I3C Hot-Join Address

The Target transmits the 7-bit Reserved I3C Hot-Join Address 7’h02 after a Start following a Bus Idle Condition to initiate a Hot-Join request to the Controller.

The 7’h02 Hot-Join Address can only be transmitted by a target device on the bus (and never by the Controller) following a Start condition. A Hot-Join request is always made in Write mode (Target pulls SDA low for R/W bit, represented as 7'h02/W). The Controller responds to this request by acknowledging (or not acknowledging) through the ACK/NACK bit that follows the R/W bit. Refer to section Hot-Join Mechanism for details on Controller actions during a Hot-Join mechanism.

The 7’h02 Hot-Join Address is transmitted in Open Drain mode since it is part of the arbitrable address header, meaning multiple devices on the bus can also drive the SDA line to transmit an address on the bus at the same time. Since 7’h02 is an extremely high-priority address, the Target will almost always win the arbitration if another device is transmitting another address at the same time. Refer to I3C Address Arbitration section for more information on the address arbitration process. If multiple target devices on the bus send the 7’h02 Hot-Join Address simultaneously, then the priority is resolved during the Dynamic Address Assignment process, which usually follows the Hot-Join request.