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8271D–AVR–05/11
ATmega48A/PA/88A/PA/168A/PA/328/P
28. Memory Programming
28.1
Program And Data Memory Lock Bits
T h e A T m e g a 4 8 A / 4 8 P A p r o v i d e s t w o L o c k b i t s a n d t h e
ATmega88A/88PA/168A/168PA/328/328Pprovides six Lock bits. These can be left unpro-
grammed (“1”) or can be programmed (“0”) to obtain the additional features listed in
The Lock bits can only be erased to “1” with the Chip Erase command.
The ATmega 48A/48PA has no separate Boot Loader section, and the SPM instruction is
enabled for the whole Flash if the SELFPRGEN fuse is programmed (“0”). Otherwise the SPM
instruction is disabled.
Notes:
1. “1” means unprogrammed, “0” means programmed.
2. Only on ATmega88A/88PA/168A/168PA/328/328P.
Notes:
1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Table 28-1.
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 28-2.
Lock Bit Protection Modes
Memory Lock Bits
Protection Type
LB Mode
LB2
LB1
1
1
1
No memory lock features enabled.
2
1
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 Programming mode.
3
0
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.