X'Address is an Ada attribute where X is any object, program unit, or label, RM 13.3(10/1).
'Address may be used to return the address of the first element allocated to X. 'Address may also be used to set the address of X for stand-alone objects and program units, RM 13.3(12).
-- A 32 bit hardware register Device_Input_Value: Interfaces.Unsigned_32; for Device_Input_Value'Address use To_Address (16#8000_05C4#);
It's not recommended to use Integer_32 in this case.