Clock control register
| MSION | MSI clock enable |
| MSIRDY | MSI clock ready flag |
| MSIPLLEN | MSI clock PLL enable |
| MSIRANGE | MSI clock ranges |
| HSION | HSI clock enabled |
| HSIKERON | HSI always enable for peripheral kernels |
| HSIRDY | HSI clock ready flag |
| HSIASFS | HSI automatic start from Stop |
| HSIKERDY | HSI kernel clock ready flag for peripherals requests |
| HSEON | HSE clock enabled |
| HSERDY | HSE clock ready flag |
| HSEBYP | HSE crystal oscillator bypass |
| CSSON | HSE Clock security system enable |
| HSEPRE | HSE sysclk and PLL M divider prescaler |
| PLLON | Main PLL enable |
| PLLRDY | Main PLL clock ready flag |
| PLLSAI1ON | SAI1 PLL enable |
| PLLSAI1RDY | SAI1 PLL clock ready flag |