SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The UART can be placed into an internal loopback mode for diagnostic or debug work by setting the LBE bit in the UARTCTL register (see Section 26.5.8). In loopback mode, data transmitted on the UnTx output is received on the UnRx input. Note that the LBE bit should be set before the UART is enabled.