Tuesday, March 6, 2012

AVR EEPROM Tutorial


 EEPROM

EEPROM (Electrically Erasable Programmable Read-Only Memory) is a type of non-volatile memory which can be programmed, erased, and re-programmed electrically while it is on the circuit board. A majority of AVR microcontrollers come with some built-in EEPROM which is a great place to store data that should not be lost when the system is powered down. This tutorial explains the MikroC EEPROM library with example


MikroC EEPROM Library

EEPROM data memory is available with a number of AVR family. The mikroC PRO for AVR includes a library for comfortable work with MCU's internal EEPROM.
  Important : EEPROM Library functions implementation is MCU dependent, consult the appropriate MCU datasheet for details about available EEPROM size and address range.
Library Routines
EEPROM_Read
Prototype
unsigned short EEPROM_Read(unsigned int address);
Returns
Byte from the specified address.
Description
Reads data from specified address.
Parameters :
  • address: address of the EEPROM memory location to be read.
Requires
Nothing.
Example
unsigned int address = 2;
unsigned short temp;
...
temp = EEPROM_Read(address);
EEPROM_Write
Prototype
void EEPROM_Write(unsigned address, unsigned short dData);
Returns
Nothing.
Description
Writes wrdata to specified address.
Parameters :
  • address: address of the EEPROM memory location to be written.
  • wrdata: data to be written.
  Note : Specified memory location will be erased before writing starts.

Example
unsigned address = 0x732;
unsigned short dData = 0x55;
...
EEPROM_Write(address, dData);
Example
This example demonstrates using the EEPROM Library with ATMEGA16 MCU.
First, some data is written to EEPROM in byte and block mode; then the data is read from the same locations and displayed on PORTA, PORTB and PORTC.
char ii;                                   // loop variable

void main(){
   DDRA = 0xFF;                            // Set signal port as output
   DDRB = 0xFF;                            // Set signal port as output
   DDRC = 0xFF;                            // Set signal port as output
  
   PORTA = 0x00;                           // Clear signal ports
   PORTB = 0x00;
   PORTC = 0x00;
   Delay_ms(2000);

   EEPROM_Write(0x02,0xAA);                // Write some data at address 2
   EEPROM_Write(0x150,0x55);               // Write some data at address 0x150

   PORTA = EEPROM_Read(0x02);              // Read data from address 2 and display it on PORTA
   PORTB = EEPROM_Read(0x150);             // Read data from address 0x150 and display it on PORTB

   Delay_ms(1000);

   for(ii = 0; ii < 32; ii++)              // EEPROM write loop
     EEPROM_Write(0x100+ii, ii);           // Write data to address 0x100+ii

   for(ii = 0; ii < 32; ii++) {            // EEPROM read loop
     PORTC = EEPROM_Read(0x100+ii);        // Read data from address 0x100+ii
     Delay_ms(100);                        //   and display it on PORTC
   }
  
}



Circuit


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