25
8025I–AVR–02/09
ATmega48P/88P/168P/328P
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.
5.6.4
GPIOR2 – General Purpose I/O Register 2
5.6.5
GPIOR1 – General Purpose I/O Register 1
5.6.6
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
7
6
5
4
3
2
1
0
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
7
6
5
4
3
2
1
0
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
7
6
5
4
3
2
1
0
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
