ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 269

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

27. Boot loader support – Read-while-write self-programming, Atmel ATmega88
27.1
27.2
27.3
27.3.1
27.3.2
2545T–AVR–05/11
and Atmel ATmega168
Features
Overview
Application and boot loader flash sections
Application section
BLS – Boot loader section
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Note:
In ATmega88 and ATmega168, the Boot Loader Support provides a real Read-While-Write Self-
Programming mechanism for downloading and uploading program code by the MCU itself. This
feature allows flexible application software updates controlled by the MCU using a Flash-resi-
dent Boot Loader program. The Boot Loader program can use any available data interface and
associated protocol to read code and write (program) that code into the Flash memory, or read
the code from the program memory. The program code within the Boot Loader section has the
capability to write into the entire Flash, including the Boot Loader memory. The Boot Loader can
thus even modify itself, and it can also erase itself from the code if the feature is not needed any-
more. The size of the Boot Loader memory is configurable with fuses and the Boot Loader has
two separate sets of Boot Lock bits which can be set independently. This gives the user a
unique flexibility to select different levels of protection.
The Flash memory is organized in two main sections, the Application section and the Boot
Loader section (see
the BOOTSZ Fuses as shown in
two sections can have different level of protection since they have different sets of Lock bits.
The Application section is the section of the Flash that is used for storing the application code.
The protection level for the Application section can be selected by the application Boot Lock bits
(Boot Lock bits 0), see
Boot Loader code since the SPM instruction is disabled when executed from the Application
section.
While the Application section is used for storing the application code, the The Boot Loader soft-
ware must be located in the BLS since the SPM instruction can initiate a programming when
executing from the BLS only. The SPM instruction can access the entire Flash, including the
BLS itself. The protection level for the Boot Loader section can be selected by the Boot Loader
Lock bits (Boot Lock bits 1), see
Read-while-write self-programming
Flexible boot memory size
High security (separate boot lock bits for a flexible protection)
Separate fuse to select reset vector
Optimized page
Code efficient algorithm
Efficient read-modify-write support
1. A page is a section in the flash consisting of several bytes (see
during programming. The page organization does not affect normal operation.
(1)
size
Figure 27-2 on page
Table 27-2 on page
Table 27-3 on page
Table 27-6 on page 281
272). The size of the different sections is configured by
273. The Application section can never store any
273.
and
ATmega48/88/168
Figure 27-2 on page
Table 28-9 on page
272. These
289) used
269