Typically, an I3C Device that supports Group Addressing can be assigned to one or more Group Addresses, but has the same I3C Target configuration and state as any other I3C Target (i.e., its role does not change). In  effect, this Device gains the ability to receive I3C transfers that are addressed (i.e., targeted) to the Group Addresses to which it might be currently assigned, but the same configuration or state applies to the entire Target, equally for its assigned Dynamic Address as well as any and all assigned Group Addresses.

For some configuration changes, the I3C Controller may use certain Direct CCCs to configure an I3C Target,  either individually (i.e., by sending the Direct Write or Direct SET CCC to its Dynamic Address) or in a multicast manner (i.e., by sending the Direct SET CCC to the assigned Group Address). When used as a multicast, the Direct CCC is received by all I3C Targets that are assigned to that Group, and all such I3C Targets apply the same configuration change (if that CCC is supported), exactly as though each I3C Target had received the same Direct CCC addressed to its Dynamic Address. No other internal state is required, and no difference in behavior is expected, when such Direct CCCs are sent to a commonly-assigned Group Address vs. each individual Dynamic Address (see the specification at Section 5.1.9.4).

For other configuration changes, specifically for Multi-Lane configuration changes (if the I3C Target supports Multi-Lane transfers and separate Group Address configurations for Multi-Lane transfers, as defined in specification Section 5.3.1.1.1), a Direct CCC sent to a Group Address is a special configuration operation,  and the I3C Target must store this configuration differently than it would for the equivalent Direct CCC sent to its Dynamic Address. The MLANE CCC is a special case requiring different handling, where the Group Address must be treated specially (i.e., differently than the MLANE CCC sent to a Dynamic Address).

Other Direct CCCs are defined in a different way, and the I3C Target must treat Group Addresses specially.  Certain Direct CCCs should never be sent to a Group Address (see the specification at Section 5.1.2.1.3 and Section 5.1.9.4.)

Note: Section 5.1.4.4 in v1.1 of the I3C specification has a technical inaccuracy when it states that the SETGRPA CCC “assigns and unassigns a Group Address” to I3C Devices. In fact, the SETGRPA CCC only assigns a Group Address, it does not unassign a Group Address. This misstatement has been corrected in v1.1.1 of the I3C specification.

FAQ Category:

FAQ Type: 
I3C