Техническая Спецификация для Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI
Модели
MEGA328P-XMINI
264
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
Atmel-8271H-AVR- ATmega-Datasheet_08/2014
27.
Boot Loader Support – Read-While-Write Self-Programming
The Boot Loader Support applies to ATmega88A/88PA/168A/168PA/328/328P
27.1
Features
•
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
Size
•
Code Efficient Algorithm
•
Efficient Read-Modify-Write Support
Note:
1. A page is a section in the Flash consisting of several bytes (see
) used during pro-
gramming. The page organization does not affect normal operation.
27.2
Overview
In ATmega88A/88PA/168A/168PA/328/328P 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-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 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 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 different levels of protection.
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-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 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 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 different levels of protection.
27.3
Application and Boot Loader Flash Sections
The Flash memory is organized in two main sections, the Application section and the Boot Loader section (see
and
. These two sections can have different level of protection since they have different
sets of Lock bits.
27.3.1 Application Section
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
level for the Application section can be selected by the application Boot Lock bits (Boot Lock bits 0), see
. The Application section can never store any Boot Loader code since the SPM instruction is
disabled when executed from the Application section.
27.3.2 BLS – Boot Loader Section
While the Application section is used for storing the application code, the The Boot Loader software 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
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