AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 265

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

24.1
24.2
24.2.1
24.2.2
24.3
4317J–AVR–08/10
Boot Loader Features
Application and Boot Loader Flash Sections
Read-While-Write and No Read-While-Write Flash Sections
Application Section
BLS – Boot Loader Section
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.
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Note:
The Flash memory is organized in two main sections, the Application section and the Boot
Loader section (see
BOOTSZ Fuses as shown in
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
Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot Loader soft-
ware update is dependent on which address that is being programmed. In addition to the two
sections that are configurable by the BOOTSZ Fuses as described above, the Flash is also
divided into two fixed sections, the Read-While-Write (RWW) section and the No Read-While-
Write (NRWW) section. The limit between the RWW- and NRWW sections is given in
7 on page 277
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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
When erasing or writing a page located inside the RWW section, the NRWW section can be
read during the operation.
When erasing or writing a page located inside the NRWW section, the CPU is halted during
the entire operation.
1. A page is a section in the Flash consisting of several bytes (see
used during programming. The page organization does not affect normal operation.
and
(1)
Figure 24-2 on page
Size
Figure
Table 24-2 on page
Table 24-6 on page 277
24-2). The size of the different sections is configured by the
Table 24-3 on page
268. The main difference between the two sections is:
269. The Application section can never store any
269.
and
AT90PWM2/3/2B/3B
Figure
24-2. These two sections can
Table 25-11 on page
Table 24-
284)
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