STMicroelectronics STM32F405 Reference Manual page 1007

RM0090
Bit 9 CTSE: CTS enable
Note: This bit is not available for UART4 & UART5.
Bit 8 RTSE: RTS enable
Note: This bit is not available for UART4 & UART5.
Bit 7 DMAT: DMA enable transmitter
Bit 6 DMAR: DMA enable receiver
Bit 5 SCEN: Smartcard mode enable
Note: This bit is not available for UART4 & UART5.
Bit 4 NACK: Smartcard NACK enable
Note: This bit is not available for UART4 & UART5.
Bit 3 HDSEL: Half-duplex selection
Universal synchronous asynchronous receiver transmitter (USART)
0: CTS hardware flow control disabled
1: CTS mode enabled, data is only transmitted when the nCTS input is asserted (tied to 0).
If the nCTS input is deasserted while a data is being transmitted, then the transmission is
completed before stopping. If a data is written into the data register while nCTS is
deasserted, the transmission is postponed until nCTS is asserted.
0: RTS hardware flow control disabled
1: RTS interrupt enabled, data is only requested when there is space in the receive buffer.
The transmission of data is expected to cease after the current character has been
transmitted. The nRTS output is asserted (tied to 0) when a data can be received.
This bit is set/reset by software
1: DMA mode is enabled for transmission.
0: DMA mode is disabled for transmission.
This bit is set/reset by software
1: DMA mode is enabled for reception
0: DMA mode is disabled for reception
This bit is used for enabling Smartcard mode.
0: Smartcard Mode disabled
1: Smartcard Mode enabled
0: NACK transmission in case of parity error is disabled
1: NACK transmission during parity error is enabled
Selection of Single-wire Half-duplex mode
0: Half duplex mode is not selected
1: Half duplex mode is selected
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