Atmega USART-SPI 16 Bit Übertragung

unsigned char write(uint16_t data){

  CLRSSLINE

  // Wait for empty transmit buffer.

  do {} while( (UCSR1A & (1<<UDRE1)) == 0 );

  // Send data.

  UDR1 = (uint8_t)(data>>8);

  // Wait for transfer to complete and return received value.

  do {} while( (UCSR1A & (1<<RXC1)) == 0 );

  // Wait for empty transmit buffer.

  do {} while( (UCSR1A & (1<<UDRE1)) == 0 );

  // Send data.

  UDR1 = (uint8_t)(data & 255);

  // Wait for transfer to complete and return received value.

  do {} while( (UCSR1A & (1<<RXC1)) == 0 );

  SETSSLINE

  return UDR1;

}