谁帮我解释一下这段代码

596142041

SPI_InitTypeDef  SPI_InitStructure;
uint16_t SPI1_Buffer_Tx[BufferSize] = {0x0102, 0x0304, 0x0506, 0x0708, 0x090A, 0x0B0C,
                                  0x0D0E, 0x0F10, 0x1112, 0x1314, 0x1516, 0x1718,
                                  0x191A, 0x1B1C, 0x1D1E, 0x1F20, 0x2122, 0x2324,
                                  0x2526, 0x2728, 0x292A, 0x2B2C, 0x2D2E, 0x2F30,
                                  0x3132, 0x3334, 0x3536, 0x3738, 0x393A, 0x3B3C,
                                  0x3D3E, 0x3F40};
uint16_t SPI2_Buffer_Tx[BufferSize] = {0x5152, 0x5354, 0x5556, 0x5758, 0x595A, 0x5B5C,
                                  0x5D5E, 0x5F60, 0x6162, 0x6364, 0x6566, 0x6768,
                                  0x696A, 0x6B6C, 0x6D6E, 0x6F70, 0x7172, 0x7374,
                                  0x7576, 0x7778, 0x797A, 0x7B7C, 0x7D7E, 0x7F80,
                                  0x8182, 0x8384, 0x8586, 0x8788, 0x898A, 0x8B8C,
                                  0x8D8E, 0x8F90};
uint16_t SPI1_Buffer_Rx[BufferSize], SPI2_Buffer_Rx[BufferSize];
uint32_t TxIdx = 0, RxIdx = 0;
__IO uint16_t CRC1Value = 0, CRC2Value = 0;
volatile TestStatus TransferStatus1 = FAILED, TransferStatus2 = FAILED;

/* Private functions ---------------------------------------------------------*/
void RCC_Configuration(void);
void GPIO_Configuration(void);
TestStatus Buffercmp(uint16_t* pBuffer1, uint16_t* pBuffer2, uint16_t BufferLength);

/**
  * @brief  Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured,
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f10x_xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f10x.c file
     */     
      
  /* System clocks configuration ---------------------------------------------*/
  RCC_Configuration();

  /* GPIO configuration ------------------------------------------------------*/
  GPIO_Configuration();

  /* SPI1 configuration ------------------------------------------------------*/
  SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
  SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
  SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;
  SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
  SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
  SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
  SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
  SPI_InitStructure.SPI_CRCPolynomial = 7;
  SPI_Init(SPI1, &SPI_InitStructure);

  /* SPI2 configuration ------------------------------------------------------*/
  SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
  SPI_Init(SPI2, &SPI_InitStructure);

  /* Enable SPI1 CRC calculation */
  SPI_CalculateCRC(SPI1, ENABLE);
  /* Enable SPI2 CRC calculation */
  SPI_CalculateCRC(SPI2, ENABLE);

  /* Enable SPI1 */
  SPI_Cmd(SPI1, ENABLE);
  /* Enable SPI2 */
  SPI_Cmd(SPI2, ENABLE);

  /* Transfer procedure */
  while (TxIdx < BufferSize - 1)
  {
    /* Wait for SPI1 Tx buffer empty */
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);
    /* Send SPI2 data */
    SPI_I2S_SendData(SPI2, SPI2_Buffer_Tx[TxIdx]);
    /* Send SPI1 data */
    SPI_I2S_SendData(SPI1, SPI1_Buffer_Tx[TxIdx++]);
    /* Wait for SPI2 data reception */
    while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET);
    /* Read SPI2 received data */
    SPI2_Buffer_Rx[RxIdx] = SPI_I2S_ReceiveData(SPI2);
    /* Wait for SPI1 data reception */
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);
    /* Read SPI1 received data */
    SPI1_Buffer_Rx[RxIdx++] = SPI_I2S_ReceiveData(SPI1);
  }

  /* Wait for SPI1 Tx buffer empty */
  while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);
  /* Wait for SPI2 Tx buffer empty */
  while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET);

  /* Send last SPI2_Buffer_Tx data */
  SPI_I2S_SendData(SPI2, SPI2_Buffer_Tx[TxIdx]);
  /* Enable SPI2 CRC transmission */
  SPI_TransmitCRC(SPI2);
  /* Send last SPI1_Buffer_Tx data */
  SPI_I2S_SendData(SPI1, SPI1_Buffer_Tx[TxIdx]);
  /* Enable SPI1 CRC transmission */
  SPI_TransmitCRC(SPI1);
/*************************************************************************/
  /* Wait for SPI1 last data reception */
  while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);
  /* Read SPI1 last received data */
  SPI1_Buffer_Rx[RxIdx] = SPI_I2S_ReceiveData(SPI1);

  /* Wait for SPI2 last data reception */
  while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET);
  /* Read SPI2 last received data */
  SPI2_Buffer_Rx[

RxIdx] = SPI_I2S_ReceiveData(SPI2);
/*******************************************************************************/
这一段我不怎么明白 它的CRC值怎么发过去的
  /* Wait for SPI1 data reception: CRC transmitted by SPI2 */
  while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);
  /* Wait for SPI2 data reception: CRC transmitted by SPI1 */
  while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET);

  /* Check the received data with the send ones */
  TransferStatus1 = Buffercmp(SPI2_Buffer_Rx, SPI1_Buffer_Tx, BufferSize);
  TransferStatus2 = Buffercmp(SPI1_Buffer_Rx, SPI2_Buffer_Tx, BufferSize);
  /* TransferStatus1, TransferStatus2 = PASSED, if the data transmitted and received
     are correct */
  /* TransferStatus1, TransferStatus2 = FAILED, if the data transmitted and received
     are different */
/***************************************************************************************/
  /* Test on the SPI1 CRC Error flag */
  if ((SPI_I2S_GetFlagStatus(SPI1, SPI_FLAG_CRCERR)) == SET)
  {
    TransferStatus2 = FAILED;
  }

  /* Test on the SPI2 CRC Error flag */
  if ((SPI_I2S_GetFlagStatus(SPI2, SPI_FLAG_CRCERR)) == SET)
  {
    TransferStatus1 = FAILED;
  }

  /* Read SPI1 received CRC value */
  CRC1Value = SPI_I2S_ReceiveData(SPI1);
  /* Read SPI2 received CRC value */
  CRC2Value = SPI_I2S_ReceiveData(SPI2);
大神们,帮我一下哈!不胜感激!