Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Atmel/AT91SAM9G20/DBGU/CR#0x0
Control Register
Reset Receiver
Reset Transmitter
Receiver Enable
Receiver Disable
Transmitter Enable
Transmitter Disable
Reset Status Bits
https://github.com/cmsis-svd/cmsis-svd-data