33.3.7 Enabling of KEY Protected Interfaces
Access to some internal interfaces and features are 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 instruction. Table 33-5 describes the available KEYs, and the condition
required when doing operation with the KEY active. There is no requirement when shifting
in the KEY, but you would for instance normally run a Chiperase before enabling the
NVMPROG KEY, to unlock the device for debug. But if the NVMPROGKEY is shifted in first,
it will not be reset by shifting in the Chiperase KEY afterwards.
KEY name | Description | Requirements for operation | Reset |
---|---|---|---|
Chiperase | Start NVM Chiperase. Clear Lockbits | None | UPDI Disable / UPDI Reset |
NVMPROG | Activate NVM Programming | Lockbits Cleared. ASI_SYS_STATUS.NVMPROG set. | Programming Done / UPDI Reset |
USERROW-Write | Program User Row on Locked part | Lockbits Set. ASI_SYS_STATUS.UROWPROG set | Write to KEY status bit / UPDI Reset |
Table 33-6 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 |
---|---|---|
Chiperase | 0x4E564D4572617365 | 64bit |
NVMPROG | 0x4E564D50726F6720 | 64bit |
USERROW-Write | 0x4E564D5573267465 | 64bit |