Clock control register
| HSION | Internal high-speed clock enable |
| HSIRDY | Internal high-speed clock ready flag |
| MSION | MSI clock enable |
| MSIRDY | MSI clock ready flag |
| HSEON | HSE clock enable |
| HSERDY | HSE clock ready flag |
| HSEBYP | HSE clock bypass |
| PLLON | PLL enable |
| PLLRDY | PLL clock ready flag |
| CSSON | Clock security system enable |
| RTCPRE0 | RTCPRE0 |
| RTCPRE1 | TC/LCD prescaler |