0x00-0x08: register (A, B, C, X, Y, Z, I, J or SP, in that order)
    0x09-0x11: [register]
    0x12-0x1a: [next word + register]
         0x1b: SP ; FREE! :D
         0x1c: PC
         0x1d: O
         0x1e: [next word]
         0x1f: next word (literal)
    0x20-0x3f: literal value 0x00-0x1f (literal)