ST STM32WL55JC Reference Manual page 1194

Universal synchronous/asynchronous receiver transmitter (USART/UART)
Bit 2 NE: Noise detection flag
Note: This bit does not generate an interrupt as it appears at the same time as the RXFNE bit
Bit 1 FE: Framing error
Note: This error is associated with the character in the USART_RDR.
Bit 0 PE: Parity error
Note: This error is associated with the character in the USART_RDR.
35.8.10 USART interrupt and status register [alternate] (USART_ISR)
Address offset: 0x1C
Reset value: 0x0000 00C0
The same register can be used in FIFO mode enabled (previous section) and FIFO mode
disabled (this section).
FIFO mode disabled
31 30 29
Res. Res. Res. Res.
15 14 13
ABRF ABRE UDR EOBF
r r r
1194/1454
This bit is set by hardware when noise is detected on a received frame. It is cleared by
software, writing 1 to the NECF bit in the USART_ICR register.
0: No noise is detected
1: Noise is detected
which itself generates an interrupt. An interrupt is generated when the NE flag is set
during multi buffer communication if the EIE bit is set.
When the line is noise-free, the NE flag can be disabled by programming the ONEBIT
bit to 1 to increase the USART tolerance to deviations (Refer to
Tolerance of the USART receiver to clock deviation on page
This error is associated with the character in the USART_RDR.
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.
When transmitting data in Smartcard mode, 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
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
28 27 26 25
Res. Res. TCBGT
r
12 11 10 9
RTOF CTS CTSIF
r r r r
24 23 22
RE
Res. Res.
ACK
r
8 7 6
LBDF TXE TC RXNE
r r r
RM0453 Rev 2
Section 35.5.8:
1137).
21 20 19 18
TE
WUF RWU SBKF
ACK
r r r r
5 4 3 2
IDLE ORE NE
r r r r
RM0453
17 16
CMF BUSY
r r
1 0
FE PE
r r