The device can be locked so that the memories cannot be read using the UPDI. The locking protects both the Flash (all Boot, Application Code, and Application Data sections), SRAM, and the EEPROM, including the FUSE data. This prevents successful reading of application data or code using the debugger interface. Regular memory access from within the application is still enabled.
The device is locked by writing a non-valid key to the LOCKBIT bit field in FUSE.LOCKBIT.
Memory Section | CPU Access | UPDI Access | ||
---|---|---|---|---|
Read | Write | Read | Write | |
SRAM | Yes | Yes | Yes | Yes |
Registers | Yes | Yes | Yes | Yes |
Flash | Yes | Yes | Yes | Yes |
EEPROM | Yes | Yes | Yes | Yes |
USERROW | Yes | Yes | Yes | Yes |
SIGROW | Yes | No | Yes | No |
Other fuses | Yes | No | Yes | Yes |
Memory Section | CPU Access | UPDI Access | ||
---|---|---|---|---|
Read | Write | Read | Write | |
SRAM | Yes | Yes | No | No |
Registers | Yes | Yes | No | No |
Flash | Yes | Yes | No | No |
EEPROM | Yes | Yes | No | No |
USERROW | Yes | Yes | No | Yes(2) |
SIGROW | Yes | No | No | No |
Other fuses | Yes | No | No | No |