The Offline capability, which is now indicated in the Bus Control Register (BCR), allows a Slave to become inactive on the I3C Bus at some times, but then return to normal activity later.
There are two basic types of Offline‑capable Slave:
- A Slave that is fully inactive on the I3C Bus (e.g., is powered off) and only becomes active again as the result of some external event. Such a Slave will then Hot‑Join to get a new Dynamic Address.
- A Slave that is inactive on the I3C Bus, but where some portion of the Slave is monitoring the Bus either for Slave Reset, or for the use of its Dynamic Address. The Slave may be mostly powered‑off, or in deepest sleep, but the monitoring portion retains the Slave’s Dynamic Address.
These Slaves can be awakened (i.e., can be re‑activated) by a Slave Reset or by the use of their Dynamic Address. They will take some time to become active on the Bus again, such as the RSTACT CCC recovery from Full Reset time. During the time that they are offline, and while awakening, they will not be responsive to the Master, nor will they record CCCs, nor will they necessarily retain state (e.g., the ENEC/DISEC CCCs), so the Master will have to wait for them to become active, and then might also need to configure them again. This is all by private contract (agreement).
See details in Section 184.108.40.206.5 for both I3C v1.0 (without Slave Reset) and I3C v1.1 (with Slave Reset).