AHB Peripheral Clock enable register 1 (CRM_AHBEN1)
| GPIOAEN | IO A clock enable |
| GPIOBEN | IO B clock enable |
| GPIOCEN | IO C clock enable |
| GPIODEN | IO D clock enable |
| GPIOEEN | IO E clock enable |
| GPIOFEN | IO F clock enable |
| CRCEN | CRC clock enable |
| DMA1EN | DMA1 clock enable |
| DMA2EN | DMA2 clock enable |