===============================================================================
                         Interrupts and flags management functions
 ===============================================================================  

  This section provides a set of functions allowing to configure the SPI Interrupts 
  sources and check or clear the flags or pending bits status.
  The user should identify which mode will be used in his application to manage 
  the communication: Polling mode, Interrupt mode or DMA mode. 
    
  Polling Mode
  =============
  In Polling Mode, the SPI communication can be managed by 6 flags:
     1. SPI_FLAG_TXE: to indicate the status of the transmit buffer register
     2. SPI_FLAG_RXNE: to indicate the status of the receive buffer register
     3. SPI_FLAG_WKUP: to indicate the state of the Wakeup event.
     4. SPI_FLAG_CRCERR: to indicate if a CRC Calculation error occurs              
     5. SPI_FLAG_MODF: to indicate if a Mode Fault error occurs
     6. SPI_FLAG_OVR: to indicate if an Overrun error occurs

  In this Mode it is advised to use the following functions:
     - FlagStatus SPI_GetFlagStatus(SPI_TypeDef* SPIx, SPI_FLAG_TypeDef SPI_FLAG);
     - void SPI_ClearFlag(SPI_TypeDef* SPIx, SPI_FLAG_TypeDef SPI_FLAG);

  Interrupt Mode
  ===============
  In Interrupt Mode, the SPI communication can be managed by 4 interrupt sources
  and 6 pending bits: 
  Pending Bits:
  ------------- 
     1. SPI_IT_TXE: to indicate the status of the transmit buffer register
     2. SPI_IT_RXNE: to indicate the status of the receive buffer register
     3. SPI_IT_CRCERR: to indicate if a CRC Calculation error occurs              
     4. SPI_IT_MODF: to indicate if a Mode Fault error occurs
     5. SPI_IT_OVR: to indicate if an Overrun error occurs
     6. SPI_IT_WKUP: to indicate if an Wake_up event occurs
  Interrupt Source:
  -----------------
     1. SPI_IT_TXE: specifies the interrupt source for the Tx buffer empty 
                        interrupt.  
     2. SPI_IT_RXNE: specifies the interrupt source for the Rx buffer not 
                          empty interrupt.
     3. SPI_IT_ERR: specifies the interrupt source for the errors interrupt.
		 4. SPI_IT_WKUP: specifies the interrupt source for the Wake-up interrupt.

  In this Mode it is advised to use the following functions:
     - void SPI_ITConfig(SPI_TypeDef* SPIx, SPI_IT_TypeDef SPI_IT, FunctionalState NewState);
     - ITStatus SPI_GetITStatus(SPI_TypeDef* SPIx, SPI_IT_TypeDef SPI_IT);
     - void SPI_ClearITPendingBit(SPI_TypeDef* SPIx, SPI_IT_TypeDef SPI_IT);

  DMA Mode
  ========
  In DMA Mode, the SPI communication can be managed by 2 DMA Channel requests:
     1. SPI_DMAReq_Tx: specifies the Tx buffer DMA transfer request
     2. SPI_DMAReq_Rx: specifies the Rx buffer DMA transfer request

  In this Mode it is advised to use the following function:
    - void SPI_DMACmd(SPI_TypeDef* SPIx, SPI_DMAReq_TypeDef SPI_DMAReq, FunctionalState NewState);