NVRCS
bus_space_write_1(iot, ioh, TUL_NVRAM, NVRCS | NVRCK);
bus_space_write_1(iot, ioh, TUL_NVRAM, NVRCS);
b = NVRCS | NVRDO; /* Write the start bit (== 1) */
b = NVRCS | NVRDO; /* Write a 1 bit */
b = NVRCS; /* Write a 0 bit */
bus_space_write_1(iot, ioh, TUL_NVRAM, NVRCS);