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 KEY - Set Activation Key or Send System Information Block. Table 1 describes the available keys and the condition required for starting the operation after the key has been loaded.

Table 1. 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 2 gives an overview of the available key signatures that must be shifted in to activate the interfaces.

Table 2. 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