Universal synchronous asynchronous receiver transmitter (USART) RM0091
624/742 Doc ID 018940 Rev 1
25.7.7 Request register (USART_RQR)
Address offset: 0x18
Reset value: 0x0000
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res Res
151413121110987654321
Res Res Res Res Res Res Res Res Res Res Res TXFRQ RXFRQ MMRQ SBKRQ
ABRR
Q
w_r0 w_r0 w_r0 w_r0 w_r0
Bits 31:5 Reserved, must be kept at reset value
Bit 4 TXFRQ: Transmit data flush request
Writing 1 to this bit sets the TXE flag.
This allows to discard the transmit data. This bit must be used only in Smartcard mode, when
data has not been sent due to errors (NACK) and the FE flag is active in the USART_ISR
register.
. If the USART does not support Smartcard mode, this bit is reserved and forced by hardware
to ‘0’. Please refer to Section 25.4: USART implementation on page 573.
Bit 3 RXFRQ: Receive data flush request
Writing 1 to this bit clears the RXNE flag.
This allows to discard the received data without reading it, and avoid an overrun condition.
Bit 2 MMRQ: Mute mode request
Writing 1 to this bit puts the USART in mute mode and resets the RWU flag.
Bit 1 SBKRQ: Send break request
Writing 1 to this bit sets the SBKF flag and request to send a BREAK on the line, as soon as
the transmit machine is available.
Bit 0 ABRRQ: Auto baud rate request
Writing 1 to this bit resets the ABRF flag in the USART_ISR and request an automatic baud
rate measurement on the next received data frame.
Note: : If the USART does not support the auto baud rate feature, this bit is reserved and
forced by hardware to ‘0’. Please refer to Section 25.4: USART implementation on
page 573.
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