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. The following table describes the available KEYs, and the condition required when doing the operation with the KEY active. There is no requirement when shifting in the KEY, but you would, for instance, normally run a Chip Erase before enabling the NVMPROG KEY to unlock the device for debugging. But if the NVMPROGKEY is shifted in first, it will not be reset by shifting in the Chip Erase KEY afterward.

Table 33-5. KEY Activation Overview
KEY Name Description Requirements for Operation Reset
Chip Erase Start NVM Chip erase. 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

The next table gives an overview of the available KEY signatures that must be shifted in to activate the interfaces.

Table 33-6. KEY Activation Signatures
KEY Name KEY Signature (LSB Written First) Size
Chip Erase 0x4E564D4572617365 64 bits
NVMPROG 0x4E564D50726F6720 64 bits
USERROW-Write 0x4E564D5573267465 64 bits