ST STM32WL55JC Reference Manual page 1158

Universal synchronous/asynchronous receiver transmitter (USART/UART)
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Figure 323. IrDA SIR ENDEC block diagram
TX
SIREN
USART
RX
Figure 324. IrDA data modulation (3/16) - Normal mode
Start
bit
0 1
TX
IrDA_OUT
IrDA_IN
RX
0
SIR
Transmit
Encoder
SIR
Receive
DEcoder
0 1 0 0
Bit period
1 0 1 0
RM0453 Rev 2
OR
USART_TX
IrDA_OUT
IrDA_IN
USART_RX
Stop
1 1 0
3/16
0 1 1 0
RM0453
MSv31164V1
bit
1
1
MSv31165V1