svd2pac has four methods for accessing a register:

- `read() -> RegValueT`
- `write(value: RegValueT)`
- `init(impl FnOnce(RegValueT) -> RegValueT)`
- `modify(impl FnOnce(RegValueT) -> RegValueT)`

where `write` requires you to either use a value you got from `read()`, `Default::default`, or an explicit conversion from an integer type, and `init` and `modify` are shorthand for deriving a value from either the register's default value or its current value, respectively