35.3.7 Enabling of Key Protected Interfaces

The UPDI key mechanism protects the access to some internal interfaces and features. To activate a key, the correct key data must be transmitted by using the KEY instruction, as described in the KEY - Set Activation Key or Send System Information Block section. Table 35-5 describes the available keys and the condition required when doing the operation with the key active.

Table 35-5. Key Activation Overview
Key NameDescriptionRequirements for OperationConditions for Key Invalidation
Chip EraseStart NVM chip erase. Clear lock bits-UPDI Disable/UPDI Reset
NVMPROGActivate NVM programmingLock bits cleared. ASI_SYS_STATUS.NVMPROG setProgramming done/UPDI Reset
USERROW-WriteProgram the user row on the locked deviceLock bits set. ASI_SYS_STATUS.UROWPROG setWrite to key Status bit/UPDI Reset

Table 35-6 gives an overview of the available key signatures that must be shifted in to activate the interfaces.

Table 35-6. Key Activation Signatures
Key NameKey Signature (LSB Written First)Size
Chip Erase0x4E564D457261736564 bits
NVMPROG0x4E564D50726F6720 64 bits
USERROW-Write0x4E564D5573267465 64 bits