
DocID024597 Rev 5
RM0351
Low-power universal asynchronous receiver transmitter (LPUART)
1411
Bit 4
IDLEIE
: IDLE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An LPUART interrupt is generated whenever IDLE=1 in the LPUART_ISR register
Bit 3
TE
: Transmitter enable
This bit enables the transmitter. It is set and cleared by software.
0: Transmitter is disabled
1: Transmitter is enabled
Note: During transmission, a “0” pulse on the TE bit (“0” followed by “1”) sends a preamble
(idle line) after the current word. In order to generate an idle character, the TE must not
be immediately written to 1. In order to ensure the required duration, the software can
poll the TEACK bit in the LPUART_ISR register.
When TE is set there is a 1 bit-time delay before the transmission starts.
Bit 2
RE
: Receiver enable
This bit enables the receiver. It is set and cleared by software.
0: Receiver is disabled
1: Receiver is enabled and begins searching for a start bit
Bit 1
UESM
: LPUART enable in Stop mode
When this bit is cleared, the LPUART is not able to wake up the MCU from Stop mode.
When this bit is set, the LPUART is able to wake up the MCU from Stop mode, provided that
the LPUART clock selection is HSI or LSE in the RCC.
This bit is set and cleared by software.
0: LPUART not able to wake up the MCU from Stop mode.
1: LPUART able to wake up the MCU from Stop mode. When this function is active, the
clock source for the LPUART must be HSI or LSE (see Section Reset and clock control
(RCC)).
Note: It is recommended to set the UESM bit just before entering Stop mode and clear it on
exit from Stop mode.
Bit 0
UE
: LPUART enable
When this bit is cleared, the LPUART prescalers and outputs are stopped immediately, and
current operations are discarded. The configuration of the LPUART is kept, but all the status
flags, in the LPUART_ISR are reset. This bit is set and cleared by software.
0: LPUART prescaler and outputs disabled, low-power mode
1: LPUART enabled
Note: In order to go into low-power mode without generating errors on the line, the TE bit
must be reset before and the software must wait for the TC bit in the LPUART_ISR to
be set before resetting the UE bit.
The DMA requests are also reset when UE = 0 so the DMA channel must be disabled
before resetting the UE bit.