RM0453
36.4.4
LPUART FIFOs and thresholds
The LPUART can operate in FIFO mode.
The LPUART comes with a Transmit FIFO (TXFIFO) and a Receive FIFO (RXFIFO). The
FIFO mode is enabled by setting FIFOEN bit (bit 29) in LPUART_CR1 register.
Since 9 bits the maximum data word length is 9 bits, the TXFIFO is 9-bits wide. However the
RXFIFO default width is 12 bits. This is due to the fact that the receiver does not only store
Low-power universal asynchronous receiver transmitter (LPUART)
Figure 333. LPUART word length programming
9-bit word length (M = 01 ), 1 Stop bit
Start
Bit0
Bit1
Bit2
bit
Clock
8-bit word length (M = 00 ), 1 Stop bit
Start
Bit0
Bit1
Bit2
bit
Clock
7-bit word length (M = 10 ), 1 Stop bit
Start
Bit0
Bit1
Bit2
bit
Clock
Data frame
Bit3
Bit4
Bit5
Bit6
Bit7
Idle frame
Break frame
Possible
Data frame
Parity
bit
Bit3
Bit4
Bit5
Bit6
Bit7
**
Idle frame
Break frame
Possible
Parity
Data frame
bit
Stop
Bit3
Bit4
Bit5
Bit6
bit
**
Idle frame
Break frame
** LBCL bit controls last data clock pulse
RM0453 Rev 1
Possible
Parity
bit
Next
Stop
Start
Bit8
bit
bit
**
Start
bit
Stop
Stop
Start
bit
bit
bit
Next
Stop
Start
bit
bit
Start
bit
Stop
Stop
Start
bit
bit
bit
Next
Start
bit
Start
bit
Stop
Stop
Start
bit
bit
bit
MS33194V2
1219/1461
1266
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