APB1 peripheral clock enable register
| TIM5EN | TIM5 clock enable |
| TIM6EN | TIM6 clock enable |
| LPTIM1EN | LPTIM1 clock enable |
| RTCAPBEN | RTC APB clock enable |
| WWDGEN | Window watchdog clock enable |
| SPI2EN | SPI2 clock enable |
| USART2EN | USART 2 clock enable |
| I2C1EN | I2C1 clock enable |
| I2C2EN | I2C2 clock enable |
| I2C4EN | I2C4 clock enable |
| PWREN | Power interface clock enable |
| DACEN | DAC interface clock enable |