow the I²C host to generate a stop or repeated start. Upon detecting a Stop condition, the Stop Received bit in the Interrupt Flag register (INTFLAG.PREC) is set and the I²C client returns to Idle state.