Clock configuration register (RCC_CFGR)
| SW | System clock Switch |
| SWS | System Clock Switch Status |
| HPRE | AHB prescaler |
| PPRE | APB Low speed prescaler (APB1) |
| ADCPRE | ADC prescaler |
| PLLSRC | PLL input clock source |
| PLLXTPRE | HSE divider for PLL entry |
| PLLMUL | PLL Multiplication Factor |
| MCO | Microcontroller clock output |
| MCOPRE | Microcontroller Clock Output Prescaler |
| PLLNODIV | PLL clock not divided for MCO |