33.3.3.8 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 Table 33-4 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 33-17. KEY Instruction Operation

The figure above 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.