29.5.1.2 I²C Client 10-Bit Addressing Mode

In 10-bit Addressing mode, the first received byte is compared to the binary value of ‘1 1 1 1 0 A9 A8 0’. A9 and A8 are the two MSbs of the 10-bit address, and are stored in bits 2 and 1 of the SSPxADD register.

After the acknowledge of the high byte, the UA bit is set and SCL is held low until the user updates SSPxADD with the low address. The low address byte is clocked in and all eight bits are compared to the low address value in SSPxADD. Even if there is not an address match, SSPxIF and UA are set, and SCL is held low until SSPxADD is updated to receive a high byte again. When SSPxADD is updated, the UA bit is cleared. This ensures the module is ready to receive the high address byte on the next communication.

A high and low address match as a write request is required at the start of all 10-bit addressing communication. A transmission can be initiated by issuing a Restart once the client is addressed, and clocking in the high address with the R/W bit set. The client hardware will then acknowledge the read request and prepare to clock out data. This is only valid for a client after it has received a complete high and low address byte match.