SWCU192 November 2021 CC1312R7 , CC1352P7 , CC2652P7 , CC2652R7
The UART can be placed into an internal loopback mode for diagnostic or debug work by setting the UART:CTL LBE register bit. In loopback mode, data transmitted on the UARTTXD output is received on the UARTRXD input. The LBE bit must be set before the UART is enabled.