APB2 peripheral clock enable register
| TIM1EN | TIM1 clock enable |
| USART1EN | USART1 clock enable |
| USART6EN | USART6 clock enable |
| ADC1EN | ADC1 clock enable |
| SPI1EN | SPI1 clock enable |
| SYSCFGEN | System configuration controller clock enable |
| EXTITEN | EXTI ans external IT clock enable |
| TIM9EN | TIM9 clock enable |
| TIM11EN | TIM11 clock enable |
| SPI5EN | SPI5 clock enable |