Block mode (T=1)In T=1 (block) mode, the parity error transmission is deactivated, by clearing the NACK bit inthe UART_CR3 register.When requesting a read from the smartcard, in block mode, the software must enable thereceiver Timeout feature by setting the RTOEN bit in the USART_CR2 register and programthe RTO bits field in the RTOR register to the BWT (block wait time) - 11 value. If no answeris received from the card before the expiration of this period, the RTOF flag will be set and atimeout interrupt will be generated (if RTOIE bit in the USART_CR1 register is set). If thefirst character is received before the expiration of the period, it is signaled by the RXNEinterrupt.Note: The RXNE interrupt must be enabled even when using the USART in DMA mode to readfrom the smartcard in block mode. In parallel, the DMA must be enabled only after the firstreceived byte.After the reception of the first character (RXNE interrupt), the RTO bit fields in the RTORregister must be programmed to the CWT (character wait time) - 11 value, in order to allowthe automatic check of the maximum wait time between two consecutive characters. Thistime is expressed in baudtime units. If the smartcard does not send a new character in lessthan the CWT period after the end of the previous character, the USART signals this to thesoftware through the RTOF flag and interrupt (when RTOIE bit is set).Note: The RTO counter starts counting:- From the end of the stop bit in case STOP = 00.- From the end of the second stop bit in case of STOP = 10.- 1 bit duration after the beginning of the STOP bit in case STOP = 11.- From the beginning of the STOP bit in case STOP = 01.As in the Smartcard protocol definition, the BWT/CWT values are defined from thebeginning (start bit) of the last character. The RTO register must be programmed to BWT -11 or CWT -11, respectively, taking into account the length of the last character itself.A block length counter is used to count all the characters received by the USART. Thiscounter is reset when the USART is transmitting (TXE=0). The length of the block iscommunicated by the smartcard in the third byte of the block (prologue field). This valuemust be programmed to the BLEN field in the USART_RTOR register. when using DMAmode, before the start of the block, this register field must be programmed to the minimumvalue (0x0). with this value, an interrupt is generated after the 4th received character. Thesoftware must read the LEN field (third byte), its value must be read from the receive buffer.In interrupt driven receive mode, the length of the block may be checked by software or byprogramming the BLEN value. However, before the start of the block, the maximum value ofBLEN (0xFF) may be programmed. The real value will be programmed after the reception ofthe third character.If the block is using the LRC longitudinal redundancy check (1 epilogue byte), theBLEN=LEN. If the block is using the CRC mechanism (2 epilogue bytes), BLEN=LEN+1must be programmed. The total block length (including prologue, epilogue and informationfields) equals BLEN+4. The end of the block is signaled to the software through the EOBFflag and interrupt (when EOBIE bit is set).In case of an error in the block length, the end of the block is signaled by the RTO interrupt(Character wait Time overflow).