ATMEGA128A_1 Datasheet, PDF (281/386 Pages) ATMEL Corporation – Write/Erase cycles: 10,000 Flash/100,000 EEPROM

ATmega128A
Table 25-2. Boot Lock Bit0 Protection Modes (Application Section)⁽¹⁾
BLB0 mode BLB02 BLB01 Protection
1
1
1
No restrictions for SPM or LPM accessing the Application
section.
2
1
0
SPM is not allowed to write to the Application section.
SPM is not allowed to write to the Application section, and LPM
executing from the Boot Loader section is not allowed to read
3
0
0
from the Application section. If interrupt vectors are placed in the
Boot Loader section, interrupts are disabled while executing
from the Application section.
LPM executing from the Boot Loader section is not allowed to
4
0
1
read from the Application section. If interrupt vectors are placed
in the Boot Loader section, interrupts are disabled while
executing from the Application section.
Note: 1. “1” means unprogrammed, “0” means programmed
Table 25-3. Boot Lock Bit1 Protection Modes (Boot Loader Section)⁽¹⁾
BLB1 mode
1
BLB12
1
BLB11
1
Protection
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
SPM is not allowed to write to the Boot Loader section, and LPM
executing from the Application section is not allowed to read
3
0
0
from the Boot Loader section. If interrupt vectors are placed in
the Application section, interrupts are disabled while executing
from the Boot Loader section.
LPM executing from the Application section is not allowed to
4
0
1
read from the Boot Loader section. If interrupt vectors are
placed in the Application section, interrupts are disabled while
executing from the Boot Loader section.
Note: 1. “1” means unprogrammed, “0´means programmed
25.6
Entering the Boot Loader Program
Entering the Boot Loader takes place by a jump or call from the application program. This may
be initiated by a trigger such as a command received via USART, or SPI interface. Alternatively,
the Boot Reset Fuse can be programmed so that the Reset Vector Reset is pointing to the Boot
Flash start address after a reset. In this case, the Boot Loader is started after a reset. After the
application code is loaded, the program can start executing the application code. Note that the
fuses cannot be changed by the MCU itself. This means that once the Boot Reset Fuse is pro-
grammed, the Reset Vector will always point to the Boot Loader Reset and the fuse can only be
changed through the serial or parallel programming interface.
Table 25-4. Boot Reset Fuse⁽¹⁾
BOOTRST Reset Address
1
Reset Vector = Application Reset (address $0000)
0
Reset Vector = Boot Loader Reset (see Table 25-6 on page 288)
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