at90pwm81-16se ATMEL Corporation, at90pwm81-16se Datasheet - Page 233

• Manufacturer Part Number: at90pwm81-16se
• Description: 8-bit Avr Microcontroller With 8k Bytes In- System Programmable Flash
• Manufacturer: ATMEL Corporation

21.1
21.2
21.2.1
21.2.2
21.3
7734M–AVR–03/10
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
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 configured 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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•
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Note:
The Flash memory is organized in two main sections, the Application section and the Boot Loader section
(see
Table 21-7 on page 246
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 protec-
tion level for the Application section can be selected by the application Boot Lock bits (Boot Lock bits 0),
see
instruction is disabled when executed from the Application 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
on page
Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot Loader software
update is dependent on which address that is being programmed. In addition to the two sections that are
configured 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
main difference between the two sections is:
• When erasing or writing a page located inside the RWW section, the NRWW section can be read
• When erasing or writing a page located inside the NRWW section, the CPU is halted during the entire
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
during the operation.
operation.
Table 21-2 on page
Figure
237.
1. A page is a section in the Flash consisting of several bytes (see
21-2). The size of the different sections is configured by the BOOTSZ Fuses as shown in
programming. The page organization does not affect normal operation.
(1)
Size
237. The Application section can never store any Boot Loader code since the SPM
and
Figure
21-2. These two sections can have different level of protection since
Table 21-8 on page 246
Table 22-11 on page
and
Figure 21-2 on page
AT90PWM81
254) used during
Table 21-3
236. The
233