Smartcard mode functions
[USART_Private_Functions]

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                     ##### Smartcard mode functions #####
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    [..] This subsection provides a set of functions allowing to manage the USART
         Smartcard communication.
    [..] The Smartcard interface is designed to support asynchronous protocol 
         Smartcards as defined in the ISO 7816-3 standard. The USART can provide 
         a clock to the smartcard through the SCLK output. In smartcard mode, 
         SCLK is not associated to the communication but is simply derived from 
         the internal peripheral input clock through a 5-bit prescaler.
    [..] Smartcard communication is possible through the following procedure:
         (#) Configures the Smartcard Prescaler using the USART_SetPrescaler() 
             function.
         (#) Configures the Smartcard Guard Time using the USART_SetGuardTime() 
             function.
         (#) Program the USART clock using the USART_ClockInit() function as following:
             (++) USART Clock enabled.
             (++) USART CPOL Low.
             (++) USART CPHA on first edge.
             (++) USART Last Bit Clock Enabled.
         (#) Program the Smartcard interface using the USART_Init() function as 
             following:
             (++) Word Length = 9 Bits.
             (++) 1.5 Stop Bit.
             (++) Even parity.
             (++) BaudRate = 12096 baud.
             (++) Hardware flow control disabled (RTS and CTS signals).
             (++) Tx and Rx enabled
         (#) Optionally you can enable the parity error interrupt using 
             the USART_ITConfig() function.
         (#) Enable the Smartcard NACK using the USART_SmartCardNACKCmd() function.
         (#) Enable the Smartcard interface using the USART_SmartCardCmd() function.
         (#) Enable the USART using the USART_Cmd() function.
    [..] 
  Please refer to the ISO 7816-3 specification for more details.
    [..] 
         (@) It is also possible to choose 0.5 stop bit for receiving but it is 
             recommended to use 1.5 stop bits for both transmitting and receiving 
             to avoid switching between the two configurations.
         (@) In smartcard mode, the following bits must be kept cleared:
             (+@) LINEN bit in the USART_CR2 register.
             (+@) HDSEL and IREN bits in the USART_CR3 register.