24.4.4.3 In-Band Interrupt (IBI) Detection and Handling

The I3C Target devices can initiate communication with the Active Controller through In-Band Interrupt (IBI). The following types of IBIs are possible on an I3C bus:
  • Hot-Join Request (HJ) from a Hot-Join capable Target
  • Target Interrupt Request (SIR) from a Target
  • Controller Ownership Request (MR) from a Controller capable Target (Secondary Controller)
The Controller detects (SDA low) and receives the In-Band interrupt (IBI ID). This enables the Controller to start providing the SCL clocks (period = I3CxSCLODTIM [ODLCNT] + I3CxSCLODTIM [ODHCNT]) to receive the IBI ID from the requesting Target device. The Controller detects the In-Band interrupt in the following scenarios:
  • Upon detecting a low on the SDA input port after a Power-On-Reset (POR).
  • Upon detecting an arbitration loss during an address phase of any Controller-initiated transfer following a START condition (not RESTART).
  • Upon detecting the SDA input port going low (not initiated by the Controller) following a STOP condition (Target Initiated IBI).