RM0440 Rev 4 1641/2126
RM0440 Universal synchronous/asynchronous receiver transmitter (USART/UART)
1733
Figure 555 shows the USART behavior when the wakeup event is verified.
Figure 555. Wakeup event verified (wakeup event = address match, FIFO disabled)
Figure 556 shows the USART behavior when the wakeup event is not verified.
Figure 556. Wakeup event not verified (wakeup event = address match,
FIFO disabled)
Note: The figures above are valid when address match or any received frame is used as wakeup
event. If the wakeup event is the start bit detection, the USART sends the wakeup event to
the MCU at the end of the start bit.
MSv40856V2
Usart_ker_ck
RX line
Idle
Start bit
Rx data 1 Rx data 2
Start bit
Stop bit
Stop bit
OFF
ON
Low-power mode
Startup time
Run mode
Address match event WUF =’1'
USART sends a wakeup event to the MCU
Data reception goes on
MSv40857V2
Usart_ker_ck
RX line
Idle
Start bit
Rx data 1
Stop bit
OFF
ON
Low-power mode
Address does not match
Idle
OFF
Startup time
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