On entry: XY?0 = XY?1 = XY?2 = XY?3 = XY?4 = XY?5 = XY?6 = XY?7 = On exit: XY?0 = XY?1 = XY?2 = XY?3 = XY?4 = XY?5 = XY?6 = XY?7 =