APB1ENR1
| TIM2EN | TIM2 timer clock enable |
| TIM6EN | TIM6 timer clock enable |
| RTCAPBEN | RTC APB clock enable |
| WWDGEN | Window watchdog clock enable |
| SPI2EN | SPI2 clock enable |
| USART2EN | USART2 clock enable |
| USART3EN | USART3 clock enable |
| I2C1EN | I2C1 clock enable |
| I2C2EN | I2C2 clock enable |
| I2C3EN | I2C3 clock enable |
| CRSEN | CRS clock enable |
| USBF | USB FS clock enable |
| PWREN | Power interface clock enable |
| OPAMPEN | OPAMP interface clock enable |
| LPTIM1EN | Low power timer 1 clock enable |