ATmega1284P datasheet(24/380 Pages) ATMEL

24 / 380 page

8059D–AVR–11/09

ATmega1284P

The following code examples show one assembly and one C function for writing to the

EEPROM. The examples assume that interrupts are controlled (e.g. by disabling interrupts glob-

ally) so that no interrupts will occur during execution of these functions. The examples also

assume that no Flash Boot Loader is present in the software. If such code is present, the

EEPROM write function must also wait for any ongoing SPM command to finish.

Note:

1. See “About Code Examples” on page 6.

Assembly Code Example

()

EEPROM_write:

; Wait for completion of previous write

sbic

EECR,EEPE

rjmp

EEPROM_write

; Set up address (r18:r17) in address register

out

EEARH, r18

out

EEARL, r17

; Write data (r16) to Data Register

out

EEDR,r16

; Write logical one to EEMPE

sbi

EECR,EEMPE

; Start eeprom write by setting EEPE

sbi

EECR,EEPE

ret

C Code Example(1)

void

EEPROM_write(unsigned int uiAddress, unsigned char ucData)

{

/* Wait for completion of previous write */

while(EECR & (1<<EEPE))

;

/* Set up address and Data Registers */

EEAR = uiAddress;

EEDR = ucData;

/* Write logical one to EEMPE */

EECR |= (1<<EEMPE);

/* Start eeprom write by setting EEPE */

EECR |= (1<<EEPE);

}

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