DocID024597 Rev 5 1355/1830
RM0351 Universal synchronous asynchronous receiver transmitter (USART)
1411
Bit 13 DDRE: DMA Disable on Reception Error
0: DMA is not disabled in case of reception error. The corresponding error flag is set but
RXNE is kept 0 preventing from overrun. As a consequence, the DMA request is not
asserted, so the erroneous data is not transferred (no DMA request), but next correct
received data will be transferred (used for Smartcard mode).
1: DMA is disabled following a reception error. The corresponding error flag is set, as well as
RXNE. The DMA request is masked until the error flag is cleared. This means that the
software must first disable the DMA request (DMAR = 0) or clear RXNE before clearing the
error flag.
This bit can only be written when the USART is disabled (UE=0).
Note: The reception errors are: parity error, framing error or noise error.
Bit 12 OVRDIS: Overrun Disable
This bit is used to disable the receive overrun detection.
0: Overrun Error Flag, ORE, is set when received data is not read before receiving new data.
1: Overrun functionality is disabled. If new data is received while the RXNE flag is still set
the ORE flag is not set and the new received data overwrites the previous content of the
USART_RDR register.
This bit can only be written when the USART is disabled (UE=0).
Note: This control bit allows checking the communication flow without reading the data.
Bit 11 ONEBIT: One sample bit method enable
This bit allows the user to select the sample method. When the one sample bit method is
selected the noise detection flag (NF) is disabled.
0: Three sample bit method
1: One sample bit method
This bit can only be written when the USART is disabled (UE=0).
Note: ONEBIT feature applies only to data bits, It does not apply to Start bit.
Bit 10 CTSIE: CTS interrupt enable
0: Interrupt is inhibited
1: An interrupt is generated whenever CTSIF=1 in the USART_ISR register
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 40.4: USART implementation on page 1304.
Bit 9 CTSE: CTS enable
0: CTS hardware flow control disabled
1: CTS mode enabled, data is only transmitted when the CTS input is asserted (tied to 0). If
the CTS input is de-asserted while data is being transmitted, then the transmission is
completed before stopping. If data is written into the data register while CTS is de-asserted,
the transmission is postponed until CTS is asserted.
This bit can only be written when the USART is disabled (UE=0)
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 40.4: USART implementation on page 1304.
Bit 8 RTSE: RTS enable
0: RTS hardware flow control disabled
1: RTS output 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 RTS output is asserted (pulled to 0) when data can be received.
This bit can only be written when the USART is disabled (UE=0).
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 40.4: USART implementation on page 1304.
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