SPI: ATMega8<=>ATMega644

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)))

    ;

}

int main(void) 

{  

  char i = 0;

  SPI_MasterInit();

  DDR_SPI |= (1<<DD_SS);

  while(1)

  {

    PORTB &=~(1<<DD_SS);    //  Aktiviere Slave

    wait_ms(1);

    SPI_MasterTransmit(i++);

    wait_ms(1);

    PORTB |=(1<<DD_SS);    // Deaktiviere Slave

    wait_ms(1000);

  }

  return 0;

}

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;

}

int main(void)

{

  uint16_t i=0;

  char string[20];

  DDRB=1;

  LCDInit();

  SPI_SlaveInit();

  while(1)

  {

    itoa(i++,string,10);

    LCDSetCursorPos(1,0);

    LCDWrite(string);

    itoa(SPI_SlaveReceive(),string,10);

    LCDSetCursorPos(0,0);

    LCDWrite(string);

  }

  return 0;

}