ATMEGA644_0702 Datasheet, PDF (159/374 Pages) ATMEL Corporation – 8-bit Microcontroller with 64K Bytes In- System Programmable Flash

ATmega644
The following code examples show how to initialize the SPI as a Slave and how to perform a
simple reception.
Assembly Code Example⁽¹⁾
SPI_SlaveInit:
; Set MISO output, all others input
ldi r17,(1<<DD_MISO)
out DDR_SPI,r17
; Enable SPI
ldi r17,(1<<SPE)
out SPCR,r17
ret
SPI_SlaveReceive:
; Wait for reception complete
sbis SPSR,SPIF
rjmp SPI_SlaveReceive
; Read received data and return
in r16,SPDR
ret
C Code Example⁽¹⁾
void SPI_SlaveInit(void)
{
/* Set MISO output, all others input */
DDR_SPI = (1<<DD_MISO);
/* Enable SPI */
SPCR = (1<<SPE);
}
char SPI_SlaveReceive(void)
{
/* Wait for reception complete */
while(!(SPSR & (1<<SPIF)))
;
/* Return Data Register */
return SPDR;
}
Note: 1. See “About Code Examples” on page 8.
2593L–AVR–02/07
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