Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Toshiba/M369/UART4/ICR#0x0
Interrupt Clear Register
RIMIC
CTSMIC
DCDMIC
DSRMIC
RXIC
TXIC
RTIC
FEIC
PEIC
BEIC
OEIC
https://github.com/cmsis-svd/cmsis-svd-data