Clock control register
| HSION | Internal High Speed clock enable |
| HSIRDY | Internal High Speed clock ready flag |
| HSITRIM | Internal High Speed clock trimming |
| HSICAL | Internal High Speed clock Calibration |
| HSEON | External High Speed clock enable |
| HSERDY | External High Speed clock ready flag |
| HSEBYP | External High Speed clock Bypass |
| CSSON | Clock Security System enable |
| PLLON | PLL enable |
| PLLRDY | PLL clock ready flag |