RCC Domain 2 Kernel Clock Configuration Register
| USART234578SRC | USART2/3, UART4,5, 7/8 (APB1) kernel clock source selection |
| USART16SRC | USART1 and 6 kernel clock source selection |
| RNGSRC | RNG kernel clock source selection |
| I2C123SRC | I2C1,2,3 kernel clock source selection |
| USBSRC | USBOTG 1 and 2 kernel clock source selection |
| CECSRC | HDMI-CEC kernel clock source selection |
| LPTIM1SRC | LPTIM1 kernel clock source selection |