help cleaning up a complex type

[dwhall256]

I'm trying to create a type to represent a microcontroller register where the 
address of the register is part of the type. This is the closest I can get to 
what I want that will compile:
    
    
    type
      RegisterType* = uint8 | uint16 | uint32
      RegisterPtr* = ptr RegisterType
      
      RegisterAttr = enum
        Readable,
        Writable
      RegisterAttrs = set[RegisterAttr]
      
      RegisterConfig[
        TAddress: static RegisterPtr,
        TReadWriteAttr: static RegisterAttrs,
      ] = distinct NimbedConfig
    
    proc initRegister*(address: static RegisterPtr, rwAttrs: static 
RegisterAttrs): RegisterConfig[address, rwAttrs] =
      discard
    
    
    Run

and I declare and use a fictional register like this:
    
    
    const PORTA = initRegister(cast[ptr uint8](0x0100), {Readable, Writable})
    let a = PORTA.load()
    PORTA.store(a+1)
    
    
    Run

Can someone suggest how I should implement `initRegister()` so that the 
declaration of `PORTA` becomes a bit cleaner:
    
    
    const PORTA = initRegister(uint8, 0x0100, {Readable, Writable})
    
    
    Run

side quest: What is it called when I put a static value such as 0x0100 into the 
datatype? Is `RegisterConfig` a "type class"? I need to learn this topic better 
and am looking for some search terms to use.