36.3.8 Enabling of Key Protected Interfaces

The access to some internal interfaces and features is protected by the UPDI key mechanism. To activate a key, the correct key data must be transmitted by using the KEY instruction, as described in 36.3.3.8 KEY - Set Activation Key or Send System Information Block. Table 36-4 describes the available keys and the condition required for starting the operation after the key has been loaded.

Table 36-4. Key Activation Overview
Key Name Description Requirements for Operation Conditions for Key Invalidation
Chip Erase Start NVM chip erase. Clear lock bits. — UPDI Disable/UPDI Reset
NVMPROG Activate NVM programming Lock bits cleared. ASI_SYS_STATUS.PROGSTART set. Programming done/UPDI Reset
USERROW-Write Program the user row on the locked device ASI_SYS_STATUS.UROWSTART set Write to key Status bit/UPDI Reset

Table 36-5 gives an overview of the available key signatures that must be shifted in to activate the interfaces.

Table 36-5. Key Activation Signatures
Key Name Key Signature (LSB Written First) Size
Chip Erase 0x4E564D4572617365 64 bits
NVMPROG 0x4E564D50726F6720 64 bits
USERROW-Write 0x4E564D5573267465 64 bits