Datasheet

26
2545T–AVR–05/11
ATmega48/88/168
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.
8.6.4 GPIOR2 – General purpose I/O register 2
8.6.5 GPIOR1 – General purpose I/O register 1
8.6.6 GPIOR0 – General purpose I/O register 0
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;
}
Bit 76543210
0x2B (0x4B) MSB LSB GPIOR2
Read/write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 76543210
0x2A (0x4A) MSB LSB GPIOR1
Read/write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 76543210
0x1E (0x3E) MSB LSB GPIOR0
Read/write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0