In order to prevent address clashes, due to the limited range of the 7 bit addresses, a new 10 bit address scheme has been introduced. This enhancement can be mixed with 7 bit addressing and increases the available address range about ten times.
After the start condition, a leading '11110' introduces the 10 bit addressing scheme.
The last two address bits of the first byte concatenated with the eight bits of the second byte form the whole 10 bit address. Devices which only use 7 bit addressing simply ignore messages with the leading '11110'.
The following picture shows the first two bytes of a transfer with a 10 bit address.
In a Combined Transfer, after the Repeated Start in some cases only the first byte of the 10 bit address is transmitted. Please consult the I2C specification for details.