DocID024597 Rev 5 1391/1830
RM0351 Low-power universal asynchronous receiver transmitter (LPUART)
1411
RS232 RTS flow control
If the RTS flow control is enabled (RTSE=1), then RTS is asserted (tied low) as long as the
LPUART receiver is ready to receive a new data. when the receive register is full, RTS is de-
asserted, indicating that the transmission is expected to stop at the end of the current frame.
Figure 428 shows an example of communication with RTS flow control enabled.
Figure 440. RS232 RTS flow control
RS232 CTS flow control
If the CTS flow control is enabled (CTSE=1), then the transmitter checks the CTS input
before transmitting the next frame. If CTS is asserted (tied low), then the next data is
transmitted (assuming that data is to be transmitted, in other words, if TXE=0), else the
transmission does not occur. When CTS is de-asserted during a transmission, the current
transmission is completed before the transmitter stops.
When CTSE=1, the CTSIF status bit is automatically set by hardware as soon as the CTS
input toggles. It indicates when the receiver becomes ready or not ready for communication.
An interrupt is generated if the CTSIE bit in the LPUART_CR3 register is set. Figure 429
shows an example of communication with CTS flow control enabled.
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