Datasheet

298
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
27. Memory programming
27.1 Program And Data Memory Lock Bits
The Atmel ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P provides six Lock bits
which can be left unprogrammed (“1”) or can be programmed (“0”) to obtain the additional fea-
tures listed in Table 27-2. 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
(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)
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.
210
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)
300
Further programming and verification of the Flash and EEPROM
is disabled in Parallel, JTAG 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
111
No restrictions for SPM or (E)LPM accessing the Application
section.
2 1 0 SPM is not allowed to write to the Application section.
300
SPM is not allowed to write to the Application section, and
(E)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.
401
(E)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.