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. Table 33-4 describes the available keys and the condition required when doing
the operation with the key active.
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 |
Table 33-5 gives an overview of the available key signatures that must be shifted in to activate the interfaces.
Key Name | Key Signature (LSB Written First) | Size |
---|---|---|
Chip Erase | 0x4E564D4572617365 | 64 bits |
NVMPROG | 0x4E564D50726F6720 | 64 bits |
USERROW-Write | 0x4E564D5573267465 | 64 bits |