Rainbow Electronics ATmega8HVD - Manual (Page 21)

21
8052B–AVR–09/08
ATmega4HVD/8HVD
The next code examples show assembly and C functions for reading the EEPROM. The
examples assume that interrupts are controlled so that no interrupts will occur during execu-
tion of these functions.
7.6.4 GPIOR2 – General Purpose I/O Register 2
7.6.5 GPIOR1 – General Purpose I/O Register 1
7.6.6 GPIOR0 –General Purpose I/O Register 0
Assembly Code Example
EEPROM_read:
; Wait for completion of previous write
sbic EECR,EEWE
rjmp EEPROM_read
; Set up address (r17) in address register
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<
;
/* Set up address register */
EEARL = uiAddress;
/* Start eeprom read by writing EERE */
EECR |= (1<
/* 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