Universal synchronous asynchronous receiver transmitter (USART) RM0351
1360/1830 DocID024597 Rev 5
40.8.8 Interrupt and status register (USART_ISR)
Address offset: 0x1C
Reset value: 0x0200 00C0
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 40.4: USART implementation on page 1304.
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 sets 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.
Note: In the case the application needs to send the break character following all previously
inserted data, including the ones not yet transmitted, the software should wait for the
TXE flag assertion before setting the SBKRQ bit.
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 40.4: USART implementation on
page 1304.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res. Res. Res. Res. Res. Res. TCBGT Res. Res. REACK TEACK WUF RWU SBKF CMF BUSY
r rrrrrrr
1514131211109876543210
ABRF ABRE Res. EOBF RTOF CTS CTSIF LBDF TXE TC RXNE IDLE ORE NF FE PE
rr rrrrrrrrrrrrr
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