stm32 /stm32wl3 /STM32WL33 /USART /ISR

PE: Parity error This bit is set by hardware when a parity error occurs in receiver mode. It is cleared by software, writing 1 to the PECF in the USART_ICR register. An interrupt is generated if PEIE = 1 in the USART_CR1 register. -0: No parity error -1: Parity error

FE: Framing error This bit is set by hardware when a de-synchronization, excessive noise or a break character is detected. It is cleared by software, writing 1 to the FECF bit in the USART_ICR register. In Smartcard mode, in transmission, this bit is set when the maximum number of transmit attempts is reached without success (the card NACKs the data frame). An interrupt is generated if EIE = 1 in the USART_CR1 register. -0: No Framing error is detected -1: Framing error or break character is detected

NF: START bit Noise detection flag This bit is set by hardware when noise is detected on a received frame. It is cleared by software, writing 1 to the NFCF bit in the USART_ICR register. -0: No noise is detected -1: Noise is detected

ORE: Overrun error This bit is set by hardware when the data currently being received in the shift register is ready to be transferred into the USARTx_RDR register while RXNE=1 (RXFF = 1 in case FIFO mode is enabled) . It is cleared by a software, writing 1 to the ORECF, in the USARTx_ICR register. An interrupt is generated if RXNEIE/ RXFNEIE=1 or EIE = 1 in the USARTx_CR1 register. -0: No overrun error -1: Overrun error is detected

IDLE: Idle line detected This bit is set by hardware when an Idle Line is detected. An interrupt is generated if IDLEIE=1 in the USART_CR1 register. It is cleared by software, writing 1 to the IDLECF in the USART_ICR register. -0: No Idle line is detected -1: Idle line is detected

RXNE/RXFNE:Read data register not empty/RXFIFO not empty RXNE bit is set by hardware when the content of the USARTx_RDR shift register has been transferred to the USARTx_RDR register. It is cleared by a read to the USARTx_RDR register. The RXNE flag can also be cleared by writing 1 to the RXFRQ in the USARTx_RQR register. RXFNE bit is set by hardware when the RXFIFO is not empty, and so data can be read from the USART_RDR register. Every read of the USART_RDR frees a location in the RXFIFO. It is cleared when the RXFIFO is empty. The RXNE/RXFNE flag can also be cleared by writing 1 to the RXFRQ in the USART_RQR register. An interrupt is generated if RXNEIE/RXFNEIE=1 in the USART_CR1 register. -0: Data is not received -1: Received data is ready to be read.

TC: Transmission complete This bit indicates when the last data written in the USART_TDR has been transmitted out of the shift register. It is set by hardware if the transmission of a frame containing data is complete and if TXE/TXFE is set. An interrupt is generated if TCIE=1 in the USART_CR1 register. It is cleared by software, writing 1 to the TCCF in the USART_ICR register or by a write to the USART_TDR register. An interrupt is generated if TCIE=1 in the USART_CR1 register. -0: Transmission is not complete -1: Transmission is complete

TXE/TXFNF: Transmit data register empty/TXFIFO not full When FIFO mode is disabled, TXE is set by hardware when the content of the USARTx_TDR register has been transferred into the shift register. It is cleared by a write to the USARTx_TDR register. The TXE flag can also be set by writing 1 to the TXFRQ in the USART_RQR register, in order to discard the data (only in Smartcard T=0 mode, in case of transmission failure). When FIFO mode is enabled, TXFNF is set by hardware when TXFIFO is not full, and so data can be written in the USART_TDR. Every write in the USART_TDR places the data in the TXFIFO. This flag remains set until the TXFIFO is full. When the TXFIFO is full, this flag is cleared indicating that data can not be written into the USART_TDR. Note: The TXFNF is kept reset during the flush request until TXFIFO is empty . After sending the flush request (by setting TXFRQ bit), the flag TXFNF should be checked prior to writing in TXFIFO. (TXFNF and TXFE will be set at the same time). An interrupt is generated if the TXEIE/TXFNFIE bit =1 in the USART_CR1 register. -0: Data register is full/Transmit FIFO is full. -1: Data register/Transmit FIFO is not full

LBDF: LIN break detection flag This bit is set by hardware when the LIN break is detected. It is cleared by software, by writing 1 to the LBDCF in the USART_ICR. An interrupt is generated if LBDIE = 1 in the USART_CR2 register. -0: LIN Break not detected -1: LIN break detected

CTSIF: CTS interrupt flag This bit is set by hardware when the nCTS input toggles, if the CTSE bit is set. It is cleared by software, by writing 1 to the CTSCF bit in the USART_ICR register. An interrupt is generated if CTSIE=1 in the USART_CR3 register. -0: No change occurred on the nCTS status line -1: A change occurred on the nCTS status line

CTS: CTS flag This bit is set/reset by hardware. It is an inverted copy of the status of the nCTS input pin. -0: nCTS line set -1: nCTS line reset

RTOF: Receiver timeout This bit is set by hardware when the timeout value, programmed in the RTOR register has lapsed, without any communication. It is cleared by software, writing 1 to the RTOCF bit in the USART_ICR register. An interrupt is generated if RTOIE=1 in the USART_CR2 register. In Smartcard mode, the timeout corresponds to the CWT or BWT timings. -0: Timeout value not reached -1: Timeout value reached without any data reception

EOBF: End of block flag This bit is set by hardware when a complete block has been received (for example T=1 Smartcard mode). The detection is done when the number of received bytes (from the start of the block, including the prologue) is equal or greater than BLEN + 4. An interrupt is generated if the EOBIE=1 in the USART_CR2 register. It is cleared by software, writing 1 to the EOBCF in the USART_ICR register. -0: End of Block not reached -1: End of Block (number of characters) reached

UDR: SPI slave underrun error flag In slave transmission mode, this flag is set when the first clock for data transmission appears while the software has not yet loaded any value into USARTx_DR. -0: No underrun error -1: underrun error

ABRE: Auto baud rate error This bit is set by hardware if the baud rate measurement failed (baud rate out of range or character comparison failed) It is cleared by software, by writing 1 to the ABRRQ bit in the USART_CR3 register

ABRF: Auto baud rate flag This bit is set by hardware when the automatic baud rate has been set (RXNE will also be set, generating an interrupt if RXNEIE = 1) or when the auto baud rate operation was completed without success (ABRE=1) (ABRE, RXNE and FE are also set in this case) It is cleared by software, in order to request a new auto baud rate detection, by writing 1 to the ABRRQ in the USART_RQR register.

BUSY: Busy flag This bit is set and reset by hardware. It is active when a communication is ongoing on the RX line (successful start bit detected). It is reset at the end of the reception (successful or not). -0: USART is idle (no reception) -1: Reception on going

CMF: Character match flag This bit is set by hardware, when a the character defined by ADD[7:0] is received. It is cleared by software, writing 1 to the CMCF in the USART_ICR register. An interrupt is generated if CMIE=1in the USART_CR1 register. -0: No Character match detected -1: Character Match detected

SBKF: Send break flag This bit indicates that a send break character was requested. It is set by software, by writing 1 to the SBKRQ bit in the USART_CR3 register. It is automatically reset by hardware during the stop bit of break transmission. -0: No break character is transmitted -1: Break character will be transmitted

RWU: Receiver wakeup from Mute mode This bit indicates if the USART is in mute mode. It is cleared/set by hardware when a wakeup/mute sequence is recognized. The mute mode control sequence (address or IDLE) is selected by the WAKE bit in the USART_CR1 register. When wakeup on IDLE mode is selected, this bit can only be set by software, writing 1 to the MMRQ bit in the USART_RQR register. -0: Receiver in active mode -1: Receiver in mute mode

TEACK: Transmit enable acknowledge flag This bit is set/reset by hardware, when the Transmit Enable value is taken into account by the USART. It can be used when an idle frame request is generated by writing TE=0, followed by TE=1 in the USART_CR1 register, in order to respect the TE=0 minimum period.

REACK: Receive enable acknowledge flag This bit is set/reset by hardware, when the Receive Enable value is taken into account by the USART. It can be used to verify that the USART is ready for reception before entering Stop mode.

TXFE: TXFIFO Empty This bit is set by hardware when TXFIFO is Empty. When the TXFIFO contains at least one data, this flag is cleared. The TXFE flag can also be set by writing 1 to the bit TXFRQ (bit 4) in the USART_RQR register. An interrupt is generated if the TXFEIE bit =1 (bit 30) in the USART_CR1 register. -0: TXFIFO is not empty. -1: TXFIFO is empty.

RXFF: RXFIFO Full This bit is set by hardware when RXFIFO is Full. An interrupt is generated if the RXFFIE bit =1 in the USART_CR1 register. -0: RXFIFO is not Full. -1: RXFIFO is Full.

TCBGT: Transmission complete before guard time flagl This bit indicates when the last data written in the USART_TDR has been transmitted correctly out of the shift register . It is set by hardware in Smartcard mode, if the transmission of a frame containing data is complete and if there is no NACK from the smartcard. An interrupt is generated if TCBGTIE=1 in the USART_CR3 register. It is cleared by software, writing 1 to the TCBGTCF in the USART_ICR register or by a write to the USART_TDR register. -0: Transmission is not complete or transmission is complete unsuccessfuly (i.e. a NACK is received from the card) -1: Transmission is complete successfully (before Guard time completion and there is no NACK from the smart card).

RXFT: RXFIFO threshold flag This bit is set by hardware when the programmed threshold in RXFTCFG in USARTx_CR3 register is reached. This means that there are (RXFTCFG - 1) data in the Receive FIFO and one data in the USART_RDR register. An interrupt is generated if the RXFTIE bit =1 (bit 27) in the USART_CR3 register. -0: Receive FIFO doesnt reach the programmed threshold. -1: Receive FIFO reached the programmed threshold

TXFT: TXFIFO threshold flag This bit is set by hardware when the TXFIFO reaches the programmed threshold in TXFTCFG in USARTx_CR3 register i.e. the TXFIFO contains TXFTCFG empty locations. An interrupt is generated if the TXFTIE bit =1 (bit 31) in the USART_CR3 register. -0: TXFIFO doesnt reach the programmed threshold. -1: TXFIFO reached the programmed threshold