Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
242
25. Memory Programming
25.1 Program And Data Memory Lock Bits
The Atmel
®
ATmega88/168 provides six lock bits which can be left unprogrammed (“1”) or can be programmed (“0”) to
obtain the additional features listed in Table 25-2. The lock bits can only be erased to “1” with the chip erase command.The
Atmel ATmega48 has no separate boot loader section. The SPM instruction is enabled for the whole flash if the
SELFPRGEN fuse is programmed (“0”), otherwise it is disabled.
Table 25-1. Lock Bit Byte
(1)
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)
Notes: 1. “1” means unprogrammed, “0” means programmed
2. Only on Atmel ATmega88/168.
Table 25-2. Lock Bit Protection Modes
(1)(2)
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.
(1)
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.
(1)
Notes: 1. Program the fuse bits and boot lock bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed