8.5.1.1.1.2 UART Receiver

The UART interface design works in half-duplex. While the device is transmitting data on TX, RX is ignored except when receiving a Communication Clear or Communication Reset. To avoid collisions during data transmission up the daisy-chain interface, the host microcontroller must wait until all bytes of a transmission are received from the device before attempting additional communication. If the microcontroller starts a transaction without waiting to receive the preceding transaction's response, the communication is not considered reliable and the microcontroller must send a Communication Clear (see Communication Clear (Break) Detection) or Communication Reset (see Communication Reset Detection) to restore normal communications to the base device. Breaks and communication resets are not sent to the stack devices. A Communication Clear or Communication Reset can be sent at any time. RX cannot be disabled, and is active even when the transmitter (TX) is disabled (COMM_CTRL[TX_EN] = 0).