1.10 Hot-Join (HJ) Transaction

A Hot-Join (HJ) Transaction is a special type of IBI transaction that begins with the reserved Hot-Join Address 7’h02. Before an HJ can be requested, the bus idle time must be configured using the I3CxBIDL register to meet the minimum 200 µs specification. The module can perform an HJ request when the Target is HJ capable (HJCAP = 1), HJ is enabled on the bus by the controller (HJEN = 1), and the Target does not have a Dynamic Address assigned.

An HJ can be requested by setting the HJREQ bit, after which the Target sends the reserved HJ Address 7’h02 in read mode on the bus for arbitration after either one of the following conditions happens on the bus:

• Bus Idle condition is detected on the bus, after which the Target issues a Start by pulling SDA low and participates in address arbitration (Standard HJ)
• Another device issues a Start on the bus before the Bus Idle condition is detected, after which the Target participates in address arbitration (Passive HJ)

If the Target device wins arbitration and the controller ACKs, the Target automatically participates in the Dynamic Address Assignment process when it sees the next ENTDAA CCC on the bus. The controller may or may not immediately send the ENTDAA CCC. Once the Target receives a Dynamic Address, the Dynamic Address Changed DACHIF flag is set, and the HJREQ bit is cleared.

If the Target device loses arbitration or the controller NACKs, the Target attempts to request an HJ again, automatically, until the Arbitration Request Limit in the I3CxRETRY register has been reached, following which the HJ Error HJEIF flag is set and HJREQ bit is cleared.