APB1 peripheral clock enable register
| TMR2EN | Timer2 clock enable |
| TMR3EN | Timer3 clock enable |
| TMR4EN | Timer4 clock enable |
| TMR5EN | Timer5 clock enable |
| WWDTEN | Window watchdog timer clock enable |
| SPI2EN | SPI2 clock enable |
| USART2EN | USART2 clock enable |
| USART3EN | USART3 clock enable |
| UART4EN | UART4 clock enable |
| UART5EN | UART5 clock enable |
| I2C1EN | I2C1 clock enable |
| I2C2EN | I2C2 clock enable |
| USBEN | USB clock enable |
| CAN1EN | CAN1 clock enable |
| BPREN | Barrery powered domain register clock enable |
| PWCEN | Power clock enable |
| CAN2EN | CAN2 clock enable |