Datasheet

9. AVR Memories

9.1. Overview

This section describes the different memory types in the device. The AVR architecture has two main

memory spaces, the Data Memory and the Program Memory space. In addition, the device features an

EEPROM Memory for data storage. All memory spaces are linear and regular.

9.2. In-System Reprogrammable Flash Program Memory

The ATmega644A contains 64Kbytes 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 64 x 16.

The Flash memory has an endurance of at least 10,000 write/erase cycles. The ATmega644A Program

Counter (PC) is 15 bits wide, thus addressing the 64 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. Refer to Memory Programming for the description

on Flash data serial downloading using the SPI pins or the JTAG interface.

Constant tables can be allocated within the entire program memory address space, using the Load

Program Memory (LPM) instruction.

Timing diagrams for instruction fetch and execution are presented in Instruction Execution Timing.

Figure 9-1. Program Memory Map ATmega644A

0x0000

0x7FFF

Program Memory

Application Flash Section

Boot Flash Section