35.3.3.8 KEY - Set Activation Key or Send System Information Block

The KEY instruction is used for communicating key bytes to the UPDI or for providing the programmer with a System Information Block (SIB), opening up for executing protected features on the device. See the Key Activation Overview table in the Enabling of Key Protected Interfaces section for an overview of functions that are activated by keys. For the KEY instruction, only a 64-bit key size is supported. The maximum supported size for SIB is 128 bits.

Figure 35-16 shows the transmission of a key and the reception of a SIB. In both cases, the Size C (SIZE_C) field in the operand determines the number of frames being sent or received. There is no response after sending a KEY to the UPDI. When requesting the SIB, data will be transmitted from the UPDI according to the current guard time setting.