Datasheet

Figure 27-2. Memory Sections
0x0000
Flashend
Program Memory
BOOTSZ = '11'
Application Flash Section
Boot Loader Flash Section
Flashend
Program Memory
BOOTSZ = '10'
0x0000
Program Memory
BOOTSZ = '01'
Program Memory
BOOTSZ = '00'
Application Flash Section
Boot Loader Flash Section
0x0000
Flashend
Application Flash Section
Flashend
End RWW
Start NRWW
Application Flash Section
Boot Loader Flash Section
Boot Loader Flash Section
End RWW
Start NRWW
End RWW
Start NRWW
0x0000
End RWW, End Application
Start NRWW, Start Boot Loader
Application Flash SectionApplication Flash Section
Application Flash Section
Read-While-Write SectionNo Read-While-Write Section
Read-While-Write SectionNo Read-While-Write Section
Read-While-Write SectionNo Read-While-Write SectionRead-While-Write SectionNo Read-While-Write Section
End Application
Start Boot Loader
End Application
Start Boot Loader
End Application
Start Boot Loader
27.5. 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 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. The fuses cannot be changed by the MCU itself. This means that
once the Boot Reset Fuse is programmed, 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.
Atmel ATmega644A [DATASHEET]
Atmel-42716C-ATmega644A_Datasheet_Complete-10/2016
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