STMicroelectronics STM32WLEx Reference Manual page 1085

RM0461
Bits 31:5 Reserved, must be kept at reset value.
Bit 4 TXFRQ: Transmit data flush request
Note: In FIFO mode, the TXFNF flag is reset during the flush request until TxFIFO is empty in
Bit 3 RXFRQ: Receive data flush request
Bit 2 MMRQ: Mute mode request
Bit 1 SBKRQ: Send break request
Note: When the application needs to send the break character following all previously
Bit 0 ABRRQ: Auto baud rate request
Note: If the USART does not support the auto baud rate feature, this bit is reserved and must
33.8.9 USART interrupt and status register (USART_ISR)
Address offset: 0x1C
Reset value: 0x0X80 00C0
X = 2 if FIFO/Smartcard mode is enabled
X = 0 if FIFO is enabled and Smartcard mode is disabled
The same register can be used in FIFO mode enabled (this section) and FIFO mode
disabled (next section).
FIFO mode enabled
31 30 29
Res. Res. Res. Res.
15 14 13
ABRF ABRE UDR EOBF
r r r
Universal synchronous/asynchronous receiver transmitter (USART/UART)
When FIFO mode is disabled, writing '1' to this bit sets the TXE flag. This enables to discard
the transmit data. This bit must be used only in Smartcard mode, when data have 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 must be kept at reset
value.
When FIFO is enabled, TXFRQ bit is set to flush the whole FIFO. This sets the TXFE flag
(Transmit FIFO empty, bit 23 in the USART_ISR register). Flushing the Transmit FIFO is
supported in both UART and Smartcard modes.
order to ensure that no data are written in the data register.
Writing 1 to this bit empties the entire receive FIFO i.e. clears the bit RXFNE.
This enables to discard the received data without reading them, and avoid an overrun
condition.
Writing 1 to this bit puts the USART in Mute mode and resets the RWU flag.
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.
inserted data, including the ones not yet transmitted, the software should wait for the
TXE flag assertion before setting the SBKRQ bit.
Writing 1 to this bit resets the ABRF and ABRE flags in the USART_ISR and requests an
automatic baud rate measurement on the next received data frame.
be kept at reset value. Refer to
28 27 26 25
TXFT RXFT TCBGT
r r r
12 11 10 9
RTOF CTS CTSIF
r r r r
Section 33.4: USART implementation on page
24 23 22
RE
RXFF TXFE
ACK
r r r
8 7 6
LBDF TXFNF TC RXFNE
r r r
RM0461 Rev 5
21 20 19 18
TE
WUF RWU SBKF
ACK
r r r r
5 4 3 2
IDLE ORE NE
r r r r
1017.
17 16
CMF BUSY
r r
1 0
FE PE
r r
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