24.4.5.2 Private Data Transfers

The Target supports private read and write transfers through the I³C interface over the SCL and SDA lines.

For Private Receive and Transmit Transfers in SDR mode of operation, if the Target can accept or transmit the transaction from the Controller, it accepts the address by providing an ACK response; otherwise, the address is NACKed.

In HDR mode, if the Target Controller is not able to accept the Private Write transaction from the Controller, the data is dropped because there is no mechanism to NACK a private write transfer. For a private read transfer, a NACK response is issued.

Receiving a NACK means that an error exists in the current or previous transfer read/write, and the Controller can choose to do one of the following:

• Issue a Start/Restart and re-attempt the transfer. If the previous transfer was NACKed because of the unavailability of internal buffer space, the second transfer might be successful.
• Issue a GETSTATUS CCC to check if the NACK is due to a more permanent condition encountered by the previous transfer because of some protocol error like parity/CRC or due to overflow/underflow errors, and then re-issue the NACK transfer.