SBUS_BASE
#define SBUS_ADDR(slot, off) (SBUS_BASE + ((slot) << 25) + (off))
#define SBUS_ABS(a) ((unsigned)(a) >= SBUS_BASE)
#define SBUS_ABS_TO_SLOT(a) (((a) - SBUS_BASE) >> 25)
#define SBUS_ABS_TO_OFFSET(a) (((a) - SBUS_BASE) & 0x1ffffff)