Memory Section Access From Cpu And Updi On Locked Device - Microchip Technology megaAVR 0 Series Manual

5.8.2.8 Lockbits
Name: LOCKBIT
Offset: 0x0A
Reset: -
Property: -
Bit 7
Access
R/W
Reset 0
Bits 7:0 – LOCKBIT[7:0] Lockbits
When the part is locked, UPDI cannot access the system bus, so it cannot read out anything but CS-
space.
Value Description
0xC5 Valid key - the device is open
other Invalid - the device is locked
5.9

Memory Section Access from CPU and UPDI on Locked Device

The device can be locked so that the memories cannot be read using the UPDI. The locking protects both
the Flash (all BOOT, APPCODE, and APPDATA 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 still is enabled.
The device is locked by writing any non-valid value to the LOCKBIT bit field in FUSE.LOCKBIT.
Table 5-5. Memory Access in Unlocked Mode (FUSE.LOCKBIT Valid)
Memory Section
SRAM
Registers
Flash
EEPROM
USERROW
SIGROW
Other Fuses
©
2018 Microchip Technology Inc.
6 5
R/W R/W
0 0
CPU Access
Read
Yes
Yes
Yes
Yes
Yes
Yes
Yes
4 3
LOCKBIT[7:0]
R/W R/W
0 0
UPDI Access
Write Read
Yes Yes
Yes Yes
Yes Yes
No Yes
Yes Yes
No Yes
No Yes
Datasheet Preliminary
®
megaAVR 0-Series
Memories
2 1
R/W R/W
0 0
(1)
Write
Yes
Yes
Yes
Yes
Yes
No
Yes
DS40002015A-page 38
0
R/W
0