GPIO alternate function low register
| AFRL0 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL1 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL2 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL3 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL4 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL5 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL6 | Alternate function selection for port x bit y (y = 0…7) |
| AFRL7 | Alternate function selection for port x bit y (y = 0…7) |