Yes, you are correct. But in most cases, you would use a driver and abstract away what individual registers get read/written. The HAL can be taken from anywher

Yes, you are correct. But in most cases, you would use a driver and abstract away what individual registers get read/written. The HAL can be taken from anywhere, really. Doesn't need to be avrgcc/Arduino. The registers in the link are C macros resolving to uint8_t*, pointing to memory locations where you read/write to.