ata6616 ATMEL Corporation, ata6616 Datasheet - Page 44

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.4.3.6
44
ATA6616/ATA6617 [Preliminary]
Preventing EEPROM Corruption
The next code examples show assembly and C functions for reading the EEPROM. The exam-
ples assume that interrupts are controlled so that no interrupts will occur during execution of
these functions.
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.
Assembly Code Example
C Code Example
EEPROM_read:
unsigned char EEPROM_read(unsigned char ucAddress)
{
}
; Wait for completion of previous write
sbic
rjmp
; Set up address (r18:r17) in address register
out
out
; Start eeprom read by writing EERE
sbi
; Read data from data register
in
ret
/* Wait for completion of previous write */
while(EECR & (1<<EEPE))
/* Set up address register */
EEAR = ucAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<<EERE);
/* Return data from data register */
return EEDR;
;
EECR,EEPE
EEPROM_read
EEARH, r18
EEARL, r17
EECR,EERE
r16,EEDR
DRAFT
9132A–AUTO–10/08