RTCSB_HALT
#define rtc_halted(vrtc) ((vrtc->rtcdev.reg_b & RTCSB_HALT) != 0)
if (changed & RTCSB_HALT) {
if ((newval & RTCSB_HALT) == 0) {
rtcout_locked(RTC_STATUSB, RTCSB_HALT | RTCSB_24HR);