APB1 peripheral clock enable register (RCC_APB1ENR)
| TIM2EN | Timer 2 clock enable |
| TIM6EN | Timer 6 clock enable |
| WWDGEN | Window watchdog clock enable |
| SPI2EN | SPI 2 clock enable |
| SPI3EN | SPI 3 clock enable |
| USART2EN | USART 2 clock enable |
| USART3EN | USART 3 clock enable |
| I2C1EN | I2C 1 clock enable |
| I2C2EN | I2C 2 clock enable |
| PWREN | Power interface clock enable |
| DACEN | DAC interface clock enable |
| CECEN | HDMI CEC interface clock enable |