March 12, 2024

Memory Organization and Data Storage in AVR Atmega-328

As a programmer, understanding how memory is organized and data is stored is crucial for optimizing code and ensuring efficient use of resources. In this blog post, we will explore the memory organization and data storage in AVR Atmega-328 microcontroller, which is widely used in Arduino boards.

Introduction to AVR Atmega-328 Memory

AVR Atmega-328 microcontroller has a Harvard architecture, where program memory and data memory are separate. It has:

• 32KB of Flash memory (program memory)
• 2KB of SRAM (data memory)
• 1KB of EEPROM (non-volatile memory)

Let’s dive into each of these memory types in more detail.

Flash Memory (Program Memory)

Flash memory in Atmega-328 stores the program code that is executed by the microcontroller. It is non-volatile, meaning the code remains even when power is removed. The Flash memory is divided into different sections:

• Reset Vector (0x0000 - 0x0001) - This is the first location where the microcontroller starts executing after a reset or power-up. It contains a jump instruction to the beginning of the interrupt vector table.
• Interrupt Vector Table (0x0002 - 0x007F) - This table contains jump instructions to interrupt service routines. Each interrupt has a specific address associated with it.
• Boot Loader (0x7800 - 0x7FFF) - The boot loader section is used to update the program memory using specialized software. It is often used in Arduino boards to update the firmware.
• Application Code (0x0002 - 0x77FF, 0x8000 - 0xFFFF) - This is the main section of the Flash memory where the actual program code resides.

It is important to note that the Flash memory has a limited number of write/erase cycles (typically around 10,000). Therefore, it is advisable to avoid frequent writing to Flash memory unless necessary.

SRAM (Data Memory)

SRAM (Static Random Access Memory) in Atmega-328 is used for storing data during program execution. It is volatile, meaning the data is lost when power is removed. The SRAM is organized as a linear array and is byte-addressable.

The first byte of SRAM is located at address 0x0100, and the last byte is at address 0x08FF. The remaining addresses (0x0000 - 0x00FF) are reserved for IO registers, special function registers, and other miscellaneous purposes.

To access data stored in SRAM, we use variable declarations in our code. Let’s consider an example:

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int myVariable = 42;

In this example, the variable myVariable is stored in SRAM, and its value can be accessed and manipulated in the program.

EEPROM (Non-volatile Memory)

EEPROM (Electrically Erasable Programmable Read-Only Memory) is non-volatile memory used for storing data that needs to be retained even when power is removed. The Atmega-328 has 1KB of EEPROM memory, divided into 512 bytes.

EEPROM data can be read, written, and erased byte by byte. However, the number of write/erase cycles in EEPROM is also limited (typically around 100,000).

To work with EEPROM, the Arduino library provides functions like EEPROM.write() and EEPROM.read() that simplify the process of reading and writing data.

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#include <EEPROM.h>

int eepromAddress = 0;
int myValue = EEPROM.read(eepromAddress); // Read value from EEPROM

// Modify the value and store back
myValue += 10;
EEPROM.write(eepromAddress, myValue);

Conclusion

Understanding the memory organization and data storage in AVR Atmega-328 is crucial for effective programming and resource management. By knowing where and how the program code, data, and non-volatile data are stored, we can write optimized and efficient code for microcontroller-based projects.

Remember to take care when writing to Flash memory and EEPROM due to their limited write/erase cycles. Utilize SRAM efficiently by using variables judiciously. Having a good grasp of memory organization will boost your ability to develop robust and optimized embedded applications.

I hope this blog post has helped you gain a clearer understanding of memory organization and data storage in AVR Atmega-328. Happy programming!

References:

• Atmega328P Datasheet
• Arduino EEPROM Library Reference

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