45.6.3.15 Hardware Handshaking

The USART features a hardware handshaking out-of-band flow control. The RTS and CTS pins are used to connect with the remote device, as shown in the following figure.

Figure 45-26. Connection with a Remote Device for Hardware Handshaking

Setting the USART to operate with hardware handshaking is performed by writing the value 0x2 to US_MR.USART_MODE.

When hardware handshaking is enabled, the USART displays similar behavior as in standard Synchronous or Asynchronous modes, with the difference that the receiver drives the RTS pin and the level on the CTS pin modifies the behavior of the transmitter, as shown in the following figures. The transmitter can handle hardware handshaking in any case.

Figure 45-27. RTS Line Software Control when US_MR.USART_MODE = 2

The following figure shows how the transmitter operates if hardware handshaking is enabled. The CTS pin disables the transmitter. If a character is being processed, the transmitter is disabled only after the completion of the current character and transmission of the next character occurs as soon as the pin CTS falls.

Figure 45-28. Transmitter Behavior when Operating with Hardware Handshaking