Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series0/EFM32G/EFM32G280F64/AES/CTRL#0x0
Control Register
Decryption/Encryption Mode
AES-256 Mode
Key Buffer Enable
AES_DATA Write Start
AES_XORDATA Write Start
https://github.com/cmsis-svd/cmsis-svd-data