Error Type TE5 covers illegally formatted CCCs that an I3C Target might see on the I3C Bus.

Due to confusion around the use of the words “illegally formatted” in the I3C v1.0 specification, I3C v1.1 more precisely defined what errors are considered to be instances of Error Type TE5. This section covers only four cases of errors, as follows.

  • The first two cases listed in I3C v1.1 are Unsupported Command Codes and Unsupported Defining Bytes (i.e., for a supported Command Code), both of which are ignored by a Target if not supported.
    Note that these are not strictly “illegally formatted” CCCs per se according to v1.1.1’s clarified definition of Error Type TE5, since the CCC format itself might be correct (if the Target happened to support that CCC). Nonetheless, a Target must still NACK any Command Code or Defining Byte that it does not support, so that the Controller will see the NACK and know that the Target is unable to respond to the CCC. In cases where these commands have a special exit condition, the Target should also still wait for the applicable exit condition.
  • The two cases addressed by Error Type TE5 are when the Controller sends the wrong RnW Bit for a Direct CCC command. That is, the Controller sends a Dynamic Address and Read bit for a Direct Write or Direct SET CCC command, or vice versa. In these cases, the Target must NACK its Address, thus notifying the Controller that an error has occurred. The Controller will then use the Retry and Escalation models.

Additional Defining Bytes, or Additional Data on CCC Payloads, are not error conditions. Targets should ignore any additional unrecognized data bytes, per the specification at Section 5.1.9.2.2.

Note: In previous versions of I3C and I3C Basic, Error Type TE5 was named Error Type S5; see Q5.2, "What is an I3C “Target” Device, and why was the I3C “Slave” Device renamed?" for name change details.

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