FE_BMPR10
bus_space_read_1(bst, bsh, FE_BMPR10),
bus_space_write_1(bst, bsh, FE_BMPR10, 0x00);
bus_space_write_1(bst, bsh, FE_BMPR10, sc->txb_sched | FE_B10_START);
left = bus_space_read_1(bst, bsh, FE_BMPR10);