ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 274

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

24. Boot Loader Support – Read-While-Write Self-Programming
24.1
24.2
24.3
24.3.1
24.3.2
274
Features
Overview
Application and Boot Loader Flash Sections
ATmega164P/324P/644P
Application Section
BLS – Boot Loader Section
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Note:
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 applica-
tion software updates controlled by the MCU using a Flash-resident 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 mem-
ory. 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 anymore. 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 differ-
ent 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
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 24-2 on page
Table 24-2 on page
Table 24-3 on page
Table 24-7 on page 286
277). The size of the different sections is configured by
278. The Application section can never store any
278.
and
Figure
Table 25-7 on page
24-2. These two sections
8011D–AVR–02/07
294) used