MK48TXX_ISEC
t1 = bcdtobin(mkclock_isa_nvrd(sc, MK48T18_CLKOFF + MK48TXX_ISEC));
t2 = bcdtobin(mkclock_isa_nvrd(sc, MK48T18_CLKOFF + MK48TXX_ISEC));
dt->dt_sec = bcdtobin((*sc->sc_nvrd)(sc, clkoff + MK48TXX_ISEC));
(*sc->sc_nvwr)(sc, clkoff + MK48TXX_ISEC, bintobcd(dt->dt_sec));