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 1 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.

Table 1. KEY Activation Overview
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 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
Chiperase 0x4E564D4572617365 64bit
NVMPROG 0x4E564D50726F6720 64bit
USERROW-Write 0x4E564D5573267465 64bit