3.1 __eeprom Keyword

The IAR __eeprom keyword places objects declared with the attribute in EEPROM and additionally ensures that EEPROM-access routines are used to access such objects either directly or indirectly via any pointer qualified with this same keyword.

Suggested Replacement

There are two changes that must both be made to IAR code to have it behave in a similar way when using MPLAB XC8.

To place an object in EEPROM, include the <avr/eeprom.h> header and use the EEMEM attribute (or its expanded form, __attribute__((section(".eeprom"))) with the object's definition. This attribute, however, does not affect how the object is accessed.

To read the object, use the eeprom_read_byte(), eeprom_read_word(), eeprom_read_dword(), or eeprom_read_block() functions as appropriate, and the corresponding eeprom_write_xxxx() functions to write to the object in EEPROM.

Caveats

None.

Examples

Consider migrating IAR code such as:

__eeprom int mode = 12;

volatile int x;
int main() {
  x = mode;
}

to MPLAB XC8 codes similar to:

#include <avr/eeprom.h>
 
int mode EEMEM = 12;
 
volatile int x;
int main() {
  x = eeprom_read_word(&mode);
}

Further Information

See the Variables in EEPROM section in the MPLAB XC8 C Compiler User's Guide for AVR MCUs for more information on these attributes.