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2467S–AVR–07/09
ATmega128
AVR
ATmega128
Memories
This section describes the different memories in the ATmega128. The AVR architecture has two
main memory spaces, the Data Memory and the Program Memory space. In addition, the
ATmega128 features an EEPROM Memory for data storage. All three memory spaces are linear
and regular.
In-System
Reprogrammable
Flash Program
Memory
The ATmega128 contains 128K bytes On-chip In-System Reprogrammable Flash memory for
program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as
64K x 16. For software security, the Flash Program memory space is divided into two sections,
Boot Program section and Application Program section.
The Flash memory has an endurance of at least 10,000 write/erase cycles. The ATmega128
Program Counter (PC) is 16 bits wide, thus addressing the 64K program memory locations. The
operation of Boot Program section and associated Boot Lock bits for software protection are
described in detail in
“Boot Loader Support – Read-While-Write Self-Programming” on page
“Memory Programming” on page 286
contains a detailed description on Flash programming
in SPI, JTAG, or Parallel Programming mode.
Constant tables can be allocated within the entire program memory address space (see the LPM
– Load Program Memory and ELPM – Extended Load Program Memory instruction description).
Timing diagrams for instruction fetch and execution are presented in
Figure 8.
Program Memory Map
$0000
$FFFF
Program Memory
Application Flash Section
Boot Flash Section
