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6. Memories
6.1
In-System Reprogrammable Flash Program Memory
6.2
SRAM Data Memory
4317I–AVR–01/08
This section describes the different memories in the AT90PWM2/2B/3/3B. The AVR architecture
has two main memory spaces, the Data Memory and the Program Memory space. In addition,
the AT90PWM2/2B/3/3B features an EEPROM Memory for data storage. All three memory
spaces are linear and regular.
The AT90PWM2/2B/3/3B contains 8K 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
4K x 16. For software security, the Flash Program memory space is divided into two sections,
Boot Program section and Application Program section.
The Flas h memory has an endur ance of at leas t 10,000 write/eras e cyc les. The
AT90PWM2/2B/3/3B Program Counter (PC) is 12 bits wide, thus addressing the 4K program
memory locations. The operation of Boot Program section and associated Boot Lock bits for
software protection are described in detail in
gramming" on page
265.
on Flash programming in SPI or Parallel programming mode.
Constant tables can be allocated within the entire program memory address space (see the LPM
– Load Program Memory.
Timing diagrams for instruction fetch and execution are presented in
ing" on page
15.
Figure 1. Program Memory Map
Figure 2
shows how the AT90PWM2/2B/3/3B SRAM Memory is organized.
"Boot Loader Support – Read-While-Write Self-Pro-
"Memory Programming" on page 279
Program Memory
Application Flash Section
Boot Flash Section
AT90PWM2/3/2B/3B
contains a detailed description
"Instruction Execution Tim-
0x0000
0x0FFF
19
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