SPI MISO Leitung funktioniert nicht (AT32UC3C)

Hallo,

ich benutze zwei Platinen, die mit dem AT32UC3C bestückt sind.
Einer arbeitet als Master, der andere als Slave.
Daten schicken über den Master funktioniert hierbei problemlos, der 
Slave empfängt sie auch ohne Probleme.

Jedoch kann ich keine Daten über den Slave schicken. Nun weiß ich leider 
nicht, was ich falsch mache und würde mich sehr über eure Hilfe freuen.

#include <asf.h>
#include "lcd.h"
#include "converter_spi_set.h"
#include "converter_spi.h"

#define SPI_EXAMPLE             (&AVR32_SPI0)
#define SPI_SLAVECHIP_NUMBER    (0)

int SPItimeout = 0;

void InitSpi()
{
  gpio_enable_module_pin(C_SPI_MISO_PIN, C_SPI_MISO_FNC);
  gpio_enable_module_pin(C_SPI_MOSI_PIN, C_SPI_MOSI_FNC);
  gpio_enable_module_pin(C_SPI_SCK_PIN, C_SPI_SCK_FNC);
  gpio_enable_module_pin(C_SPI_CS0_PIN, C_SPI_CS0_FNC);


  static spi_options_t spi_options = {
    .baudrate = C_SPI_SCLK,
    .bits = 16,
    .reg = 0,
    .spck_delay = 8,
    .spi_mode = SPI_MODE_1,
    .stay_act = 0,
    .trans_delay = 0,
  };


  spi_reset(&C_SPI);
  spi_status_t retval = spi_initSlave(&C_SPI, 8, SPI_MODE_1);


  if (retval != SPI_OK) {

    LcdWriteString(LCD_LINE1, "                    ");
    LcdWriteString(LCD_LINE2, "   Error SPI       ");
    LcdWriteString(LCD_LINE3, "                    ");
    LcdWriteString(LCD_LINE4, "                    ");
    delay_ms(5000);
    return; //TODO: error handling
  }

  // same chip options for each of the four independent group

  // with CONFIG_SYSCLK_PBA_DIV = 3: 28000000
  spi_status_t ret = spi_setupChipReg(&C_SPI, &spi_options, PBA_CLOCK);
  if (ret != SPI_OK) {
    LcdWriteString(LCD_LINE1, "                    ");
    LcdWriteString(LCD_LINE2, "   Error SPI       ");
    LcdWriteString(LCD_LINE3, "                    ");
    LcdWriteString(LCD_LINE4, "                    ");
    delay_ms(5000);
    return;
  }


  spi_enable(&C_SPI);

  return;
}


void sendDataSPI (uint16_t data)
{
  while(!spi_is_tx_ready(SPI_EXAMPLE))
  ;

  spi_put(SPI_EXAMPLE, data);

  while(!spi_is_tx_empty(SPI_EXAMPLE))
  ;
}


uint16_t readDataSPI (void)
{
  uint16_t data = 0;

  spi_status_t ret = spi_read(SPI_EXAMPLE, &data);

  //if (ret != SPI_OK) {
    //LcdWriteString(LCD_LINE1, "                    ");
    //LcdWriteString(LCD_LINE2, "   Error SPI  CON   ");
    //LcdWriteString(LCD_LINE3, "                    ");
    //LcdWriteString(LCD_LINE4, "                    ");
    //delay_ms(5000);
    //return data;
  //}

  return data;
}