APB1ENR1
| TIM2EN | CPU1 TIM2 timer clock enable |
| LCDEN | CPU1 LCD clock enable |
| RTCAPBEN | CPU1 RTC APB clock enable |
| WWDGEN | CPU1 Window watchdog clock enable |
| SPI2EN | CPU1 SPI2 clock enable |
| I2C1EN | CPU1 I2C1 clock enable |
| I2C3EN | CPU1 I2C3 clock enable |
| CRSEN | CPU1 CRS clock enable |
| USBEN | CPU1 USB clock enable |
| LPTIM1EN | CPU1 Low power timer 1 clock enable |