DS_SCRATCH_ADDR
x = bus_space_read_1(paa->pb_bt, h, DS_SCRATCH_ADDR);
bus_space_write_1(paa->pb_bt, h, DS_SCRATCH_ADDR, 0xAA);
if (bus_space_read_1(paa->pb_bt, h, DS_SCRATCH_ADDR) != 0xAA) {
bus_space_write_1(paa->pb_bt, h, DS_SCRATCH_ADDR, 0x55);
if (bus_space_read_1(paa->pb_bt, h, DS_SCRATCH_ADDR) != 0x55) {
bus_space_write_1(paa->pb_bt, h, DS_SCRATCH_ADDR, x);