33.3.8 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 33.3.3.8 KEY - Set Activation Key or Send System Information Block. The table below describes the available keys and the condition required when doing the operation with the key active.

Table 33-4. 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.NVMPROG set Programming done/UPDI Reset
USERROW-Write Program the user row on the locked device Lock bits set. ASI_SYS_STATUS.UROWPROG set Write to key Status bit/UPDI Reset

The table below gives an overview of the available key signatures that must be shifted in to activate the interfaces.

Table 33-5. 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