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 KEY - Set Activation Key or Send System Information Block. Table 33-4 describes the available keys and the condition required when doing the operation with the key active.

Table 33-4. 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 33-5 gives an overview of the available key signatures that must be shifted in to activate the interfaces.

Table 33-5. Key Activation Signatures
Key NameKey Signature (LSB Written First)Size
Chip Erase0x4E564D457261736564 bits
NVMPROG0x4E564D50726F6720 64 bits
USERROW-Write0x4E564D5573267465 64 bits