ATMEGA48-15AZV Просмотр технического описания (PDF) - Atmel Corporation

Номер в каталоге

Компоненты Описание

производитель

ATMEGA48-15AZV

8-bit Microcontroller with 8K Bytes In-System Programmable Flash

Atmel Corporation 

5.3.5

Assembly Code Example

EEPROM_read:

; Wait for completion of previous write

sbic EECR,EEPE

rjmp EEPROM_read

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

out EEARH, r18

out EEARL, r17

; Start eeprom read by writing EERE

sbi EECR,EERE

; Read data from Data Register

in r16,EEDR

ret

C Code Example

unsigned char EEPROM_read(unsigned int uiAddress)

{

/* Wait for completion of previous write */

while(EECR & (1<<EEPE))

;

/* Set up address register */

EEAR = uiAddress;

/* Start eeprom read by writing EERE */

EECR |= (1<<EERE);

/* Return data from Data Register */

return EEDR;

}

Preventing EEPROM Corruption

During periods of low VCC, the EEPROM data can be corrupted because the supply voltage is

too low for the CPU and the EEPROM to operate properly. These issues are the same as for

board level systems using EEPROM, and the same design solutions should be applied.

An EEPROM data corruption can be caused by two situations when the voltage is too low. First,

a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Sec-

ondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.

EEPROM data corruption can easily be avoided by following this design recommendation:

Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can

be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal

BOD does not match the needed detection level, an external low VCC reset Protection circuit can

be used. If a reset occurs while a write operation is in progress, the write operation will be com-

pleted provided that the power supply voltage is sufficient.

22 Atmel ATmega48/88/168 Automotive

7530J–AVR–03/12

Share Link: