21
XMEGA B [DATASHEET]
8291B–AVR–01/2013
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, as shown in
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 4-1.
Flash memory sections.
4.3.1
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.
4.3.2
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.
4.3.3
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.
Application Flash
Section
0x000000
End Application
Start Boot Loader
Flashend
Application Table
Flash Section
Boot Loader Flash
Section
Summary of Contents for XMEGA B
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