Datasheet

172
ATmega323(L)
1457E–11/01
Memory
Programming
Boot Loader Support The ATmega323 provides a 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. This makes it possible to pro-
gram the AVR in a target system without access to its SPI pins. The Boot Loader
program can use any available data interface and associated protocol, such as USART
serial bus interface, to input or output program code, and write (program) that code into
the Flash memory, or read the code from the Flash memory.
The ATmega323 Flash memory is organized in two main sections:
• The Application Flash section
• The Boot Loader Flash section
The Application Flash section and the Boot Loader Flash section have separate Boot
Lock Bits. Thus the user can select different levels of protection for the two sections.
The Store Program Memory (SPM) instruction can only be executed from the Boot
Loader Flash section.
The program Flash memory in ATmega323 is divided into 256 pages of 64 words each.
The Boot Loader Flash section is located at the high address space of the Flash, and
can be configured through the BOOTSZ fuses as shown in Table 59.
Table 59. Boot Size Configuration
BOOTSZ1 BOOTSZ0
Boot
Size Pages
Application
Flash Addresses
Boot Flash
Addresses
Boot Reset
Address
11
256
words
4 $0000 - $3EFF
$3F00 -
$3FFF
$3F00
10
512
words
8 $0000 - $3DFF
$3E00 -
$3FFF
$3E00
01
1024
words
16 $0000 - $3BFF
$3C00 -
$3FFF
$3C00
00
2048
words
32 $0000 - $37FF
$3800 -
$3FFF
$3800