HW_RTC_CTRL_CLKGATE
RTC_WR(sc, HW_RTC_CTRL_CLR, HW_RTC_CTRL_CLKGATE);
while (!(RTC_RD(sc, HW_RTC_CTRL) & HW_RTC_CTRL_CLKGATE))
RTC_WR(sc, HW_RTC_CTRL_CLR, HW_RTC_CTRL_CLKGATE);
while (RTC_RD(sc, HW_RTC_CTRL) & HW_RTC_CTRL_CLKGATE)