ATtiny261-ESSZ datasheet(20/227 Pages) ATMEL

20 / 227 page

7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

The calibrated Oscillator is used to time the EEPROM accesses. Make sure the Oscillator fre-

quency is within the requirements described in “OSCCAL – Oscillator Calibration Register” on

page 32.

The following code examples show one assembly and one C function for erase, write, or atomic

write of the EEPROM. The examples assume that interrupts are controlled (e.g., by disabling

interrupts globally) so that no interrupts will occur during execution of these functions.

Assembly Code Example

EEPROM_write:

; Wait for completion of previous write

sbic

EECR,EEPE

rjmp

EEPROM_write

; Set Programming mode

ldi

r16, (0<<EEPM1)|(0<<EEPM0)

out

EECR, r16

; 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

void

EEPROM_write(unsigned char ucAddress, unsigned char ucData)

{

/* Wait for completion of previous write */

while(EECR & (1<<EEPE))

;

/* Set Programming mode */

EECR = (0<<EEPM1)|(0<<EEPM0);

/* Set up address and data registers */

EEAR = ucAddress;

EEDR = ucData;

/* Write logical one to EEMPE */

EECR |= (1<<EEMPE);

/* Start eeprom write by setting EEPE */

EECR |= (1<<EEPE);

}

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