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ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
27. Memory programming
27.1
Program and Data Memory Lock bits
The Atmel ATmega165A/165PA/325A/325PA/3250A/3250PA/645A/645P/6450A/6450P provides six Lock bits
which can be left unprogrammed (“1”) or can be programmed (“0”) to obtain the additional features listed in
Table27-2. The Lock bits can only be erased to “1” with the Chip Erase command.
Note:
1. “1” means unprogrammed, “0” means programmed
.
Table 27-1.
Lock Bit byte
Lock Bit byte
Bit no.
Description
Default value
7
–
1 (unprogrammed)
6
–
1 (unprogrammed)
BLB12
5
Boot Lock bit
1 (unprogrammed)
BLB11
4
Boot Lock bit
1 (unprogrammed)
BLB02
3
Boot Lock bit
1 (unprogrammed)
BLB01
2
Boot Lock bit
1 (unprogrammed)
LB2
1
Lock bit
1 (unprogrammed)
LB1
0
Lock bit
1 (unprogrammed)
Table 27-2.
Lock Bit Protection modes
Memory Lock bits
Protection type
LB Mode
LB2
LB1
1
No memory lock features enabled.
21
0
Further programming of the Flash and EEPROM is disabled in Parallel and Serial
Programming mode. The Fuse bits are locked in both Serial and Parallel
30
0
Further programming and verification of the Flash and EEPROM is disabled in
Parallel and Serial Programming mode. The Boot Lock bits and Fuse bits are locked
in both Serial and Parallel Programming mode
.(1)BLB0 Mode
BLB02
BLB01
1
No restrictions for SPM or LPM accessing the Application section.
2
1
0
SPM is not allowed to write to the Application section.
30
0
SPM is not allowed to write to the Application section, and LPM executing from the
Boot Loader section is not allowed to read from the Application section. If Interrupt
Vectors are placed in the Boot Loader section, interrupts are disabled while
executing from the Application section.
40
1
LPM executing from the Boot Loader section is not allowed to read from the
Application section. If Interrupt Vectors are placed in the Boot Loader section,
interrupts are disabled while executing from the Application section.
BLB1 Mode
BLB12
BLB11
1
No restrictions for SPM or LPM accessing the Boot Loader section.