177
4317I–AVR–01/08
AT90PWM2/3/2B/3B
Note:
1. The example code assumes that the part specific header file is included.
The following code examples show how to initialize the SPI as a Slave and how to perform a
simple reception.
Assembly Code Example
SPI_MasterInit:
; Set MOSI and SCK output, all others input
ldi
r17,(1<<DD_MOSI)|(1<<DD_SCK)
out
DDR_SPI,r17
; Enable SPI, Master, set clock rate fck/16
ldi
r17,(1<<SPE)|(1<<MSTR)|(1<<SPR0)
out
SPCR,r17
ret
SPI_MasterTransmit:
; Start transmission of data (r16)
out
SPDR,r16
Wait_Transmit:
; Wait for transmission complete
sbis
SPSR,SPIF
rjmp
Wait_Transmit
ret
C Code Example
void
SPI_MasterInit(
void
)
{
/* Set MOSI and SCK output, all others input */
DDR_SPI = (1<<DD_MOSI)|(1<<DD_SCK);
/* Enable SPI, Master, set clock rate fck/16 */
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
}
void
SPI_MasterTransmit(
char
cData)
{
/* Start transmission */
SPDR = cData;
/* Wait for transmission complete */
while
(!(SPSR & (1<<SPIF)))
;
}
