Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Nuvoton/M05x_registers/UART0/UA_RBR#0x0
UART0 Receive Buffer Register.
Receive Buffer Register By reading this register, the UART will return an 8-bit data received from Rx pin (LSB first).
https://github.com/cmsis-svd/cmsis-svd-data