ATMEGA48V_09 Datasheet, PDF (284/378 Pages) ATMEL Corporation – 8-bit Microcontroller with 8K Bytes In-System Programmable Flash

27. Memory Programming
27.1
Program And Data Memory Lock Bits
The ATmega88/168 provides six Lock bits which can be left unprogrammed (“1”) or can be pro-
grammed (“0”) to obtain the additional features listed in Table 27-2. The Lock bits can only be
erased to “1” with the Chip Erase command.The ATmega48 has no separate Boot Loader sec-
tion. The SPM instruction is enabled for the whole Flash if the SELFPRGEN fuse is programmed
(“0”), otherwise it is disabled.
Table 27-1. Lock Bit Byte⁽¹⁾
Lock Bit Byte
Bit No
7
6
BLB12⁽²⁾
5
BLB11⁽²⁾
4
BLB02⁽²⁾
3
BLB01⁽²⁾
2
LB2
1
LB1
0
Description
–
–
Boot Lock bit
Boot Lock bit
Boot Lock bit
Boot Lock bit
Lock bit
Lock bit
Default Value
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
Notes: 1. “1” means unprogrammed, “0” means programmed
2. Only on ATmega88/168.
Table 27-2. Lock Bit Protection Modes⁽¹⁾⁽²⁾
Memory Lock Bits
Protection Type
LB Mode
LB2
LB1
1
1
1
No memory lock features enabled.
Further programming of the Flash and EEPROM is disabled in
2
1
0
Parallel and Serial Programming mode. The Fuse bits are
locked in both Serial and Parallel Programming mode.⁽¹⁾
Further programming and verification of the Flash and EEPROM
3
0
0
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⁾
Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
284 ATmega48/88/168
2545R–AVR–07/09