SPI: Clock ist in Idle-Status Low - Warum?

void Init_GPIOA()

{

    // enable peripheral clock for GPIOA

    RCC->AHBENR |= RCC_AHBPeriph_GPIOA;

        GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_5);   // set alternative Funktion f. SPI1 (I_SCLK)

        GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_5);   // set alternative Funktion f. SPI1 (I_MISO)

        GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_5);   // set alternative Funktion f. SPI1 (I_MOSI)

        pGPIOx_InitStruct->GPIO_Pin   = (uint32_t)(GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7);   // SCLK, MISO, MOSI

        pGPIOx_InitStruct->GPIO_Mode  = GPIO_Mode_AF;

        pGPIOx_InitStruct->GPIO_Speed = GPIO_Speed_Level_1;                         // high speed (50MHz)

        pGPIOx_InitStruct->GPIO_OType = GPIO_OType_PP;                              // push-pull

        pGPIOx_InitStruct->GPIO_PuPd  = GPIO_PuPd_NOPULL ;

        GPIO_Init(GPIOA, pGPIOx_InitStruct);                                        // set pins

        pGPIOx_InitStruct->GPIO_Pin   = (uint32_t)(GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3 | GPIO_Pin_4);  //Chip-Select: CS1, CS2, CS3, CS4

        pGPIOx_InitStruct->GPIO_Mode  = GPIO_Mode_OUT;

        pGPIOx_InitStruct->GPIO_Speed = GPIO_Speed_Level_3;                         // high speed (50MHz)

        pGPIOx_InitStruct->GPIO_OType = GPIO_OType_PP;                              // push-pull

        pGPIOx_InitStruct->GPIO_PuPd  = GPIO_PuPd_NOPULL ;

        GPIO_Init(GPIOA, pGPIOx_InitStruct);

}

void Init_SPI1(void)

{

    // Enable peripheral clock

    RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;

    SPI_I2S_DeInit(SPI1);

    SPI_InitTypeDef SPI_InitStructure;

    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;

    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;

    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;

    SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;         // CPOL is set -> SCK pin has a high-level idle state

    SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;        // second edge on the SCK pin captures the first data bit transacted (rising edge because the CPOL bit is set)

    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;

    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

    SPI_Init(SPI1,&SPI_InitStructure);

    SPI_CalculateCRC(SPI1, DISABLE);

    SPI_SSOutputCmd(SPI1, ENABLE);

    SPI_Cmd(SPI1, ENABLE);

    while(true)

    {

        SPI1->DR = 0x6;

//        SPI_SendData8(SPI1,0x6);

        while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET);

        while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == 1);

        delay_1us(10);

    }

}