Registers will be formatted under `UpperHex`, notice in the example that arrays are of size less than 32, hence `Debug` of array (`[T; N]`) is implemented by default. Notice that the `reserved` fields falls back to the default integer formatting (as not wrapped by the `volatile-register` abstraction).
For register arrays with more then 32 items, `array-debug` provides a newtype over array, replicating the array behavior while providing `Debug`.