13
XMEGA A4U [DATASHEET]
Atmel-8387G-AVR-ATxmega16A4U-34A4U-64A4U-128A4U-Datasheet_03/2014
7.3
Flash Program Memory
The Atmel AVR XMEGA devices contain on-chip, in-system reprogrammable flash memory for program storage. The
flash memory can be accessed for read and write from an external programmer through the PDI or from application
software running in the device.
All AVR CPU instructions are 16 or 32 bits wide, and each flash location is 16 bits wide. The flash memory is
organized in two main sections, the application section and the boot loader section. The sizes of the different sections
are fixed, but device-dependent. These two sections have separate lock bits, and can have different levels of
protection. The store program memory (SPM) instruction, which is used to write to the flash from the application
software, will only operate when executed from the boot loader section.
The application section contains an application table section with separate lock settings. This enables safe storage of
nonvolatile data in the program memory.
Figure 7-1.
Flash Program Memory (Hexadecimal address).
7.3.1
Application Section
The Application section is the section of the flash that is used for storing the executable application code. The
protection level for the application section can be selected by the boot lock bits for this section. The application section
can not store any boot loader code since the SPM instruction cannot be executed from the application section.
7.3.2
Application Table Section
The application table section is a part of the application section of the flash memory that can be used for storing data.
The size is identical to the boot loader section. The protection level for the application table section can be selected by
the boot lock bits for this section. The possibilities for different protection levels on the application section and the
application table section enable safe parameter storage in the program memory. If this section is not used for data,
application code can reside here.
7.3.3
Boot Loader Section
While the application section is used for storing the application code, the boot loader software must be located in the
boot loader section because the SPM instruction can only initiate programming when executing from this section. The
SPM instruction can access the entire flash, including the boot loader section itself. The protection level for the boot
loader section can be selected by the boot loader lock bits. If this section is not used for boot loader software,
application code can be stored here.
Word Address
ATxmega128A4U
ATxmega64A4U
ATxmega32A4U
ATxmega16A4U
0000
Application Section
(128K/64K/32K/16K)
...
EFFF
/
77FF
/
37FF
/
17FF
F000
/
7800
/
3800
/
1800
Application Table Section
(4K/4K/4K/4K)
FFFF
/
7FFF
/
3FFF
/
1FFF
10000
/
8000
/
4000
/
2000
Boot Section
(8K/4K/4K/4K)
10FFF
/
87FF
/
47FF
/
27FF