Low-power universal asynchronous receiver transmitter (LPUART) RM0440
1686/2126 RM0440 Rev 4
Figure 558. LPUART word length programming
38.4.4 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
MS33194V2
Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8
Start
bit
Stop
bit
Next
Start
bit
Idle frame
9-bit word length (M = 01 ), 1 Stop bit
Possible
Parity
bit
Break frame
Data frame
Clock **
Start
bit
Stop
bit
Start
bit
Stop
bit
Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7
Start
bit
Stop
bit
Next
Start
bit
Idle frame
8-bit word length (M = 00 ), 1 Stop bit
Possible
Parity
bit
Break frame
Data frame
Clock **
Start
bit
Stop
bit
Start
bit
Stop
bit
Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6
Start
bit
Stop
bit
Next
Start
bit
Idle frame
7-bit word length (M = 10 ), 1 Stop bit
Possible
Parity
bit
Break frame
Data frame
Clock
** LBCL bit controls last data clock pulse
**
Start
bit
Stop
bit
Start
bit
Stop
bit
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