Datasheet

34
XMEGA B [DATASHEET]
8291B–AVR–01/2013
4.15.6 LOCKBITS – Lock Bits register
 Bit 7:6 – BLBB[1:0]: Boot Lock Bit Boot Loader Section
These lock bits control the software security level for accessing the boot loader section. The BLBB bits can only be
written to a more strict locking. Resetting the BLBB bits is possible only by executing a chip erase command.
Table 4-9. Boot lock bit for the boot loader section.
 Bit 5:4 – BLBA[1:0]: Boot Lock Bit Application Section
These lock bits control the software security level for accessing the application section. The BLBA bits can only be
written to a more strict locking. Resetting the BLBA bits is possible only by executing a chip erase command.
Table 4-10. Boot lock bit for the application section.
Bit 76543210
+0x07 BLBB[1:0] BLBA[1:0] BLBAT[1:0] LB[1:0]
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 11111111
BLBB[1:0] Group Configuration Description
11 NOLOCK
No lock – no restrictions for SPM and (E)LPM accessing the boot
loader section.
10 WLOCK Write lock – SPM is not allowed to write the boot loader section.
01 RLOCK
Read lock – (E)LPM executing from the application section is not
allowed to read from the boot loader section.
If the interrupt vectors are placed in the application section,
interrupts are disabled while executing from the boot loader
section.
00 RWLOCK
Read and write lock – SPM is not allowed to write to the boot loader
section, and (E)LPM executing from the application section is not
allowed to read from the boot loader section.
If the interrupt vectors are placed in the application section,
interrupts are disabled while executing from the boot loader
section.
BLBA[1:0] Group Configuration Description
11 NOLOCK
No Lock - no restrictions for SPM and (E)LPM accessing the
application section.
10 WLOCK Write lock – SPM is not allowed to write the application section.
01 RLOCK
Read lock – (E)LPM executing from the boot loader section is not
allowed to read from the application section.
If the interrupt vectors are placed in the boot loader section,
interrupts are disabled while executing from the application section.
00 RWLOCK
Read and write lock – SPM is not allowed to write to the application
section, and (E)LPM executing from the boot loader section is not
allowed to read from the application section.
If the interrupt vectors are placed in the boot loader section,
interrupts are disabled while executing from the application section.