Datasheet

251
ATmega48PA/88PA/168PA [DATASHEET]
9223F–AVR–04/14
28. Memory Programming
28.1 Program And Data Memory Lock Bits
The Atmel
®
ATmega48PA provides two lock bits and the Atmel ATmega48PA/88PA/168PA provides six lock bits. These can
be left unprogrammed (“1”) or can be programmed (“0”) to obtain the additional features listed in Table 28-2. The lock bits
can only be erased to “1” with the chip erase command.
The Atmel ATmega48PA 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.
Table 28-1. Lock Bit Byte
(1)
Lock Bit Byte Bit No Description Default Value
7 – 1 (unprogrammed)
6 – 1 (unprogrammed)
BLB12
(2)
5 Boot Lock bit 1 (unprogrammed)
BLB11
(2)
4 Boot Lock bit 1 (unprogrammed)
BLB02
(2)
3 Boot Lock bit 1 (unprogrammed)
BLB01
(2)
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 ATmega48PA/88PA/168PA.
Table 28-2. 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