Clock configuration register (RCC_CFGR)
| SW | System clock Switch |
| SWS | System Clock Switch Status |
| HPRE | AHB prescaler |
| PPRE1 | APB Low speed prescaler (APB1) |
| PPRE2 | APB high speed prescaler (APB2) |
| PLLSRC | PLL entry clock source |
| PLLXTPRE | HSE divider for PLL entry |
| PLLMUL | PLL Multiplication Factor |
| USBPRES | USB prescaler |
| I2SSRC | I2S external clock source selection |
| MCO | Microcontroller clock output |
| MCOF | Microcontroller Clock Output Flag |