To prevent any single software error from corrupting USART behavior, certain registers in the address space can be write-protected by setting the WPEN bit in the USART Write Protection Mode Register (US_WPMR).
If a write access to a write-protected register is detected, the WPVS flag in the USART Write Protection Status Register (US_WPSR) is set and the field WPVSRC indicates the register in which the write access has been attempted.
The WPVS bit is automatically cleared after reading the US_WPSR.
The following registers can be write-protected: