In I3C v1.1 and v1.0, the SETXTIME Broadcast and Direct CCC had a Defining Byte. However, the new Direct CCC framing model introduced in I3C v1.1 used Defining Bytes differently after the Direct CCC. This was done to allow the I3C Controller to send the Defining Byte after the Command Code and before the first Repeated START; doing so gives an individual I3C Target the opportunity to ACK or NACK its Dynamic Address, based on its cached values of the Command Code and Defining Byte (see Q18.3, "What has changed in CCC use or coding in I3C v1.1 or v1.1.1?"). The SETXTIME CCC’s definition of a Defining Byte was not aligned with this new standard framing model, which was a source of confusion.

Since the SETXTIME CCC used this byte as a Sub-Command, the I3C v1.1.1 specification now clarifies this by renaming the SETXTIME CCC Defining Byte: it is now called the Sub-Command Byte, since in the Direct CCC format the byte is sent after the Dynamic Address.

FAQ Type: 
I3C